prophet_01

That seems like a big waste of money. it's likely not build something 100m below the surface considering the budget ;) It might survive the heat at the edge of a blast and might be useful if a war with conventional non-nuclear arms is going on. But even without considering the fallout, that vault would have to be in the midle of nowhere to have enough distance from the centre of a nuclear detonation... There is a good reason why many countries stoped building bunkers. To resist even a small hydrogen bomb that detonates something like 50km away from a vault it would need to be pretty deep underground and requires a suspension between it's walls and the material surrounding it. With just a regular basement like shelter, the walls will colapse due to shockwaves. The US and former USSR actually did build some VERY large facilities into big mountains located in the midle of nowhere. Those bunkers have building like structures on springs and are very, very deep underground. Guess what, that's expensive as hell. They were build in the 70's and 80's when bombs got bigger and bigger with the intent of having at least a chance of surviving a direct hit. 'Direct hit' is relative when it comes to nuclear arms though... If ww3 is coming, go camping in australia, sibiria or alaska :P

Since when is dropping a part that free falls back to earth a seperate stage? Is a fighter jet a staging vehicle because it drops a free falling payload at a target? BO did achieve something great here, no doubt. Any comercial company that gets a launcher to space is already impressive just by doing that. However, it's not rly comparable to what spacex does, not rly because spacex is better (they have yet to get it done), but because the problem is a different one. The falcon9's first stage HAS to operate on vastly stricter margins in order to be somewhat efficient and of any use for an orbital launch with a payload. NS is more like an oversized lander and is build to be reliable, but not to be as efficient as the first stage of launcher that goes to orbit. Again, they did something cool here (and say that they are the first ->comercial<- company to do that kind of thing; they never compared themself to NASA on any source I saw). For the task at hand NS is a pretty good vehicle from what it looks lile. However, BO would be facing a vastly harder challenge if they were trying to build a similar craft, but with falcon9's margins. NS can easily get away with a heavy multi-purpose engine, any orbital launcher would have bigger problems with that.

What's the difference between now and 100 years at that time scale? And now think what humans where capable of 100 years ago. My point is that we currently lack the capabilities to anything more with human space flight than a very expensive sightseeing trip. On the other hand we also were flying bi-planes in 1915. We probably won't progress as rapidly in the field if aerospace as we did back then, but I'm pretty sure that space flight will be a lot cheaper in a couple of decades and definitely in 100 years. And there rly are more important tasks at hand that are worth throwing money at. Even if we were able to set up a space colony by cutting funds on basically everything else, what's the point? Especially if it's likely not nearly as much of a challenge in, say 50 years. Human space flight is cool, interesting and the stuff that inspires people, but it has a price tag that we can't ignore.

Orion is a lot bigger. 8.95 vs 5.9 cubic meters of habitable space (numbers vary slightly on different sources). Also, 6 is the maximum crew. Regular crew is 4 and with a life support of 21 days any long duration mission (most asteroids or eventually mars) would require an additional habitat module. If I'm not mistaken that 'deep space habitat' module which gets mentioned once in a while isn't much more than a conceptual design right now. I'm pretty sure that a full crew of 6 would only be considered for transfer flights, reentry or in combination with a habitat module of some sort anyway. Anything else would seem 'uncomfortably crowded' to me :P With a crew of 4 it actually offers slightly more space per person if I'm not mistaken.

Without another shuttle accident until the end of the program my question would be if there might have been a new shuttle design. Not that I would expect it to be competetive with the comercial programs we have right now and especially not with reusable first stage concepts. But still, I wonder if the focus of R&D would be as concentrated on capsules and expendable launchers as it is now. Maybe ideas like the aerospike, dreamchaser or unmaned reusable uppers stages would have been used in new ways or would generally receive more interest and funding. It often seems to me that they are now labled as ancestors of a program that failed on almost any level. Though I'm not sure wether that would be good or bad.

Hydrogen is very tricky to begin with... The gravity to hold on to it and to actually hold onto enough of it to get that kind of pressure would be massive. We're talking about an object much bigger than earth here. So a dwarf planet isn't exactly what you're looking for. It's very unlikely at best that such a heavy object could form out there. There's not enough mass at that distance as far as I know

Yep. That would definitely violate it. Tbh, I didn't know about conservation of momentum when it comes to rotation. I was only aware of the conservation of linear momentum. ->Yeah I'm a scrub :P Anyway thx for clearing that up and providing the key phrase to help me fill that particular gap of my knowledge :) Will still take me some time to figure out the particular mistake with that thought experiment though.

I always wondered what happens if you do the following: You have 2 reaction wheels next to eachother and let them spin up (x-axis), in opposite directions so they cancel each other out relative to the sattelite. The wheels would build up a maximum momentum while the sattelite remains stable, right? Then you stop one wheel. As a result the sattelite rotates on the x-axis. The second wheel however just continues to spin. Now you 'rotate' the second wheel by 180° (y-axis) so it ends up with the same orientation as the first wheel. You stop the second wheel and rotate the sattelite further on the x-axis. To counter the rotation of the second wheel on the y-axis, you could use a dummy weight which rotates 180° the other way around. Would that work? Or am I missing something? Could that reduce the amount of RCS used on a sattelite?

