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But I will say that nothing lasting or of any real significance will happen in space until we ditch the whole expendable rocket paradigm and start building real reusable launchers.

For example?

The SSME is a ludicrous design for a reusable vehicle. The chamber pressure is incredible, requiring extremely high performance pumps. Extreme performance requires extreme maintenance.

Reusability requires extreme reliability. The engines have been reliable. Extreme performance is what the Shuttle delivered. The SSME isn't a ludicrous design.

All the things you are listing are problems with the shuttle, not reusability.

Strange that the USSR didn't learn from the alleged US mistakes and build a vehicle which took off as well as landed like a plane. The most complex machine ever built (in its time at least) wound up being knocked off by the USSR with its Buran system.

Even NASA has concluded an SSTO can be built, and yes they stipulate the unobtanium, but that has more to do with a built in excuse for failure than a real need. The one piece of technology actually needed is altitude-compensating nozzles, whether in the form of an aerospike are simply a telescoping bell.

The fact is, that's just wishful thinking. The has been one SSTO, and that is the LEM, which took off from the Moon, not the Earth. That isn't a problem with nozzles, it's a problem of mass budget. The unobtainium referred to above would be the material out of which the single stage would be constructed -- strong enough to hold sufficient fuel to reach orbit, but light enough that most of the mass of the vehicle doesn't have to be dumped, as is the case with every vehicle which has ever reached Earth orbit.

The real point of reusability, SSTO or not, isn't a one off reduction in launch costs. It is the economics of scale. The whole point of reusability is not to reduce the cost with the same number of launches currently consumed... The point of reusability is to reduce the marginal cost of launches.

And reusability doesn't do that. Expendibles are cheaper, and will remain so, unless and until an SSTO can be done. But the cost per pound to orbit will also have to improve, or what is the point?

you really do need to craft your requirements around it and not sacrifice that one all important capability for something more sexy.

What you're saying is, reusability of the vehicle, and not costs or lift capacity or anything else -- is all important. And that doesn't make sense. Space vehicles need to be built to get specific payloads to orbit (and beyond).

Here's an example of a reusable system proposal that doesn't involve SSTO or getting to orbit.

Roadmap To Mars
Buzz Aldrin, with David Noland,
illus by Jeremy Cook,
Buzz portrait by Michael Kelley
Popular Mechanics
December 2005
My blueprint for manned travel to Mars, based on reusable spacecraft that continuously cycle between Earth and Mars in permanent orbits, requires much less energy over the long term. Once in place, a system of cycling spacecraft, with its dependable schedule and low sustaining cost, would open the door for routine travel to Mars and a permanent human presence on the red planet. Its long-term economic advantages make it less susceptible to cancellation by congressional or presidential whim. In effect, this system would go a long way toward politician-proofing the Mars program.

For example?

The example is negative: We made great strides going to the moon and haven't been back in thirty years because it was so expensive. Every time there has been an incident in a launch system, we stand down for two years going over it in grueling detail, even when we plan on ditching the thing anyway.

How much clearer can you get that politicians and even NASA regard space as an expensive but ultimately unnecessary stunt?

Reusability requires extreme reliability. The engines have been reliable.

Meaningful reuseability requires more than reliability. It requires low cost maintainability. The reliability of the SSME comes with a huge maintenance cost.

Extreme performance is what the Shuttle delivered. The SSME isn't a ludicrous design.

Bleeding edge performance will always be expensive to operate and maintain. And note that I said the SSME is a ludicrous design for a reusable vehicle.

Yes, and they got so much use out of that too, didn't they? I guess you can add that to the Shuttle legacy: It helped win the cold war by becoming the same resource sink for the Soviets it is for us.

That isn't a problem with nozzles, it's a problem of mass budget.

Altitude compensating nozzles are very helpful for SSTO designs. That is the only piece of new technology needed. The mass fraction isn't a matter of unobtanium, even NASA has concluded that SSTO mass fraction is obtainable. And quite a few rocket engineers have been saying it is possible since the 80s and a few were promoting it all the way back to the sixties. Mass fraction isn't a matter of magic technology, it is a matter of exercising engineering discipline. Several vehicles including the Saturn IVB stage have exhibited SSTO-like mass fractions. I may be mistaken, but I believe the Titan II only dropped an engine ring with two engines on the way up.

I will grant you the point that these are a long way from being reusable SSTOs, but materials technology has improved considerably since the sixties. What you're saying is, reusability of the vehicle, and not costs or lift capacity or anything else -- is all important. And that doesn't make sense. Space vehicles need to be built to get specific payloads to orbit (and beyond).

Don't be facetious. Of course payload is important. But your question betrays a misunderstanding of what reusability and/or SSTO is all about. The status quo is so hung up on performance at any cost that ends up being exactly what they pay. It would be far more useful to put 10,000lbs into orbit 100 times than it is to put 40,000lbs into orbit once. It is all about access.