In article ,
meiza writes:
In sci.space.history Peter Stickney wrote:
In article ,
Pat Flannery writes:

In times of crisis, the launch restrictions would be put aside, as long
as the booster stages came down over open ocean; it would be a lot
easier (and cheaper) to keep some of these things loaded and ready to go
than a fleet of Lockheed Tristars or B-52's, like Pegasus uses.

The same would hold true for Pegasus.
...

Well, Pegasus has a lot more unmanned explosive solid rocket mass
(19 tons). Considering the RASCAL is smaller and the manned first
stage gives a more significant portion of the energy, the whole
expendable should be about 3 tons, most of which is the
non-explosive hybrid stage. (Ok, still wouldn't want to be
hit by that.) And it's flying more predictably, outside the atmosphere
to start with.

Yoou're still going to have to track it, and the lauanch airplane, on
the way up. What's really needed is an equally portable tracking and
monitoring system. I woudn't be sirpriosed if somebody could put
something together with an E-3 (AWACS) and a couple of hte EC-18
(ARIA) aircraft. It's a lot more feasible these days, since the
airplanes can actually tell where they are with some certainty.

The old Preston Carter pdf also says the release from the aircraft
stage is at about 60 km height. If there's some performance margin,
you can get a few tens of kilometers lateral distance from the
launch site too, doesn't that help enough to get over the ocean for
care-free release?

Not necessarily. The concern isn't so much failure on release, as the
rocket goes haring off on its own while under power. Ideally you'd
like it to hit something soft, cheap, adn which won't due.

I understand that the NF-104 rocket-augmented Starfighter was very
hard to control when coming down from ~40 km (reason for SS1's
shuttlecock), how is RASCAL going to solve these problems, if it's
supposed to operate routinely?

The F-104 configuration had some particulalry nasty high Angle of
Attack behavior. A large part of its mass was also taken up by the
spinning compressor/turbine rotor in the engine, which led to
gyroscopic precession of the aircraft. (That's always there, but
without any airflow over the aircraft to stabilize it, it becomes
significant) The problem was gatting keeping the airplane entering
nose first. With no air to stabilize it, it enters very nose high. I
suspect that in the case of Yeager's last NF-104 flight, it was high
enough to blank the tail. The precession will tend to make it enter
sideways, IIRC.

The stability reasons were one factor in Rutan developing the
"Feather" or "Shuttlecock" mode for SS1. The other main factor is
that he wanted as much drag early on as posssible, so that the
reenteriing aerospacecraft wouldn't accelerate to a high Mach Number,
and thus generate a lot of heat.


The gating itemis getting the
proper payload selected, figuring out just what trajectory you want to
use, and getting the payload and the booster mated and ready to go.
That's a People Thing, and it's hard to reduce it.

Couldn't one design standard quick-to-configure spysat payloads, or is
75 kg so small that you have to have specialized ones because of
instrument tradeoffs? Computers can anyway determine the needed
trajectory (if/when it's possible with launch constraints) parameters
in seconds.

As for payload size - it depends on what you want to do. I'd venture
to say that it is rather small for a high resolution imaging system or
an ELINT system, especially if you want to cover several bands of teh
EM spectrum. You'd need a lot of specialized payloads, and you'd need
to keep them around. One thing we've found is that long-term storage
of satellites, and transporting them all over, isnt a good idea.
The inital trajectory is easy enough to figure out, but factoring in
weather conditions & such - especially for a quick reaction
"one-pass-look" system like we are, at the moment, postulating, is a
much more complicated problem. It doesnt' do any good if you go
through a cras effort to launch you satellite, then have it not able
to see the target on the first pass, for whatever reason. A mussed
opportunity on the first shot couldn't be made up by the same
satellite for something like 18 hours. If you're cramming sensors
into a small, short-lived payload, you won't have much mass/volume
available for power.


--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster



--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster