wumpus

But they went through falcon9 1.0 (could launch into orbit, no reuse), falcon 1.1 (60% more mass), full thrust, block 5. While 1.1 managed to land, you can be pretty sure that all (Falcon) R&D after 1.0 made orbit was for recovery. That's a huge amount of Spacex's expenses (although, as you noted they never had to throw away a ~$100,000,000 rocket just to test the lander). I suspect that this has a lot to do with the difference in hours worked by Spacex people vs. NASA people. This might be some of the cheapest R&D (that doesn't involve specifically donated R&D) around.

I'm fairly convinced that the only possible way Spacex could claim to save money on Falcon 9 launches through recovery is by convincing his rocket scientists and engineers to work harder/cheaper for a "cool" goal (there were obviously plenty of savings, and Musk does convince his people to work almost as obsessively as he does). If the original falcon 9 could be used (even vaguely) in "heavy" configuration, it would be enough to support the much heavier masses currently being sent to orbit. Presumably adding COTS solid boosters to the side would be enough for the current "block 5" cargoes. Launching "flight proven" Falcon 9 block 5 will certainly save a ton of money, but will it ever match all the R&D that it took to go from an orbiting Falcon 9 to the final design of block 5? It will make plenty of sense getting the same process to go much faster with the raptor (when the costs are vastly higher), but doing so just for Falcon 9 is a harder sell.

I strongly suspect that the difference between lunar orbital speed and minimum orbital speed either won't be a factor or will be a factor largely because the simulator isn't quite good enough. You should be able to do a series of aerobraking orbits that cut your orbital speed enough such that the re-entry speeds are similar (and probably lower than) the shuttle's. This has been shown to work on Mars (although don't try the Mars Reconnaissance Orbiter's 6 month plan with people on board). The biggest reason for not doing this is uncertainty: the difference in velocity needed for a one-day orbit and a one-week orbit is tiny. Don't expect the simulation to be sufficiently exact. Also, I think the one-day orbit might spend too much time in the Van Allan Belts. You will need to hit exact orbits and that might not be possible to pre-plan. Of course, all of this pales compared to the two elephants in the room: adding the extra wing mass to your payload and compounding the disaster with a direct ascent. Either one makes mass spiral out of control and the penalties multiply together.

I suspect that was in the fine print, because it was the only crewed launch system that NASA was developing and they were canceling everything else. Perhaps with a manned space station they wouldn't be so obsessed with using any [unmanned] exploration mission as an excuse to tie 7 astronauts to the launch system.

It is entirely possible that the rocket can't support the extra force of the acceleration for all rockets firing right before they are empty. I'd expect this with crewed vehicles, but there are always support issues with any rocket. It should be easier to configure the solid booster for more thrust (to a limit, and of course your rocket has force limits as well), and if the Isp is less than burning it up first is better still.

This was true for population values <<7.5 billion (see note about "problems of fifty years ago"). Global warming and overall fish depletion are two obvious current dangers of large population. Consider the issue of distant population centers demanding the deforestation (and other ecological havoc) of low density areas. The flip side is that low population is hardly a panacea. Technology (all knowledge growth really, but things go bad fast without the tech) and specialization really depends on population size (and population density helps in many ways).

I'd expect that you would want to evade a hurricane. Presumably it would be deep enough that a tsunami wouldn't be noticed.

KSP: probably just scales the "g" force of the SOI you are in to the radius(squared) you are from the center of the SOI. Other SOI (typically Kerbin, plus the main planet if you are in a moon's SOI) are almost certainly included a constant over the entire SOI (but they are obviously there, otherwise you would be flung out of the SOI during approach). Principia: Presumably using F=Gm1m2/r**2. Don't expect the "on rails" time acceleration to work (KSP's works because it cheats) "on rails". Don't expect the plotted trajectory to be all that accurate (although it should be good enough unless you loaded Principia to do the things KSP's gravity can't). I haven't played with Principia, and am amazed that KSP's cheat works as well as it does (down to the "slingshot maneuver").

I think Molniya orbits work with countries with significant East-West width. Like Russia, USA, Canada (possibly China, but they manage with a single time zone). Not so much with North Korea, but you could claim a China-watching Molniya was supposed to look at North Korea (and indeed spends plenty of time doing so).

Congress deals with what is in the public mind, not reality. And the public thinks Three Mile Island was a big thing and never heard of the London Smog of 1952. You'll need Bezos to cough up for the nuclear rocket, because getting Congress to pay just won't happen.

While the saying "the customer is always right" takes plenty of abuse, customer infallibility is at its peak when they say "shut up and take my money". Congress absolutely insisted on sending a 100 ton vehicle 5 times. And yes, "congress" appears to be the antonym of "progress". "Nuclear ferry"? Was it there as a sacrificial program (they wanted just one cut, not 3) or did it have a much better chance before Three Mile Island? I'm a bit too young to remember nuclear attitudes before that event.

There's a reason NASA (and DoD) launch satellites into polar orbits from Vandenberg flying due south* (or at least Vangenberg was chosen so you could launch south). Rockets heading north (across the pole) look like ICBMs in flight. Heading south (same orbit, no delta-v difference) makes everybody less twitchy. * modulo the vector thanks to the rotation of the Earth.

