todofwar

Nat sure about the physics of this but from a chemistry standpoint I would rather stand in a room full of hydrogen and oxygen dewars than one bottle of anhydrous hydrazine or peroxide. Those things are not happy being themselves and will happily detonate, hence why hydrazine is a useful rocket fuel. Peroxide is so bad you can't even buy higher than 30% cause it starts spontaneously detonating above that. So if the argument is around storage vs LH2/LO2 than I would say the safety concerns would outweigh other benefits.

This is one of those things that still doesn't make sense to me. I understand the velocity of a gas goes up as you decrease its mass, but the rocket equation also depends on mass of fuel exhausted. If you can speed up Argon to match H2 it should give you more umph. I guess if there was a way to do that someone would have done it, but for some reason something in the back of my mind keeps saying that's not right. Another thing, someone was asking about why different gases don't exactly track with mass, and I'm willing to bet it has more to do with deviations from the ideal gas law than it does with decomposition. Water and ammonia are "sticky" while helium or methane will bounce off each other more, and of course methane is bigger in size and stores more energy in vibrations so you need to get it hotter to have the same amount of kinetic energy in its translational modes.

Allot of hate for the shuttle here, but it's probably my favorite design that actually flew, and was the workhorse of the space program long after it was supposed to be retired. It remains the only succesful reusable system, and while it demonstrated many flaws with reusability a part of me still thinks we abandoned the basic concept too early. Who knows, maybe a few more iterations on the shuttle would have made it cheaper to refit in between missions.

The moon is benefitial because it gives you a relatively stable platform, and you can test drive all your colonization equipment with the relative safety of being able to return to Earth in a week if everything fails. As far as a long term home for humanity it's pretty bad, but the proximity to our home planet makes it sustainable in the long run. Plus, a space elevator is actually possible on the moon making it the most attractive source of materials for large scale material exports to burgeoning colonies. An easy way to make money now is to harvest oxygen from the lunar soil (not easy at all, you have to drive the SiO2 -> Si + O2 reaction which is pretty uphill, but the Si byproduct will let you make more solar panels providing a feedback loop for your energy production) and ship it to LEO. Then you just have to get the payload to LEO with enough hydrogen to consume the oxygen you have provided.

I remember a study someone did where they created a rat utopia, but then ramped up the pop density. As the density increased they saw more and more aberrant behavior in the rats, they started eating each other even though they had enough food and things like that. There seems to be something about dense cities that sparks increased crime and other problems, probably because our monkey brains are evolved to handle 150 social relationships at max, anything beyond this and we start seeing people as scenery or obstacles. If we ramp up density like this you're going to have to take into account the psychological stress and have quite a bit of focus on community building.

Well if it will require constant maintenance runs no matter where you put it in orbit than I say crash it or repurpose it, but I'm getting convinced that the best option is to deorbit it carefully so it hits an unpopulated area. XKCD What If? did a nice break down of the environmental effects of things burning up in orbit, granted he did the calcs for a volkswagon not the ISS, but overall probably not the worst thing we've done to the environment.

I'm picturing the Congressional hearings when NASA says "Yeah, we did the analysis and it would be better for the future of space exploration to just give all our money to India and claim credit later."

7 page long thread so no, and I assume with a three option topic like this everything is going to be repeated. I know others have mentioned the idea of putting it into a stable orbit and leaving it there, I was saying it might be the safest option not necessarily the cheapest or most useful option.

On that note, has there been any though given to what the impact of that would be? We've never had anything that big come back from orbit, it could be dangerous for a number of reasons (I guess you would aim for a pacific "landing" and hope nothing goes wrong). I wonder if from a safety stand point it makes more sense to boost it to a more stable orbit and leave it as a museum piece.

I would say its "making more of the same better and cheaper" vs "risking it all on something untested and expensive". Nothing has topped the Saturn V in terms of payload, so we really haven't advanced at all by that metric (yeah yeah Falcon Heavy, not done yet so it doesn't count). In terms of launching we have all the tech we need to reach Mars (or Venus) or anywhere else we like. There are plenty of other challenges associated with such missions, and we should absolutely be investing in how to solve those. But in terms of launch vehicles, I think it's time to shift focus a little.

Fair point, but we have tried and failed for 50 years to improve, when we could have been turning those efforts to manufacturing technology instead. At the end of the day, getting to space is hard because of the ridiculous physics involved just in terms of energy. Engines that can start more than once are difficult, engines that can throttle are difficult, mostly because they go through such extreme stresses during launch. I still think any engine that has burned its way to space is going to need all kinds of refitting to be used again, which is what killed the shuttle in the end. I don't disagree with what people have said here about the issues that will be faced, but as has been pointed out SpaceX has managed to get costs down but doing some of the things I mentioned, now if they cut out their reuse program and poured all that RnD into an assembly line that can pump out a Merlin engine on the cheap, they could probably see similar savings to what they would get with successfully reusing boosters.

