A vision of CATS

Presuming a reusable spacecraft

- Have to avoid armies of technicians to operate/maintain the
spacecraft. Thus:
- Components must have an appreciable operating lifetime. When
inspections and repair are needed access should be convienent. Thus:
- Can't use razor thin structural margins. Thus:
- No SSTO with near term tech. Must use 2-3STO. Thus:
- We have stage(s) dropped to be recovered and returned to launch site.

Choice: Fishing stages out of the ocean vs. flyback. I suspect flyback
to be less problematic, but it requires wings and return engines. With
3 stage launch, where does stage 2 come down? Ocean touchdown may not
even be an option, and airspace clearance may be needed.

- design orbiter for surviving reentry. Modest lift/drag for reducing G
load. High hypersonic lift/cross range are of limited value outside of
military operations.

- flyback booster running kerosine-LOX. Same kerosine can fuel flyback
engines.
- Orbiter running either LH2-LOX (light but bulky and very cold) or
kerosine-LOX (heavier).
- total stack is on the heavy side, favoring durability over performance.

Penguinista wrote

Presuming a reusable spacecraft

- Have to avoid armies of technicians to operate/maintain the
spacecraft. Thus:
- Components must have an appreciable operating lifetime. When
inspections and repair are needed access should be convienent. Thus:
- Can't use razor thin structural margins. Thus:
- No SSTO with near term tech. Must use 2-3STO. Thus:
- We have stage(s) dropped to be recovered and returned to launch site.

Choice: Fishing stages out of the ocean vs. flyback. I suspect flyback
to be less problematic, but it requires wings and return engines. With
3 stage launch, where does stage 2 come down? Ocean touchdown may not
even be an option, and airspace clearance may be needed.

- design orbiter for surviving reentry. Modest lift/drag for reducing G
load. High hypersonic lift/cross range are of limited value outside of
military operations.

- flyback booster running kerosine-LOX. Same kerosine can fuel flyback
engines.
- Orbiter running either LH2-LOX (light but bulky and very cold) or
kerosine-LOX (heavier).
- total stack is on the heavy side, favoring durability over performance.


I can't find fault with any of that.

I'd go for 2 stages, and Lox/LH2 in the second stage, it's probably easier
overall. Lox/kero in the second stage makes it too hard to get a decent
payload. Lox/LH2 also means that the orbiter has a low weight/area ratio,
probably necessary for a resueable TPS without maintenance between flights.


Which only leaves the question of horizontal or vertical takeoff.

As you need landing gear anyway, it seems to me to be better to have
horizontal takeoff. If MTOW is around 340 tons then you can use the landing
gear from a 777 or A340.

You can fly from an existing airport, you only need extra Lox and LH2
supplies on the ground, you don't have to build a launch pad (Berlin airport
already has LH2 supplies, though it wouldn't be a good choice for flight
path reasons).




You'll probably need both jets and rocket engines. You need jets for flyback
anyway, and if you use them as part of the first stage (perhaps with a bit
of rocket assist on takeoff) you can take advantage of the greater ISP, but
you'd need rockets as well if you aren't going for high mach airbreathers
which don't work well yet.

I see no real need for the jet part to be supersonic. If you amble up to
where the air is thinner at medium subsonic speed you can lower the MaxQ
substantially, and use a lighter airframe.

You could perhaps use Trent 800/900 series jet engines without turbofans
(Rolls Royce are considering developing a fanless Trent for SST use, and
might do a deal; if not it will cost around $50 million for the jet engines
plus pumps as below).

You could put the first stage rocket pumps on the jet engines, and bleed GOX
with gaseous nitrogen diluent into the intakes to keep them turning when you
get too high for air. Gives a little extra thrust, and a lot more horizontal
delta-v if you have aerodynamic lift at the beginning of the first stage
burn.

That means just developing some reuseable chamber/nozzles for the first
stage rockets. I'm interested in the possibility of a combined jet/rocket
engine, but it would likely be much more expensive to develop.

Should the first stage be human-piloted? Yes. It's just a glorified airplane
after all.




You can also get some timely sat-launch income, and paid-for test flights,
if you have a choice of second stages, a partly-reuseable cargo stage and a
fully reuseable people stage, developing the cargo stage first.

You will have to develop a second stage engine, there isn't one available
that's "refuel-and-fly-again" with a lifetime of around 1,500 flights. If
both second stages use the same engine you can test and develop the engine
to reliability almost for free and without risking people.

Put the engine and the flight electronics of the cargo stages behind an
ablative heat shield and return them, leaving the tanks in orbit for
construction purposes. You have to build a hotel too, for tourism.


