All I'll say is that it is mass fraction, not Isp, that needs to be improved, and additionally, if one develops an SSTO and if falls short of expectations, it can be salvaged as an operational system by various expedients such as a zero-stage, air-launching, sled-launching, recoverable strap-ons, etc. If you start your design process with a goal of two-stages, you'll never magically reach SSTO capability. But if you start with an SSTO goal, you might get there by incremental improvements that come from learning due to higher flight rates with time.Would that the human race could have evolved on a 0.9 G planet, so that these arguments might be moot.
I think the case of exoatmospheric suborbital refueling will likewise be one of those crazy things that we wonder how we ever lived without.
All I'll say is that it is mass fraction, not Isp, that needs to be improved,
and additionally, if one develops an SSTO and if falls short of expectations, it can be salvaged as an operational system by various expedients such as a zero-stage, air-launching, sled-launching, recoverable strap-ons, etc.
If you start your design process with a goal of two-stages, you'll never magically reach SSTO capability. But if you start with an SSTO goal, you might get there by incremental improvements that come from learning due to higher flight rates with time.
Would that the human race could have evolved on a 0.9 G planet, so that these arguments might be moot.
{snip}Would that the human race could have evolved on a 0.9 G planet, so that these arguments might be moot.
Was there any particular factor that lead to the resurgence of interest in SSTO in the mid-1990s? I'm guessing it was just a desire to take a second crack at cheap Earth-to-orbit transportation, after the failure of the Shuttle. But was there some other trigger that I'm missing?
X33 seems to have been captured within NASA by the "Let's get lots of new tech developed" arm. This is a very bad idea for an X plane project.
Quote from: HMXHMX on 11/17/2015 04:47 pm{snip}Would that the human race could have evolved on a 0.9 G planet, so that these arguments might be moot. There is a 0.376 g planet ready and waiting.
Why was there lots of research into space planes and or single-stage-to-orbit (or SSTO ) in the 90's? But we are not doing it today? Why is that?
A lot of that "heat" was my fault.HMXHMX, what are you up to? BTW, do you have a nice summary document of DC-Y/DC-X or any of the other high-mass-fraction vehicles you worked on?
Quote from: john smith 19 on 11/17/2015 03:58 pmX33 seems to have been captured within NASA by the "Let's get lots of new tech developed" arm. This is a very bad idea for an X plane project.It's the very intent of the X programs though. With a few rare exceptions, research is the main intent, not a sustaining program.
Unfortunately, as usual, I can't comment on my current work except to say it isn't SSTO. Close, though.
One other approach that hasn't been mentioned yet is beamed power propulsion, which escape dynamics is working on. It is still at Robert Goddard levels of TRL and scale compared to chemical propulsion, but it is great to see someone finally taking on the task of maturing the technology to some extent. The key complete unknown here is what engine thrust to weight ratios are possible with such designs.
Quote from: Nilof on 11/19/2015 03:14 amOne other approach that hasn't been mentioned yet is beamed power propulsion, which escape dynamics is working on. It is still at Robert Goddard levels of TRL and scale compared to chemical propulsion, but it is great to see someone finally taking on the task of maturing the technology to some extent. The key complete unknown here is what engine thrust to weight ratios are possible with such designs.The beamed power approach trades a large LV for large expensive ground facilities. I don't think it will work out financially but the idea has merit for lunar landers. The power could be beamed from Solar Power Satellite, which could also be used for beaming power to lunar facilities the other 99.99% of the time.