Interesting to hear about the engine developments. Any idea whether this will allow them to bump up the vehicles max altitude?

A minor point, but it happens to relate to a pet peeve of mine: carbon footprint is not a serious consideration on which kind of reentry vehicle to use. Rocket use already makes up an infinitesimal part of total carbon emissions (and by the metrics of kg CO2/$, is surely an efficient industry). Even if we were to consider this a serious metric, the Dreamchaser would not come out as the winner, not when we take into account the fact that it is a heavier vehicle per kg cargo or astronaut, and the effects of this fact on the size of the launch vehicle required to put it into orbit. Sorry to be such a pedant, sometimes I just can't help it.

Hindsight makes this look like a tempting shuttle alternative, but our hindsight incorporates the true flight rate that the shuttle was able to operate at, and the amount of funding it could ultimately count on. The article notes flight rate in particular as deciding factor, if decision makers at the time had access to that information, they might well have gone down another path.

Agreed, I am a big fan of the push for reusable launch vehicles, but we need to recognize that reusable designs come with very real costs, and the farther up the staging of your mission architecture you get, the less reusability makes sense. Consider the Falcon 9: reusable first stage, disposable second. Should the second stage have been reusable? No, because recovering this stage is more difficult than the first, and extra mass on this stage is much more detrimental than on the first. Perhaps by their next vehicle, SpaceX or BO will have enough experience and enough margin in their design to economically recover the second stage. But what John Strickland is proposing is jumping all the way to making the very last stage of a complex architecture reusable. There are several problems with this:

1. Mass: While I agree with benefit of ISRU for propellants, even the empty mass of a reusable SSTO vehicle would be vastly greater than an equivalent disposable design. Because this is at the end of a long logistical chain, that extra mass cascades back to an exponentially greater starting mass for the mission. It is true that over enough missions this initial effort would be repaid by not having to send more MAV's but you also need to worry about...

2. Reusability is hard: Even on earth, it's not easy, the space shuttle shows us that even when we succeed, we may still fail. Even if SpaceX's efforts pay off, they will do still no doubt rely on the ability to check and maintain the reused stages periodically. If they ever employ reused stages for manned launches, you can be sure that the maintenance will be very thorough indeed. There is no equivalent infrastructure on mars, and even with astronauts, the capacities for maintenance and repair will be limited. Operating in a rocky, dusty environment with vicious temperature cycles, refueled by ISRU-generated propellants, how many launches can you expect before it fails? Which brings us to…

3. The economics of reusability depend on the frequency of use: Reusable vehicles are much more expensive, both in development cost and vehicle cost. They only save you money if the volume is sufficient. Will there be enough missions to mars, in the early exploratory phase, to justify this choice? Especially when we consider that the extra development budget for this supposedly ideal architecture comes out the same limited pot that is to ultimately pay for the missions?

One day, I hope that what John proposes will make economic sense, and that a bustling colonization effort will be serviced by reusable martian shuttles. But until that time, I suspect that perfection will be the enemy of completion.

"Inside the Earth's magnetosphere nuclear propulsion is verboten because any byproducts eventually get sucked down into the atmosphere."

Not really. Fission-based nuclear power tends to take the form of nuclear thermal, where sealed fuel rods are used to heat (hydrogen) propellant. No nuclear exhaust unless you have a meltdown. Some forms of fusion propulsion might contain fusion products in the propellant stream, but these are generally no more harmful than the solar wind, or are not captured by magnetic fields (neutron).

Launch safety is certainly a concern, although we've already launched nuclear reactors into orbit.

I'm glad that you bring up the issue of aneutronic fusion, because this one of the primary advantages given for He3, and was not addressed in the original article. I agree with Dwayne that we are technically farther from He3 fusion than many other forms, and that it is a fanciful motivation for lunar development at this point (perhaps ever).

However, while He3 is not a realistic energy source in the near term for a number of reasons, it is worth noting that in many respects it is an "ideal" fusion reaction. It is aneutronic, with a very high energy density, and a lower activation energy B-H fusion. It is understandable that the Daedalus project chose it as their fuel for a proposed interplanetary probe (they explicitly focused on fundamental physical limits and ignored current technical limitations). Yes, the scarcity of fuel is only one of the barriers to He3 fusion, but the enthusiasm over it, while somewhat misdirected, is not entirely arbitrary.

"While Bezos wouldn’t give his vehicle’s payload performance data, it’s possible that it might overlap with ULA’s existing vehicles, or the BE-4-powered Vulcan, putting Blue Origin in the position of both a potential supplier and competitor to ULA. Bezos, asked about that potential competition, suggested that Blue Origin would not compete with ULA in the latter’s largest current market of national security missions."

If they stick to this, it would certainly help deconflict them from ULA. But I thought that part of the argument for developing the Vulcan was that it would be cost-competitive enough to operate in the commercial market. I suppose we still need to see the specs on BO's vehicle, but if there is much overlap with the Vulcan, I'm guessing that any chance ULA had of competing in that market is going to disappear, on account of BO controlling the rocket supply (although a reusable rocket pod would decrease BO's leverage somewhat).

With Blue Origin today touting plans for their own launch vehicle based around the BE-4, ULA must be considering the long-term wisdom of choosing this engine. It is one thing to rely on an external supplier for your engines (a condition ULA is quite familiar with). It is another thing when your supplier is also a competitor; ULA's business has been almost exclusively governmental, so Energomash was never actually a competitor, but if Blue Origin's vehicle gets off the ground, it's easy to imagine them trying to get it Air Force certified. If that happens, the BE-4 may suddenly become a very expensive engine. Could considerations like this strengthen the case for an AR acquisition?

Best option is to develop your simulation, then do a real-world test to calibrate how well it works. I don't know anything about SpaceX's abort models, but I am sure that they exist, and after they get the data back from the in-flight abort, they can be much more confident about their conclusions, not only for the Max-Q point where they did the test but over the whole envelope.

Yeah, if you don't include development the Shuttle cost comes out more like $1.2B, but nowhere near $450M. Whereas the $6B cited for the CC program does include development. The "per mission" cost is more like $133M for Dragon and ~$190M for the Starliner. These costs may not represent all of the facility costs, but suffice it to say that price difference between the CC program and shuttle is drastic.