[Russian freight launch to ISS fails to orbit]

True; I was also wondering, though, if an SM of a different length might result in different potential maximum rates in the event of a booster failure, requring requalification of the LES for these new rates.

Why? The LES didn't pull the SM off the stack, just the CM.

It'd also allow you to modify the configuration to put the main TPS at the base of the OM and permanently attach the CM to the OM, with the requisite beefed-up LES and recovery systems, to allow a larger crew for space station missions, a la McDonnell's 'Big Gemini' proposal of 1969 that would have given us a larger-than-Shuttle-sized crew capacity in a spacecraft with about the same mass as the Apollo CSM.

Were the astronauts supposed to put on big red noses and floppy shoes before they climbed into that thing?

Hmm. I know NASA doesn't like to forgo a separate OMS setup, simply for redundancy's sake--witness how Shuttle could have deorbited on the aft RCS (using OMS fuel) if the OMS engines failed to light.

The CM had four RCS quads with four thrusters each; losing one aft thruster would still permit deorbiting, and if more were lost, there's always the option of turning around and deorbiting eyeballs-out. I'd say that's plenty of redundancy. MY biggest concern would be the low thrust:weight possibly complicating orbital maneuvering - 400 lbs for a 30,000 lb spacecraft is a little marginal.

Or, if that's still overkill, a multistart, gimbalable version of the LM Ascent Engine (Wiki sez RS-18, so does this article on one being fired successfully in 2008(!) http://www.flightglobal.com/articles/2008/07/25/226066/nasas-apollo-lunar-module-ascent-engine-roars-again.html, EA sez TR-201)?

Yeah... now we're getting there. That's what they should've used in the first place. It's still a bit hefty for LEO work, but not unreasonably so.

Both would have the advantage of being almost-zero development cost engines. (The Ascent engine would just need the multiple-operation propellant valves used in the SPS to feed the AJ-10, and testing of a gimbal mount; the LMDE could be used as-is, or with the variable throttle deleted for weight savings.)

Was the SPS gimballed? I don't think it was.

Ah, OK. So really, the difference is mainly that the Soviets designed a spacecraft capable of lunar flight with the use of kicker stages, but still well-adapted to LEO, whereas us Yanks went and designed a spacecraft optimized purely for the lunar mission, with our usual lack of foresight as to what the hell we'd do *after* the lunar program. Sounds pretty typical, actually! (i.e., the Soviets went a more complicated route that wasn't as technically or financially demanding, whereas the USA went with the money-is-no-object route of building the 'perfect' vehicle for the mission, and not caring what mission it might be asked to carry out in the future!)

... Yeah, I think that pretty much sums it up.

This is a surprise to me. I knew that STS-135's crew was required to meet the standard Soyuz physiological requirements, just in case they needed to be brought back on Soyuz instead of Atlantis, but clearly, Soyuz isn't *quite* as tight as I'd been told!

Yeah. And it was a TMA, meaning the dude had a suit on too.

I bet they stuck him in the middle, though.

The original plan had STS-2 (in 1979) docking with Skylab to boost its orbit; that plan wasn't abandoned until it became clear that Skylab would re-enter before STS-1 could happen. (Granted, this was an early enough plan that it still had STS-1 as a suborbital flight ending in a planned-RTLS abort, but that was the original plan.) The reboost plans would have kept it aloft until the mid-80s without further reboosts, so by that time, the Shuttle would have been able to reach it. (Besides, weren't the things needed to accomplish high-elevation orbits in Shuttle mainly software changes, and elimination of the paint on the ET? It might have been awkward without the TDRS constellation up, but beyond that...)

It was much more than just that. The paint only weighed around 600 lbs, which really wasn't very significant. Still, they elected to eliminate it from the Standard-Weight Tank largely on cost and labor grounds, since its purpose was wholly aesthetic (the ET doesn't need to worry about solar heating during its short mission). Later (though apparently not nearly as much later than I thought, seeing how its first usage was STS-6), the tank underwent some major design changes which shaved over 10,000 lbs, resulting in the Lightweight Tank which was used on most Shuttle missions. THAT was significant, and allowed the shuttle to reach higher-inclination orbits with more payload (well, in theory, at least). Of course, the bigger issue with POLAR orbits was simply that SLC-6 wasn't ready yet, and they weren't willing to drop SRBs on Georgia or Cuba.

I'm going to assume it was for the Earth Science mission, somehow. Either that, or they found that the INT-21 configuration would overperform in a 28-degree orbit and it was simpler to just tell it to fly a different trajectory than to make the adjustments to get it into a nice 28-degree orbit instead.

How is stuffing in a few thousand pounds of ballast (or, better yet, something USEFUL) difficult?

Maybe they wanted to use it for Earth survey or perhaps espionage as well. Or maybe they just wanted to rub it in the Russians' faces.

Yeah, I remember reading about that. Not nice, that...

Well from the sound of things, it isn't clear whether the abrasion was caused by the rod itself or just the suction. Either way, he didn't notice it until he got inside again.

I think the 2.5 PSI for 'normal breathing' is more the total outside pressure required to deflate the lungs on exhale, without the use of mechanical breathing to force air out. Remember, we don't have any muscles that will force air *out* of the lungs, only the diaphragm generating a vacuum in the chest cavity to suck air *into* them.

That pressure is gonna push on both the outside AND the inside of the thoracic cavity, y'know... adding or subtracting pressure to both sides isn't gonna change a thing (though lower-density mixes are easier to breathe for dynamic reasons).

Though I looked up a bit more, and it looks like part of the reason they use more ppO₂ in space suits is because CO₂ and H₂O being expelled from the bloodstream dilute this oxygen within the alveoli, and without 10+ PSI partial pressure of other gasses to compress these waste gasses (which, by the way, sum to about 1.7 PSI partial pressure), this dilution becomes more significant. So apparently an external 4.7 PSI of 100% O₂ corresponds to an alveolar ppO₂ of 3.0 PSI, though even this is slightly more than the (somewhat diluted) alveolar ppO₂ encountered at sea level, and substantially more than that normally encountered at altitude.

I think the Wiki description may be a little confusing; the way I see it, as the wearer inhales, the air/O2/whatever that he takes into his lungs comes out of the bladder, which, as the chest expands, would shrink to maintain the same net pressure.

Yeah, that makes the most sense. Thinking about it, I think you'd need a stiff wrap (perhaps even a hard shell) around the outside of the bladder to ensure that inflation/deflation of the bladder won't cause any net volume change to the thorax/bladder/helmet system.

Then, when the wearer exhales, the air coming out of his lungs is piped through a mask into some other system (be it a simple overboard-dump, or, more likely, a rebreather to scrub out the CO2 and recycle the remaining O2, extending the life of the onboard O2 supply)

I don't think an open-loop breathing system has EVER been used on a space suit (unless you count early pressure suits). And a rebreather doesn't need to DIRECTLY be hooked up to the wearer's face, just so long as the suit is sufficiently ventilated to prevent CO₂ buildup in the helmet area.

while the bladder is reinflated by a pressure-maintenance valve on the O2/air supply, possibly using a mechanical pump to forcibly feed it. (Alternatively, you could probably use some sort of circulation pump to suck the 'used' air out of the helmet and eliminate the mask, now that I think of it.)

Yeah, like that. Who knows, for a low-volume helmet system, maybe a couple of reed valves is all you need - put your scrubber in the bladder, squirt fresh O₂ into the bladder->helmet valve, and ta da! Passive ventilation.

Though we'd need a way to manage moisture as well... (part of why I like the concept of cryogenic CO₂ scrubbing - it removes ALL volatiles from the mix, using only the heat of vaporization of LOX.)

There's the small issue of what the micrometeoroids would do to the astronaut's skin after puncturing the suit, though. That could be Bad.

QuikClot is good stuff.

And not even veterans get to say they have fragments of a METEOR inside them... 8)

See my comments earlier about NASA having determined that a 5PSI O2 environment was a pain in the ass (well, more often, in the knees) for most of the crew, when you have an airlock.

Well, from what I can find, there was still 1.45 PSI ppN₂ in Skylab, and presumably similar quantities aboard Apollo and Gemini as well - mixes not unlike that encountered at extreme altitudes with an oxygen mask. It seems pretty apparent that the Nitrogen just wasn't properly purged from the system (if at all) - as if they just corked the module at that pressure altitude, along with all the nitrogen in it.

Now, oxygen embolism IS possible, but it is FAR less likely and severe than nitrogen embolism owing to oxygen's substantially higher diffusion rates (this is why hyperbaric oxygen therapy is the primary treatment for the bends).

But the point is much more simple: Even if it's still an issue, there is NO WAY it could be any worse in a low-pressure, high-O₂ environment than in a normal 14.7 PSI nitrox environment. There's no POSSIBLE way that making the transition even greater could possibly lessen these effects. It just doesn't make any sense.

I get the feeling that this sort of thing is just a pointless gesture to appeal to politicians who don't fully understand the situation. There's something fundamentally wrong with placing the responsibility for conducting these accident hearings in the hands of a congressional committee.

I'll note that the Soviets switched to a mixed-gas system before their first flight, due to Valentin Bondarenko's training accident. Mixed-gas systems are troublesome, but apparently, they're considered less of a problem than the issues with pure-oxygen systems.

Well for one thing, UNlike an airplane, a spacecraft must be completely sealed up at some point. In many ways, its easiest to just overbuild your pressure vessel and then treat the sucker like a space submarine, completely closed-cycle, all the time. This is actually pretty easy to do if you want to take the simple route - just bring a few chemical oxygen generators, some carbon scrubbers, a condenser or lots of desiccant (because we don't want it raining inside our spaceship now, do we?), a hull that can handle 14.7 PSI internal pressure, and you're good. It's heavy, but it's easy and it works.

