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If we want to colonize the moon, we'd have to develop a good way to get there first. That's exactly what NASA wants to do now. In the 60's and 70's we went to the moon. Now we want to go there in a more decent way. Next step: stay there. Next step: Mars. One thing at a time. Otherwise, we might end up making something that just barely gets people to Mars, not to return for another 50 years. It may be better to do things in a more developed, less experimental (with all respect for Apollo hardware, but it couldn't be called the ultimate suitable-for-all no-brainer way to get to the moon) way this time.
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No, NASA often don't spend their budget wisely. But that's not really their fault- it's not a homogeneous institution, they have many 'parts', and all need a share of the overall budget.
Second, going back to the Moon is still as much of a frontier as it ever was. It's not easy! Third, I am a huge fan of private sector involvement in space, but I'm also a business man and investor. From my perspective, it's far to early in the game to invest in Lunar transport. So far, we've had 2 suborbital flights, by one company. That's it. Lastly, you seem to be ok with a Mars mission and Lunar colonisation. Well, this is the way to do it I think. ![]() |
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Private companies have a lot of motivation. They can develop new spacecraft quickly and cheaply. Scaled/Virgin isn't the only endeavor, there are plenty of other companies catching up. They have made the most progress so far, however.
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Look, I don't think you're far wrong. It's just that I think you're being a trifle optimistic with your private sector time-line, that's all. |
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Scaled Composites, while they make some neat aircraft, has no experience in spaceflight. You would be better off with a company like SpaceX, which has actually put hardware of their own into orbit. But yeah, looking at NASA's plans, I get the unsettling feeling we'll end up with another horribly expensive launch system that requires enormous manpower to use and lots of money spread across the usual voting districts and contractors to build. I have some doubts about the ability of a small company like SpaceX to feasibly grow fast enough to handle a moon landing in the timeframe involved, though.
I do wonder sometimes about splitting off manned spaceflight to a separate agency, but then worry about the far less pathological parts of the agency that handle the robotic science missions getting cut down to nothing while funding focuses on the new agency. Contracting entire vehicles and launch systems out to one or two companies might be a better approach. I definitely support going to the moon if we're developing the infrastructure to stay. People arguing for the Mars first option seem to be pushing for another "touch down and then go back home for a half century" mission. The moon missions shouldn't be a dry run for a Mars-and-back mission, they should be a permanent expansion of our capabilities in space. |
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Sure, Scaled is inexperienced, but they have a huge advantage compared to other spaceflight companies in that they're backed by a billionaire and a giant multinational corporation.
Also, while the Orion is "meh", the SpaceShipTwo just speaks awesome. It's clean and efficient, and being designed by Burt Rutan, looks beautiful. You have to agree that this is really, really cool. Shame about those cheesy spacesuits. That's a real deal killer. :P
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I really think that orbital spaceplanes will eventually serve as transit between space stations and Earth. But for actually building those space stations, a launch loop is what we totally need, and the only budget that could afford that would be a government budget, which is one of my main points against a NASA moon mission: if we are planning on spending tens of billions of dollars in space, we should spend it on the thing that gives the most in return. That would either be interstellar travel research, or a launch loop. I cannot stress enough that these are the two things we need most.
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NASA does the best they can with what they've got- they have resources that no private company has access to and they aren't motivated by profit, so they try out things before anyone else does. NASA is where the best and brightest go- even if they could make more money elsewhere. what scientist or aerospace engineer wouldn't want to have NASA on their resume? the only real problem i can see with NASA is that they are totally dependent on the whims of the current leadership- we have three more national election cycles (2 congressional and one presidential) before the new launch system is due to start lobbing people into LEO, and a couple more election cycles before they are scheduled to send people towards the moon. that is a LOT of time for the enthusiasm of the leadership of this country to decide that they'd rather send the money elsewhere.
