Atlas Centaur AC-3 Press Kit

8/8/2019 Atlas Centaur AC-3 Press Kit

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*LINATIONAL AERONAUTICS AND SPACE ADMINISTRATION TELS WO 2-4155 4N E W S WASHINGTON, D.C. 20546 WO 3-6925

FOR RELEASE. A.M. 's MondayJune 22, 1964 4RELEASE NO: 64-143

NASA SCHEDULES THIRD CENTAUR FLIGHT

The third hydrogen-powered Centaur launch vehicle will betest flown from Cape Kennedy, Fla., no earlier than June 25 bythe National Aeronautics and Space Administration.

The Atlas-Centaur mission, designated AC-3, is one of eightplanned engineering development missions to qualify Centaur as amedium weight launch vehicle for NASA lunar and planetary explora-tion programs.

When operational, Centaur's primary mission will be to soft-land the Surveyor spacecraft on the Moon to make surface studiesin support of later manned landings. Surveyor missions arescheduled to begin in 1965. Centaur also is being considered forMariner missions to Venus and Mars.

Centaur (AC-2), launched from Cape Kennedy, Nov. 27, 1963,was the first rocket to fly with a hydrogen-oxygen propulsion sys-tem. The second stage of AC-2 was placed in an Earth orbit withan apogee of 1100 miles and a perigee of 295 miles. The AC-2mission successfully accomplished all flight objectives.

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AC-3 has similar flight objectives except that secondstage insulation panels and a Surveyor-type nose fairing willbe jettisoned after Centaur passes through the Earth's atmos-phere. In addition, after a six-minute burn of the Centaurengines and a coast period, the RL-10 engine boost pumps will berestarted to determine that propellants are sufficiently "bottomed"in their tanks so that the engines could be ignited again. Therestarting of the engines is not planned, however, until AC-4.

On AC-3, the single burn of the Centaur engines will insertthe empty second stage -- weighing about 8200 pounds -- into anelliptical orbit with an apogee of 3600 miles and a perigee of 340miles. The apogee will be higher than that of AC-2 because thejettisoning of the insulation panels and nose fairing greatlyreduces the weight of the Centaur stage by the time the RL-10engines ignite. Achievement of orbit, however, is not an objectiveof the AC-3 flight.

This third test flight originally was scheduled in April. Itwas postponed for redesign of the insulation panels and furthertesting of how they are Jettisoned after Centaur has climbed abovethe atmosphere.

In early tests, it was round that air between the panels andthe tanks, containing the liquid hydrogen fuel at -423 degrees F.,froze solid causing the panels to stick. A system using

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helium gas to purge air from between the panels and tank wallwas modified and successful panel jettison tests were completedat Point Loma, Calif., before the AC-3 flight was rescheduled.

Centaur is a program of the Launch Vehicle and PropulsionPrograms Division of NASA's Office of Space Science and Applications.It is being developed by General Dynamics/Astronautics (GD/A),San Diego, Calif., under technical direction of the NASA LewisResearch Center, Cleveland, Ohio. Pratt and Whitney AircraftDivision of United Aircraft Corp., West Palm Beach, Fla., isassociate prime contractor for the RL-10 hydrogen engine undertechnical direction of the NASA Marshall Space Flight Center,Huntsville, Ala. More than 300 other contractors throughout thecountry are participating in the program.

Centaur launches are conductea by GD/A under the directionof Goddard Space Flight C nter's Launch Operations Branch for theLewis Research Center.

BACKGROUNDTHIRD TEST FLIGHT OF ATLAS-CENTAUR (AC-3)

The third test flight of the hydrogen-powered Atlas-Centaurlaunch vehicle is scheduled at Cape Kenredy, Fla., no earlierthan June 25.

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This section contains additional information on the missionobjectives, vehicle description, flight sequence, instrumentation,tracking aad program participants.

MISSION OBJECTIVES

Primary test objectives of the AC-3 mission are:1. Demonstrate the ability oP the Centaur nose fairing and insula-

tion panez i to withstand loads encountered during flight throughthe atmosphere and to jettison properly.

2. Verify the structural integrity of the Atlas and Centaur stagesduring all phases of flight.

3. Demonstrate the satisfactory operation of the Atlas-Centavrseparation system.

4. Demonstrate the ability of the Centaur propulsion system tostart in the flight environment and burn for full duration.

5. Demonstrate system integrity and obtain data on the measuringaccuracy of the guidance system.

6. Obtain data on the launch-on-schedule capability of the Atlas-Centaur vehicle from Lau.ch Complex 36A.

Although the Centaur stage will be placed into Earth orbit,this is not a mission objective. The purpose of flight-testingthe vehicle is to obtain additional data, to verify ground test

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results, to demonstrate and verify information that cannotbe obtained through ground testing and to obtain other datanecessary for vehicle and subsystem performance evaluation.

