If - and it’s not a major “if,” IMO - SSTOs are capable of faster
turnaround than TSTOs then the annual flight rate goes up and the cost per
launches goes down *significantly*. Flight rate is the driving factor on
launch costs.
Of course this really depends on whether or not there’s a market for that
kind of volume to get lower launch costs. I’m highly skeptical of that.
Either way, great to see a real SSTO effort.
On Fri, Jan 21, 2022 at 12:54 AM Henry Spencer <hspencer@xxxxxxxxxxxxx>
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?
A first stage, especially one which can land where it took off, could
better achieve that sort of flight rate.
A first stage doesn't necessarily need a second stage. :-)
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