Existing Jets
An airplane such as Scaled Composite's White Knight
or
the L1011 used for Pegasus can get a relatively small rocket above most
of the atmosphere. There is also a
Russian high-altitude jet called the M55. The L1011 has launched many
Pegasus rockets already and there are plans to use both the Proteus and M55 to
launch rockets.
A
NASA web page on the Proteus has some interesting information.
The Proteus was designed as a pilot optional jet.
Not having a pilot could save the weight
of the pilot and some of the pilot support stuff (seat at least). Cruising
speed is Mach 0.42. The empty weight is 5,900 lbs.
It can fly up to 65,000 ft when carrying a load of 7,000 lbs and 58,000 ft when carrying 12,500 lbs.
So it is about 5,000 kg to about 60,000 feet.
A
C5-Galaxy
should have
room under the wing
to carry a rocket of 50 tons or more. In fact, a 78,000 lb Minuteman
missile was launched from a C5-Galaxy [REF UCDAVIS paper]. In 1987 these
cost $92.25 million new.
Several Russian bombers or cargo planes, such as the Antonov An 22, the Kuznetsov NK 12,
or the Tupolov Tu 95 are able to lift 100 metric tons, and might be available for lease.
Modified Jets
If you inject some oxidizer into the input of a jet engine it becomes sort
of a mix between a jet and a rocket engine and can operate at very high
altitudes. The oxidizer
could be nitrous-oxide or liquid oxygen. This is a modification that
can be done to existing jets. In one place this is
called Mass Injecting & Pre-Cooling (MIPC).
There are
5 companies working on MIPC technology.
With something like this the Proteus could go even higher.
New Jets
Initially it makes sense to use an existing jet. Mostly you just need to get up
above most of the atmosphere.
But in the long run
it could well make sense to invest the effort
to design a jet just for the purpose of launching a rocket.
It may also be necessary to custom build a jet to get the
characteristics that we want. This jet should
be able to carry an external payload under it and be able to
fly high. Low operating costs are a plus, but fuel efficiency probably
is not as important as most jets.
It is interesting to note that
Scaled Composites built a custom jet called the White Knight
to launch their rocket SpaceShipOne.
Most of the fuel weight in a rocket is the oxidizer and a jet does not have to
carry oxygen. This can make a jet smaller and cheaper to operate.
The RASCAL project
is developing a new high speed jet for air-launching rockets.
Back in 1964 the
XB-70 Valkyrie
could carry 50,000 lbs to 2000 MPH at 72,000 feet .
The
NASA jet engine simulator
indicates that it is possible to design a jet that would get
a 5000 lb rocket up to 3000 MPH and 100,000 feet.
By doing this,
the delta-V the proposed SSTT needs to provide can be reduced by another 1 km/sec.
In fact, the HyFly hypersonic missile for which
Boeing got the contract
is expected to get to 90,000 feet and 4,000 MPH by the year 2005.
By the time this new fast jet could be built, we would probably also have a stronger tether spinning
1 km/sec faster, so the rocket would only need to do about 4 km/sec instead of 5 km/sec.
This could make our 6,000 kg rocket now have a 9500 kg payload instead of
just 4000 kg payload.
Powered Parafoil
Powered parafoil could be a cheap launch platform.
It would be much less expensive to build a parafoil than to build a new airplane.
It would be far easier to lift a really large rocket this way.
It could be made to fly slow enough that launching from a ship aimed into the wind could work.
Could even launch it like a kite from a ship so it was up in the air before the jet started.
Jets at slow speeds and high altitude have little thrust.
For a powered parafoil it is probably best
to use a propeller and engine with compressor to handle the low air pressure.
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Copyright (c) 2002, 2003 by Vincent Cate. All rights reserved.