Now alternatively, you could attempt an Apollo and vent pressure during ascent for little more technical complication, permitting lighter and more voluminous spacecraft construction (the mass of a pressure vessel is directly proportional to the pressure and volume it must contain, ceteris paribus). Of course, if you DON'T completely purge the nitrogen out on the ground, you'll need to displace it out somehow to make room for the higher percentage of oxygen required; it appears Apollo eventually did this by simply metering oxygen into the cabin during ascent and allowing a reduced (but significant) residual ppN₂ to remain. Nice and simple, and ALMOST as light and low-pressure as a pure-oxygen solution, but without all the fire hazards of launching in Apollo 1 conditions.

Now, these of course are not the only options. You could, for instance, launch with the cabin completely unpressurized with the crew wearing pressure suits, fully purging all nitrogen during ascent. You could use my proposal of purging with a condensible, fire-resistant gas for launch then corking the vent and gradually replacing it with oxygen once you reach the target pressure (unlike nitrogen condensable gasses can be completely scrubbed without a full purge).

[These are getting too long - the board's complaining to me about a 20,000-character limit. Why couldn't I write pointless technical descriptions of spacecraft life support systems back in high school instead of pointless persuasive essays?]

[We will not weaponize space]

Launch:

[orbit and deorbit goes here](forgot to screencap 'cause this was like my fourth attempt)

Come to papa...

Ooh, you're mine now...

QUIT FLYING AND GET DOWN THERE, DANGIT

MONEY, BABY!!

(I'm actually surprised my first stage reentered. I separated RIGHT AFTER orbital injection and didn't touch a thing until I deorbited. Though I did have an extremely low perikee...)

Do I win?

[Challenge: Drag race to 100KM altitude]

Any questions?

Yeah. Are you man enough to wrestle it into orbit in 2:00 flat? (Judging by your screencap, it should be capable).

[Russian freight launch to ISS fails to orbit]

Nuts. Well, even then, one that's structurally all-new, but built to the same dimensions, with the same engine, could still be a relatively low-cost engineering job, and one that wouldn't require new aerodynamic sims to see if the booster would still fly straight with it.

Yeah, reengineering the service module would be less costly than reengineering the entire spacecraft, for sure. But running a few aerodynamic sims or modifying some wind tunnel models and firing off the old 10x10' is probably not THAT high on your list of expenses. Pressurizing it is a bit of a task, though, but it'd probably be worth it, especially if you intend to use it to supply a space station in the short term (pressurized cargo capacity is a valuable thing indeed).

And I wouldn't use the AJ-10 for LEO operations. Heck, that thing was overkill for lunar transfers! It was only there because it was developed while they were still considering the direct-ascent route. No... something smaller would be much more sensible. Perhaps forgo it altogether and increase the RCS propellant capacity.

True. Now that I think of it, though, isn't the main reason Soyuz is lighter than Apollo the fact that most of its internal volume--and a lot of expensive equipment--is carried in the Orbital Module, which is *not* designed to survive re-entry? Minimizing the size of the recoverable portion of the vehicle is a great way to reduce mass, since it lets you get rid of a *lot* of thermal protection, which then has a cascade effect on all other parts of the system. (Less orbital propellant needed reduces the mass of the service module, which then reduces the required total force for the top stage of the booster and thus reduces its required fuel load, which continues on down until you get to the first stage.)

BARELY. An ablative heat shield for Earth entry weighs something like 1/6th the mass it protects. This is significant, but not nearly enough to explain away the massive disparity between Apollo and Soyuz. Even if Soyuz cuts its TPS mass by half by leaving stuff in an orbital module (which it doesn't - not even close), that's still only 1/12 of the pressurized module mass you've eliminated by removing it's TPS. And this actually DOESN'T get magnified within the propulsion module in terms of propellant mass, because the amount of propellant required in LEO is actually very small.

If you combine the Soyuz Orbital and Reentry modules, though, you get around 4000 kg of pressurized mass on more recent, three-man variants. That's not THAT much lighter than the Apollo CM's ~5800 kg. Thus, it appears that the vast majority of savings to be had are within the service module - and I'm beginning to understand more and more why that is. Apollo had an oversized engine, lots of propellant for the lunar insertion and return, and all the tankage and structure to match; and shrinking these to an LEO-appropriate scale would cut the spacecraft's mass roughly in half.

I suspect the fact that it was originally planned as a two-man spacecraft helps with keeping the mass down, too, as do its fairly stiff ergonomic limits. Isn't the upper limit on height for someone flying in Soyuz 5'8'? (NASA set their design point at six feet even, meaning that Apollo had to accomodate astronauts who were up to four inches taller than Soyuz... and then there was C.C. Williams, who was about half an inch taller than that, and got into the program by staying up all night jumping up and down to compress his spine the night before his selection-screening physical...)

Well... http://en.wikipedia.org/wiki/Soyuz_TMA-20#Tallest-ever_crew_member

Take that as you will.

Also consider how they figured out a way to cram five astronauts into one CSM for Skylab rescue.

Yeah. This is why I'm incredibly frustrated that we didn't either launch S-IVB-513 as a second Skylab, or at least authorize the Skylab 5 mission with the vehicle--fully stacked and tested during all Skylab missions, mind, and even rolled out to the pad during one (when Skylab 3's CSM thruster quads started failing in flight) to give the first one a higher boost to avoid any chance of re-entry before Shuttle was ready to fly. It would have given us many more missions *for* the Shuttle to do in the early phases, without having to rely on subsidized launches to fill the cargo bay.

It was a while before the Shuttle could even reach a 50-degree orbit. A second Skylab could be put in a lower-inclination orbit, but even if you reboosted the first Skylab, the shuttle wouldn't have been able to reach it right away. Well, not unless they changed a few things during the design process to suit it...

(Why the heck did they even put it in such a high-inclination orbit in the first place, anyways? Were they planning to invite the Russians to come visit?)

Ah, here we are, from the Wiki article: 'Tests of punctures showed that up to a square millimeter of skin could be directly exposed to vacuum for extended periods with no permanent effect, unlike conventional suits which would lose pressure and breathing air along with it.'

About pressure-suit punctures, it's actually happened before on the shuttle:

http://en.wikipedia.org/wiki/List_of_spaceflight-related_accidents_and_incidents#Non-fatal_incidents_during_spaceflight

1991 April 8: STS-37: spacesuit puncture: During an extravehicular activity on STS-37, a small rod (palm bar) in a glove of EV2 astronaut Jay Apt's extravehicular mobility unit punctured the suit. Somehow, the astronaut's hand conformed to the puncture and sealed it, preventing any detectable depressurization.[59] During postflight debriefings Apt said after the second EVA, when he removed the gloves, his right hand index finger had an abrasion behind the knuckle. A postflight inspection of the right hand glove found the palm bar of the glove penetrating a restraint and glove bladder into the index finger side of the glove. NASA found air leakage with the bar in place was 3.8 sccm vs a specification of 8.0 sccm. They said if the bar had come out of the hole, the leak still would not have been great enough to activate the secondary oxygen pack. The suit would, however, have shown a high oxygen rate indication.

Just goes to show that the tensile strength of skin and connective tissue becomes a significant pressure membrane at such low pressures as those used for EVA.

So it could presumably be used for shorter times with larger holes in it--for example, to 'get the hell back inside the spacecraft' after a major tear. My guess is that they didn't test it with *multiple* holes, either; it may be that a square millimeter could be exposed in any one place without problems, but having four or five holes of that size in various locations wouldn't be a problem.

Even still, that seems unworkable to me. There are bound to be gaps or folds with areas PROBABLY on the order of a square centimeter in even the best mechanical pressure suits. If you used a low local pressure in regions where such gaps and folds are likely to occur, the pressure GRADIENT between the vacuum and local internal pressures can be reduced, likely reducing local trauma as well. Who knows, maybe you could get it to the point where skin's tensile strength was sufficient to tolerate exposed regions several cm² in size...

Most likely. As a note, according to the wiki article, 2.5PSI is required for 'normal breathing,' and 4.3PSI is required for 'human physiology,' although I expect that's more a general goal.

That seems high. 4-5 PSI sounds like a good pressure for inside a spacecraft, since it's plenty to keep astronauts alert (on a side note, maybe 'dilution masks' would be a good idea for helping astronauts sleep in such an oxygen-rich environment ) yet not absurdly and unnecessarily high like the 14.7 PSI diluted-oxygen mixture that is currently used. But during EVA, I'd think it'd be reasonable to reduce pressure to more of a high-altitude equivalent for the sake of making the suits more workable. For instance, ppO₂ at 10,000' altitude is just 2.1 PSI, and I can 'breathe normally' up there without an oxygen mask. And perhaps oxygen/suit pressure could be varied depending on the demand; high-exertion tasks could be supplemented with an extra shot of oxygen before and after.

Oh, and hey, apparently, the original suit tested in 1971 actually worked a lot like your proposed concept: 'The positive-pressure breathing system consisted of three main portions; a pressurized helmet, the breathing bladder, and the tankage system in a backpack. The bladder and helmet were connected together to pump air out of the bladder over the torso when the user breathed in, reducing the amount of pressure on the user's chest.'

That's pretty much exactly what I was thinking of: a ~2.5-3 PSI pneumatic bladder - directly-plumbed to the oxygen helmet - around the thorax that would inflate as the airlock vented, with ~1.5 PSI elastic garments for the abdomen and extremities. If properly executed. Are they suggesting mechanical ventilation, though? I don't see why any pumps would be necessary.

