USAF Proposes Affordable Rocket Plane - NUCLEARSPACE MESSAGE BOARD (ACTIVE)

Members Login

Post Info

TOPIC: USAF Proposes Affordable Rocket Plane

10kBq jaro

Date: May 1, 2005

USAF Proposes Affordable Rocket Plane	Permalink

World News & Analysis USAF Proposes Affordable Responsive Spacelift Rocket Plane Aviation Week & Space Technology 05/02/2005, page 33 Michael A. Dornheim Los Angeles U.S. Air Force has $280 million to fly a rocket plane demonstrator by 2010 A Quick Response Air Force Space Command wants to try a rocket plane to put medium-weight payloads in orbit quickly and cheaply, and it intends to have a contractor build a subscale demonstrator to test the idea over the next five years. The concept, called Affordable Responsive Spacelift (ARES), uses the rocket plane as a first stage carrying typically two upper stages on its back. After releasing them, the plane would fly back to the launch base under jet power for reuse. The upper stages could be similar to ones used now, or to ideas being generated by the Falcon launcher program of the Defense Advanced Research Projects Agency (Darpa). The Space Command budget has $280 million for ARES over Fiscal Years 2005-11, including $29 million from the Air Force Research Laboratory, which wants to piggyback on tests done by the subscale demonstrator, called ARES-SD. These funds cover building and testing the demonstrator. http://www.aviationnow.com/media/images/awst_images/large/AW_05_02_2005_1857_L.jpg The Air Force's Operationally Responsive Spacelift study has produced a reference design for the ARES rocket plane medium-lift launch system, shown here. Upper stages are carried piggyback and released 200 mi. from the launch base at Mach 7 and 200,000 ft. Jet engines, seen here by the canards, are needed to fly the first stage back to base. Requests for proposal for ARES-SD have already been issued and responses are due by the end of this month. This first phase is called concept development and demonstration planning, and contractors are to be selected in June. That will be followed by issuing a separate contract at the end of 2006 for detailed design, construction, and ground and flight tests of ARES-SD by 2010. The program has been briefed to and approved by then-acting Air Force Secretary Peter Teets, says Col. William Dean, director of Development and Transformation at the Space & Missile Systems Center in El Segundo, Calif. Dean's office is overseeing the program. The current schedule has ARES beginning operations by 2018, lifting 10,000-15,000-lb. payloads to low Earth orbit, Dean says. Variants with different performance could be developed later. The ARES concept is an outgrowth of the "analysis of alternatives" (AOA) part of Space Command's recently completed Operationally Responsive Spacelift (ORS) effort (AW&ST Apr. 7, 2003, p. 70). The AOA produced a reference design and architecture for ARES, as well as requirements of: Ability to launch a pre-integrated payload with 24-48 hr. notice. Two-day turnaround. The rocket plane will be ready to lift off with another payload within 48 hr. of its prior launch. A 10,000-15,000-lb.payload capacity to low Earth orbit, with growth to more than 45,000 lb. in an ARES family. A cost goal of $1,000 per lb. to orbit. "We think we can get roughly $2,000 per lb.," Dean says. That is just one-third the current cost of $6,000-7,000 per lb. for Delta medium-lift launchers. The cost is lowered by reusing the first stage instead of throwing the entire launcher away, Dean says. Also, the quick response time means that large teams don't spend months stacking the launcher. Using components like Peacekeeper ICBM stages or the Falcon design, which are built for responsiveness, will help, Dean says. The upper stages' expendability should make them light and small. Parts of the cost argument are familiar, such as "aircraft-like" operations that are to save money. This clearly backfired on the space shuttle, and schemes with similar claims like the DC-X and X-33 were vaporized by reality. So why should ARES be any different? One reason is that the reusable part is just the first stage, Dean says. This avoids the complex necessities of reaching Mach 25 to get to orbit and withstanding the stress of entry. Instead, the ARES rocket plane just goes to the more benign environment of Mach 7 and 200,000 ft. to release the upper stages. The hybrid reusable-expendable design transfers some of the difficult tasks to the expendables. Another reason is that the three-stage design doesn't require ultra-high motor and structural performance, which should improve both cost and reliability. "We don't push technology," Dean says. "The key is how to integrate technology. It's a systems engineering leap." The AOA's government reference design for the rocket plane features: Vertical takeoff and wheeled landing. RP-1 kerosene and liquid oxygen propellants. Smaller thrusters will not have toxic propellants like hydrazine. Engine cutoff at 12,100 fps., and upper stage separation at Mach 7 and 200,000 ft. at 200 mi. from the launch pad. Mach 7 was chosen as it is fast enough to reduce the upper stage size, but slow enough to do without a complex thermal protection system. "TPS is a main manpower driver and ARES will have almost no TPS maintenance," says Robert A. Hickman, director for advanced launch concepts at The Aerospace Corp., which is supporting the effort. Jet-powered flyback. Once the rocket plane accelerates beyond Mach 4, it is too far away to glide back. Drawings show the jets located toward the front of the vehicle, and they might burn the RP-1 fuel. They are not used for ascent. A gross liftoff weight (GLOW) of 700,000-800,000 lb. for a 15,000-lb. payload, Hickman says. That means the payload fraction is 2%. Using a slightly different set of numbers that have a GLOW of 670,000 lb. and a 13,500-lb. payload, the first stage itself at liftoff weighs 530,000 lb. and has a dry mass of 61,000 lb. It would touch down at about 65,000 lb., Hickman says. That means that 87.7% of the first stage liftoff weight is consumed as fuel, but some of that is used by the jet engines and does not contribute to ascent. The rocket plane fuel mass fraction can be as low as 80% and still be viable, Hickman says. Main engine specific impulse (Isp) and thrust-to-weight (T/W) parameters that are the same level as current engines. A ballpark vacuum Isp would be 300-330 sec. and T/W may be about 85, Hickman said. Engine cycle could be either gas generator or more complex staged combustion. Upper stages may have liquid or solid propellant, such as Peacekeeper stages 1 and 3, weighing 140,000 lb. ARES-SD would have a dry mass about one-fourth the operational vehicle, Hickman says. The demonstrator will be suborbital and carry a dummy upper stage to test separation. "We want to find out from ARES-SD what the real cost of an operational system would be," Dean says. "We have one reusable launch vehicle data point, the space shuttle. ARES is a significantly different concept than that. And we want to demonstrate the operability, reliability and turn time. What is implied by a 48-hr. turn time?" The Air Force Research Laboratory is interested in ARES-SD as a vehicle to test technologies such as thermal protection systems and hypersonic craft, Hickman said. Darpa is not involved with ARES. "They didn't see it as Darpa-hard," or enough of challenge for the agency, Dean says. Given that many Darpa projects are failures, that may be a good thing.* __________________

Page 1 of 1 sorted by

Tweet this page

Post to Digg

Post to Del.icio.us

Create your own FREE Forum
Report Abuse