Fully-powered USAF Aero Propulsion Laboratory low-altitude, short-range missile sled configuration is shown during test run. Test vehicle consists of one payload sled with Terrier Mk. 12 solid propellant rocket motors with two Recruit motors mounted on top.
LASRM ramjet propulsion test vehicle was assembled at Holloman AFB prior to first rocket-powered run conducted by the 6585th Test Group of USAF's Aero Propulsion Laboratory. Note three of four aft-mou nted inlet projections.
Rocket-Sled Tests Fill Ramjet Data Gap By Michael L. Yaffee
Wright-Patterson AFB, Ohio—Rocketsled test series for the ramjet propulsion system of the USAF/Marquardt low-altitude. short-range missile (LASRM) indicates the feasibility of using this type test to fill in the gap between ground and flight tests of ramjets. Data from the last two of the seven test runs, carried out by the 6585th Test Group at Holloman AFB, N. M., are still being analyzed by Ramjet and Laser Aerodynamics Div. personnel of USAF’s Aero Propulsion Laboratory, but already are showing good correlation with earlier ground and flight test data on the LASRM (AW&ST May 8, 1967, p. 24).
The data also are providing valuable inputs to Navy’s low-volume ramjet program with LTV Aerospace. In the last test run on June 19 (AW&ST July 2, p. 9). the LASRM test sled was boosted to a top speed of Mach 2.52 at a 4-deg. angle of attack, achieved combustion and burned for 4 sec. above the nominal target speed of Mach 2.3 for which it was designed. This was with the full-scale (92—in.) forebody of the complete missile, which contained the aft-mounted inlets and ramjet burner. The integral rocket motor and nozzle designed into the original missile (AW&ST Dec. 12. 1966. p. 93) for the supersonic chemical propulsion for low-altitude, short-range missile (SCP/LASRM) technology program were of no value in the most current series of ramjet propulsion tests and so were eliminated. Fuel was Shelldyne H heavy hydrocarbon and the fuel tank was transferred to the sustainer sled.
Rockwell International Missile Systems Div. was the contractor for modification and integration of LASRM and its sustainer sled. University of New Mexico, third major contractor, provided the thrust balances for test runs. In earlier ground tests, LASRM had to be tested at zero angle of attack because there were no wind tunnel facilities that could handle the full scale unit at a 4-deg. angle of attack. In flight tests, the missile was tested at different angles of attack but couldn’t be recovered. The rocket sled tests achieved both of these objectives.
Originally, the Aero Propulsion Laboratory planned to have four cold flow runs and two tests with the ramjet burner operating. In addition to gathering cold flow inlet engine data, the first tests were designed to find out if the sled could reach desired velocities and if the loads encountered were within design limits.
Test run No. 5 failed to achieve ignition and a seventh run was added to the ramjet sled test program. There also is a possibility that an eighth test will be added to the program, according to APL project engineer Lt. Jerry L. Ross. The personnel. equipment and facility are still available should a sound reason arise. The first sled test was run at Holloman test track on Aug. 4. It used a shortened
forebody (67 in.) for greater stiffness to test the loads. It ran on a single (sustainer) sled powered by a Terrier Mk. 12 Mod. 1 solid propellant rocket motor. Velocity objective was 1,500 fps. and the sled reached a maximum speed of 1,760 fps. (about Mach 1.5). A brief rundown on the other sled tests shows:
I Second test ran on Sept. 20 with a full-scale forebody. Again the sustainer sled was powered by a Mk. 12 Mod. 1 solid propellant rocket. A pusher sled with two Terrier Mk. 7 solid propellant rocket motors was used to push the speed to 2.000 fps. Nominal objective was 2,100 fps.
I Third test run Oct. 26. It used two pusher sleds each carrying four Terrier Mk. 7 motors in an all-out attempt to reach 2.700 fps. (Mach 2.4 to Mach 2.5, depending on type of day). This sled train (each stage drops off after motor burnout leaving only the sustainer stage with LASRM forebody and burner) reached a velocity of 2,445 fps. (about Mach 2.2), which was not sufficient for starting the, inlets, which were designed to start at Mach 2.3.
