A proven 25-lbF H2/O2 thruster for Space Station auxiliary propulsion

A 25-lbF G02/GH2 t h r u s t e r f o r the Space S t a t i o n p ropu ls ion system has been designed, fabr i c a t e d and s u c c e s s f u l l y t e s t e d under a NASA Lewis Research Center (LeRC)-sponsored technology program. A n a l y t i c a l models have been developed t o p r e d i c t thermal and performance c h a r a c t e r i s t i c s o f the t h r u s t e r . Although o r i g i n a l l y designed t o operate over a m ix tu re r a t i o range o f 3.0 t o 5.0, t h e t h r u s t e r has been t e s t e d over the range from 2.2 t o 8.1. The t o t a l accumulated f i r i n g t ime and impulse t o date a re 22,198 seconds (6.166 hours) and 538,457 1bF-sec, r e s p e c t i v e l y , w i t h t h e longest steady s t a t e burn being 2200 seconds a t 7.5 m i x t u r e r a t i o . I n t r o d u c t i o n The Space S t a t i o n p ropu ls ion system prov ides f o r veh ic le reboost, a t t i t u d e c o n t r o l , and docking and avoidance maneuvers. Gaseous oxygen/hydrogen (GOp/GH2) has many advantages over a l t e r n a t i v e propel lants , i n c l u d i n g safety , c lean l iness , ease o f maintenance, wide temperature to lerance, and potent i a l l y f r e e p r o p e l l a n t through the e l e c t r o l y s i s o f waste water. A key technology of the G02/GH system has been miss ing -t h e t h r u s t e r s . To p u t { h i s technology i n place, NASA-LeRC has sponsored a program (NAS 3-24398) t o design, f a b r i c a t e , and t e s t a t h r u s t e r meeting t h e design requirements o f Table I. Table I. Thrus te r Design Requirements Propel 1 ants GO /GH Mixture Ratio, O/F 4.6 2 f .0 Spec i f i c Impulse 2400 1bF-sec/lbM Fuel I n l e t Temperature >ZOO "R Oxid izer I n l e t Temperature ~ 3 0 0 " E Tota l Impu 1 se 2 X 10 -1bF sec Based on system considerat ions, the t h r u s t e r has been designed t o operate a t a t h r u s t o f 25 l b F and a chamber pressure o f 75 ps ia. Several programs192*3 conducted by A e r o j e t f o r NASA i n t h e e a r l y 1970's p rov ide t h e bas is f o r t h e t h r u s t e r desiqn, namely a proven spark t o r c h i g n i t e r . his i g n i t e r has been demonstrated i n more than 100,000 f i r i n g s over a m ix tu re r a t i o range o f 2 t o about 250 and i n l e t temperatures from normal b o i l i n g p o i n t t o ambient. A r e s i d u a l i g n i t e r f rom these programs was used as t h e i n j e c t o r f o r bo th r a d i a t i o n and r e g e n e r a t i v e l y cooled t h r u s t e r s developed i n a program sponsored by t h e J e t Pr p l s i o n Laboratory (JPL) i n the e a r l y 198O1sBY'. The JPL t e s t experience served as t h e s t a r t i n g p o i n t f o r t h e Space S t a t i o n t h r u s t e r design. F igure 1 shows the complete Space S t a t i o n t h r u s t e r assembly. Figure 1. Space Station Thruster Assembly