NASA engine designations

Was there any rhyme or reason to the early NASA engine designation system? I've looked pretty extensively at the available historical material from the late 1950s and can't seem to find a rationale for the designations.

Known designations:


E-1

450K RP-1 gas generator, used on early Saturn concepts


F-1/F-1A

1.5M/1.8M RP-1, used on S-IC and numerous Saturn/Post-Saturn/Nova concepts


H-1

205K RP-1 gas generator, used on Saturn I/IB


HG-3

300-700K LH2 high-pressure staged combustion, proposed as J-2 replacement for upgraded Saturns; SSME precursor


J-2/J-2S

200/250K LH2 gas generator, used on S-II, S-IVB, early MSFC STS "Mark I orbiter", and many upper stage proposals


J-2T

250K LH2 gas generator, toroidal aerospike based on J-2S turbomachinery, proposed as J-2 replacement for upgraded Saturns


J-2X

295K LH2 gas generator, under development for SLS


M-1

1.2M/1.5M LH2 gas generator, developed and proposed for follow-on Saturn upper stages and Post-Saturn/Nova concepts


MA-5

NASA designation for LR-89, 425K RP-1 two-chamber gas generator, used on Mercury-Atlas


X-1

RP-1 gas generator, experimental precursor to E-1 and F-1

I am not aware of NASA using any designation system, ie for aircraft or engines.
I would therefore be inclined to see the 'designations' you refer to as assigned by the manufacturer, eg the Rocketdyne H and Rocketdyne J. Whether Rocketdyne used some designation system is another matter and depends what you call a 'designation system'. In my opinion two or three types of anything (aircraft or engine or other equipment) in a sequential order, does not constitute a designation system but is simply an 'identifier', especially when there are other identifiers which are clearly different - but then other readers might disagree with me.

I understand your point, Jos, and I would agree that a system has to be, well, systematically applied to be useful.

I don't know if it was a Rocketdyne thing or it just looks that way because the majority of boost engines NASA procured were Rocketdyne products. For example, I just came across a reference on NTRS to an "A-3" engine which turns out to be the RL-10 variant on the S-IV (a Pratt & Whitney product).

Thinking of the history of these programs, e.g., the ARPA involvement and the Silverstein committee, I wouldn't be surprised if there was a simple arbitrary letter designation in some report that was applied to all known programs of the era, and the names became commonly used.

GeorgeA said:

I understand your point, Jos, and I would agree that a system has to be, well, systematically applied to be useful.

I don't know if it was a Rocketdyne thing or it just looks that way because the majority of boost engines NASA procured were Rocketdyne products. For example, I just came across a reference on NTRS to an "A-3" engine which turns out to be the RL-10 variant on the S-IV (a Pratt & Whitney product).

Thinking of the history of these programs, e.g., the ARPA involvement and the Silverstein committee, I wouldn't be surprised if there was a simple arbitrary letter designation in some report that was applied to all known programs of the era, and the names became commonly used.

Click to expand...

No, there is no over arching nomenclature using simple arbitrary letter designation

I t was a Rocketdyne thing. Read Rocketdyne: Powering Humans into Space.

Ed Monteath came up with the Rocketdyne system.

As for the A-3, that was just shorthand for RL-10A-3. RL-10 had many variations from Astronautix.
RL-10A-1.

• Pratt and Whitney lox/lh2 rocket engine. 66.7 kN. Isp=425s. Version used on Atlas Centaur LV-3C, and proposed for various early Saturn launch vehicle designs. First flight 1961.
  

RL-10A-3.

• Pratt and Whitney lox/lh2 rocket engine. 65.6 kN. Study 1968. Isp=444s. First flight 1967.
  

RL-10A-3A.

• Pratt and Whitney lox/lh2 rocket engine. 73.4 kN. Isp=444s. Used on Centaur stage atop Atlas G, Atlas I, Atlas II, Titan 4. First flight 1984.
  

RL-10A-4.

• Pratt and Whitney lox/lh2 rocket engine. 92.5 kN. Out of production. Isp=449s. Centaur stage for Atlas IIA, Atlas IIAS. First flight 1992.
  

RL-10A-4-1.

• Pratt and Whitney lox/lh2 rocket engine. 99.1 kN. Out of production. Isp=451s. Used on Atlas IIIA launch vehicle. First flight 2000. Version with one of engines removed; remaining engine re-positioned to center-mount; new electro-mechanical gimbals.
  

RL-10A-4-2.

• Pratt and Whitney lox/lh2 rocket engine. 99.1 kN. In production. Isp=451s. Used on Atlas IIIB launch vehicle. First flight 2002. Two engines; electro-mechanical thrust vector control actuators replaced earlier hydraulically actuated system.
  

RL-10A-5.

• Pratt and Whitney lox/lh2 rocket engine. 64.7 kN. Isp=373s. Throttleable to 30% of thrust, sea level version of RL10. Four engines were built and were used on the DC-X and the upgraded DC-XA VTOVL SSTO launch vehicle demonstrators. First flight 1993.
  

RL-10A-5KA.

• Pratt and Whitney lox/lh2 rocket engine. 100.488 kN. Kistler proposal. Design 1992. Isp=398s. Throttleable to 30% of thrust, sea level version of RL10 with extendable nozzle for high altitude operation.
  

RL-10B-2.

• Pratt and Whitney lox/lh2 rocket engine. 110 kN. In production. Isp=462s. Used on Delta 3 , Delta IV launch vehicles. First flight 1998. Extendable exit cone for increased specific impulse; electromechanical actuators replace hydraulic systems.
  

RL-10B-X.

• Pratt and Whitney lox/lh2 rocket engine. 93.4 kN. Design concept 1994. Isp=470s.
  

RL-10C.

• Pratt and Whitney lox/lh2 rocket engine. 155.7 kN. In Production. Used in Delta 3 - 2. Isp=450s. First flight 1998.
  

RL-10C-X.
Pratt and Whitney lox/lh2 rocket engine. 110.8 kN. Design concept 1994. Isp=450s.