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![]() About that launch loop: yes, it's important. NASA knows. They've got some experience with launching stuff. Both in the throw-away and reusable variant. Turns out that with the current state of technology, a fully reusable space plane is still a bit of a stretch both on budget and technical possibilities. Throw away is relatively cheap, and for Ares, they do incorporate reusable aspects into the capsule concept. It doesn't have to have wings to be good or cheap. One could say that NASA is showing a pragmatic approach normally only seen in the private sector by not going for a fully reusable space plane. Now I'm not trying just to get at you. But not everything that private companies do is good, cheap, fast. Not everything that governments do is bad or a waste of money. And just as your "launch loop" is so important, a "moon loop" is important for the lunar colonisation you want. Orion is a good step in developing such a "moon loop". As for interstellar: don't hold your breath. Look at how long it takes for Orion to get merely to Pluto, and that is the fastest thing we've ever thrown off our planet.
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It is a mystery to me how adding useless wings and the heat management systems and physical structure needed to plow through atmosphere at hypersonic velocities for an extended amount of time will get you to orbit cheaper. Spaceplanes are "cool", but they aren't even remotely describable as cheap or efficient.
As for launch loops and other advanced launch concepts like mass drivers...the moon is an ideal environment for testing out such things, due to the lack of atmosphere and shallower gravity well. Once they're in place, simple materials like nickel-iron, basalt fiber, and plain old moon-dirt could be cheaply delivered into orbit for the purpose of constructing and shielding space facilities. |
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1. Less reaction mass 2. Less oxidiser 3. Less gravity drag But yes, on the other side of the scale, are a ton of disadvantages, some of which you mention. But I'm still fascinated. ![]() |
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Not true...you just get some of it from the atmosphere. And it's already moving at hypersonic speeds in the direction you're trying to accelerate it in, making it rather difficult to use for the purpose of producing thrust.
But if you're air-breathing, you need LH2 fuel...nothing else burns fast enough. LH2 is more expensive and harder to work with than LOX. And very low density...you need a monstrously huge deeply-cryogenic fuel tank. And you still need the LOX tank to get you up to orbital velocity once you finally leave the atmosphere, just a somewhat smaller one. Are you sure reducing its size is really that helpful? You're climbing up an inclined plane over a much longer period of time. I wouldn't expect gravity drag to be that much lower, and aerodynamic drag at hypersonic velocities is...significant. |
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about the "less reaction mass" and "less gravity drag": with multi-stage, you have a lighter ship once you've dropped the first stage(s), so I'm not sure the advantage would be with the SSTO craft.
The one advantage I see for SSTO is that you need to take care of only one piece. Which can be important when the craft is reusable (so it matters what happens to the pieces) and you go into space really often (otherwise it's no burden to take care of all stages). So, SSTO may be nice once we get towards space flight similar to what air traffic was in the 50's. Air breathing can be very interesting, but it can also be applied as a first stage of a multi-stage craft. The same can be said about wings, although I consider them less interesting during ascent, rather a burden. In short: you can have wings and air-breathing also without SSTO, and I see very very little use of SSTO in the current state of affairs of space flight. I'd be happy to hear good arguments pro SSTO.
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http://www.flightglobal.com/articles...-succeeds.html http://www.space-tourism.ws/spaceshipthree.htm Rutan also briefly mentions going to the moon in the first one. Quote:
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I would say that the launch loop would be more important, because it would be the start of a "moon loop".
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I can only give you an end-user's point of view. If one of you scientists/engineers can build one, I'd fly it!
My reasons are partly psychological, partly cultural. It's gotten to the stage where it just seems a more natural way of doing things. We're habituated to travelling in vehicles that stay in one piece. We don't like bits falling off them! And, whether this is eventually true or not, it seems at first glance that a single-piece vehicle would be easier, and cheaper to maintain. I suspect that the market for an SSTO spacecraft might be larger than what one would expect, given our cultural, social, and transportation history. I would like to have something clarified though. Do the laws of physics completely rule out SSTO? Or is it simply a very poor alternative to current methods? |
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![]() You've got a point about end-user perception. But I think that in that case, it's time to change that perception. Just like the ultra-ugly LEM, spacecraft at this time in history need to do what they do as good as possible. If we get in the future to the stage where there's room for improvisation in appearance, we can go down that road. But just to put things into perspective: aircraft hardly are at a stage where we can go wild on appearance. They are meant to fly safe and efficient in the first place. We can play around with paint schemes a bit and do our best to make the windows larger, but that's it. Look at the 787's shark tail: a minor variant on the real 787, but it would have meant a decrease in efficiency, so they went for the better but more ugle "regular" tail. Now look at spaceflight: the STS ET is not painted white but remains ugly rusty brown to increase efficiency (less useless mass). That is the stage spaceflight is in regarding room for appearance issues...