NASA has a pretty good app, not sure if you can program notifications.

I have been saying for a while now India is really kicking ass. They're not "good for a third world country" they're just damn awesome at this whole space thing. The Mars mission showed just how good their people are, and at a fraction of the cost. Interested to see what they can do for launch system technology going forward.

Well the moon is most logical stepping stone to the solar system, and will allow us to refine the ISRU technologies that have wide applicability like getting your life support as close to a closed loop as possible. And another problem I just thought of for Titan, you need oxygen. You can harness it from the ice on the surface or from rocks if someone can find a way to run SiO2 -> Si + O2 in a way that doesn't eat all your energy, but you will end up spending so much energy on getting the oxygen that I don't think you will see a return if you burn the fossil fuels for energy. Someone could check the thermodynamics, but assuming you use water as your oxygen source because it's easier, you need to see if the overall equation 2H2O + CH4 -> CO2 + 3H2 buys you any energy. I'm assuming not much at all, probably costs energy. So Titan has even worse energy problems than Mars cause solar is out, so you need some nuclear power. Wind shear is not too bad, depending on where you are. In fact, it provides a ready source of energy. From pictures of Venus I'm thinking any kind of long term settlement will be away from the equator because it looks like there's quite a bit of turbulance at the lower lattitudes, compared to those gentle looking collars closer to the polls. Getting back to Europa, I think the benefits of getting radiation shielding and access to geothermal (remember, solar is out for a settlement so far from the sun) outweighs the complications of being in an underwater base. I could be wrong, someone would have to do a detailed cost/benefit on transporting the geothermal generated energy closer to the surface or just building deep underwater.

If Kerbal, even RO, actually simulated rocket designing it would be a rather boring game, NASA has teams of engineers working on this full time for a reason. But I'm not saying sloppy manufacturing, I'm saying smart manufacturing. Cars have to work for ten years with hundreds of thousands of miles on them and we mass produce those no problem. Rockets have to work for ten minutes. Granted, they have to work flawlessly for those ten minutes, but there has to be a way to lower the cost of manufacturing without sacrificing reliability too much. I'm not arguing this is doable right away, I'm arguing it's no less achievable a goal than going for SSTO spaceplanes or reusable VTVL rockets. I would imagine at first you maybe bring costs down by 5%, not really much. But you use that extra cash to continue to refine and improve, slowly you work down your costs per launch. It's not as sexy to design a better robot arm in a factory than a better VTVL booster, but it might actually be the better investment in the end.

If you make a set of designs you always use, and have most components interchangeable, you can have some benefits of scale. The infrastructure would be very expensive to build yes, but you allow a fifty year repayment plan (probably the real reason it won't happen: no one has that kind of patience in the private sector) and then you have made space incredibly cheap. I'm not denying this plan is full of problems that need to be worked out, and the "five guys and a rocket" goal is probably 100 years away when we have straight up robots out of that Will Smith movie (I need to read that book...) but in the shorter term, I still think it might be feasable to cut down your labor costs thorugh more automation, your testing through more streamlining, and probably several other measures. Let's do a comparison: reusable needs the ability to refit rocket engines for a second launch, which the shuttle tried and failed to make cost effective, and ultimately you only get so many launches out of any one booster no matter what your design. You either invest the money in getting that refurb cost as low as possible and your number of launches per unit as high as possible, or you take that money and throw it at manufacturing infrastructure and tell people they get three or four options for a launch vehicle and they can deal with it. It could very well prove more cost effective depending on what your payback timeframe is on that initial investment.

This is getting at half my point, and definitely proves that we already have perfectly good rockets. But space is still expensive, because even the Soyuz is pretty pricey to build even though its design costs were paid off long ago. That's why I think you can develop a sound design, something that gets you to orbit with a high success rate, and then spend all that money currently going towards new launch systems on manufacturing tech. Automate as much as possible, streamline the testing process, get it to a point where a crew of five guys can build your booster in a month. Is that hard? Very. Is that impossible? Maybe, but reusable is also hard yet people are throwing money at it.