The problem with the shuttle wasn't the budget, it was the requirements. The requirements were from politicians, the engineers made a rocket that fit them all (thus the required budget). The engineers weren't given the same job "go into space" for the shuttle (and I'm sure the Soyez had politics, I just don't know that story. Look up Korolev's biography to see how serious Soviet politics were). The more I hear just how outlandish the requirements were for the shuttle the more I am impressed with what they made. It doesn't make a better rocket. A design broken in the spec is still broken. It just wasn't broken by the engineers.

Because if you tell congress you are making four separate launch vehicles, you will be only be making the cheapest (depending on which districts it is made in, natch) in a week. NASA made the shuttle with what Congress would let them build, they didn't have the option to make something effective. Remember there were 4 parts to the "Shuttle" program (the shuttle, a space station and probably a trip to Mars, not sure about the other thing), and all but the Shuttle was cut. We had a ferry to nowhere. Near as I can tell, SLS *is* the "better shuttle" (or at least shuttle 2.0). I can't say I'm a big fan, but there it is. Amy Shira Teitel over at her Vintage Space youtube channel [as of April 28, 2017] has a current video on "followup Apollo rockets". From the looks of it, it would have been "ALS" or "Apollo Launch System" and have most of the benefits and issues of SLS. While it does look like a better program than the shuttle (except for other pesky political issues like being tied to a previous president), don't underestimate the "paper rocket problem". Those "recoverable" F-1 engines would hit the water at >200km/hr and while they can take a quick dunk at shallow depths I'm not counting on them surviving what the Shuttle SRB cases did (which were much more boyant). Remember everything spacex went through with parachutes (and plenty on this board took much convincing that parachutes wouldn't work) and also remember that 1970s computers simply weren't up to a proper sci-fi landing.

For those wondering why ICBMs don't use kerolox and similar fuels, this is why. They need[ed] to be ready to fire in only a few minutes, thus use hypergolics (soviet and early US missiles) and solid fuels (later US fuels). There's no point in attacking a silo: either it already launched or the booster is a dud. Perhaps you are playing that all-time favorite game: "Bounce the rubble: the nuclear third strike game*". Except they already worked out in the 1940s that trying to "win" nuclear war was a fool's game. Building any system capable of "winning" only means your enemy has to launch before then. Cost should be roughly similar to a battleship or carrier (plus a bunch of nukes). And when it was being designed there were still people who knew how to build/weld battleships and all that armor plating, which is probably the main cost of an Orion. Wasn't there a Salyut with some sort of gun on it? Not just the Soviet "space gun" useful for fending off bears in Siberia, but a mounted space-to-space gun? I don't think they fired it and it have no idea if they had a sufficient system to aim it, but I'm pretty sure it was in orbit. * From "File 13: the Tom Wham game of making games". Included in Dragon Magazine near the height of the cold war (Reagan's local maxima, anyway).

A human needs about 2kW/hr of energy (via food) per day. Traditionally, nearly all this energy is solar via plants or indirectly going plants->cattle/fish->people. An arcology could conceivably produce this with nuclear energy (pretty much a requirement for Belters and anyone else beyond Mars). Technological advancements also are dependent on a large population (or more accurately, a large number of people doing things that advance technology). Don't be too surprised when a large population solves the problems it creates. Just don't assume that the problems (especially the ecological ones) it creates are the same as the ones as 50 years ago (or whenever the project started).

And this is likely not worth it for Mars since the moon is 3/4 of the delta-v needed to get to Mars. You might bother with cargo to Mars (orbit/surface) if you have several years to get it there. Nuclear's political problems will be worse than any technical problem. The technical problems are solvable and may well be best for certain problems being faced right now. But nobody is seriously considering them due to the political issues. Also, I'm not suggesting a nuclear thermal rocket (although that certainly is a possibility for Mars, and has certain red-tape advantages for NASA as it is grandfathered in as "flight ready tech"), but an actual nuclear reactor to power the VASIMR. Presumably something related to modern pebble based designs, and yes the cooling would be extreme (it would presumably resemble the solar panels it would replace, but resistant to van allan belts). I think the real killer for both is the hydrogen supply, although it might work for a "land on Mars for a week and use the early return window" that would the slightly less impossible choice for Mars within 8 years. And I really don't think their were "conventional solutions" in going to the Moon from 1960-1969.