If you have something that is not stable at all, like a tall top heavy lander, you could also deploy grid fins at the top of your craft (somewhat similar to air brakes on a plane). The additional drag will help to stabilize you. Some reusable booster concepts use that kind of thing in combination with a gimbaling engine or a chute to keep a correct orientation during the landing.

I work for/with a number of individuals that travel a lot as it's their job to maintain and expand relationships with different govermental organisations across the globe. If they were allowed to do so, they would most certainly want to fly with this instead of regular planes. The additional time spend in a tegular plane might not be that significant, but an hour or two less can make all the difference between being able to work the same day or just feeling horrible and wanting to stay in the hotel. They often fly business class, usually even first class for that exact reason and everytime I see how much more that costs our goverment I'm pretty amazedthat they get through with that. But even with first class, planes aren't such a comfortable place and quite a lot of people can neither sleep nor relax during a flight. An hour or two less when going transatlantic would help to get jobs done more effectively and quicker. Spending a night in a hotel to recover after a flight isn't cheap either, especially in places like NY, and if you were able to start working as soon as you leave the plane, cause you don't feel like trash, that's when you actually have a benefit. It's down to the costs either way. But I'm pretty sure there is a market for this kind of thing that's not focused on the super rich, but business instead.

Assuming gravity doesn't pass through such a portal (how should I know anyway? :P) and you do that accelerated continouus jump thing, isn't this just a very fancy version of a gravity assist? Correct me if I'm completely wrong hrre, but to me this just seems like you're just using the gravity the same way a probe does when doing a slingshot, just with portals. So you basically use the planet's energy by slightly moving it. The total energy however, should remain at the same level.

I'm definitely not a fan of regular use of nuclear bombs, regardless of their potential use. It would likely require the construction of new bombs to match the requirements of space flight and to get the best results. There are enough security hazards regarding nuclear weapons out there that have been traded on the black market and somehow ended up in very instable nations. That's already a huge concern as we can't keep an eye on or even know about all of them. So even if I'd trust some of the space agencies with keeping an eye on their nukes and taking care of a fully enclosed and safe production line, there is still the question about what might happen if it's not just NASA that starts using nukes for their missions. If one agency uses this conceot, others might follow for prestige or whatever reasons. And even if they all intend to only use them for peacefull missions in the name of science, I still think this is like opening pandora's box. The production and storage of new nukes in certain countries that repeatedly 'lost' some of their warheads during political instable periodes is the stuff that most goverment's nightmaes are made of. This is not just about baseless paranoya, it's about avoiding unpredictable situations with potentially dangerous results. The problems and concerns with those concepts don't start once the nukes are in orbit. It's a lot easier to keep track of stuff up in orbit compared to what it's like with the nukes in storage down here on earth.

Can't you 'just' redirect a big asteroid to stationary orbit and use that to set up the required counter weight? That should reduce the required payload quite a lot. And for the propulsion of the lift, why not use a ground based laser and downward facing 'solar' panels on the capsule that you send up? If you're constructing the laser emitter a couple of km's away from the ground station of the lift, you're also not firing that laser parallel to the cable which should mostly eliminate the threat of heating up the cable. Also, aren't there concepts for stations that could produce energy with solar panels in orbits and wend it to earth? If I remember correctly that approach uses remote energy transfers as well and I'm pretty sure the major problem here were the costs, not the technology. I have to look it up though. Sure, it's likely a decade or two down the road until graphene can be mass produced at that quantities, but a space elevator definitely seems more reasonable to me than fusion powered lift vehicles.

As far as I know it's a lot easyer* (still not easy at all) to find planets near other stars than it is to find an object this far out. It would have almost no heat signature and it's rly far out which means that it doesn't receive much light to reflect. The concepts used to track exo-planets won't work either. And since most of it's potential effects on the solar system could just as well be caused by other phenomenas, were pretty much down to russel's tea cup. We might never know for sure. But I certainly wouldn't rule it out. Edit: btw, do we rly need 2 threads on this? An older one is also on the front page.

Lifting bodies create a lot of their lift by a typically high angle of attack (watch a video of a landing shuttle, the angle of attack is pretty impressive). To get a better idea of how that works look at capsules that reenter the atmosphere. Apollo for example also created lift by not flying perfectly straight through the airstream, but angled. The heat shield was jsed to create lift. It's typically used to stay longer in the high parts of the atmosphere which helps to reduce reentry temperatures as you reduce your velocity slower and over a longer periode of time. Lifting bodies also create some lift like regular wings do. Compare the shape of a wing (or basically the concept drawings that pop up if you google 'lift') to a MiG-105 for example. (From doing that kind of stuff in KSP with FAR) a lifting body usually tries to roll and fly upside down, because your center of lift is very low and often even below your center of gravity. In order to counter the resulting roll movement you can use big fins and/or the boat like belly to keep it stable. The space shuttle had a huge fin and also slightly upwards angled wings.