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So, in summary, retro rockets are not a particularly good idea for slowing down from orbital/transit velocities. Heat shields at least and perhaps parachutes too are the obvious way to go. The retro-burn for the Altair Lunar lander is the major reason why the Lunar surface payload is less than a sixth of the Ares-V LEO payload.
Why would I not make use of aerobraking, heat shields, parachutes, or any other innovations to land such large payload? I'm simply saying that eventually your going to have to employ retrorockets for at least the last few miles to have a controlled landing.
Hey don't look at me, its Louis' idea.
So many 'probablys'.
Astronauts so far have managed to reacclimatise to Earth Gravity. The longest stay was 1 year wasn't it?
The problems with gravity seem to be about embryos and children.
Some have "reacclimated" better than others though.
It wouldn't be a "colony" but more like an outpost. Just about everything except base metals, glasses, and Oxygen would have to be imported, and a solar-powered base that isn't near the poles would require a huge amount of energy storage and related excess production. And managing the day/night cycle indoors, buried under regolith to hide from radiation and small space rocks... what a lovely way to live.
And the Moon lacks many basic elements, it lacks Carbon, Hydrogen, Nitrogen, and probably some of the Halogens too. All things made from these elements would have to be imported from elsewhere! I reject the statement that Hydrogen is "available" on the Moon: it has not been proven that it is even on the Moon in any quantity, much less in a form that is reasonably easy to extract. Without Hydrogen, ISRU is a half-measure at best, adding a major Delta-V/cargo mass penalty for returning reusable vehicles.
Mars on the other hand... billions and billions of tonnes of Hydrogen and Carbon right there on the poles. Double the gravity, so people can probably walk half-way normally on Mars. Day and night cycles almost identical to Earth's, enough atmosphere to block most of the radiation and rocks and solar flares, and while transit is longer most cargo - which will comprise a major fraction of interplanetary travel I bet - won't care if its six days or six months, the Delta-V is about the same.
You mean slowing to near-zero relative to Mars before reaching the atmosphere? The fuel bill would be enormous.
So would the payload.
No. The payload would not be bigger, and in fact would be much smaller.
Think about it, if thrust-to-weight ratios or atmospheric drag aren't an issue, it will take you about as much rocket fuel to slow down and land as it takes to launch into orbit (or transit) from the ground. Even with the reduced Martian gravity, you'd therefore need a lander of the same scale as the Ares-V rocket.
But it doesn't just double the fuel bill, oh no, remember that the fuel bill increases exponentially with Delta-V, so if the same vehicle must launch from Earth and land on Mars, the rocket would have to be truly and hugely immense. It would easily dwarf the NOVA and SeaDragon superheavy rockets. The all-retro-rocket lander would be Ares-V size, imagine the size of rocket you would need to launch a fully-fueled Ares-V to Mars!
Or you want to employ orbital refueling? Then you would need to lug an Ares-V sized amount of fuel into orbit! Millions of pounds of rocket fuel, massive tankers, huge launch facilities able to build and fire dozens of heavy lifters annually...
So, in summary, retro rockets are not a particularly good idea for slowing down from orbital/transit velocities. Heat shields at least and perhaps parachutes too are the obvious way to go. The retro-burn for the Altair Lunar lander is the major reason why the Lunar surface payload is less than a sixth of the Ares-V LEO payload.
Hmm, ten times easier than the Moon? Getting there is 80% of the problem, and the Moon is a LOT easier to reach.
Yes, ten times easier than the Moon. Mars is far more hospitable (gravity, radiation, temperature, length of day), has all the major chemical elements for life and industry (CHON, halogens), and doesn't require much more delta-V to get there than the Moon (aerobraking for Mars orbit insertion/deorbiting). If you want to build a more-or-less self sustaining civilization on another body in the solar system, Mars is the obvious choice.
You mean slowing to near-zero relative to Mars before reaching the atmosphere? The fuel bill would be enormous.
Um, the conditions on Mars make it ten times easier to colonize than any other body in the solar system.
Good point.
Asteroids can't rotate very fast or they break apart - typical period is around 5 hours.
But they do rotate, so if you have a man down on the asteroid and stationary to it, then he's not stationary respective to Orion anymore...