The two real "Hail Mary" techs you need are VASIMR and a nuclear power plant for it. VASIMR at least works in the lab, so it has a leg up on any other "better than methylox" Isp solutions. The real killer is that you need more power than solar can realistically provide (if you are limited to solar, ion engines make more sense. Just don't expect to keep [the solar panels] working long enough to get out of the Van Allan belts). So plan on building a space nuclear reactor (it has been done, but I'm assuming there was a good reason nobody at NASA tried again (I think the Soviets made a few). I'm betting on cooling issues). Most of the problems with the reactor (other than being a cooling nightmare) are political, so I get a free pass to ignore those issues in this thread [snicker]. Don't expect NASA to have such an easy ride. If you were willing to take more than eight years, it might be possible to build a solar panel that can deal with the van allen belts. Build one of those and you can use ion thrusters to cache "fuel" (read entire dockable stages) in various orbits of Earth and defeat the rocket equation's tyranny once and for all. This was my old answer, but I have no idea how to deal with the shielding/radiation issue. How close to "a dozen independent programs simultaneously" was Apollo? Didn't they start to design the Saturn about the time Kennedy "chose to go to the Moon"? And had to rush to build Gemini to prove all the tech they needed for Apollo (docking, long flight survival, navigation?) but didn't have the "right" rocket to do it yet. I think the L[E]M was in Apollo 10, but a dummy weight was in Apollo 8. They had to work around a ton of schedules, and didn't have the limited launch windows Mars has.

Considering the thing landed hard on the pad (launch 2), there were many ways for that thing to kill people that an LES couldn't fix (especially coming down on a nearby town). Apparently it landed close enough to the pad that nobody was there (I've always heard the story that the director and anybody who couldn't get out of it was in the blast zone, but that seems to be a myth). When you are playing with millions of pounds of explosives, there are *many* ways for those things to kill lots of people.

Obviously. But it takes a much bigger rocket to launch a slightly larger payload and then land the booster (and I'm sure going from ~1.1 to at least 1.3 TWR helped a lot with gravity losses). That's a lot of R&D to reuse a single rocket (so far. And I'm not sure they will reuse anything else that isn't B5).

Tesla is doing remarkably well (although the stock has been inflated beyond reason*. This can be hazardous to the company in question unless they can buy something like Alcoa** or some other less exciting company with decent income). Solar city seemed to be doing ok, and after being bought by Tesla is presumably equally over-valued. Hyperloop was something Musk didn't sink his own money in, but flung it out for others to run with (and/or lose their shirts). There is less hype about "the Boring company", but few here are certain it isn't a hoax. * The goal of Tesla was to steer the market to build solar cars. Presumably the exit strategy was to be bought by GM. According to Wall Street, they expect Tesla to be more likely to buy GM. ** Alcoa appears to be losing money, but aluminum is sometimes called "frozen electricity" since most of the cost is in the electricity needed to produce it. I wanted to state a "boring company", but Elon beat me to it.

From wiki, so take them with a grain of salt: Falcon9 1.0: 333,400 kg Falcon9 v1.1: 505,846 kg Falcon9 FT: 549,054 kg Falcon9 block 5: unknown (likely not much more than FT) So there was some improvement in mass (and of course a less-than-fully-recoverable falcon heavy could provide heavier launches) even with recovery, but at significant R&D costs. I've heard of plenty of other rockets pitched as re-usable (I'm certain I heard the claim that at least one Ariane was supposed to do the trick) but only the shuttle (and suborbitals: don't forget the X-15 in there with spaceship1 and new Sheperd) had managed it, and still couldn't do so profitably.

Building a "one launcher does it all" isn't about costs, it's about politics. If NASA tried to build the Shuttle and Shuttle-C at the same time, Congress would simply kill the shuttle, as the DoD (and commercial satellite owner/users) absolutely needed a launch platform (they didn't need astronauts). NASA had an entire plan of how to use the shuttle sanely, but the whole thing cost Apollo money and Congress wasn't remotely interested so they pretty much left a single program (for apparences of keeping up with the Soviets) and cut anything else they could. If they split the shuttle in half (or more) there's no way Congress would fund both (even if the end result was cheaper). As mentioned above "what went wrong with N-1" was largely politics. The shuttle may well be an ideal design for the requirements Congress foisted on it, but much of "what went wrong with the shuttle" was the politics of crafting those requirements. Only Bezos can [largely] ignore politics. Even Spacex has the US government as its biggest customer (but at least is much more at arms length than ULA). At the design levels visible to the public, managing funding sources are often as important as the rocket equation in the design of a rocket program.

This can't be stated enough. Don't forget, there have been 31 new falcon9 boosters used/destroyed and one "flight proven" booster launched. Expect it to take quite a while to pay for all the "extra tech" poured into earlier falcon launches. I'd assume that spacex would add a large "R&D benefits for Raptor" bonus to falcon9's side of the ledger to get things to balance. Of course, the falcon9 has some pretty cheap launch costs (especially to customers), so it isn't like they could be spending all that *much* on recovery (not like NASA did). From the sound of it, block 5 is the "reusable falcon 9" and the 30+ earlier ones were essentially prototypes*. No idea if they can recover all the costs to get to block 5. Remember, even 1.0 could likely launch more [unrecoverable] mass than block 5 can with recovery. * my definition of prototype is anything that requires an engineer's (or scientist's) job to get the thing working and out the door. At least one [small volume] circuit board I was involved in was shipping in this state for *years*.

Hold retrograde is easily my favorite. Especially with the "hold what used to be retrograde until you just barely switched the signs" patch tacked on. Of course the latter might be an even smaller thing that makes me happier than most big changes (unlike most games, the big changes rarely make me unhappy).