[AR] Re: Radian One spaceplane
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Fri, 21 Jan 2022 19:26:27 -0500 (EST)
On Fri, 21 Jan 2022, Peter Fairbrother wrote:
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...
I guess that's OK if a] no astronauts and b] the target space assembly
station has a tug to collect payloads.
Maybe not with *astronauts* :-), but there's no problem in doing it with
*passengers*. Think of it as a train stopping for a moment to uncouple
and drop off a passenger car -- something that's done quite routinely with
passengers aboard. Yes, either the passenger module needs to be a
self-contained habitat, or there needs to be somewhere for them to go, but
one of those things was needed anyway.
Yes, in the absence of rails :-), the "somewhere to go" case probably
requires a tug to move the passenger module the last kilometer, but that's
no big deal either, and it's easier and cheaper than having the orbital
transport vehicle do it. (We have to get away from the idea that every
spaceflight is on its own in virgin wilderness -- that hasn't been
necessary for a long time now.)
But a tsto gives flexibility here to have the orbital delivery vehicle
faff around a bit without tying up the expensive main launch engines.
The upper-stage engines may well cost more, since they're more
performance-critical. You don't really want *any part* of your transport
system doubling as a camper van -- that's not the way it makes money most
efficiently.
Also you can have different second stages for different purposes.
Better to have specialized orbital tugs for different purposes, and keep
the Earth-to-orbit vehicles (whether one or multiple stages) doing what
they do best.
Doesn't have to be winged, but wings allow operation from an airport
rather than a dedicated launch pad. Less capital outlay for a start.
Not unless it's an abandoned military base out in the middle of nowhere.
No rocket system is likely to meet the noise regulations of today's
airports.
Actually, maybe it could be done -- *without* wings. Noise within the
airport is no big deal; the problem comes when your departure path goes
low and slow over surrounding areas. Vertical ascent and descent is
probably *better* for rocket operation from airports.
Radian's system in particular uses sled launch, so it almost certainly
needs a dedicated "runway" for the sled. And the sled will probably be
rocket-powered too. The one for Boeing's RASV would have had a pair of
F-1 engines, which an airport's neighbors, um, would not appreciate. :-)
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.
I envisaged a module with three detachable tanks. The tanks could be
supplied already tested, and all that would be required would be a
little plumbing - the tanks are just tanks with level sensors, nothing
else.
Unless they're carried *inside* a vehicle, there are still structural
issues, ascent heating, etc. to worry about -- not as simple as it might
look at first glance. At the very least, they'd want other sensors too.
(Among the connections joining the External Tank to the Shuttle orbiter
were electrical connectors -- *huge* ones, with hundreds of pins.)
And even tanks cost money. Even military aircraft generally don't drop
their drop tanks in peacetime.
I think we would be past testing here...
Aviation tests *every vehicle*, and tests it again after major maintenance
or upgrades -- there's no such thing as "past testing". Testing the
individual vehicles is part of production and operation, not development.
and it's mainly for cheap cargo like fuel etc anyway...
I've never understood the idea that unreliable vehicles are acceptable if
they're only carrying cheap cargos. There are too many undesirable side
effects of failures, even if the *cargo* is cheap.
Henry
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