And the 'powernet' material used in one layer generated 0.97 PSI on the torso (the largest and thus lowest-pressure area), while the bobbinet material used in lower tension areas could generate 0.29 PSI over the torso, and 0.77 PSI over areas like the wrists and ankles. Sounds like they targeted a total pressure from the suit by itself of about 2.5 PSI, though they had to cheat and include a pressure bladder on the torso. (MIT's current one-layer version demonstrates 3.6 PSI minimum, and they want 4.4 PSI minimum for the final baseline design.)

Still seems a TEENSIE bit high... after all, the Armstrong limit is just under 1 PSI total pressure, and with only <3 PSI oxygen with no nitrogen in the breathing system, that 1 PSI plus normal diastolic blood pressure should be sufficient to prevent embolism, I'd think...

It'll still be tiring to put on (maybe schedule a nap in the depressurized airlock, hooked up to spacecraft O2, for after putting it on?), and even though it's much more flexible than any bladder-type pressure suit, it'll still be tiring to use, but it should make life a lot easier, because even if you put a micrometeoroid garment, SAFER, helmet visors, battery pack, radio, and lights over it, it would still be lighter and easier to move in than the current bladder-type suits. (It'd be even more useful on a lunar spacecraft-maintenance job, since then, one could just literally have a work *tent* that the spacecraft is moved into for service, to provide micrometeoroid protection, and thus eliminate that layer.

I almost wonder if you could simply eliminate most of the micrometeoroid garment anyways. After all, punctures are far less critical, except for on the helmet and bladder...

And there's ANOTHER thing that I've been wanting to see used more often: inflatable spacecraft and habitation modules. How hard would it be to set up an inflatable tent around a lander?

Actually, NASA chose to use mixed-gas starting with the Shuttle for two reasons. First, they had a lot of trouble with pre-breathing being inadequate for preventing the 'bends' on Gemini and Apollo missions--some outside air would inevitably leak in during the switch from the portable oxygen mask to the pressure suit, then during the switch from the suit's onboard O2 supply to the spacecraft supply, and that was enough that astronauts would report having some joint pain from the 'bends' in flight. Secondly, they'd found, during Skylab, that communicating across the cabin took more effort in a low-pressure environment, since the 'thin' air wouldn't actually transmit sound as well. (It also resulted in voices becoming higher and squeakier, though not so much as the heliox mixture used in deep-submergence diving and bathyscapes.) This actually was made much simpler by the Shuttle being the first American spacecraft to have an airlock, instead of depressurizing the entire cabin for EVAs, since that allowed the (eventually-adopted) 'camping out' procedure that purges the nitrogen from the EVA crew's blood far better than any two-hour pre-breathing exercise could.

Let me put it this way: nitrogen is a nuisance. It does nothing for the human physiology. It does nothing for the spacecraft's engineering considerations. It does NOTHING OF VALUE.

What it DOES do is get into astronauts' bloodstream, saturates it, and then threatens to bubble out and cause potentially permanent injury to these astronauts. It requires them to perform time-consuming procedures before EVA to prevent decompression sickness. It adds another 10 PSI of pressure that the entire spacecraft must contain. It adds one more consumable that you have to bottle and carry and regulate and launch. It's a useless detail that ought to be removed from the equation.

I don't know about those Skylab accounts. I don't know if a lower-density gas mix would have trouble carrying sound. I DO know that the bit about it causing squeaky voices is BS, though. Pure oxygen at standard temperature (and ANY pressure) has a (slightly) lower speed of sound than dry air. If anything, it'd cause a slight DEEPENING of the voice. Even if the bit about sound carrying is true, so what? Deal with it. Use an intercom. Use a friggin' cup and string, for all I care. It's a relatively minor complication.

The gains to be had, on the other hand, are massive. Life support is significantly simplified. Lengthy acclimation procedures before EVA become completely unnecessary, since The Bends is now completely a non-issue. Spacecraft mass can be significantly reduced owing to the lower pressure demands (a factor of THREE, and that's for a comfortable 5 PSI of oxygen). Consumable weight is moderately reduced. Less consumable mass would be lost to a leak or during normal airlock operation. Astronaut comfort may be improved, since heat conduction to and from the body will be reduced (allowing perspiration to straitforwardly manage thermoregulation, much like with a SAS). Fire hazards are not necessarily any greater than they currently are, unless you do something stupid like use a 100% O₂ mix at LAUNCH (I sorta feel like a 100% CO₂ environment and oxygen masks would be ideal for launch, eliminating any fire hazard and allowing astronauts to purge nitrogen from their bloodstream before they even leave the ground).

Personally, I'd want at least two waldoes along with any sleeve/glove options, simply because even here on Earth, I constantly find myself needing a third or fourth hand; I have to assume that's even more of a problem in zero-gee, and a couple of waldoes on the front could help out greatly with that.

Heh, yeah, I suppose. At the very least, they could be used as a way to anchor yourself in place while you worked, since that's probably the only thing feet are ever used for in microgravity. Though, I think I'd rather go with simpler, more solutions: a few short carabiner-terminated tethers to clip myself in wherever I'm working, a friction pad near my 'feet' to push against and keep the tethers taught, and some simple, manually-manipulated clamps to perform the 'third hand' job - y'know, like a bigger version of these:

And of course a handful of accessible bags and pouches. Because really, a robotic arm isn't THAT intuitive to work with.

OOH. And what about a teenie airlock, so you can take stuff from outside the pod, bring them inside to work on in a pressurized, glove-free environment, and then take it out again to install it. It'd be easy to figure when it'd be worth it, too - just whenever the oxygen lost from cycliing the airlock would be more than that consumed during the extra time of doing the job outside.

Hmm. Looks like that means having to extend the total glide distance about 1200 miles to reach Moron AB. Since it's about twice that far back to the States, I think the landing in Europe would be a better option.

OOOH, no. You're not gonna make it to Moron. No way, nohow. Not on the typical Apollo launch azimuth. Not even the Shuttle could pull off that kinda crossrange. If you're landing anywhere, it's either the Ocean or Africa.

And I'm still dubious a pullout and gliding reentry of that magnitude would be possible. In fact, I'm starting to wonder if S-II recovery of ANY sort would be possible without major modification. It looks like S-II was going 7 km/s at some 175 km at separation; considering apogee was even higher than that, that's a pretty steep and hot reentry. Remember that 21-G ballistic post-abort Soyuz reentry I told you about? Yeah. I think that's pretty much what we're looking at.

Though SpaceX seems to think they can recover the upper stage of the Falcon 9 with nothing more than a bit of cork insulation for TPS, so who knows?

Dunno. I'd assume that we're looking at maybe 1000kg for the full parafoil system, and that the landing gear would, with adequate extension system and shock absorption, need more than that. I'd probably use wheels, simply so that they could tow it clear of the runway quickly, rather than having Moron AB shut down for a day or so as they fit a dolly to the underside, but that's open to debate.

BAH. Just DRAG the darned thing. You're just gonna replace the skid shoes anyways, right?

And why bother landing at an airbase? Any large, flat patch of desert should do for a parafoil landing, no?

Here, observe:

[Russian freight launch to ISS fails to orbit]

Oh, certainly. You could also shave a few hundred kilos off by replacing that thick direct-lunar-return heat shield with a thinner one designed for the less-demanding LEO re-entry; Apollo was *definitely* optimized purely for the lunar mission, and using it unmodified for LEO missions would be wasteful in a long-term program, though a lightweight LEO-only version could have been engineered at... *relatively* little cost. (How about making part of the SM into additional volume akin to the Soyuz Orbital Module, accessed through a heat-shield hatch of the type tested on the Gemini 2 capsule's second flight, like was planned for the Gemini B/MOL combination? Shrink the consumables to what's needed for an LEO-only mission, and concentrate them and equipment at the rear, and that frees up a lot of volume in the SM that could then be used as an orbital module.)

It looks like I misjudged a bit; you could probably eliminate HALF the service module's weight by just short-fuelling it. Yeah, I thought ~6000 kg of propellant seemed a bit light for 2.8 km/s...

And unfortunately, the SM's sector-divided construction was not well-adapted for being contracted lengthwise into a lighter LEO-only variant, nor for being pressurized to serve as an orbital module either.

But, y'know, Soyuz was designed for Lunar expeditions as well, albeit with help from separately-launched tugs and tankers which provided most of the propulsion mass. But Soyuz easily has enough consumables for a lunar excursion, even as light as it is.

Well, it's partly that, and partly that NASA had only intended the cargo bay to be about half that length, even after the decision to eliminate expendable boosters; the Air Force, however, demanded the final length and payload to accomodate the KH-11 as payload on a polar launch. That made it a hell of a lot harder to be affordable for the payloads that *were* available.

And the fact that the Shuttle never made it into polar orbit in the first place severely cut back on payload opportunities, including the vast majority of reconnaissance and Earth-survey satellites. Pretty much all there was left for it were sats in high-altitude orbits (including geostationary orbit) where changing the inclination with a kick-motor was no big deal, or heavy satellites in odd orbits that don't really matter (such as Hubble or LDEF).

Well, according to that article, MIT is currently doing a study of an advanced version, and is using pressurized gloves instead of mechanical counterpressure ones to simplify matters. Maybe it's a matter of fitting and the number of joints in the hand?

Ah, yeah, I guess the flexibility of the human hand vs. the elasticity of modern materials may be the issue. What other part of the body is capable of curling itself into a fist-like ball so tightly?

(Not that you could achieve that with pressurized gloves on, though...)

NASA tests in the 70s showed that, in a 0-psi altitude chamber, you could have a Space Activity Suit with a one-square-millimeter hole in it and not have any negative effect at all; I'd assume that above that, you start getting serious discomfort that would make you want to return to a pressurized environment.

Pfft. If you have to distribute the suit's pressure over EVERY SQUARE MILLIMETER of the body for it to work right, it's never gonna work right.

just how much suction CAN someone take at a local level without pain?

