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.
Click for SpaceTethers.com
Copyright (c) 2002, 2003 by Vincent Cate. All rights reserved.