I do think that digging asteroids will be harder than most realize... we're so used to working in gravity, we can hardly think in terms of zero gravity.
Why would it be risky? Orion will be in exactly the same orbit as the asteroid so there should be almost no relative motion between them. Thrusters would only be needed to move Orion around the asteroid, once in place astronauts will be able to safely explore.
Because the asteroid will be rotating relative to Orion.
"Imagine what a politician would do to the moon program with the statement "It can be all destroyed in the first year"."
The same can be said of almost any space mission, or for that matter almost any engineering project of any kind, anywhere. Sure its a possibility, there is also a possibility that a hypervelocity space rock could defeat any practical amount of armor.
Absolutionist statements like "its possible" or "there has to be zero risk" and other such anti-rational nonsense grease the rails taking us back to the stone age.
With those kind of forces, were really talking about armor. And not just for permanent structures, but for anything exposed. You wouldn't want your accent module turned into swiss cheese.
And we'll probably need an orbital radar system to at least get some warning.
Well to some point there is an acceptable risk of possibly getting hit versus cost (and mass) of all this armor, which would have to be exceptionally strong to resist high-speed space rocks.
...the astronauts while working out doors allows them to use much cheaper, flexible even expendable suits, and allows them to be much more effective.
Of course just how much depends on how well you can temporarily seal it to the surface.
Yeah thats the catch, the seal has to be pretty good to eliminate the need for pressure against the body. Radiation isn't a big concern either way though.
Four catches though:
First, it will be very hard if not impossible to build a pure-fusion atomic bomb. They also will probably not be all that efficient, requiring lots of heavy chemical explosives and a thick radiation case. And even then, they will be too expensive to make enough for common use.
Second, the "pusher plate" becomes more efficient geometrically as it gets wider, so bigger and bigger ships can carry more and more massive loads... however the reverse is also true, that small Orion's are awful and don't get that great of an efficiency at all.
Third, how does one land such a contraption? Getting all that mass up there is nice and all, but what then? How do you get up and down to it efficiently? ...And if you can do that efficiently, what do you need Orion for?
Fourth, you can't fly the thing often from a launch pad that keeps getting hit by atomic bomb blasts, now can you?
The radiation protection would be trivial unless the roof is relatively thick and heavy, which will make constructing such things "expensive" as far as resources and machinery go. Also, Mars doesn't really have much of a micro-meteoroid problem, because the air is thick enough to burn up small stuff like on Earth.
If any process is too hazardous to do in the pressurized confines of a base/colony, then we ought to just leave the machines outside. About the only benefit to the "machine tent" I can think of would be dust control, which might be an issue during dust storms and would make working outdoors difficult.
T"ATV evolution with Viking capsule" one, that is still kind of short on details, but it would seem to be 9 mT ship for 3 crews that would be made from ATV propulsion module + 3,3m Viking capsule launched on top of Ariane 5. Being only 9 mT heavy would mean that it could be launched directly to HEO or Moon orbit by upgraded Ariane 5 (ECB).
First one is classic copy of Orion that could go to the moon with extra EDS launched with another rocket.
Second one looks like very interesting to me, since it would use Ariane’s strength (cryogenic upper stage) to compensate for the higher cost of a rocket (compared to Soyuz). Having direct manned access to HEO would allow Europe to meaningfully participate in any manned mission beyond LEO. And since neither Europeans nor the Russians seem likely to build HLV anytime soon, that puts them into position where they have to be more innovative in what kind of approach can they use. SEP/NEP assembled in LEO from 25 mT pieces, spiraled to HEO where the crew from Earth would board it would be one such approach. Having fast, relatively cheap (1 Ariane 5) and simple (no LEO dockings) manned access to HEO would make that kind of thing much more realistic and doable.
Or maybe the Europeans will need all the extra payload of the Ariane-V for the escape tower and extra structural strengthening required for man-rating and whatnot.
What would these health and safety advantages be? Working outside in a suit always entails significant risk. You'd die inside this "machine tent" if your suit failed just as quick as if you were outside of it.
