NASA Ames’ Worden reveals DARPA-funded ‘Hundred Year Starshi

[Nik]

SSTO engineering and technical issues are very scary unless you pull a game-changer, like Reaction Engine's remarkably efficient heat exchanger...

http://www.reactionengines.co.uk/heatex_man.html

Putting the power source on the ground does simplify things, of course...

[CaptainBeowulf]

To me a logical solution has been a TSTO with a flyback first stage for the last couple of decades.

Take all the development work done on aerospike engines back in the 70s and then in the X-33 program, put two delta-wing airframes together, and fly it that way.

NASA and the aerospace complex seem unnecessarily pigheaded - it's either crash SSTO-or-nothing programs or else huge great expendable rocket programs - like a deliberate attempt to avoid the logical, financially feasible middle road.

Not that I have anything against a true shuttle-derived heavy cargo lifter. In fact, I'm mildly in favour of it. The Direct/Jupiter design seems most logical. Minimal changes to design and infrastructure - you re-engineer the main tank to carry payload on top and mount SSMEs on the bottom. You can mount 2, 3, or 5 SSMEs on the bottom of the tank as needed. It requires modification to the launch pads on the crawlers, but not new crawlers. You should be able to launch 60-120 metric tons of cargo depending on the configuration.

Make a relatively small TSTO lifter for crew launch - but it can still carry 6-8 people and a chunk of equipment. Let the private sector try it first, but if they fail, use all the best bits of pieces from the last 3 or 4 decades of canceled programs. You'll still need several years to integrate them into a working system - rocket building isn't just lego pieces - but don't tie a new program into development of fundamentally new technologies.

Such a set of systems would probably provide adequate capability for decades until - hopefully - new physics would be discovered to allow more efficient earth-to-orbit.

[CaptainBeowulf]

With a shuttle-derived HLV with a 60MT cargo size, you could easily launch a dozen 5T each prospecting probes. They can all be fitted with ion engines. To me, that's generous. I could see the prospecting vehicles being 1 ton each, or even less. You could send up 60 at once...

[D Tibbets]

Rare Earth's are not that rare. They are a byproduct of Phosphate mining as well as Aluminum refining. The reason why the Chinese dominate the market is that they are the low cost producer of Rare Earths. All of their rare earths come from a single huge mine near Mongolia with essentially ......

The only materials worth the cost and expense of asteroid mining as Platinum Group Metals (PGM) and maybe Hafnium.

I have a friend who knew a mining engineer who analyzed meteorites for the purposes of determining the feasibility of mining asteroids. He said the best asteroids are types that have metal phases in them. These phases can be separated by grinding and sifting (meaning no chemistry has to be done on the asteroid) and the resultant phases sent back to Earth.

The difficult part is prospecting. Since the phases are mostly inside the asteroid, identifying the ideal asteroid cannot be done with spectroscopy using telescopes on Earth. A prospecting probe has to be sent out to the target asteroid to prospect. 10 or more such probes may have to be sent before the motherlode asteroid is identified. This is costly and time consuming. .....


An asteroid prospecting and mining venture would be a multi-billion dollar venture and would take probably 10 years before final payoff. Of course the payoff could be worth a $100 billion or more.

Its a highly speculative venture that is unlikely to happen in the next 2 decades.

Actually, this carbonaceous type of asteroid is in the majority, perhaps greater than 75%, especially in the outer asteroid belt. And, the asteroid type can be determined spectroscopically from far away (like the Earth).
Returning even a moderately concentrated mineral cargo back to the Earth would be the greatest challenge. Even with slow acceleration, and decade long transit times, it would take a tremendous amount of thrust to deliver the cargo to Earth intercepting trajectories. Only the truly precious material might make economic sense. Harvesting from sea water or even the Moon would probably be much cheaper.

Dan Tibbets

[kurt9]

Spectroscopy will only tell you about the stuff on the surface. You can assume that the interior of the asteroid will be the same if the asteroid is homogeneous in structure (No layered structures). This may be true for the small ones (less the 1km in diameter) which are the best targets.

You're correct that returning the PGM (Platinum Group Metals) phases back to Earth is time consuming. I agree with you that sea water extraction mining is likely to be done first and will be cheaper.

BTW, the Japanese are developing sea water extraction mining for Uranium.