Well... I found another write-up, this time on breast pumps, that suggests about 4 PSI as a pain threshold.

It may be (and probably is) dependent on where and how large the exposed tissue is.

See above. I do wonder, given the small surface area involved, if it would be possible to use a form of spray-on or paint-on liquid latex to make a new set of mechanical counterpressure gloves every time you suited up to go outside. If so, that would *greatly* simplify the matter of fitting gloves. (You couldn't use it for the whole suit, because part of the point of the SAS is that you can eliminate the cooling system by allowing perspiration to wick through the suit and sublimate into space, resulting in natural cooling--and latex doesn't 'breathe' to allow that.)

I don't think that'd work well at all. It's pretty much obligatory that the garment either have some pre-tension when it is adorned, or be fairly inelastic such that minimal swelling is required to produce the adequate counterpressure. Spray-on latex would have little to no pre-tension upon drying, and is very elastic. But if you want to try it, just dip your hand in some rubber cement - it's the same stuff.

And I dunno if the spacecraft's air reprocessing system could handle the solvents, so you may want to wait until you're inside the airlock to put it on, let it dry while O₂-conditioning through a mask. (On a side-note, I think it's positively retarded that space agencies use a diluted mixed-gas air analogue rather than a low-pressure pure-oxygen environment, like those used in space suits, within spacecraft. I guess it's just another one of those things that got a mostly unjustified stigma as the result of a disaster - Apollo 1, in this case.)

Pretty similar. The thrusters would have been more for maneuvering to various grapple points, in my way of thinking. Honestly, I think the concept would be seen as vastly superior to the simple pressure suit, particularly for long-duration EVA like those done on Hubble servicing and ISS assembly missions. (Though honestly, for many missions, DEXTRE would probably be an even better solution...)

Yes, robotic arms don't need consumables or pressure suits or radiation protection to work for extended periods within a vacuum environment...

And I don't like the idea of using reaction jets for mobility during EVA mainly because it's a waste of consumables (the mass of which is only becoming proportionally more and more significant, with the increased efficiency of life support systems). It's nice to HAVE them just in case you need them (for instance, if there happens to be something that can't be reached via robotic arm or grappling), but they should not be your primary means of locomotion.

Of course, the other question is how far downrange the S-II impacted, telling us how far we'd have to stretch the glide.

Just south of the Azores, I believe.

It might be possible to make it an Apollo or Soyuz-style lifting reentry, relying entirely on mass asymmetry to generate the lift.

The Shuttle relies on CG positioning to make its lifting reentry possible, too. Just about every free aerodyne does. If the center of pressure and center of gravity are not lined up properly, you're gonna have a hard time producing much lift at all.

But I get what you mean - using a non-axisymmetric CG-placement on an axisymmetric blunt body to try and get lift out of it.

Yeah... you might be able to get a SMALL amount of lift out of just shifting the CG, but I don't know if you'd get sufficient AOA/lift out of that alone, and if you DID, your rocket may be unacceptably lopsided already.

Hmm... are we even sure if the S-II would be stable nose-first or tail-first? With five engines on the bottom and nothing but a light interstage on top, it may be prone to a tail-first orientation without the mass of the payload on top of it. Perhaps radically so. In fact, that'd probably be the MOST pressing issue - with an extreme tail-heavy or nose-heavy static stability state, you'll have a hard time getting to a decent lifting AOA without tweaking some things. I think some fins of some sort would be necessary, simply to shift the center-of-pressure close enough to gain some attitude control. Perhaps some flip-out grid fins to keep it in a nose-first orientation after separation.

I expect that the landing gear would weigh quite a bit more than the parafoil, for example, so I might be able to get the CG far enough off-center to 'stretch the glide' until within parafoil range. (Of course, this would then result in a decrease in payload, as the engine thrust would have to be gimballed off-center to compensate!)

EEK. I hope your landing gear isn't THAT heavy...

Heck, I probably wouldn't even use wheels at all. For a parafoil landing, skids are fine.

Maybe the engines could all be gimballed hard-over to offer some amount of CG-shift.

[Russian freight launch to ISS fails to orbit]

Very true. Personally, I think it's easier to make the rockets flexible than the payloads, although Soyuz and Apollo both proved quite adaptable (Apollo could have done most of the things Soyuz did, albeit with a 'mission module' launched in place of the lunar module for the extended-duration solo missions)

Yeah, probably... except for one little issue - Apollo is surprisingly heavy. The CM alone weighs nearly as much as a whole Soyuz spacecraft (especially the earlier ones with three crew and no spacesuits), and the service module weighs another FOUR TIMES that. Even without the LM to lift, that's a lot of mass to put in orbit for just three guys and some supplies. (just think, a Saturn IB could probably put three or four modern Soyuz spacecraft in orbit at once!) And you can go and try to justify it, but in the end Soyuz still puts three guys with spacesuits on in orbit with enough consumables for an entire month (vs. half that for the CSM) and more internal volume to boot.

Now, you could probably knock off about 5000 kg (~1/5 the overall mass) just by short-fuelling the massive service module (since who REALLY needs 2.8 km/s of delta-V in LEO?), or perhaps double that if you redesigned the service module for LEO-only operations. Its still much heavier than Soyuz, but it's a start.

Shuttle, of course, was designed to do anything and everything. (Part of the reason I think it never met its economic goals--when you try to build an Everyplane for Everypurpose, you end up with the F-111... something that is slightly better than mediocre at one thing, and can't do much of anything else it was supposed to do at all.)

Partially, yeah - though I think it was more in the sense that you had to fill up that cargo bay with SOMETHING to justify launching it, and there just weren't enough heavy and valuable payloads (ESPECIALLY ones going to low-inclination orbits) to make the checkbooks balance out like they hoped. If anything, they failed to account for the semiconductor industry making satellites so light and cheap to launch.

As for the F-111, I actually do think it's a superb tactical bomber (every bit as good as the F-15E in such roles). But hey, it's the Air Force we're talking about here - if there's something new and good-looking, they'll buy it.

Right, I meant that I couldn't see a mission for also having a spaceplane small enough to fly on the Ares I. Eh, the point was the same.

Ah. Yeah, I suppose not, unless they were trying to make a Kliper analogue - something which can do the same job as the capsule AND the service module all in one, while being fully reusable (and possibly being able to carry more crew).

I wasn't sure which. Isn't aniline pretty nasty stuff to metals, too?

Actually, quite to the contrary - it is sometimes used as a corrosion inhibitor in acidic environments.

Corrosion is always the result of the oxidation of metal. Certain metals are more reactive than others, but all metals are reducing agents - they will tend to surrender electrons to strong oxidizers in their presence, forming ionic compounds (commonly simple and inert metal-oxides). Now, strong reducing agents like aniline are looking to surrender electrons as well, not seize them, and thus pose no threat to metallic containers, but will actually protect them by reacting with any oxidizing contaminants before they reach the metal. In fact, the weaker the reducing agent is, the greater a threat it poses, as certain weak reducing agents (such as alcohol) can actually act as oxidizers when exposed to highly-reactive metals.

So how, then, can metal fuel tanks contain oxidizers at all, you ask? Well, as strange as it seems, they slow the rate of corrosion by... being corroded. You see, for some metals (including the very reactive aluminum and titanium; or notably, chromium), the metal-oxide product of the oxidation reaction does not flake away like rust does, but rather form an inert protective barrier between the metal and its surroundings. This is known as 'passivation,' or 'anodization' when it's done on purpose. Other metals (such as steel or nickel) usually depend on their relatively lower reactivity to slow corrosion, but in the presence of a strong oxidizer like LOX, this is not enough - and they must be alloyed with another metal (usually chromium) to enable passivation to take place.

(And RFNA is just... hell, even Jeb would think that stuff's too dangerous to mess with!)

Yep. Strong oxidizer + strong acid = icky stuff (though a great precursor to more stable nitro-compounds).

Quite likely. Ironically, the one place that astronauts could MOST use it--the gloves--is the one place that's hardest to make work.

Really? I knew they had issues with concave regions, but I figured the gloves would be one of the smaller challenges (compared to, say, armpits or the crotch), since you wouldn't need nearly as much tension there, and since you don't have to slide an entire LIMB through them (only your fingers).

And I wonder if you could get away with omitting the gloves altogether... just how much suction CAN someone take at a local level without pain?

Erm. Ahem. I just googled... and the results... are about, erm...

...yeah.

(But I got a number - they say 5' (of mercury! 2.5 PSI! Not length. Sheesh.) can be harmful. No mention of pain thresholds, though.)

So, based on that, from a bare-minimum-pressure environment, you probably COULD handle a short duration of time with your hands exposed directly to a vacuum with no injury, but I imagine discomfort would be present. Small holes or gaps in your gloves may not be bothersome, though.

(Every EVA type I've ever heard said that the gloves are the worst part, because it's almost impossible to flex a pressurized glove. Other parts of the suit are much easier to flex, simply due to longer moment arms and larger muscles used.)

Well that's a different issue. The gloves are also extremely thick too... not only must they retain the pressure, but they also are required to resist puncture as well. I doubt they're easy to flex UNpressurized either.

And I don't think the forces needed for moving arms and legs should be taken for granted, either; while it may be easier to move them initially owing to the larger muscle groups, it still requires much more energy and causes exhaustion quickly (notice how even on the Moon, astronauts rarely stretched their suits very far from the relaxed position).

I'm starting to wonder if something akin to the Russian equivalent of the 2001 space pods, as seen in the movie version of 2010, might not end up being the way to go--essentially, a slightly-larger hardsuit with waldoes and built-in maneuvering thrusters. Not as easy to maneuver in, but they could be one-size-fits-all, and I expect it'd reduce fatigue on the operator.