AC-3 also will serve as a test bed to assist in determiningfinal operational design.

In addition to primary test objectives, areas of specialinterest on the AC-3 mission include obtaining data on the abilityof the RL-10 boost pumps to re-start in flight; on environmentssuch as pressures, temperatures and vibration levels; and obtainperformance data on all Atlas-Centaur systems.

VEHICLE DESCRIPTION

AC-3 consists of a modified Series D Atlas (SLV-3C) boostercombined with a high-energy Centaur second stage. Both stagesare 10 feet in diameter and are connected by an interstageadapte-. Both the Atlas and Centavr stages maintain their siapethrough pressurization.

AC-3, including its Surveyor-type nose fairing, standsapproximately 112 feet high. Its weight at liftoff is about 300,000pounds.

The Atlas first stage, 66 feet high including the interstageadapter, uses a standard MA-5 propulsion system consisting of twobooster engines and one sustainer engine powered by liquid oxygen

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-6-and RP-1. The engines, which develop more than 360,000 poundsof thrust, are produced by Rocketdyne Division of North AmericanAviation, Inc., Canoga Park, Calif. Two small vernier enginesprovide roll directional control.

The Centaur second stage, including the nose fairing, is46 feet long. It is powered by two RL-'.0 hydrogen-fueled enginesdeveloping a total of 30,000 pounds of thrust at altitude.

The RL-10 which has performed flawlessly on three NASAengineering development flights, has accumulated more than 190hours of ground static firing time in some 5,000 tests.

The engine is capable of being shutdown and restarted duringflight.

The AC-3 flight vehicle will carry jettisonable insulationpanels and a Surveyor-type nose fairing. The insulation panels,fabricated by the Fort Worth Division of General Dynamics, coverthe second stage liquid hydrogen tank from the nose f iring to theinterstagr; adapter.

Liquid hydrogen must be kept at a cryogenic temperature of423 degrees below zero F. or it will vaporize. The insulationpanels surround the Centaur stage during powered flight through

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the Earth's atmosphere to prevent the heat of air friction fromcausing undue liquid hydrogen boil-off. They also preventair around the hydrogen tank from freezing solid, weighing downthe vehicle and holding the insulation panels on after they areneeded.

The four panels, which weigh a total of over 700 pounds, con-sist of a Fiberglas honeycomb, foam-filled sandwich construction.About three minutes after lift-off, when the vehicle is at analtitude of about 80 miles, the panels are separated from eachother and from Centaur by flexible linear-shaped charges. Jettisonhinges rotate the panels away from the flight vehicle. The separationsystem consists of pyrotechnic V-shaped charges, which cut struc-tural angles bolted to each panel.

Because of the weight penalty imposed by the insulationpanels and to improve the reliability of the vehicle, the LewisResearch Center is studying and testing various lightweight, non-Jettisonable insulation systems, including non-rigid, filament-wound foam systems. Other systems under study would be fabricatedof ablative or sublimative materials.

Small hydrogen peroxide rockets mounted on the second stageprovide additional thrust for propellant ullage control -- to'bottom" the propellants before ignition -- as well as attitudecontrol during coast periods.

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The Centaur vehicle is controlled in flight by an all-inertialguidance system consisting basically of a four-gimbal, three gyroinertial platform and a general purpose digital computer. Duringthe AC-3 mission, the vehicle will be flown "open loop," exceptfor use of the inertial platform for attitude reference duringCentaur (second stage) powered flight.

All main flight events, such as Atlas engine shutdown, separa-tion, starting and shutdown of Centaur engines, will be controlledby preset timers.

Test conditions necessary for the AC-3 launch includeacceptable vehicle wind loads calculated from winds aloft and sur-face wind data. Also, to insure adequate photographic coverage,the launch and ascent must be in relatively clear sky and duringthose hours favorable for photo coverage -- roughly between 10 a.m.and 4 p.m. EDT.

FLIaHT SEQUENCEAt liftoff from Launch Complex 36A, the Atlas engines are

ignited, developing more than 360,000 pounds of thrust. Atlas-Centaur will rise vertically for the first 15 seconds and roll slowlyfrom the launcher heading of 105 degrees to the desired flight planeazimuth of 100.5 degrees, placing the vehicle over desired trackingstations.

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-9-At T plus 15 seconds, when AC-3 is about 900 feet above the

launcher, the vehicle will begin pitching over to the preset flighttrajectory.

About 150 seconds after launch, the two Atlas booster engineswill shut down and the booster section containing the two engineswill be jettisoned. At this point, AC-3 will be at an altitudeof 50 miles, 35 miles downrange, and traveling about 7,700 feetper second.