And, while machines must operate in a cold atmosphere, remember that the atmosphere is very thin and a poor conductor of heat. Thus, it is easy to keep the machines warm with internal heaters when night-time power is not a problem (nuclear reactor) or may even keep warm enough just from normal operation.
You mean pressurized or unpressurized?
Gas core ("GC") rockets handle and contain the nuclear fuel in a gaseous state. Its already melted down, and boiled even.
In a "traditional" GC-NR (nuclear rocket) the fuel gas is contained in the center of what is basically a "whirlpool" of liquid hydrogen, so that it does not touch the walls of the engine at all.
"Stand off?" That sounds pretty dang risky for the astronauts.
Don't forget that the Orion capsule SM is supposed to have some space for science payload.
The hard part might be getting the capsule steady with respect to the asteroid though. Could a simple "landing gear" be added to the SM or something?
For the time being, all we have is disposable space craft!!
It would be a very expensive way to mass transport people - but we know its feasible!I heard that some version of the Russian Energia was going to be fully reusable. All stages and boosters would be able to glide back down to Earth using wings/parachutes. If that were true - its a pity they stopped that program.
Although, the same kinda idea was implemented in the Shuttle program, and it didn't really make it cheaper.
And for the time being, we don't need mass people transport either. Furthermore, if it is very expensive, then it is not feasible, mass people transport has to be cheap. A 50 seat megacapsule on top of Ares-V would cost around a billion a launch easily, which makes for twenty million dollars a ticket, which is just not that good. You could only launch a few of those a year anyway most likely.
We also can't fall for the "gaetanomaronian" aversion to development costs: since we have to have a reusable vehicle thats cheap to fly, it will undoubtedly cost a lot of money to develop, which we will just have to pay as the price of doing business.
As far as Energia, or for that matter any low-tech multistage vertical launch rocket, just takes too much trouble to launch and would have too low of a reliability. Something with wings, probably launched horizontally, is all but definitely the way to go: less thrust required, easier to abort, efficient air breathing engines, much much easier to recover.
The Ariane-V rocket was also developed with launching the Hermes European mini-shuttle way back when, so it is a smaller leap to man-rate it then most think I believe. It also has a pretty decent service record since they fixed the bugs in the software and engine nozzles.
Take the ATV, swap out the cargo carrier for a capsule, and viola'. If not for the Europeans lack of experience with space capsule technology, they could probably beat NASA to making an Ares-I/Orion style launch system.
Mass transport is never going to happen with expendable vehicles of any sort. Something reusable is absolutely necessary, especially when it will be packed with expensive life support and escape equipment. Furthermore, a big expendable cargo rocket consciously trades high reliability for increased payload efficiency since it does not need to carry people. A reusable vehicle on the other hand has to be reliable, otherwise it won't come back enough times to make it worthwhile.
The problem with VASIMR for manned use is that no power plant of that output is available that doesn't weigh too much, except the exotic vapor-core fission reactors.
I'm all for fission engines in space, but using them in the atmosphere is a bad idea. It gives only limited benefit anyway, air-breathing chemical is the way to go, something like the Saenger-II/Shuttle LSA or maybe even a single-stage like the X-30 NASP/Reaction Engine's Skylon.
Yeah, I know that. thats the whole point.
The consequences of a serious nuclear accident happen to be a lot more dire than a car, plane or normal power station breaking down.
But this is the thing, with enough development the risk of a disaster will be acceptable. I believe that the risk is acceptable now with modern designs, like the Westinghouse AP1000 design.
The design is 20% as complicated as previous reactors, and there are valves holding the moderator in the core and coolant water in gravity-fed tanks. If the worst possible thing goes wrong, if all control and power is lost and everyone at the plant is abducted by aliens, and the pressure vessel of the reactor fails...
...then the multi-redundant valves release, since without power they don't hold shut, moderator is dumped, the nuclear reaction stops, and the pressure is relieved. Plus the emergency coolant is dumped under the force of gravity to cool the core. And even if the core did leak, the radioactive material would be contained in the thick steel containment building.
And don't get me started about how safe the pebble-bed or Uranium Hydride reactors are. Modern reactors are so far removed from the stupid primitive Chernobyl design that it is dishonest as well as ignorant to compare them.