sign in sign up
<<
Home , Atlas (rocket family), Centaur (rocket stage), Convair, Liquid oxygen, Range safety, Rocketdyne

The Space Congress® Proceedings 1981 (18th) The Year of the Shuttle

Apr 1st, 8:00 AM

Centaur for the 1980's

John E. Niesley Advanced Systems Project Engineer, Advanced Programs, Division

Follow this and additional works at: https://commons.erau.edu/space-congress-proceedings

Scholarly Commons Citation Niesley, John E., "Centaur for the 1980's" (1981). The Space Congress® Proceedings. 4. https://commons.erau.edu/space-congress-proceedings/proceedings-1981-18th/session-6/4

This Event is brought to you for free and open access by the Conferences at Scholarly Commons. It has been accepted for inclusion in The Space Congress® Proceedings by an authorized administrator of Scholarly Commons. For more information, please contact [email protected]. CENTAUR FOR THE 1980s

JOHN E. NIESLEY

Advanced Systems Project Engineer Advanced Centaur Programs General Dynamics Convair Division ,

ABSTRACT Currently, Centaur is undergoing additional per­ Centaur is currently the world's only operational high- formance improvements for Intelsat, which will energy upper stage, and is the United States primary enhance its capabilities for the 1980s. NASA has also upper stage for launching probes, large recently decided to integrate Centaur with the Space geosynchronous communication satellites, and obser­ Shuttle for solar exploration missions, large future vatories to study the farthest limits of space. Centaur is geosynchronous commercial satellites, and potential currently launched on , but has also flown with Department of Defense (DoD) missions. These appli­ the larger booster. NASA recently decided to in­ cations will ensure continued use of Centaur through tegrate Centaur with the for future solar the remainder of the 1980s. system exploration missions. CENTAUR RECORD Current status of the Centaur program is discuss­ A little over ed including: vehicle characteristics, planned perfor­ two decades ago, Centaur was conceived as the mance improvements, and launch schedules. Modifica­ upper stage for United States' solar system ex­ ploration and geosynchronous tions required to integrate Centaur with Shuttle and communications sat­ the resulting capabilities are discussed. ellites. Today that dream has truly been fulfilled by the accomplishments of this vehicle. Centaur has launched INTRODUCTION 22 solar system exploration missions including Centaur development began in 1958 when General Voyager, , , Mariner, and Dynamics/Convair was awarded a contract to develop Pioneer. Its selection by NASA for launching the the first space vehicle to use fuel. and International Solar Polar missions from Because NASA's Lewis Research Center (LeRC) did Space Shuttle means continuation of this enviable much of the pioneering work in tech­ record. In addition, 24 geosynchronous communica­ nology, LeRC was later assigned technical manage­ tion satellites have been launched as well as 6 space ment of Centaur and contributed to the first successful observatories (Figure 1). Centaur has flown 55 times launch in 1963. This successful working relationship with Atlas and 7 times on Titan for a total of 62 flights continues today. After completing the development and is now ready for integration with the Space phase in 1966, the resulting operational vehicle, called Shuttle. Centaur D, was launched 21 times on Atlas. During the past fifteen years of operational In the early 1970s, Centaur electronics and guid­ flights, Centaur has established itself as a reliable up­ ance systems were completely modernized. A new per stage. 96% of all operational flights were suc­ high-speed digital computer was added that permits ex­ cessful, with 100% or 36 consecutive successes since tensive use of software to perform functions previously 1971. The Pratt and Whitney RL-10 engines have a requiring hardware, thus simplifying new mission perfect flight success record and the current Centaur adaptation. Computer controlled launch set (CCLS) D-l guidance and navigation system has also perform­ was added to provide rapid automatic checkout of the ed 100% successfully on all countdowns and launches Centaur and diagnostic capabilities for anomalies. as indicated in Figure 2. This new version of Centaur, designated D-l, was in­ tegrated with both the Atlas vehicle and the more ATLAS CHARACTERISTICS powerful Titan booster, and has flown 32 operational The Atlas vehicle that boosts Centaur is a stage-and-a- missions. half configuration in which all engines are ignited on

6-39 Missions • Solar system exploration (22) - Voyager, Viking, Helios - Mariner, Pioneer, Surveyor • Communications(25) - Intelsat, Fltsatcom, Comstar • Astronomy (6) - HEAO, OAO

Launch platforms • Atlas • Titan Figure 1. Centaur enabled the United States to achieve many dramatic firsts in space and provided a valuable capability for geosynchronous missions.