About 230 seconds after launch, the Atlas sustainer enginewill cut off. Two vernier engines will continue to provide finalvelocity and attitude trim until AC-3 is 138 miles downrange atan altitude of 130 miles. At that time the verniers shut down.

Immediately after the verniers stop, the interstage adapterwill be cut by a shaped explosive charge, freeing the Centaurstage from its Atlas booster. Eight solid propellant motors onAtlas will fire to slow the vehicle and prevent it from bumpingthe second stage. At the same time, four vernier motors onCentaur will fire to increase the rate of separation.

The Centaur verniers will continue to fire for a few secondsafter separation to settle propellants at the end of the tank.Also liquid hydrogen will flow through the Center propulsion systemto chill the boost pumps.

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Second stage ignition occurs about 245 seconds after launch.The RL-10 engines are programmed for one burn lasting 377 seconds.This burn of the RL-10's will inject the stage into an orbit atperigee altitude of 340 miles.

Following shutdown of the second stage engines, Centaur willcoast for about 400 seconds, stabilized by small attitude rockets.The four 50-pound thrust vernier motors will be restarted to settlepropellants nea? the rear of the tanks. The boost pumps will thenbe restarted for 30 seconds to determine if propellants would be ina satisfactory position to restart the pumps during weightlessflight.

Following the boost pump experiment, attitude control ofCentaur will be stopped and it will go into drifting flight in anelliptical Earth orbit with an apogee of 3600 miles and a perigeeof 340 miles. Its internal power supply will permit telemetrytransmission of environmental data for about eight hours.

After orbital injection, Centaur will cross Southern Africa,the Indian Ocean, Pacific Ocean (north of Australia and nearHawaii) and Central America. Its second orbit will begin overSouth America.

The orbital period will be about 155 minutes. In a nominalorbit, Centaur will remain in Earth orbit for 2,000 years.

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In orbit, the weight of Centaur will be about 8200 pounds,

INSTRUMENTATION

Although the AC-3 vehicle will not carry a scientific pay-load, it will be heavily instrumented. The telemetry systemwill radio data measurements from Centaur for about eight hoursafter launch.

Of the 540 measurements on the AC-3 vehicle, some 360 are onthe upper stage, sending information on engine performance,guidance system and autopilot operation, and structural behavior.

The remaining data measurements are )n the booster stage andrelate primarily to engine function and guidance systems, plusstandard vibration, bending and temperature measurements.

TRACKING

AC-3 will be carefully tracked during powered and orbitalportions of its flight to obtain performance information.

Initial powered fLight tracking down the Atlantic MissileRange will be accomplished by C-band radar and Azusa Mark II/Glotracsystems by stations at Cape Kennedy, Antigua, Grand Bahama, SanSalvador and Bermuda.

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These tracking data will be used to compare the actualvehicle podition and Velocity during powered flight with thetelemetered guidance system computed data.

Following injection into orbit, a C-band transponder attachedto the Centaur stage will be tracked until depletion of itsbattery power -- about two hours -- by radar tracking stationslocated at Ascension, South Africa, Australia, Hawaii andSouthern California. This network is coordinated by the NASAGoddard Space Flight Center using NASA and national range facilities.

Precision tracking data for a longer period will be suppliedby the Smithsonian Astrophysical Observatory's world-wide networkcf Baker-Nunn cameras.

Tracking data also will be used to accurately determine param-eters of orbital injection at the time of burnout which in turn willbe a measure of the vehicle's performance.

PROGRAM PARTICIPANTSNASA Headquarters

Dr. Homer E. Newell Associate Administrator forSpace Science and Applications.Vincent L. Johnson Director, Launch Vehicle andPropulsion Programs Division andActing Centaur Program Manager,

OSSA

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Lewis Research CenterDr. Abe Silverstein Director, Lewis Research Center.Bruce T. Lundin Associate Director for Develop-ment.David S. Gabriel Centaur Project Manager.

Goddard Space Flight CenterRobert Gray Chief, Goddard Space Flight CenterLaunch Operations.

ContractorsGrant L. Hansen Centaur Program Director and vice-president, General Dynamics/Astronautics.Gordon Titcomb RL-10 Project Manager, Pratt andWhitney Aircraft Division ofUnited Aircraft.

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LOW DRAG FAIRINGL TANKINSULATION PANELS (4) LOX TANK

P AND WENGINES (2)15 K NOMINAL THRUST EACH

LOX TANK tl|

FUEL TANK

NAA SUSTAINER ENGINE 51 K THRUST

"AA $uSTER ENGINES 52 16 5 K EACH

Atlas Centaur AC-3 Press Kit

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