DoctorEvo

Why? The LES didn't pull the SM off the stack, just the CM. Were the astronauts supposed to put on big red noses and floppy shoes before they climbed into that thing? 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. 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. Was the SPS gimballed? I don't think it was. ... Yeah, I think that pretty much sums it up. Yeah. And it was a TMA, meaning the dude had a suit on too. I bet they stuck him in the middle, though. 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. 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. 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. 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. 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. 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. 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.) QuikClot is good stuff. And not even veterans get to say they have fragments of a METEOR inside them... 8) 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. 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?]

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?

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

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. 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. 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. 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?) 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 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. 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... 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. 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. 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... 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? 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). 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. 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? 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:

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. 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). 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...) 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. 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. 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.) 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. Just south of the Azores, I believe. 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. 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.

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

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

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).

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).

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?

Yeah, I've seen those. Didn't used to see 'em, but they've become annoyingly common. 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. Hands-on space tourism. Pay more; but get to fly it yourself. Orion could do anything that Apollo or Soyuz could do... (albeit on a slightly larger scale...) 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. 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. 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). 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...

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

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. Like this? Not ALL government is immune to FAA jurisdiction. Police don't get to follow military rules (though sometimes they act like it >). 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 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. 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. 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? Why not? OOOH. Yeah, yeah. Good one. 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. 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.) 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. 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. 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? 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? If only Morocco had the infrastructure for launching an LH2-fuelled rocket...

My kinda challenge. 8)

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.

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

It looks like a table leg. Or a pepper grinder. How will supporting normal maps help reduce the ridiculous amount of polygons and nodes that sculpting software spits out?

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. 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. 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. 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. 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. 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. 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...

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. Four words: United States Air Force. Well any reusable system only makes sense as a long-term option, given the greater development and production costs. 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. Slap EDO back on it and you're good for a few weeks...

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? 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. 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. 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. 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. 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)

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.)

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.

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. 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. 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 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. HOW is that any worse than Gemini? 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!). 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. 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? 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?) 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. 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. 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.

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:

They weren't droptanks. 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. Well... that's... fun...