I kind of think that that something similarmay end up being the ultimate solution for microgravity EVA; a legless hardsuit with arms that the astronaut can wiggle in and out of when manipulation is required. I don't know about maneuvering thrusters though; while they're just great for getting around, it's not easy to work while stationkeeping :. I think they've already realized the best solution so far is to use a robotic arm as a platform for moving around and working from, like so:

True. The only question is how much help the lifting body shape provided in the early parts of the descent, before they popped the parafoil...

A lot, I'm afraid. Most of the downrange distance is controlled by modulating altitude (and thus air density) during reentry.

I wonder how much lift:drag you could get out of a simple cylinder with a few canards, maybe some small fins or strakes, and no nosecone... and if the S-II's reentry wasn't too steep already for a pullout and long lifting glide...

[Build an arbitrarily large SSTO rocket]

Err, that's what I meant. Stack decouplers. Gah.

I need sleep.

[What part modelling software are you using?]

Normal maps mean all the detail of a mesh is represented by a single image file, so you could just import a ~1500 poly KSP part into ZBrush, add millions of polygons of detail and save all that out as a normal map image so in-game the part is still ~1500 polys.

Hmm, I didn't know it went down to that level of resolution. I thought it was just an interpolation between some manually-specified normals at each vertex (which, for some software, it is).

[Build an arbitrarily large SSTO rocket]

Yeah, I've been thinking about it; tricouplers allow for much better efficiency. Your lofted mass per stack with a radial-SFB-radial-SFB-decoupler-tricoupler-<stack> is 1.2 instead of 0.2, and going straight to the tricoupler on the main stack gives you a carry weight of 8.8 right there.

Hum. E'en with that I'm not sure how you managed. Evidently my math is out somewhere. Perhaps that sixth LFT is more trouble than it's worth.

He also omitted the radial decoupler between the SRBs and the liquids. I'm not sure you realize, but in theory, this multiplies your payload-per-stack by 5 since it frees up an additional 0.8 on top of the 0.2 you mentioned. So I believe this works out to... 12 stacks, WITH the Command Pod and no SAS?

Also, do you think you could fire the boosters without stuff exploding? I bet that'd help even more, if only because they'd be empty by the time you got to altitude (thus reducing the mass your liquids must accelerate to orbital speeds).

[Do It Like Jebediah: Orbit and land safely using only boosters]

As long as you're in orbit and can prove it, nope. My run had an apogee of 206km and a perigee of 66km, but I screwed up my re-entry approach. =(

If I launch, kill my ascent rate and snap a shot at perigee to prove I'm at orbital speeds and eccentricities, do I still have to complete an orbit or can I just deorbit immediately?

[Russian freight launch to ISS fails to orbit]

Er... exactly. Yeah. Just like that. (Grah. I was thinking of the Blackhawks they used to use that were the real 'black helicopters' and had no airworthiness certificate or registration numbers or even running lights.)

Yeah, I've seen those. Didn't used to see 'em, but they've become annoyingly common.

Right, at that point, I was thinking more the actual spacecraft itself, on a semi-reusable low-cost booster.

For the spacecraft, you have a solid point; then again, look at Soyuz and the absurd number of projects and missions they've used it for... And the Shuttle (though it was part of a complete new system) was designed to be highly versatile as well (though ultimately failed to achieve the economics it was designed to for one reason or another).

As for rockets, they're usually pretty flexible. It's not hard or expensive to change payloads as long as they fit within the rockets' lift capabilities. Look at the R-7 family and all the different odd jobs IT did with hardly any modification... I feel the same should apply just fine to reusable rockets like the Falcon 9.

For example, small two-man spaceplane for... well, I can't think of an application for it,

Hands-on space tourism. Pay more; but get to fly it yourself.

but your choice of either that small two-man spaceplane, or the Orion, depending on application, both launched on the same Ares I. (Not a realistic situation, of course, but it gets the concept across.)

Orion could do anything that Apollo or Soyuz could do... (albeit on a slightly larger scale...)

Well, not many S-IVBs. I think there are... three of them in heliocentric, plus the Apollo 12 one that's in that weird orbit that transfers between geocentric and heliocentric. I'd assume there's a *lot* of Centaurs and Agenas out there, though.

Now that I think of it... it MIGHT not be all that hard to drop the stage on a free-return trajectory, and then massage it back to LEO through a prolonged aerobraking sequence. I still don't see much benefit in it, though. Upper-stage transfer engines are usually small and light and and few in number, and you're still going to have to haul the propellant mass to orbit to refill it, and the tankage as well since you need something to hold that propellant during ascent - and at that point, you might as well just be lifting a whole new transfer stage anyways.

They tend to be pretty nasty to the inside of the tanks; remember how Titan had to be defueled and have its tanks cleaned out and inspected after 30 days on alert? I expect reusing a transfer stage with hypergols would require someone in an EVA suit going inside the tankage to clean it out and inspect it.

That'd be the oxidizer. They tend to be corrosive. LOX is no different - except for the fact that it boils off in much less than 30 days.

I'm hoping they figure out some inert non-metallic containers (or ones with inert ceramic coatings) that can hold cryogens soon. I think ULA is working on something like that for the ACES that's slated to replace Centaur.

It might be feasible to service them outside if we can make the mechanical counterpressure suit (http://en.wikipedia.org/wiki/Space_activity_suit) work right. That would be a lot less difficult to work in, once worn. I could see a variation on the current hardsuit where the torso is still the same, but the limbs use mechanical counterpressure in place of pressurization.

I've read about it. It's appealing, but I think the challenges of just fitting such a suit will prevent it from ever actually being used.

I kind of wonder about sort of a low-pressure hybrid suit; one which used a mere 1 PSI of air pressure to push it just behind the Armstrong limit, then applied mechanical counterpressure to the thorax and used a positive-pressure oxygen mask to ensure the ~2.5 PSI PPO2 necessary to prevent hypoxia under exertion. I know that pilots during WWII experimented with such thoracic counterpressure garments, and I think derivatives of this have been implemented in modern pilots' pneumatic G-suits in case of high-altitude cabin depressurization. (One more thing - for reference, normal systolic blood pressure is about 2 PSI, just to get a vague idea of what internal body tissues can handle without ill-effect).

I doubt that would be an issue, given that Gemini was supposed to land on a runway at Edwards with the parafoil, so it's just a question of if there's enough energy to get across the Atlantic.

Yeah, and the X-38 was supposed to use a larger parafoil to land at pretty much any major runway on the planet in an emergency, and it had a gross landing weight right near that of an empty S-II...

[Space X - Merlin engine]

Okay, so I found out that radial couplers have a fuelCrossFeed parameter... but it feeds the wrong way - outwards only.

[Russian freight launch to ISS fails to orbit]

Whoa, wait, what? I could see commercial, but military?

I said similar to, not identical. Of course the military has their own certification standards - but their new rules for UAV regulation came around at the same time due to pressure from the FAA.

After all, government operations are not required to comply with the FARs. (I challenge you to find a registration number or airworthiness certificate on airplanes and helicopters operated by Customs, for example.)

Like this?

Not ALL government is immune to FAA jurisdiction. Police don't get to follow military rules (though sometimes they act like it >).

Probably; this is the version I got off the FAA's website, and I don't have a source for the prior version. Since the FAA's link to the FARs is all about ensuring compliance, I expect that they keep that one *very* up-to-date.

Here's the one I posted before, only the entire table of contents instead of just the one subsection:

http://www.access.gpo.gov/nara/cfr/waisidx_04/14cfr101_04.html

I'd forgotten just how much we launched on expendables even when we were *supposed* to use Shuttle for everything, but after posting that, I looked out of curiosity, and... wow. Yeah, we never really did threaten the production side. Fortunately, as it turned out...

Well, yeah. You gotta understand, even before the Challenger disaster and all the safety changes, there were still a lot of things they COULDN'T do or weren't willing to with the Shuttle. They didn't want to use it for polar orbits until Vandenberg's SLC-6 was ready, as Florida had other countries to the North and South (wheras a Southerly Vandenberg launch threatens only the Pacific Ocean). That obviously was never finished, and thus expendable launches out of Vandenberg maintained a dominant hold over polar orbit launch services. And while the Shuttle COULD potentially ferry several satellites up in a single mission (and regularly did), these satellites were often constrained to similar-inclination orbits, and thus lighter sats in odd orbits warranted their own launches instead.

Right, I just meant that you should probably make the determination on a per-program basis. Some programs, like ones where you're flying dozens of missions to low orbit, would probably cost less with a reusable system; others, particularly ones where there's only going to be maybe a dozen total missions, it might cost less to simply make it an expendable system, saving time and money on engineering when the higher per-launch equipment costs wouldn't add up to more than that savings.

Well, even then... if you can use the hardware for multiple different programs, its better to build a more advanced, more adaptable rocket with a lower cost per launch than to fool around with a short-term solution.

Now, of course, with Apollo, they HAD to use a short-term solution in order to meet Kennedy's deadline, but I feel like the rockets we'd be launching now would be a lot larger and more economical if they had been somewhat more deliberate and thoughtful about it.

It depends on the application, of course. Transfer stages, for example, would probably be fairly appealing to reuse if possible--just tank them up again and replace the ignition system.

That 'tank them up again' bit isn't nearly as easy as you'd think. If you look at many existing EOR proposals, it often requires half a dozen launches to fill the stage on-orbit. If you can get it down to one launch, then you're pretty much already there in terms of just launching a whole new stage instead.

And besides, the difficulty of getting a transfer stage BACK to where you can use it again after its first use kinda defeats the purpose, too. HOW many S-IVBs and Centaurs are there floating out in heliocentric orbit?

