 
|
|
Unmanned Space Vehicles
The U.S.' use of rockets to place military payloads into orbit started with the U.S.' first entry into space, a payload atop the Redstone Rocket. Today, the launch vehicles fall into two classes, the expendable, and re-useable launch vehicles.
The primary example of the re-useable launch vehicle class is the Shuttle Transportation System (STS) otherwise known as the Space Shuttle. In fact, the USAF had very ambitious plans to operate their own space shuttle launch faclity at Vandenburg, AFB, California, until the Challenger disaster curtailed launches of the STS system, and the resultant weakening political environment made it impossible to continue.
Currently one other re-useable space craft launch system is under consideration, as part of the National AeroSpace Plane (NASP) program (also known as the X-30A program. Few details are available on the actual system, but it is intended to be a re-useable, hypersonic vehicle, capable of one stage insertion into space, and launch and recovery from standard airfields. Currently the program is under the management of NASA.
The expendable launch vehicles are currently based upon liquid fueled, multi-staged rockets, with rather enormous lifting cababiliity. In the case of military launches, NASA launches help fill some of the lift needs of all the services, with the USAF launch facility at Vandenberg AFB, CA. providing all other launches.
Expendable launch vehicles have been mostly centered around the same boosters used in the U.S. civilian space program. For instance, an old standard for U.S. military launches was the Atlas launch vehicle series.
Today, payloads have increased to a size that requires the Space Shuttle in order to place them in orbit, and with Shuttle's mission load, it has placed the services in position of not having the launch vehicles they need against the time table required.
To insure that this occurrance would not repeat itself, the military is expediting the delivery of the Titan IV launch vehicle.
Another alternative has been proposed by McDonnel Douglas, using the Delta launch vehicle to base a new launch system. "The Delta IV concept uses the Delta II and Delta III knowlege to provide a scaleable launch vehicle to compete with other expendable launchers." (McDonnell Douglas)
The following is a list of the current launch vehicles in use by the U.S. military (date verified in Air Force Magazine 1 in 1997):
Thrust
Payload at
Name Stages Type Lift-lbs/Orbit liftoff User
Space Shuttle 3 Liq., strap ons, 65,000 lbs 6.1 Mill. NASA
(STS) Spaceplane pounds (USAF pay-loads).
Titan IV 3 Liquid, Strap on 10,000lbs to 2 million USAF
Solids geosynchronous
or 39,000 to low
equatorial, or
31,000 low polar
Titan III-44D 3 Liquid, Strap on USAF (retired)
Solids
Titan II 2 Liquid 4,200lbs+ to low 430,000 USAF
earth polar orbit.
Atlas E/II 3 Liquid 11,000 lbs to 414,000 NASA/USAF low earth orbit
Using the Centaur
upper stage, boosts
5K to 8.5 Klbs to
to geo-synch orbit
from Florida or
12.2K to 15.7Klbs
to low earth orbit
from Vandendurg AFB
in California.
Delta-II 3 Liquid/9 Solid 11,000lbs to 1.5 Mill. NASA/USAF
strap-ons 100nm orbit
4,010 to geo
synch transfer
orbit.
Scout 4 Solid 100 lbs to 109,000 NASA/USAF
16,000 mile
orbit, or 377lbs
into 310 mile
polar orbit.
Payload Initial
Name Used on Type Lift-lbs/Orbit Thrust User
Centaur Atlas,TitanIV Liquid 10,200 lbs to 33,000 NASA/USAF
geo-synch orbitIUS - Inertial Titan IV, Solid 5,350 lb into 25,000 NASA/USAF Upper Stage Shuttle geo-synch.
IUS - Interial Aft Stage of IUS Solid 59,000 NASA/USAF Upper Stage (aft)
PAM-D II Delta, Liquid 4,200 lbs to ? NASA/USAF (Payload Assist Atlas, Geo-synch Module) Shuttle orbit
On August 16, 1988, the USAF awarded contracts to Boeing Aerospace, General Dynamics Space Systems Division, and the team of McDonnell Douglas Space Systems for design and technology demonstration of a heavy-lift Advanced Launch System (ALS) capable of lifting 160,000 pounds into low-earth orbit. NASA is a major participant in this effort as well. Intended IOC was to be in the year 2000, but budget problems may slip this as "stretchouts" occur.
Also, recently Congress appropriated funds to develop both a vertical takeoff and landing launch vehicle system (Clipper Graham) and the X-33 low cost replacement for the Space Shuttle.