•••^•••••••••••••••••^^^^•^^••••••••••••[^•••i^BaBBBMMBHBBaBBHMI Vehicle operational successes • 96% overall • 100% since 1971 (36 consecutive successes)

P&W RL-10 engine • 100% successful flight record (66,000 sec in space) Guidance & Navigation — D-1 (Honeywell IRU & Teledyne DCU) • 100% flight & countdown success (33 missions with 450 operational hours) Figure 2. Centaur's success record proves its reliabilty as a high-energy upper stage. the ground and share common tanks. The control is accomplished by gimbaling the Atlas engines booster engines are jettisoned at approximately 140 during flight under direction of the Centaur guidance seconds into the flight when vehicle acceleration and navigation system. reaches 5.5 g. The sustainer engine continues to burn CENTAUR CHARACTERISTICS •until propellant depletion occurs about 110 seconds later. Two -small vernier engines burn throughout the Centaur is a high energy upper stage powered by two booster phase and provide all roll control during the Pratt & Whitney RL-10 engines developing 33,000 Ib sustainer phase* All engines use liquid (L(>2) total vacuum thrust at a rated Isp of 446 seconds (see and RP-1 fuel,, which is similar to kerosene. Vehicle Figure 4). The stage burns 30,000 Ib of liquid hydrogen characteristics are shown in Figure 3. (LH2) and (LC>2) . Tanks are The Atlas vehicle is 10 ft in diameter and approx­ made of thin-walled type 301 stainless steel welded imately 70 ft in length, not including the interstage construction that is pressure stabilized. They are adapter. Tanks are made of thin-walled stainless steel separated by a double-wall vacuum-insulated inter­ bands which are welded together and pressure stabi­ mediate common bulkhead and pressurized with ­ lized for structural strength, A helium pressurization eous helium. Until now, tank-mounted boost pumps inlet , system maintains tank pressure for structural integrity have been used to provide the required engine and pressure head during flight. Vehicle pressures. The boost pumps are driven by turbines

640 Liquid oxygen tank

Intermediate bulkhead Oxidizer boiloff valve RP-1 tank

^S&&3s^^ Length: 70 ft Vernier ^^vvj^ engine (2) x Diameter: 10 ft Jett wt: Sustainer •Avionics Booster 7,916 Ib engine equipment Sustainer 8,035 Ib Propellants: 286,000 Ib Propulsion; MA-5 Booster k Booster section Rated thrust (SL); Booster 370,000 ib engine (2f Sustainer 60,000 Ib 01100698-8 Vernier 2,000 Ib Figure 3. The Atlas booster vehicle is a state-and-a-half configuration with a sustainer engine that continues to burn 90 seconds after the initial booster engines are jettisoned.

Avionics equipment module

Stub Radiation adapter shield or Length: 30 ft insulation Diameter: 10 ft panels - LH2 tank Dry weight: 3,850 Ib Guidance: Inertia! Propulsion: P&W RL-1OA-3-3 Intermediate Rated Thrust: 16,500 Ib per engine bulkhead Rated Isp (vac): 446 sec Propellants: LO.2/LH2; 30,750 Ib LO2 Aft bulkhead

Thrust barrel

RL-1 0 engines 02030698-9A

Figure 4. Centaur characteristics. powered by hydrogen peroxide, the same monopropel- engine bleed for LH2 tank pressurization during iant used in the reaction control system. Beginning engine operation, and monopropellant for with vehicle AC-62, minor tank and engine changes the reaction control system., have allowed the elimination of boost pumps. Reduced The Centaur integrated, astrionics system is - illus­ cost and improved reliability and performance will trated in Figure 5. The heart of this system is the Tele- result. Associated changes are gaseous hydrogen dyne Digital Computer Unit (DCU) which has 16,000

6-41 C-BAND AND

ABBREVIATIONS Digital Computer Unit PAYLOAD/VEHICLE" Inertial Reference Unit SEQUENCING System Electronics Unit Sequence Control Unit Servo Inverter Unit Remote Multiplex Units Propellant Utilization Computer Controlled Launch Set Control Unit Pyrotechnic ATLAS Computer Controlled Vent and Pressurization System INTERFACES