(I'm assuming cryogenic or semi-cryogenic fuel, because hypergolics are not really well suited to reusability.)

Why not?

If it's an ion drive system, then it's even more attractive, since the propellant mass required would be low and the cost of the engine would be (relatively) high.

OOOH. Yeah, yeah. Good one.

Likewise, I suspect that a lot of the other components could be built more heavily and redundantly if they were only going to be put into orbit once, but used repeatedly. (Witness how much heavier and tougher airliners are compared to spacecraft.)

Sounds like a performance toll to me. But yeah, I suppose 90% of what you'd get in terms of reliability would come in the first 20% performance loss.

Designing them for regular operations with minimal service might be simpler than expected, if you've decided that mass and cost is less of an issue than in the service-on-Earth system.

Oh yes, in terms of technical and logistical considerations, it is much more appealing, but there is also the 'what if' factor. That's why I think this hardware should be cycled out and retired after not more than maybe a dozen missions if it isn't being serviced and inspected. (However, unmanned stuff can just be used until it breaks.)

(Lunar landers could be serviced relatively easily, too, without the need to be able to fly through the atmosphere; service them on the lunar surface instead of in orbit. Getting parts there would be expensive and annoying, but the work would be *much* easier.)

Yeah, I thought about that... but I think that microgravity is actually a minor impairment to working in space. It certainly takes getting used to, but it isn't what causes astronauts to become exhausted during EVA. No, it's the vacuum that causes the biggest trouble. Pressure suits of any sort are very clumsy and unwieldy, and require considerable energy to bend and contort. Within a zero-G shirtsleeve environment, astronauts do not seem to have much trouble moving about and working, but outside everything must be very careful and deliberate and you often see them trying to move their entire bodies rather than having to bend an arm to reach something.

Thus, if you wished to service landers extensively on the Moon, I believe you'd need a large, hazmat-safe (so perhaps not entirely shirtsleeve) airlock at your Moon base to work within.

Right. I was thinking in terms of the Pan Am spacecraft seen in '2001' that ran flights between the space station and the Moon, which was depicted as a single-stage fully-reusable (and rather large) transfer stage and lander in one. However, all the spacecraft in the book and movie were technically plausible, but only because they were all based on the assumption of the widespread use of large nuclear-thermal rockets; with that, getting the delta-vee to land and launch from the Moon in a single stage is a much more viable option. (While never seen in the movie, the book explained that the famous Pan Am Clipper spaceplane was a 2STO design, with a manned mothership taking it from the runway to about 50,000 feet before its nuclear rocket kicked in and took it to orbit.)

Yeah. 2001 is one of the few movies I've seen (along with The Abyss and Deep Impact) where inaccuracies are few and far-between.

Realistically, though, the only way to have a reusable lunar lander would be to build a lunar space elevator from the surface to L1. (Which is a very interesting idea, actually...)

Nah, I think a reusable lander would be FAR less of a technical challenge than a space elevator. After all, 3.2 km/s of delta-V is easily doable... but doing it with lander legs and a throttleable and reliable propulsion system - and at a reasonable scale - is considerably more difficult. I've always felt that space elevators were absurd and unfeasible at least for the foreseeable future, but I do wish they'd play around more with long space tethers so we can at LEAST get a better idea of HOW unfeasible it is. And while we're at it, can we run a reality-check on the concept of draining the Van Allen belts?

Logically, I'd go with some sort of ship-based return system, be it from a land-based recovery or a water recovery. (I'd rather land it on a runway simply because that way, the J-2s aren't going to be damaged by salt water, and thus could be refurbished akin to the SSMEs--that's probably why MSFC wanted a winged S-IC instead of parachutes, now that I think of it.)

Seems like an awful lot of trouble to go through just to keep your engines dry. Would it be at all possible to stretch S-II's trajectory to a parafoil-arrested transatlantic landing instead? Or would reentry simply not be precise enough without wings?

Or, if you're REALLY batshit insane, you could figure out a way to use the J-2s to power it all the way back across the ocean on LH2... think Jeb would like that idea? ;P

If only Morocco had the infrastructure for launching an LH2-fuelled rocket...

[Do It Like Jebediah: Orbit and land safely using only boosters]

My kinda challenge. 8)

[Space X - Merlin engine]

1) Nope.

2) Very hard. Might be impossible. If you could fool the game into thinking the booster tanks were stacked 'above' the core tank through a little attach node black magic, then maybe it'd work. Maybe.

[KSP Orbital Calculator [V0.10.1] - Now with selectable Celestrial Bodies]

I haven't hit orbit in .10x yet, been trying with other things, but can someone check on this?

Sorry Foamy, but even I'm not good enough to nail down my orbit to within 60 meters.

[What part modelling software are you using?]

Not exactly, Zbrush and other sculpting software can produce some very nice mechanical models using hard surface techniques, take a look at this missile for example:

It looks like a table leg. Or a pepper grinder.

But until normal maps are supported such software is way too polycount inefficient.

How will supporting normal maps help reduce the ridiculous amount of polygons and nodes that sculpting software spits out?

[Russian freight launch to ISS fails to orbit]

...wow, I never knew that. I figured that it'd fall under either Part 91 (most likely 91.319, http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=626b29974f73e42ada983047ce0c6cf6&rgn=div8&view=text&node=14:2.0.1.3.10.4.7.10&idno=14) or, if you were launching someone else's payload, Part 121 (http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=626b29974f73e42ada983047ce0c6cf6&tpl=/ecfrbrowse/Title14/14cfr121_main_02.tpl).

Heh, no. Until somewhat recently, unmanned aircraft of any type required no certification of any sort (though they obviously were still subject to regulation, of course). Since 2005 they've begun to require that some larger commercial and military UAVs go through certification similar to Part 121 aircraft.

I do wonder if they might have dinged you for launching a privately-owned Atlas from a privately-owned launch site, though, under the use of the word 'Amateur' in the regulation, since that isn't an amateur operation!

That is a big issue with the newer UAV regulations. Many commercial operators have been abusing the 'amateur' UAV category (meant to protect hobbyists with model airplanes) since the rules changed.

But anyways, if you'll look, part 101 said nothing about 'amateur' rockets until the 2007 revision - merely 'unmanned' rockets.

Oh, and I thought that they might have applied Part 33 (engine certification requirements, http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=1be78a2ac74408fb04dcbd1b5d837c3e&tpl=/ecfrbrowse/Title14/14cfr33_main_02.tpl) to block you, too.

HAH

Most of my hours have been logged behind a non-certified 'O-360-A1A' that was rebuilt from an O-320 case.

Anything that's not type-certified (i.e. experimental aircraft) are completely exempt.

*reads more carefully* Whoops, OK, I found a 'gotcha' in Part 101 there.

§ 101.23 General operating limitations.

(a) You must operate an amateur rocket in such a manner that it:

(1) Is launched on a suborbital trajectory;

(2) When launched, must not cross into the territory of a foreign country unless an agreement is in place between the United States and the country of concern;

To wit:I'd say both 1 and 2 would be violated by launching your own satellites before Parts 400 through 460 went into effect.

It appears this is also part of the 2007 revision.

And in any case, it applies to AMATEUR rockets, which - as you so conveniently stated - is NOT the case with the scenario we're discussing. And we BOTH know that there are ways for commercial operators to legally perform space launches NOW.

That'd work for the solid-fuel industry, as would the US Navy. Liquid-fuel expendables, not so much, given that the entire DoD was supposed to shift all orbital launches over to the shuttle. (They ended up not doing so, by keeping some expendables in reserve for 'time-critical launches' and such, in case STS couldn't meet the claimed 26-flight-per-year launch rate--which DoD never really believed it would--but they were SUPPOSED to do so, and it saw all expendable space launch vehicle development in the US ended from about 1974 to 1986.)

The USAF, NRO, and even NASA maintained a steady stream of payloads that needed launching throughout the period. Development may have slowed due to fear of competition with the Shuttle, but business was just fine.

Right. For relatively short-term programs intended to expand technological limits and perform initial surveys, single-use spacecraft probably make more sense. (The main Apollo program was essentially a short-term one, in that it was intended to have less than a month of total lunar surface time and last maybe five years from first to last flight. Apollo Applications would have been a long-term program, where it would have made sense to develop a reusable or semi-reusable version of the Apollo spacecraft, and semi-reusable boosters.) Thus, I figure that whatever spacecraft we eventually use for the initial 'flags and footprints' Mars landing mission will *not* be the spacecraft used to actually construct a permanent base--not even close. Even a permanent lunar base would probably require a fully reusable lander and transit vehicle, most likely both assembled in LEO and never designed to return to Earth. (They *might* be combined, as seen in '2001,' but the engineer in me screeches at the thought of hauling all the crap needed only in the cislunar transits down to the surface, then trying to get it back into lunar orbit...)

I dunno. I feel like if you can commit to making the investment in a more economical option such as a reusable system or an expendable with streamlined, single-manufacturer production, then you should do it sooner rather than later. Otherwise you may scare the politicians away when they see those big per-launch numbers on the budget.

And from a technical standpoint, it's often easy to tell when not to bother reusing stuff. Things should be reused wherever it is convenient, and discarded when it isn't. The arrangement they went with for the Shuttle made sense - boosters were nice and easy to recover during ascent, and recovering the orbiter's mass from LEO was relatively cheap, since minimal propellant was needed to nudge it into the atmosphere - and thus the weight penalty for bringing back the Orbiter, with all its expensive systems was merely that of providing thermal protection for reentry. A reusable reentry capsule makes perfect sense, although it doesn't recover nearly as much as you could get by recovering the orbital/service module with it... and at that point you're already better off just designing a monolithic spacecraft from the ground up (like the Russians tried to do with Kliper). All these recovered components can theoretically be serviced and reused (or cannibalized for parts if they're unserviceable) for a fraction of the per-launch cost of expendable analogues.