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Aside from the opportunity to drop a lot of unneeded engine, tank, and structure mass, a launch very naturally divides into two different stages. Early on, you need a lot more thrust than you do in later flight, because you're both lifting more fuel and trying to get out of the atmosphere and to orbital velocity, minimizing time spent "hovering" against gravity. Engines are optimized for operation in atmosphere or for vacuum...you can make an engine that can adapt, but it will never perform as well as a specialized one. The second stage also needn't carry protection against supersonic airflow or present an aerodynamically clean profile if the separation is made high enough and it isn't destined to return intact. A first stage, on the other hand, is relatively easy to protect for reentry, as it does so at far less than orbital velocity. If you carry it all the way into orbit, you need to drag along even more thermal protection in order to have it reenter and be reused. And if you're lifting large amounts of material into orbit that's going to stay there, why drag along an entire vehicle that's capable of reentering? You'll just end up making many launches with smaller payloads than you're technologically capable of lifting, wearing out your reusable launch vehicle, increasing chances for a failure, and spending a lot more money. The SpaceX approach of reusing the first stage and using a disposable second stage just makes sense. |
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![]() Oh, and to answer the OP: No, it is not at all certain. In fact, given the events that transpired since President Bush announced Vision for Space Exploration, I find it not even very likely.
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![]() And, have I understood you correctly? You think we're not going to the moon? You referring to the problems with Ares? |
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"Ignorance more frequently begets confidence than does knowledge" -- Charles Darwin "Your right to hold an opinion is not being contested. Your expectation that it be taken seriously is." -- Jason Thompson Meet the OOONG TOE. |
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![]() Thanks for that cjameshuff. It might be a bad thing that physics doesn't completely rule out the spaceplane, (leaving aside my wants for the moment). As long as there's a glimmer of hope, I think designers will keep coming back to it. An article once explained to me the conceptual reasons behind spaceplanes. Now, it was a long time ago, and I'm not even sure if I understood it then, but here goes: The author used that school textbook problem of a lifeguard having to rescue a swimmer who's not directly in front of him. The trick is to find the path that takes the shortest time, and this path is the one between the direct one (too much water) and the totally indirect one (too much distance). Everyone remember that? Anyway, his point was that 'horizontal' velocity is the primary goal of getting to orbit (obviously). The best way then, would be to acquire all of this velocity by flying horizontally 1 metre off the ground. But gravity and aerodynamic drag rule this out. Current methods get round this by going straight up, and then, once out of the atmosphere and sufficient velocity has been built up, keeling over to the horizontal. His contention was that there's a happy medium- a flatter trajectory. At low velocities, air helps you to accelerate. At higher velocities the air becomes a hindrance. So a spaceplane is supposed to take advantage of this, using the atmosphere up until the point where it's disadvantages begin to outweigh it's advantages. Then, having timed it's trajectory and acceleration, that the spaceplane 'emerges' from the atmosphere and switches to 'pure rocket mode'. Did that make sense? Or maybe I didn't understand the author correctly? ![]() |
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That makes sense. However, traditional curved rocket launches also make sense: you go out of the thick atmosphere as soon as possible (straight up), and once you're outside the area that would give most resistance to it, you start building your horizontal speed while further gaining altitude. Doesn't sound bad eh.
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An issue with scramjet engines is their need for a large velocity before they work. there's a range of possibilities to get around that. Simple one: make scramjet boosters that only kick in once the stack reaches say mach 2. Alternative: use start rockets inside the scramjet and have them work from the beginning. There's more possibilities. The question to ask is whether they have an advantage over just using rockets, both in the sense of added weight or their ability to only start working at a speed that is reached when we've already had quite a bit of atmosphere behind us. But hey, that's what research is for. Apparently it was not a clear "no", as they are seriously investigating the possibility of scramjet (booster) stages for launch vehicles.
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