AFT SIGNAL CONDITIONER

INSTRUMENTATION SIGNALS 25031215-3 Figure 5. Centaur astrionics system. words of memory, fast execution speed, and extensive apogee kick motor changes. These included an engine input-output capabilities allowing it to perform many thrust increase (1,500 Ib/eng), a zero-gravity parking functions that previously required separate hardware. coast, earlier nose fairing jettison, and weight im­ A Honeywell Inertial Reference Unit (IRU) con­ provements. Additional changes are being incor­ taining four-gimbals, three reference gyros, and three porated to the Atlas/Centaur for the first Intelsat VA pulse-balanced accelerometers provides the required launch. These changes include adding a silver throat to navigation data for the DCU. The DCU generates out­ the Centaur engine ( + 2.4 sec Isp), deleting the boost put commands to provide vehicle stability and guid­ pumps, and using hydrazine for reaction control. The ance steering that are routed through the servo inverter resulting capability for synchronous transfer is shown unit (SIU) during powered flight and through the se­ in Figure 6, and indicates a payload system weight quence control unit (SCU) during coast phase. Centaur capability of 4,900 Ib for a near optimum transfer. flight software is modularized into several special- Recently, the Intelsat Board approved an 80-inch Atlas purpose subroutines that are operated in real time by stretch for the 1984 launches that will increase the an executive program. This allows the DCU to provide Atlas/Centaur peformance capability to 5,300 Ib. total vehicle command and control including: tank pressurization and vent management, dynamic stabili­ Additional performance growth could be avail­ ty, sequencing, propellant consumption management, as shown in Figure 7, by adding four IV telemetry formatting, and pre-flight testing, as well as solid propellant motors and igniting two on the ground guidance and navigation functions. and two at altitude after the first two burnout. These are the same motors currently used with and PERFORMANCE IMPROVEMENTS would result in a synchronous transfer capability for A number of performance improvements have been in­ launching two full size Delta class 2,800 Ib spacecraft corporated into Atlas/Centaur in order to meet in­ on a single Atlas/Centaur using a Centaur tandem creasing Intelsat V requirements without spacecraft adapter (CTA) as indicated in Figure 8.

6-42 5,500 2,500

1 984 capability (80 in. Atlas stretch)

5,000

Payload system (Kg) weight capability (Ib) 1983 capability (Intelsat improvements) 4,500 50 Ib propellant contingency 2,000 225 Ib propellant flight performance reserve 90 nmi perigee Not constrained by 4,000 ascension tracker elevation

16 18 20 22 24 26 28 30 Transfer orbit inclination (deg) 250310698-1 1B Figure 6. Atlas/Centaur synchronous transfer performance.

f.,: .1

Current Stretched Strap-on (baseline) Atlas (80 in.) solids (4)

Performance • Ib (kg) 4,900 (2,220) 5,300 (2,400) 6,400 (2,900) 250310698-19B Figure 7. Atlas/Centaur can provide additional performance growth.

6-43 Centaur tandem adapter (CTA) Hinge fittings (2) Payload sep planed Retract spring (2) Payload envelope (2) places

Existing nose fairing Boron-aluminum struts Separation fitting (10)

Weight (Ib) Spacecraft A 2,800 Spacecraft B 2,800 Centaur tandem adapter 560 Mission peculiar adapter 65 Total 6,225 Capability — strap on solids 6,400

Figure 8. Dual spacecraft can be flown with Atlas/Centaur capability. 25031 0698-25A

LAUNCH SCHEDULE and replacing these vehicles with additional Atlas/Cen­ The current firm Atlas/Centaur launches are shown in taurs for launch in 1984. Figure 9. Three Intelsat V launches, one COMSTAR SHUTTLE/CENTAUR and one Fleetsatcom launch are scheduled in 1981. General Dynamics Convair Division, under a number COMSTAR 4 was successfully launched on 21 of separate contracts and company funded activities, February 1981 with the second Intelsat V as the next has been studying the integration of the Centaur stage scheduled launch in May. into the Space Shuttle since 1971. This activity culmi­ Currently, Intelsat is considering accelerating the nated with a 1979 Centaur-in-Shuttle integration study production schedule for the three Intelsat V-A vehicles which defined in detail the modifications to Centaur in order to be able to launch them starting in mid-1983, required for interface compatibility and mission safety.

TFirm Calendar Year V Potential 1980 1981 1982 1983 1984 1985

Fttsatcom 1 . Comstar Complex 36 A / /rsatcom

Complex 36B Intelsat V Intelsat VA ...... ,-,.,„. Intolo at v r r? r7r- ^ -»r ?r7r-> Sj V V Y v/ V V \/ T 1 V v v V V V Figure 9. Atlas/Centaur launches are planned through the mid 1980s. 250310698-13A

