On 21/01/2022 05:54, Henry Spencer wrote:
On Thu, 20 Jan 2022, Peter Fairbrother wrote:
...There are lots of good things about Radian, but SSTO isn't one of them - a crewed winged fast turnaround first stage would be brilliant, but a SSTO would spend a lot of it's time just loitering in orbit - two day turnarounds (probably too long) would not be possible.
Why not? If you must put big wings on an SSTO, one benefit is that you can do a once-around flight, using aerodynamic lift to get enough crossrange to land back at the launch site 90ish minutes after takeoff.
It does mean kicking the payload out *immediately* on achieving orbit, but there's nothing fundamentally wrong with that, if you think of the vehicle as a delivery truck, not a camper van. How long does a delivery truck park in front of your house when delivering a package?
For cargo you might want to reuse the engines and guidance electronics, but you don't really want to have to return the tanks.
Even ULA, which is currently planning to recover only engines and avionics for the Vulcan first stage, has been heard to say that recovering the whole thing *would* be preferable.
Remember, it's not the metal that costs the real money -- it's the labor. The more inspection and integration and checkout you have to repeat to reassemble your vehicle, the less you save by reusing just *some* of it. Getting the whole thing back intact potentially avoids all that.
To say nothing of the ability to test-fly the exact vehicle you're about to use to carry valuable cargo, or passengers. Reusability is about reliability too, not just fabrication cost. To eventually match the reliability of aviation, we should learn how they do it, and flight-testing every vehicle is part of it.
Henry