Now, the idea of reusing components (such as the lander or transfer stage you mentioned) without recovering them between missions is a very different ballgame. I've never been a big fan of the EOR concept, mostly because its generally only considered as a crutch for when you lack a large-enough booster to perform a mission with a single launch. However if the components you're rendezvousing WITH are left over from previous missions, then it actually becomes quite appealing from a technical standpoint. Of course, there is a downside; servicing components without recovering them is next to impossible. This means parts would probably have to endure several missions without service or inspection. Redundancy would be a must for reused survival-critical parts such as lunar-descent/ascent and earth-return engines, and short life spans (perhaps five or six missions) would be probable.

And a reusable lander is a pretty tall order; it takes 1.6 km/s not only to get off the Moon, but to LAND as well. Remember, the Apollo LM was actually two distinct stages, with the heavy descent stage being left on the surface. It would be nice to have a reusable lander seeing as it's an important and frequently-used part of any moon base habitation and supply scheme, but a cursory examination of the concept suggests it isn't really very feasible.

Probably not much fuel. The way I'd do that would be to have the S-II glide most of the way to a recovery at a site on the east side of the Atlantic, perhaps Moron AB in Spain or... I'm blanking on the name, but the shuttle's TAL recovery site in Morocco.

Yes, but you're not the crackpot who thought up the concept.

A water recovery seems so much more rational to me. For hauling a stage all the way across the ocean, I think I'd want a semi-submersible barge to lift it out of the water, though.

And do you think the S-II's LH2 tanks could hold and feed kerosene properly without any issues? It seems odd, but I'm sorta inclined to say yes...

[Russian freight launch to ISS fails to orbit]

Not to my knowledge. Now, it might be that the way it worked, you could buy the booster, but wouldn't be allowed to use NASA's facilities to launch it... and since the FAA wasn't yet in the business of certifying spacecraft, you couldn't legally fly them from within the US with*out* the government being involved.

Who said something needs to be certified in order to be legal? As long as it was unmanned, all the FAA cared was that it didn't pose a hazard to aviation or property.

Here, these are the rules that have been around since the CAA became the FAA in the '60s: http://edocket.access.gpo.gov/cfr_2004/janqtr/pdf/14cfr101.23.pdf

There weren't any FAA rules beyond that. If it was unmanned and you followed those, it was fair game as long as the FAA was concerned. Of course, for a space launch, you'd have to make the arrangements for your own special restricted area to get through the controlled class-A airspace between 18 and 60 thousand feet. That would be the only way the FAA could stop you without writing new laws - by denying you clearance through the blanket of Alpha over the entire country.

Add in the policy that went into place in the early 70s, where the Shuttle became the sole US government launch vehicle, and it's a wonder that the expendable booster industry survived the early 80s.

Four words: United States Air Force.

Yeah, as long as it's a nice small bird meant for hauling people instead of heavy/bulky items, it's a very viable long-term option, though I think we'll probably end up sticking with capsule designs for exploration missions, due to their probably being the most weight-efficient option, unless we use a true EOR mode where the crew cabin is not used to carry the crew to and from LEO.

Well any reusable system only makes sense as a long-term option, given the greater development and production costs.

I know that the MSFC proposal for the Winged Saturn V also studied a flyback S-II, but found that it would result in a 70% reduction in payload to LEO. If you didn't need the sheer lift capacity of the S-II, INT-20 would have been the way to go for probably 90% of LEO missions that would use a Saturn deriative.

I wonder how much of that payload penalty was structural- and thermal-protection weight and how much was just fuel for the lengthy return trip.

Honestly, I'm not sure how well it would have worked; the Shuttle was never intended to be left sitting around powered-down for an extended period, so I'm not sure how well it would have been able to power back up quickly after months powered down on orbit...

Slap EDO back on it and you're good for a few weeks...

[Russian freight launch to ISS fails to orbit]

Actually, that's not quite true. Parts of the National Aeronautics and Space Act of 1958, which founded NASA, 'made extensive modifications to the patent law and provided that both employee inventions as well as private contractor innovations brought about through space travel would be subject to government ownership. By making the government the exclusive provider of space transport, the act effectively discouraged the private development of space travel. This situation endured until the law was modified by the Commercial Space Launch Act of 1984, enacted to allow civilian use of NASA systems in launching space vehicles.' (Quoted from Wikipedia.) So until 1984, there wasn't a legal option to buy your own boosters and launch them commercially in the US--if you didn't want to let the government have control of the booster, you had to go with an Ariane.

Wow, I didn't know that. You sure the 'government' ownership of the patents wasn't actually just a 'public' ownership of the patents, in order to prevent a patent-enabled monopolies such as those often encountered within the pharmaceutical industry?

Ed White didn't have to depressurize his suit to 1.5 psi to get back into Gemini 4, like Leonov did on Voshkod 2.

No, but White was a pretty strong dude. Cernan nearly passed out trying to bend his way into Gemini. And of course, with Cernan unconscious, there would've been no way to cram him through the hatch at all - essentially forcing the crew to abandon him.

Oh, I certainly agree there. A reusable shuttlebus with about the same freight capacity as an Apollo CSM would make excellent sense for crew ferry missions to a space station; I'm a big fan of something akin to the old ESA 'Hermes' program for that.

Yeah, Hermes was a sweet concept, and a pretty sexy spaceplane if you ask me (beaten only by the X-38 CRV, IMO). It's one of the few addons I downloaded for Orbiter, mostly because it looked so friggin' cool.

Of course, I'm partial to the HL-20 based largely on its greater capabilities and longer heritage, though the fact that the Shuttle already existed by that time pretty much made it redundant. However, the fact that its legacy continues in SpaceDev's commercial launch proposal is intriguing.

MSFC claimed that the 1.5STO S-ID could directly inject 80,000 pounds (an Apollo CSM and ten tons of freight, for example) into a 118-mile circular orbit. Not really high enough to be truly stable, but enough that a fairly small upper-stage could move you into a higher orbit.

Well, S-IC (and presumably D as well) was pretty friggin' humongous, which I suppose makes up for its comparatively low mass fraction...

But with Atlas, 1.5STO was the optimal solution, since (thanks to Bossart's balloons) the added weight of spitting the fuel tank into two stages was actually heavier and slower than carrying all that tankage to orbital velocities.

That was the way I'd have done it, particularly since the plan was to replace the F-1s after every flight, presumably with new-build ones instead of refurbs. Much lighter, much easier to engineer, and no need to have some poor bastard riding along next to one of the F-1s...

Yeah. The only problem with using that is that S-II can't be saved as well. The INT-20 would probably be better-optimized for maximizing recovered hardware, I think, since S-IC separation would be closer to that threshold where you'd need strengthening and thermal protection for recovery.

Sporadic beats the hell out of a six-year standdown, in my opinion. And yeah, my thinking of 'minimal cost' was just using up the already-procured hardware. I suspect that part of the reason Nixon didn't allow that was so that he wouldn't have to worry about funding manned flights after getting re-elected; even if Shuttle had first flown on time, it would have come on Carter's watch. (The only reason I don't have a similar level of frustration over Shuttle's retirement is that Falcon 9/Dragon should be operational by the end of 2012, so it's about an 18-month standdown, and we *did* use up pretty much all the stockpiled flight hardware by adding STS-135 to the roster.)

Yeah. My only wish with the Shuttle retirement is I wish they'd just left one on the ISS to serve as a substitute for the X-38 (allowing a 7-man permanent crew) and also provide additional living volume and an extra Canadarm. They'd never even think to try it with their a post-Challenger 'RISK IS INTOLERABLE' attitude, but it'd be awesome if they had... 8)

[[challenge] land a spaceplane at KSC after one orbit]

my thinking was that with a spare tank of fuel and moveable fins you could compensate for the inaccurate method of landing at KSP. if you aimed a litle short with a transfer orbit you could fly the rest of the way back.

i cant test this yet as im still having problems getting a spaceplane into orbit any suggestions?

Yeah. Use more boosters.

No, but seriously - use lots of winglets down low, and as few winglets as you can get away with up high. My only (semi) successful orbital spaceplane has only two AV-T1s on the final stage, and six AV-R8s on the bottom of the core stage - and it STILL becomes unstable as fuel burns off unless you get out of the atmosphere first.

Also, my 'automatic orbiter' used three winglets on the base of the upper stage simply for orientation (rather than maneuvering) purposes. Again, I had to use several winglets (I think 8) on the lower stage to make it stable, PLUS some nose-ballast consisting of a single useless liquid-fuel engine mounted atop the command pod. It also used two SASs on the lower stage - not as a crutch to make up for instability, but only as an autopilot so I didn't have to touch the controls at all. (And just so you know, it worked - the only control I touched during the entire ascent was the spacebar.)

[[challenge] land a spaceplane at KSC after one orbit]

I've already gotten winglet-based 'spaceplanes' into space and then crashed into the launch tower with them, even with earlier versions.

I've attempted several times to repeat this after performing one orbit, but given the uncontrollable ballistic nature of Kerbin orbital reentries, I've yet to reenter close enough to glide back to the space center (though I'm nearly always within sight of it). With further attempts, I'll probably get it eventually - I just find it exhausting having to sit through a 30-minute orbit for every attempt.

[Russian freight launch to ISS fails to orbit]

Assisted, of course, by the fact that there were exactly two markets for boosters at the time, DoD and NASA. (Remember, NASA had a legal monopoly on American civilian space launches--including commercial comsats--until after Challenger.)