6-44 Shuttle modifications were defined by Rockwell Inter­ Safety considerations required additional redun­ national under the direction of NASA-Johnson Space dant valves and tank pressure transducers for pro­ Center (JSC). The ability to safely integrate Centaur- pellant control, a new propellant dump system, recon­ in-Shuttle was determined by JSC and Kennedy Space figuring of the helium purge system, and a new radio Flight (KSC) center personnel during Phase 1 safety command link to inhibit engine firing after separation reviews. All of these activities concluded that Centaur from the orbiter should a problem arise. These is ready for Space Shuttle integration (Figure 10). modifications still leave 95% of Centaur stage com­ During the last two months of 1980, NASA con­ ponents unchanged. stages to ducted a concentrated study of Shuttle upper WIDE BODY CENTAUR perform the Galileo and International Solar Polar studies were based on us­ (ISPM) missions. The conclusion of that analysis was The 1979 Centaur-in-Shuttle stage, which is 30 ft in length the FY 1981 and 1982 budgeted resources would allow ing the current Centaur and integrating it directly into NASA to begin modification of Centaur for integra­ and 10 ft in diameter, requirements for the 1985 tion with the Shuttle so this powerful combination the Shuttle. Performance dictated a significant in­ would be available for first launch in 1985. Shuttle/ Galileo and ISPM missions that would be required to Centaur would satisfy the NASA planetary mission re­ crease in propellant weight Since stretching the current quirements and also be available for future commercial accomplish the missions. result in inefficient use of and national security missions. In January 1981, Dr. Centaur in length only would stretch the LH2 tank to Frosch made the decision to recommend to Congress the cargo bay, it was decided to thus utilizing the full orbiter and the administration that NASA pursue this course 170 inches in diameter, available for of action. bay available and increasing the length spacecraft as shown in Figure 11. The LC>2 tank CENTAUR MODIFICATIONS FOR SHUTTLE diameter was held constant while a 30-inch cylindrical The Centaur stage modifications required for Shuttle section was added. Centaur's propulsion system is un­ compatibility can be separated into two distinct areas: changed; however, the forward equipment module and (1) interface compatibility and mission requirements adapter diameter was increased to match the hydrogen and (2) safety considerations. For interface com­ tank diameter. patibility, the structural adapters must be modified; fill, drain, and vent systems are changed; a new LH2 PERFORMANCE CAPABILITIES tank insulation blanket is added; and zero-g vent Shuttle/Centaur performance capability significantly devices are required. Mission requirements dictate a expands NASA's capability to perform solar explora­ TDRS compatible transponder and may require a tion missions. Galileo can be launched in 1985 as a tracker for guidance update to meet mission accuracies combined orbiter/probe using either a modified Type I if a number of Shuttle are required prior to Cen­ trajectory (broken plane) or a Type II trajectory which taur deployment. arrives somewhat later. This is one of the most difficult

Centaur integrated support system • Centaur integration & modifications defined by General Dynamics & NASA LeRC

• Shuttle modifications defined by Rockwell & NASA JSC

• Safe integration determined by NASA & Kennedy Space Flight Center

25031 088-30B Figure 10. Centaur is ready for Shuttle integration.

6-45 Increased diameter forward Uses 15 ft diameter structure available in orbiter payload bay Increase LH2 Increases Centaur tank diameter propellant loading to 170 in. Increases length 30ft available for Add 30-in. 29.1 ft spacecraft LOp tank cylindrical Maintains LO2 tank section diameter & propulsion system unchanged

Current Shuttle 09021088-16A

//, The body Centaur is a minimum modification to the current Centaur,

for could not be accom- tion missions such as Orbiting Imaging Radar stage, even by launching (VOIR), Orbiter Probe, Uranus Orbiter Probe the (Figure 12). and Solar Probe will benefit from this improved can also be launched in capability. a for spacecraft and dur­ Shuttle/Centaur will have a geosynchronous ing the as Galileo; however, a capability of 14,000 Ib in orbit with the standard wide 4S is required. Future solar explora­ body configuration. This is nearly three times the pro- Solar system exploration Geosynchronous

25 r o

- VOIR Spacecraft 144 20 j - mass 2 - Shuttle/Centaur | (103 Ib) 0 Galileo 8 -

6 |_

4 i~

IUS 2 JUS + spin!/ """•—..." ~ 0 0 20 40 60 80 100 120 140 IUS1 Shuttle/ Shuttle/ Ca (KM2 per sec2 ) Centaur Centaur low thrust Figure 12, Centaur dramatically enhances Shuttle capability. 02031088-19B of ffcr on be lit m tow lie teii is m de to lib tn will the in be and lit, out in The iiliiit for iiii Q^ lib on tils to lib, THs of got . toln dhe •of the is far and the far it ft* are and the has iiii or safe by tor A this is Ib frith a erf iinn for -use lib for a tow will lit the tow be for this In v Iiii and

6-47