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Hohmann, Bernhard

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Hohmann Bernhard Credit: NASA

Born: 1916-05-12. Died: 1984-05-11.

A glider pilot and engineer before the war, he joined the Luftwaffe and became a test pilot at Peenemuende, making 37 test flights of the Me-163 rocket fighter and its unpowered prototypes. He survived a crash landing which resulted in the partial destruction of the aircraft as its airframe was consumed by the acid rocket propellants. After the war he surrendered to the Americans, and by January 1947 was working at Wright Field, Ohio. He became the Chief of Flight Development Section at Wright Field, before leaving to work for Aerospace Corporation as a consultant for the space program in 1957. He worked on both Mercury and Gemini programs. He authored two publications along with noted scientist Joseph F. Wambolt.

• Birth of Bernhard Hohmann - . Nation: Germany. Related Persons: Hohmann, Bernhard. German test pilot. Chief of Flight Development at Wright FIeld, consultant on astronaut flight safety on Mercury, Gemini, and MOL programs..

• Three methods of Apollo descent from lunar parking orbit reviewed - . Nation: USA. Related Persons: Hohmann, Bernhard. Program: Apollo. Spacecraft: Apollo LM, LM Weight.

  North American, NASA, and Grumman representatives discussed three methods of descent from lunar parking orbit:

  1. descent of the LEM only (the minimum energy Hohmann transfer),
  2. the combined descent of both spacecraft, and
  3. the synchronous equal period method.
  While neither contractor felt that weight factors should be of primary concern, Grumman favored the Hohmann transfer and North American the combined descent, which represented the extremes of energy requirements. After considering reliability, fuel consumption, and operational flexibility, NASA chose the synchronous method as the prime mission mode but recommended continued investigation of the other two techniques.

• Apollo weight reduction suggestions - . Nation: USA. Related Persons: Hohmann, Bernhard. Program: Apollo. Spacecraft: Apollo CSM, LM Weight, LM Weight.

  An MSC Spacecraft Technology Division Working Group reexamined Apollo mission requirements and suggested a number of ways to reduce spacecraft weight: eliminate the free-return trajectory; design for slower return times; use the Hohmann descent technique, rather than the equal period orbit method, yet size the tanks for the equal period mode; eliminate the CSM/LEM dual rendezvous capability; reduce the orbital contingency time for the LEM (the period of time during which the LEM could remain in orbit before rendezvousing with the CSM); reduce the LEM lifetime.

• Velocity budgets for the Apollo spacecraft reduced - . Nation: USA. Related Persons: Hohmann, Bernhard, Shea. Program: Apollo. Spacecraft: Apollo LM, LM Ascent Propulsion, LM Descent Propulsion.

  ASPO Manager Joseph F. Shea asked NASA Headquarters to revise velocity budgets for the Apollo spacecraft. (Studies had indicated that those budgets could be reduced without degrading performance.) He proposed that the 10 percent safety margin applied to the original budget be eliminated in favor of specific allowances for each identifiable uncertainty and contingency; but, to provide for maneuvers which might be desired on later Apollo missions, the LEM's propellant tanks should be oversized.

  The ASPO Manager's proposal resulted from experience that had arisen because of unfortunate terminology used to designate the extra fuel. Originally the fuel budget for various phases of the mission had been analyzed and a 10 percent allowance had been made to cover - at that time, unspecified - contingencies, dispersions, and uncertainties. Mistakenly this fuel addition became known as a "10% reserve"! John P. Mayer and his men in the Mission Planning and Analysis Division worried because engineers at North American, Grumman, and NASA had "been freely 'eating' off the so-called 'reserve'" before studies had been completed to define what some of the contingencies might be and to apportion some fuel for that specific situation. Mayer wanted the item labeled a "10% uncertainty."

  Shea recommended also that the capacity of the LEM descent tanks be sufficient to achieve an equiperiod orbit, should this become desirable. However, the spacecraft should carry only enough propellant for a Hohmann transfer. This was believed adequate, because the ascent engine was available for abort maneuvers if the descent engine failed and because a low altitude pass over the landing site was no longer considered necessary. By restricting lunar landing sites to the area between ±5 degrees latitude and by limiting the lunar stay time to less than 48 hours, a one-half-degree, rather than two-degree, plane change was sufficient.

  In the meantime, Shea reported, his office was investigating how much weight could be saved by these propellant reductions.

• Attitude control of docked vehicles using the Apollo LEM's RCS - . Nation: USA. Related Persons: Hohmann, Bernhard. Program: Apollo. Spacecraft: Apollo LM, LM RCS.

  ASPO asked Grumman to study whether attitude control of the docked vehicles was practicable using the LEM's stabilization and control system (RCS). Grumman also was to evaluate the RCS fuel requirements for a five-minute alignment period to permit two star sightings. ASPO further directed the contractor to determine RCS fuel requirements for a second alignment of the LEM's inertial measurement unit during descent coast. This second alignment was needed for the required landing accuracy from a Hohmann descent.

• Gemini Agena target vehicle (GATV) engine modification and test program. - . Nation: USA. Related Persons: Hohmann, Bernhard. Spacecraft: Gemini Agena Target Vehicle.

  Lockheed presented its proposed Gemini Agena target vehicle (GATV) engine modification and test program to Colonel A. J. Gardner, Gemini Target Vehicle Program Director, Air Force Space Systems Division (SSD). The proposal was immediately turned over to a three-man team comprising B. A. Hohmann (Aerospace), Colonel J. B. Hudson (Deputy Commander for Launch Vehicles, SSD), and L. E. Root (Lockheed) for consideration. On November 18, the group decided on a final version of the proposal that called for: (1) modifying the Agena engine to provide oxidizer lead during the start sequence, (2) demonstrating sea-level engine flightworthiness in tests at Bell Aerosystems, and (3) conducting an altitude test program at Arnold Engineering Development Center. The final proposal was presented to the GATV Review Board at Manned Spacecraft Center on November 20.

• Death of Bernhard Hohmann - . Nation: Germany. Related Persons: Hohmann, Bernhard. German test pilot. Chief of Flight Development at Wright FIeld, consultant on astronaut flight safety on Mercury, Gemini, and MOL programs..