Posts: 19 From: Washington, DC USA Registered: May 2005
posted 05-28-2013 03:46 PM
Could one of you aerospace engineers or physicists please explain to me the virtues of the "hot stage" technique that the Russians use on their liquid fuel rockets?
------------------ Cathleen S. Lewis
Robert Pearlman Editor
Posts: 27328 From: Houston, TX Registered: Nov 1999
posted 05-28-2013 03:55 PM
I'll let someone else chime in with more details but quoting from the "Handbook of Space Technology" (2009, John Wiley & Sons) edited by Wilfried Ley, Klaus Wittmann and Willi Hallmann:
A technical specialty is the "hot" stage separation. Differing from most other launchers, the stages are separated while in the thrust decay phase of the first stage, with the second-stage engine already running. Using this principle an additional pre-acceleration system is not needed for orienting the upper stage propellants at the tank outlet prior to engine ignition.
The U.S. Titan II, as was used to launch Gemini manned spacecraft, also employed hot stage separation.
Jim Behling Member
Posts: 537 From: Cape Canaveral, FL Registered: Mar 2010
posted 05-28-2013 05:40 PM
Also known as "fire in the hole" staging.
Acceleration isn't always required by the upper stage. Delta and Falcon use springs to push the upper stage away from the booster. The upper stage ignites after a short coast. Atlas employs retrorockets to pull the booster away. The upper stage thrusters are used to provide the little acceleration at engine start.