http://apcnasa3ozl2j74htizuzba5b6nhugbg2qze2nrz43siunkct555fpid.onion
A large engine using O 2 /H 2 (pump fed SSME, for instance) is capable of a very high specific impulse value of 450 lb f -s/lb m . A smaller engine, which is pressure fed, has an I sp of 423 lb f -s/lb m .