RD-160/161 Q & A

• RD-160/161 Q & A by Hyperion5 on 20 Dec, 2012 21:11
• Strangequark and I recently were recently flummoxed when someone suggested a truly unique set of small upper stage engines for use on a rocket.  The suggestion was that the RD-160 metholox engine would make a great third stage engine, as would its kerolox cousin, the RD-161.  As it happened even a propulsion engineer like Strangequark thought these engines were weird and we can't find many sources on either.  Here's why they looked weird; look at the chamber pressure, thrust and combustion cycle listed on the RD-161:
  
  http://www.astronautix.com/engines/rd1611.htm
  
  RD-161-1
  Glushko Lox/Kerosene rocket engine. 19.6 kN. Development ended 2000. Proposed for use on Soyuz M-3. Basic version. Engine Cycle: closed gas generator. Feed Method: turbopump. Isp=360s.
  
  Engine: 119 kg (262 lb). Chamber Pressure: 117.70 bar. Area Ratio: 351.6. Thrust to Weight Ratio: 16.8. Oxidizer to Fuel Ratio: 2.6.
  
  Status: Development ended 2000.
  Unfuelled mass: 119 kg (262 lb).
  Height: 1.70 m (5.50 ft).
  Diameter: 0.78 m (2.55 ft).
  Thrust: 19.60 kN (4,406 lbf).
  Specific impulse: 360 s.
  Burn time: 900 s.
  
  http://www.astronautix.com/engines/rd160.htm
  
  RD-160
  Glushko Lox/LCH4 rocket engine. 19.6 kN. Upper stage. Developed 1993-1996. Isp=380s. Methane version of lox / kerosene upper stage engine RD-161. Gimbaling +/- 6 degree in two planes.
  
  Engine: 129 kg (284 lb). Chamber Pressure: 118.00 bar. Area Ratio: 352. Thrust to Weight Ratio: 15.5. Oxidizer to Fuel Ratio: 3.69.
  
  Status: Developed 1993-.
  Unfuelled mass: 129 kg (284 lb).
  Height: 1.70 m (5.50 ft).
  Diameter: 0.76 m (2.51 ft).
  Thrust: 19.60 kN (4,406 lbf).
  Specific impulse: 381 s.
  Burn time: 900 s.
  First Launch: 1993-.
  
  
  That brings me to a list of questions.  Resident rocket engineers are strongly encouraged to answer questions number one and four. 
  
  1) Why would anyone add a staged combustion cycle and turbopump setup to engines this small? 
  
  2) Was the RD-160 metholox engine ever built? 
  
  --I've seen it come up several times in various forum posts on this site but I cannot find a source or picture confirming it ever fired. 
  
  3) Has the RD-161 ever been flight-tested, and if so, when and on what rocket? 
  
  4) Could an RD-160 actually achieve the Isp listed?  Alternatively, if the RD-160 exists, has it achieved that performance? 
• #1 by kevin-rf on 21 Dec, 2012 13:30
• An observation from a non rocket engineer on number one. Pressure fed engines require higher tank pressures, hence heavier tanks. Might the be a method to reduce the dry mass (couple that with the improved ISP...).
  
  But that is just an observation.