Only one problem with that: NASA is a non-profit government agency, not a company. Monopolies don't exactly apply. There was nothing keeping the private sector from trying their hand at commercial launch services; save that there really wasn't a significant market for it until the early '80s. Pretty much everything prior to that was heavily subsidized.

Boeing or Chrysler *might* have been willing to take on developing a Saturn-class booster on their own

No, no. They didn't, because they couldn't have. There was a REASON Von Braun turned to other manufacturers to help out - because Chrysler couldn't do it by themselves. The whole rocket was DESIGNED to minimize development costs on each manufacturer - using existing Redstone/Jupiter tooling at Chrysler and initially using Titan tooling at Martin and the then-in-development Centaur from Convair - and with little regard to high-volume production. Plans eventually changed, and development costs went up somewhat, but so did the capabilities of the rocket.

--note how Chrysler spent billions of dollars over thirty years trying to make the gas turbine-powered car work, and how betting more than the company's worth (B-17, B-29, 707, 747, 777) is almost a rite of passage at Boeing--if they'd been able to market it to a wide array of customers, but with only the two government agencies as potential customers, and the resultant requirement to go through design competitions to sell the boosters, there was no way they could guarantee recouping the investment.

Right. Saturn was perfect for what it was because it ONLY required a handful of launches to recover its development costs. It would have a hard time competing in a high-volume market.

I'd always heard that in the Russian aviation industry, secrecy ran rampant enough that often, MiG wouldn't know what Sukhoi was doing, for example. Not necessarily as a matter of official security protocol, but rather just because people didn't talk, lest they accidentally let something slip around a KGB guy who'd inform on them. Might be wrong, but I somehow suspect there was a lot of duplicated effort due to secrecy. (Witness how NASA duplicated much of the design effort for an upper stage for Atlas and Titan boosters until the Air Force finally declassified the Vega program, just before renaming it Agena--which had exactly the same performance as NASA was going for, and would be ready two years sooner. If that happened in the 'open' world of the US, I'm sure similar SNAFUs happened in the more secretive Soviet system.)

I find that EXTREMELY hard to believe. I mean, have you LOOKED at some of the contemporary aircraft designs from the various Russian bureaus? It's almost like Sukhoi looked at everything MiG did and said, 'That's cool. Let's build the same thing only twice as big and expensive.' Convergent evolution is one thing, but COME ON, man.

Don't forget an inflatable airlock where you need to partially depressurize the EVA suit to reach the repressurization controls!

HOW is that any worse than Gemini?

That's the most likely scenario for the earth-orbit Apollo Applications missions, complete the Titan III development and use those to fly Apollo CSMs in low orbit to 'dry workshop' space stations launched on INT-21. NASA was leaning towards Saturns, of course, because von Braun was still around and trying to urge their use because they avoided putting people boosters that used solid rockets, which he did not trust at ALL. (Can't blame him... ever since Challenger, I held my breath all the way from SRB ignition to SRB sep, every shuttle launch.)

Yeah, Von Braun was a fantastic leader, but I do feel like his pride only served to hurt the space program.

I also kinda feel like the concerns about SRBs are overblown - a proper launch-abort system shouldn't have any more trouble escaping them than from any other stack. Sorta like how I feel the Hindenburg disaster gave hydrogen WAY more of a public stigma than it deserved (though I don't think I'd try to sell a manned airship that used hydrogen... I'd gladly ride one, though!).

I'm not sure, just due to the need to lug deadweight equal to roughly three times the payload up to orbit, every single time, plus the need to fly it crewed for simple satellite launches where the crew's entire input was 'Point orbiter in correct direction, open sun shade, spin up PAM-D, release clamps.' Did that really require sending up a four-man crew? No, but every time the Shuttle was used as a comsat launcher, that's what they did.

Well let's see... the Orbiter weighs up to about 110 tons at liftoff. Of this, roughly 25 tons is straight payload. This leaves some 85 tons of upmass for the spacecraft itself.

Now, comparing this to, say, two Apollo CSMs (based on the fact that this is the Apollo equivalent for supporting a crew of six throughout a mission), rougly 60 tons of this is necessary mass for basic spacecraft functions - life support, reentry protection, orbital maneuvering, mission equipment and all that jazz. That leaves approximately 25 tons of upmass 'wasted' on making the orbiter reusable. Call me crazy, but I think that just might be a reasonable sacrifice to make in the name of reducing production costs.

Now, you do have a point about using the Shuttle for satellite deployment jobs. A smaller, unmanned, expendable rocket (well, maybe with a reusable lower-stage) would make substantially more sense for such menial tasks. This is, once again, why I prefer to think of the shuttle as an 'orbital shuttlebus' than the 'orbital pickup truck' it has often been referred to as. One way or another, its primary mission was putting lots of people in orbit - the cargo capacity was just a desperate attempt to justify manned spaceflight as being practical somehow.

I certainly agree there. This is why most of the Saturn-derivative schemes attempted to reduce the number of stages to simplify some of these issues, with the ultimate example being the Saturn V-B (described in detail here: http://astronautix.com/lvs/saturnvb.htm) that MSFC proposed in 1968, a 'stage-and-a-half' version of the Saturn V's first stage that could put a payload comparable to Shuttle into the same orbit. You'd end up with a single-manufacturer, horizontally-assembled rocket somewhat akin to if someone took Atlas and injected it with a mixture of horse steroids and Miracle-Gro. ;P If you needed a higher orbit for a somewhat smaller payload, an upper stage engine could be mounted on top of it, of course, and the development time and cost would have been *very* attractive by comparison to Shuttle!

Wow, that could work...

Well, maybe not from a TECHNICAL standpoint, but from a PRODUCTION standpoint, it makes a lot of sense. I have a hard time believing anything as heavy and kludgy as Saturn could pull off 1.5STO efficiently, though... :

And on the topic of modular upper-stages, am I the only one who's extremely disappointed that Centaur wasn't ever adopted as S-V?

The versions I've seen were relatively simple modifications of the S-IC, removing the fins (which were of almost no value) and part of the thrust structure fairing for weight reduction to add 45m wings with vertical stabilizers at the tips, jet engines, and a one-man cockpit just forward of the left wing(!), with plans to replace the F-1s after each flight; MSFC and Boeing estimated about a 20% payload reduction as a result. (See http://astronautix.com/lvs/winturnv.htm)

JET ENGINES? MANNED COCKPITS?!

Oh man... this WAS a crazy idea.

I've always thought the downrange recovery scheme used by the Shuttle's SRBs was elegantly efficient. Just some parachutes, a retrieval ship, and a crane and you're good to go. Of course, a saltwater landing would've certainly destroyed a cluster of F-1 engines unless they could be kept reasonably dry somehow (nose-first splashdown and some enclosed fairings, perhaps?)

INT-20, along with INT-18 and INT-19, was proposed as the replacement for the IB; INT-21 was always seen as a heavy-lifter.

Yeah, my bad, I mixed up the numbers. My statement still stands, though - INT-20 seemed to be a new, intermediate-weight launch system designed to COMPLIMENT the Saturn IB, not replace it. Certainly not the proper system in a time where funding is being scaled back.

What really annoys me about Skylab/Apollo Applications is that we could have, at minimal cost, kept flying almost right up until the Shuttle was ready.

Sporadically, sure. But nowhere near at the frequency of the Apollo or Shuttle eras - not unless you want to hurl that 'minimal cost' detail out the window with all the force you can muster.

After all, in 1972, after the last lunar flight, NASA's inventory included six complete and one partially complete Apollo spacecraft (if you count 102, the Pad 34 checkout vehicle, and 105, used in acoustic tests; 115 was never fully completed after the original Apollo 15 mission was cancelled in 1969), six complete and three partially complete Saturn IBs (S-IVB-212 had been converted to the Skylab orbital workshop while S-IVB-213 and -214 were cancelled in 1968), and two complete and one partially complete Saturn Vs (S-IVB-515 had been converted to the backup Skylab orbital workshop). The Skylab program, as flown, expended one of the Saturn Vs (SA-513, with S-IVB-513 being replaced with the prime Skylab workshop), three of the Saturn IBs (SA-206, -207, -208), and three of the Apollo spacecraft (116, 117, 118).

Yeah, I do agree it was pretty silly not to let NASA use up the rest of the hardware before completely shutting down the program.

[Space Time]

OK, I *think* (although now, I'm what the geologists joked NASA stood for in the Apollo days--Never Absolutely Sure of Anything) that the delta-vee required to escape is *lower* in a parabolic/hyperbolic orbit rather than a radial departure, with a lower escape speed, too. But now my brain is starting to hurt because, as Weird Al told us, everything I know is wrong! 8)

The tangental parabolic escape does require less delta-V due to the Oberth effect, but it requires a higher peak speed.

Here, somebody illustrated the effect in KSP:

[SRB vs. Liquid]

(X-15-3 also gained drop tanks for extreme high-altitude work.)

They weren't droptanks.

As a side note, there was a plan to mount the X-15 on top of a Titan II or III and fly it into orbit

Actually, it was a Navajo, and I hardly think they were serious about it at all. By the time the Air Force started looking at man-rated Titans, they had already moved onto what would become the X-20 Dyna-Soar.

Not long after, they realized the Titan didn't have enough payload to lift the X-20 without modification. This led the Air Force and to put out a request for proposal for a larger booster, which is what ABMA's initial Saturn concepts were intended to fulfill, while Martin frantically tried to improve Titan so it could meet the requirements.

the Air Force pretty much considered that about as seriously as NASA did the proposal of a one-way lunar mission. (A real proposal--send a one-man lander to the moon RIGHT NOW, then just keep sending supply ships to keep the astronaut alive 'until we figure out a way to get him back.' There were some *really* psychotic ideas spitballed back in the late 50s and early 60s...)

Well... that's... fun...