Is all this money spent on reusability really worth it? Honestly, I understand the sentiment that if we had a fully reusable system or SSTO we save money, but not too long ago I had a long argument with a friend over why they don't build a new set of space shuttles. In the course of that I looked into the shuttle system in quite a bit of detail. After realizing just how expensive it is to get any launch system launch ready again, you realize that any reusable system is not going to save you nearly as much money as you think it will. I say why not go the other way, stop trying to reinvent the wheel and settle on three launch designs (light medium and heavy) and let them pay for their design costs over the next fifty years. Make as many parts as possible interchangeable between them, and pump them out of an assembly line. Bring mass production to the space launch world. Invest all that RnD money into getting the manufacturing process as cheap as possible. Stop trying to build perfect ferraris and start going for the reliable subaru. Granted, you would never want to use such a system for manned launches, and you will need to incorporate the cost of failed launches into the price you charge for succesful ones. Still, I think overall it might be possible to beat reusable systems at cost this way.

Of course, hence it was never finished. I actually found this wikipedia page after I made my own, funny enough I accidentally replicated what had already been done. Went from just a couple wings and some light jet engines to, as someone else pointed out, a pair of airbus jets that also happen to have rockets on them. Still, the system I ended up with in Kerbal did work, and saved me tons of money while I built up to SSTO spaceplanes (landing three planes every launch got old fast though). I still think it could work as a fully reusable system IRL, but I happen to like VTHL systems more than VTVL so I might be biased. And the OP did say to point out systems that were or weren't made, this is my favorite of the failed projects I've read about.

If you think Titan is habitable I have bad news for you. We're talking all the problems of our own moon plus you are at liquid methane temperature. Most of your energy use will go towards heating your base up. Granted, you are in a litteral sea of fossil fuels, but for my money Europa is the most promising of the potential moons (excluding our own). You can harness the geothermal from tidal heating, all the water you can drink and split into H2 and O2 for rocket fuel, and if you are on the bottom of the ocean there will probably be substantial shielding from radiation already. Supercritical CO2 is actually a pretty good solvent, used for industrial extractions all the time. I'm not saying as a solvent for life it's any better than methane, as you said we have no idea if either can host life. I just think supercritical CO2 is as promising as methane as a potential sovlent for life to form in, and the higher temps mean chemistry can move a bit faster. But this is all getting off topic.

Always thought this one: https://en.wikipedia.org/wiki/Liquid_fly-back_booster was worth a second look. Basically, slap some wings and engines on your boosters so they fly themselves back when they're done. I actually got this to work using the FMRS mod in Kerbal.

CH4 is probably as different from water as you can possibly get. Water is polar, an acid and a base, and has other properties that make it a unique solvent for chemistry to happen. CH4 is non polar, can't dissolve salts, and at liquid methane temps all chemical reactions will proceed extremely slowly. At least CO2 (I wouldn't say either is "closer to water") is at high temperature so chemistry can happen at a fast rate.

Never said they were being paid to look into it, just that enough of the physics makes sense for it to be looked at academically. Ozone is magentic yes, but so is oxygen, yet you don't see people running particle accelerators concerned about accidentally concentrating oxygen close to their magnets. The electrical field that would be produced by the rapidly moving magnets is what you use to power the components of the structure at higher altitudes actually, so not a problem that they will produce electrical currents. We are not talking about atoms here, by the way, but micro scale particles. And not related but nanotubes have had no real use yet, or graphene, or bucky balls. Interesting forms of carbon, good fodder for grant money, but so far useless. I might be very bitter about this because of how much press they get despite no payoff, but seriously all that is much further away from real applications then people think. I was talking about https://en.wikipedia.org/wiki/Space_fountain. One of the other useful things about it, is that you can slowly raise its height, and once you are above a certain altitude it looks very promising as a high altitude launch platform, to avoid fighting the lower atmosphere. So you start charging enough to slowly raise the height further.

I second the Selene suggestion

I agree with your assessment of the elevator, but I don't think we're talking about the same fountain. A space fountain works by shooting a constant stream of magnetic particles that are then redirected by a bending magnet. The bending magnet is kept aloft by the extreme forces of redirecting the magnetic stream. Because of the physics of it, the actual materials encasing all this don't have to support themselves, they couple to the stream of superfast magnets which is what is actually keeping everything aloft. Now, you have a payload that also couples to this magnetic stream accelerate at 4g straight up, and the fountain is just tall enough such that the payload has enough kinetic energy to reach the geostationary point with nothing more than minor correction burns. Do both ideas sound ridiculous? Of course, but enough serious scientists and engineers are investigating them because of the incredible savings over current space launches. The elevator gets talked about the most (I'm a chemist and I sit in on so many seminars talking about carbon nanotube space elevators, which is ridiculous because carbon nanotubes are nothing but hype) but really, it's pretty much impossible until a major breakthrough in materials science.