Ye Olde Rocket Forum - STUDY SUMMARY- Reactor In Flight Test Systems Study (RIFT)

Here's an interesting study from 1961, about the Reactor In-Flight Study.... The plan to launch nuclear-powered rocket stages. The RIFT was an advanced proposal based on the test nuclear rocket engines (KIWI and NERVA). They were proposing launches of various RIFT proposals on various boosters, including Atlas and Saturn I. Atlas would have required a basically "mini-size" RIFT stage that would have had little application beyond the test phase itself, so was rejected. Saturn boosters could lift a full size RIFT, a short tank flight test version where the RIFT was flown as the second stage, and, using the then-proposed 260 inch four-J-2-powered S-II stage as a second stage, a full-length RIFT would fly as a full third stage for in-space propulsion.

The study summary also includes some interesting conclusions about what would happen with various incident scenarios if there was an accident on the launch pad or in flight. To study the problem, they had to break the possibilities down by the actual flight phase. Probably the worse scenario would have been an accidental opening of the hydrogen valves to the engine on the launch pad with the control drum (basically, control rods) withdrawn-- instant catastrophic meltdown sufficient to vaporize the core... and equal an explosion of about 14 tons of TNT! This would result in a cloud of fallout that would make its way downwind. Another bad scenario would be for the rocket to blow up or range safety to blow it up shortly after liftoff... if the intact nuclear engine fell into the shallow waters off Cape Canaveral, the seawater would flood into the engine and the reactor would go critical-- the seawater would act like hydrogen, acting as a moderator, and slow neutrons enough to create a sustained uncontrolled fission reaction-- a "nuclear excursion event". Since the reactor would be underwater, there would probably not be an outright explosion, but it would produce lots of radioactive radionuclides and undoubtedly radioactive steam that would contaminate the environment. To prevent these "excursions", the reactor was designed with a redundant safety system to blow it up into pieces small enough to prevent the nuclear reaction (excursion). Once the rocket was further along in flight, where it would impact deep water, the risks were considered minimal. Range safety was as serious concern, though, as any discrepancies from the flight plan would result in near-instant destruction of the rocket and the nuclear engine to disperse the radioactive fuel to prevent an excursion. There was also consideration given to the effects of a reactor returning to the Earth's atmosphere after having operated in space for the nominal operating time... it would be highly radioactive and the reactor would probably survive mostly intact due to it being designed to survive in the extreme operating temperatures it would be exposed to... so a failsafe system to blow up or break up the reactor was instituted to make sure that the reactor material didn't come down intact over a populated area... They wanted to make sure there was no chance of a nuclear excursion. There's a lot of interesting research that I summarized on the various incidents that they studied and the methods of dealing with them.

Anyway, there's also lots of good drawings and specification of the RIFT vehicle and ground systems as well...

First, the summary,
Second, the ground tracks of various RIFT launch types from both the AMR and PMR...
Third, various RIFT configurations studied...
Fourth, the basic nuclear stage construction and components...
Fifth, the nuclear rocket engine and external components...

Enjoy! OL JR :)