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KH-9B HEXAGON Reconnaissance Imaging Spacecraft

“Big Bird”

By © Charles P. Vick 2007 All Rights Reserved



The opinions and evaluations stated here in are only the author’s and cannot be construed to reflect those of any Government agency, company, institute or association. It is based on public information, circumstantial evidence, informed speculation, and declassified U.S. intelligence community documents, official US government documents and histories, oral histories, interviews and engineering analysis. As with all data regarding the intelligence programs of the US intelligence community, this analysis is subject to revision--and represents a work in progress.

KH-9B, HEXAGON “Big Bird” Spacecraft Details

The longer KH-9B Hexagon spacecraft weighed in at a fueled Mass of approximately 20,985 pounds fueled with an approximate dry mass of 13,606 pounds. I was still the same ten foot maximum diameter with an estimated length of 53.17 feet not including the manoeuvering nozzle which equals 55.17 feet. It still used the same four film return capsules and earth, solar and horizon sensors as well as the SSB service module based navigation system. The ingenious optical film system essentially remained the same. It carried it allotment of three or four ELINT, COMINT and SIGINT mission specific sub satellites.

KH-9B “SSB -Satellite Support Bus (p.5)

Table 1-1 Summary of SSB Characteristics and Capabilities

  • Diameter: 120-in.; adaptable to Space Shuttle cargo bay
  • Length: (including engine) 114-in.; (9.25 feet) Equipment Rack 38-in. Orbit Adjust/Reaction Control Section 38-in., Booster Adapter 17-in. (not required for Shuttle).
  • Weight: 3,606-lb. excluding propellants and gases
  • Equipment section is 38 inches long and has 12 equal size cargo bays capable of supporting 550-lb. with a total of 12 cubic feet.
  • Motor: Hydrazine monopropellant with quad-redundant propellant valves.
  • Thrust level: 145- to 230-lb.
  • Specific impulse: 230-see minimum.
  • Propellant load: 7300-lb hydrazine in a 76.0-in. inside diameter aluminum tank.
  • Pressurization: Internal blow down system with external re-pressurization; nitrogen pressurant.
  • Propellant Temperature range: 70 to 100 degrees F.
  • Passive propellant management device.
Altitude Reference System
  • Altitude determination accuracy for level flight at 100-300 nm using horizon sensor references: Higher altitudes require different Horizon Sensor look angle than presently used minor change.
  • 0.24 degrees Roll, 0.28 degrees Pitch, and 0.35degrees Yaw
  • Attitude control accuracy, with 0.12 degrees Dead-bands (0.13 in roll) is O.13 degrees in Roll) is 0.37 degrees roll. 0.40 degrees Pitch and 0.47degrees Yaw.

    less than 0.001 deg/per sec for disturbance-free limn cycles.
  • Typical settling time for small disturbances: 6 sec.
  • Attitude accuracy for non-level menial night is subject to gyro drift at rates up to 1.0 deg/hr.
Reaction Control System
  • Motors: 16 hydrazine engines in 4 modules.
  • Thrust level: 2.5-lb minimum.
  • Minimum impulse bit: 0.03- to .18-lb/sec to 1.0 cps.
  • Specific impulse: 119 sec at 0.01 cps to 203 sec minimum steady state.
  • Solar arrays: 172-sq-ft of active area in two deployable arms of 11 panels each. (Baseline arrays are not retractable.)
  • Batteries: Four 60-ampere-hour nickel-cadmium secondary batteries.
  • Arrangement: One-fourth of each array arm charges each battery.

  • Average power: 600 waits, of which SSB requires 270 watts, with 330 watts available for payload. Peak power 2 kilowatts.
  • Provides unregulated 28 v dc to main bus.
Tracking System
  • Compatible with SGLS capabilities and procedures.
  • Up-link in 1750 to 1850 MHz band, down-link in 2200 to 2300 MHz band.
  • Accuracies at 80 to 1440 nm: per SGLS specifications
Telemetry System
  • Uses a Stored program and remote sub-multiplexers for flexibility.
  • Each of tape recorders can store 45 minutes of 64 kbps data for later readout at 256 kbps.
  • Command selection of format and bit rate changes in flight.
  • Accommodates analog, discrete, and serial-digital input data.
Command System
  • Optional selection based on customer needs.
  • Capable of executing real-time and stored commands.
  • Digital data link capability.
  • 174-lbs weight allowed for the command system.

Table 1-2 Weight Summary (p.2)

Item Weight
Equipment Rack Assembly 547
Battery Modules (2) 502
Orbit Adjust System (Dry) 821
Reaction Control System (Dry) 725
Solar Array Module 317
Electrical Distribution and Power Module 103
Attitude Reference Module 216
Telemetry & Tracking Module 153
Command Module 174
Pyro Module 48
Total SSB Dry Weight 3,606
Consumables {Capacity)  
OAS/RCS Propellant 7.300
OAS/RCS Pressurizarion Gas (Nitrogen) 79
Total Weight 10,985

Ref. (SSB Satellite Support Bus, Lockheed Missile & Space Company. Space Systems Division)”

Page last modified: 08-08-2011 11:28:13 ZULU