If separation occurs high up (in near-vacuum) you can also enclose the
second stages within the first stage and have no aerodynamic forces on the
second stage, making them (the cargo version especially) lighter.




The expensive parts are the first stage airframe, the second stage engine,
and the orbiter TPS/structure; but the second stage engine starts to
generate income halfway through it's development cycle, and you should
already have some income to pay for the orbiter, you don't need to pay for
it with initial capital. Which I estimate at around $700 million.


If all this sounds familiar...

--
Peter Fairbrother

"Peter Fairbrother" wrote in message
...

snip

You could put the first stage rocket pumps on the jet engines, and bleed
GOX
with gaseous nitrogen diluent into the intakes to keep them turning when
you
get too high for air. Gives a little extra thrust, and a lot more
horizontal
delta-v if you have aerodynamic lift at the beginning of the first stage
burn.

A quick question from the lurking.. Has anyone done any testing (wind
tunnel, etc.) on the performance of jet engines with GOX injected into the
combustion chambers - presumably for high-altitude use??

Would there be any appreciable benefit in doing this?

TIA,
Cameron:-)

"Cameron Dorrough" wrote in message ...
"Peter Fairbrother" wrote in message
...

snip

You could put the first stage rocket pumps on the jet engines, and bleed
GOX
with gaseous nitrogen diluent into the intakes to keep them turning when
you
get too high for air. Gives a little extra thrust, and a lot more
horizontal
delta-v if you have aerodynamic lift at the beginning of the first stage
burn.

A quick question from the lurking.. Has anyone done any testing (wind
tunnel, etc.) on the performance of jet engines with GOX injected into the
combustion chambers - presumably for high-altitude use??

A major goal of DARPA's RASCAL program is to inject
water, LOX and/or other fluids into the inlet for
pre-compressor cooling. There are also some proprietary
variations of these basic schemes. As part of our Phase I
RASCAL contract, we found effective ways to enhance F-14
performance as a launch vehicle for small satellites.

We did not get a Phase II contract, but we are actively
pursuing the use of F-14's for potential launch of small
(100 kg) satellites as part of a "post-RASCAL" project.
In this latter project, we are not constrained by DARPA's
technological goals, and we are considering some interesting
alternatives.

Best regards,
Len (Cormier)
PanAero, Inc. and Third Millennium Aerospace, Inc.
( http://www.tour2space.com )

Would there be any appreciable benefit in doing this?

TIA,
Cameron:-)

lou wrote

Why on earth does Berlin have LH2 on hand? I hate to be the one to
break the news, but the Hindenburg is NOT coming back...

It's for expensive test BMW's with LH2 engines. Afair the tanks weigh 90 kg
and hold 18 kg LH2, or perhaps weigh 180kg and hold 9kg, or something like
that.

Just a curiosity really. I wish LH2 was as easily available here in the UK
though - I can get Lox in small quantities no problem (well, it involves a
bit of bribery and nepotism in my particular case, but no-one loses from
that).


--
Peter Fairbrother

Penguinista :

Presuming a reusable spacecraft

- Have to avoid armies of technicians to operate/maintain the
spacecraft. Thus:
- Components must have an appreciable operating lifetime. When
inspections and repair are needed access should be convienent. Thus:
- Can't use razor thin structural margins. Thus:
- No SSTO with near term tech. Must use 2-3STO. Thus:
- We have stage(s) dropped to be recovered and returned to launch site.

Ok.

Choice: Fishing stages out of the ocean vs. flyback. I suspect flyback
to be less problematic, but it requires wings and return engines. With
3 stage launch, where does stage 2 come down? Ocean touchdown may not
even be an option, and airspace clearance may be needed.

Wings? Why does the flyback require them? What is wrong with just using the
rockets already built into the stage?

- design orbiter for surviving reentry. Modest lift/drag for reducing G
load. High hypersonic lift/cross range are of limited value outside of
military operations.

Not completely true, but the less the crossrange, the simpler the design
becomes.

- flyback booster running kerosine-LOX. Same kerosine can fuel flyback
engines.
- Orbiter running either LH2-LOX (light but bulky and very cold) or
kerosine-LOX (heavier).
- total stack is on the heavy side, favoring durability over performance.

Why are you preselecting the fuel before ironing out the design? LOX I
understand, it is cheap and available just about everywhere that you would
want to lanuch from, but there is a wide range of fuels that you could look
at. Also limiting your upper stage to the same fuel as the lower stage(s)
may make handing operation easyier.

Earl Colby Pottinger

--
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