I Fourth test ran Jan. 17. For this test, two solid propellant Recruit rocket motors were mounted on top of the Mk. 12 sustainer sled motor. With these 11 rocket motors, LASRM reached a velocity of 2,820 fps. against a predicted 2,825 fps. It was still a cold flow test but inlets were started and the ramjet ran for 3.6 sec. at speeds above Mach 2.3. APL ramjet engineers said that in addition to inlet start, they got a good set of cold flow data on the ramjet engine; the braking system worked fine; loads were within design limits, and the test time and velocities were right.
All LASRM forebodies were full-scale after the first run.
Total Thrust
Total thrust generated by the 11 solid propellant rocket motors during a test run is 530,000 lb. The total of eight Terrier Mk. 7 rockets on the two pusher sleds produced 400,000 lb. thrust (50,000 lb. each) for 3.5 sec. The Terrier Mk. 12 sustainer on the payload sled burned for approximately 4 sec. and generated 70,000 lb. thrust, and the two Recruit motors produced 60,000 lb. thrust total for the 1.6 sec. they burned.
I Fifth test, which ran Feb. 15, was supposed to be the first hot test but ignition was not achieved. The squib valve that was to release triethyl borane ignition fluid failed. Test vehicle configuration was the same as in the previous test and the sled reached the required velocities above Mach 2.3.
I Sixth run, on Apr. 6, achieved ignition and the ramjet combustor operated stably for approximately 3.5 see. above Mach 2.3. In this test, LASRM ran at zero angle of attack using the same configuration of two pusher sleds and 11 solid propellant rocket motors as in the previous two runs.
Some of the data from this run and the last sled test on June 19 remain to be analyzed. So far the data look as though they will correlate well with data from earlier ground test and flight test programs, according to William G. Beecroft, deputy director of the Ramjet and Laser Aerodynamics Div.
Mission Envelope
The original SCP/LASRM ramjet engine was designed to cruise at a 1-deg. angle of attack over a very small mission envelope.
Inlets available today are much superior to those on LASRM and would enable new ramjet or rocket/ramjet-powered missiles to operate over a much broader mission envelope and angle of attack range, according to Aero Propulsion Laboratory researchers.
Low-Altitude Supersonic Missile
Marquardt low-altitude supersonic missile (LASV), shown mounted beneath the wing of a North American F-100, is undergoing flight tests at White Sands Missile Range, N.M., for the Air Force Aeronautical Systems Div. The weapon is also called low-altitude short-range missile (LASRM). Its two-phase propulsion system comprises a ramjet engine for highspeed flight and a Thiokol solid-propellant rocket mounted in the ramjet nozzle. On firing, the rocket boosts the missile to ramjet operating speed. Ignition of the ramjet blows rocket from the nozzle. Before ignition of the ramjet, covers on the air inlets, forward of the fins, are ejected. The missile has been flown five times in the Marquardt development program. The sixth and final flight in the current program is scheduled for the latter portion of the month.
Rocket-Ramjet
Los Angeles—Marquardt Corp. is developing a rocket-ramjet combination in a low-altitude short-range missile (LASRM) technology program under an
$11-million contract from USAF's Aeronautical Systems Div. North American Aviation’s Columbus Div., as subcontractor to Marquardt, will develop the flight test vehicle, which would represent the missile body configuration, and Aerojet-General Corp. will develop the solid—propellant rocket which would boost the ramjet to supersonic operating speed.
The rocket-ramjet combination probably will be arranged in tandem, with the rocket aft for ejection when the ramjet begins to function for sustained supersonic flight. First flight of the system is scheduled for spring, 1966, at Holloman AFB and the program is expected to extend over a two—year period. Test mode will be to drop the flight test vehicle from an aircraft for a low—level flight trajectory, which would be employed as an operational technique for approach below hostile radar scanners. Seven complete systems are planned for the test program, together with four additional systems for static test.
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LASRM ramjet propulsion test vehicle was assembled at Holloman AFB prior to first rocket-powered run conducted by the 6585th Test Group of USAF's Aero Propulsion Laboratory. Note three of four aft-mou nted inlet projections.
