Nuclear Shuttle
NERVA (Nuclear Engine for Rocket Vehicle Application)
In 1952, Los Alamos Scientific Laboratory began researching the challenges and applications of nuclear energy in rocketry,
which lead in 1955 to Project Rover, an R&D program for the development of nuclear rockets for military applications.
By 1961, with the start of Project Apollo, NASA began incorporating nuclear thermal rockets into it's concepts interplanetary mission designs. While the burning of chemical fuels would be sufficient for the first interplanetary probes and small sorties to the Moon, engineers knew it was too inefficient to allow for the operation of a large-scale lunar base or manned interplanetary expeditions.
Nuclear propulsion was recognized as enabling these more ambitious goals by cutting the required launch mass from thousands of tonnes to hundreds of tonnes. Though development on nuclear-propelled missiles was cancelled by Kennedy,
the Los Alamos continued it's development throughout the 1960s for space-based civilian applications.
In the 1968-1970 planning phase for NASA's post-Apollo Odyssey Program, NERVA rocket engines were selected as the propulsion system needed for transporting large payloads through cislunar and interplanetary space in reusable spacecraft.
Although attempts to cut it from the budget were made in 1973, NASA's Reusable Nuclear Shuttle (RNS) survived cancellation,
Thanks to the help of Senator Clinton P. Anderson of New Mexico. Anderson proved vital in protect the expanding Los Alamos scientific laboratory working on NERVA. The Atomic Energy Commission (AEC) also played a key role in fighting for NERVA, in self-interest to save the Agency from Congress. The tipping point however was the sense that, by giving up on nuclear propulsion,
NASA would be forever behind the Soviet Union in space. At a time when the United States was losing confidence in itself,
and the Soviet Union seemed to be passing America by economically, strategically, militarily and technologically,
such an admission was not tolerable for much of Congress.
However Congress had no clue the kind of technical challenges which faced the NERVA program.
In 1973, during the final test of the NERVA XE prototype engine, a 38 pound reactor fragment shot out the engine nozzle.
As a result, the engineers at Los Alamos had to completely overwork the reactor core design. They moved from a reactor core based around a composite mixture of graphite, to a design which used UC-ZrC alloy to give the reactor more stability and protect it from inhibited hydrogen corrosion.
This new design called NERVA Alpha was first tested in 1974 before evolving into several later iterations in the years that followed. Finally came NERVA-Gamma, the test-flight configuration.
1979 the first RIFT (Reactor In Flight Test) was conducted, simulating a Nuclear Shuttle flight to Moon.
It used a Saturn VB, outfitted with a modified third stage, the S-IVN. The third-stage had to include a second Hydrogen propellant-load within it's Oxygen tank to simulate the method of using hydrogen propellant to provide additional radiation shielding.
The J-2S was replace by the NERVA Gamma, equipped with hundreds of sensors to monitor every aspect of the engine's behavior.
The Instrument unit, a repurposed Apollo 22 CSM adapted for higher radiation during NERVA operation,
NASA relabeled the capsule as Biosatellite 4 and packed it full of radiation monitors and laboratory animals.
This simultaneous example of expensive high-technology, animal-testing and nuclear power united anti-nuclear groups
with "Animal liberation" organisations and such as Rainbow Warrior.
On March 12 1979, a group of ecoterrorists was intercepted by the National coastgaurd and US Navy before an attempt was made to bomb Launch Pad 39 (and the Saturn VB).
The incident was later cited by then-United States Republican Presidential candidate Ronald Reagan as an example of radical environmentalism run amok.
In May 1979 the countdown finally began for RIFT-1. Outside the Kennedy Space Center the police had to stop angry mobs of citizens from attacking peaceful environmentalists demonstrating against the use of Nuclear energy.
The Mission started well, with the Saturn VB bringing the S-IVN into it’s parking orbit.
There, ground control made it's final pre-TLI checks before unleashing the NERVA engine for the first time.
The first engine fire for Translunar injection was satisfactory. Although the NERVA reactor Core did suffer from xenon contamination issues, making the cool-down time longer than planned, in Moon Orbit the CSM return chemical to Earth.
Afterwards the S-IVN restart it NERVA engine towards interplanetary disposal orbit.
The mission was an overall success and paved the way for the first operation Nuclear Shuttle in the following years.
Final Tests, Reusability, A Cislunar Toehold
Following the RIFT-1 test, engineers continued work on the Reusable Nuclear Shuttle (RNS)
With help of computer simulations MSFC determined the best radiation protection for both crewed and uncrewed payloads.
Rockwell's two cylindrical tank design won had won the contest. Using internal 10 ft. diameter cylinder tanks ended up providing better radiation shielding as compared to other competing proposals, the cylindrical tanks offered better storage of hydrogen propellant. Despite this, MSFC demanded supplemental changes, such as the refuelling option Boeing had proposed for their RNS.
With this modification, the Nuclear Shuttle would dock with additional fuel tanks, a practice necessary for Manned Mars Missions.
The first two Nuclear Shuttle were build by Rockwell/General Dynamic in co-operation of the Los Alamos National Laboratory.
With the engineering issues sorted out, the next biggest challenge to the RNS face came from astronaut corps, as some of them had look into the documentation and design studies.
Many reacted with outrage and indignation at the radiation recommendations made. Due to the high radiation exposure astronauts would receive from the nuclear engines, astronauts were to be limited to 10 RNS flights before being grounded for the rest of their life. Despite the fact that no astronaut to that had actually flown into space (let alone the Moon) more than ten times,
NASA partially relented by changing the regulation. Instead of being grounded after 10 RNS flights, astronauts would instead be limited to Low Earth Orbit operations. The measure was also sold as a cost-saving measure to reduce the number of astronauts who would need to be trained at taxpayer expense, as the sheer number of missions planned was leading to a dramatic increase in astronaut recruitment, screening and training costs, as well as a shortage in space veterans.
After two years of additional development, NIFT-2 was launched in 1981, although this was only the second launch of NERVA engines.
It was first time NASA tested them in their full Nuclear Shuttle configuration (albeit, in its unmanned mode).
As a result of information gathered from the previous NIFT test, a third radiation shield composed of a polyethylene foam block was placed on top part of the main hydrogen tank. If all went well, the newly modified NERVA engine in the RNS would be reusable for 20 operation before decommission.
RIFT-2 was launched by the second Saturn VC, with the Nuclear Shuttle itself only partly fueled. To top off its tanks the RNS stage maneuvered in orbit to rendezvous and dock with the Hydrogen fuel tank, launched by the first Saturn VC days earlier.
After refuelling with liquid hydrogen, the RNS performed an unmanned simulation of a typical lunar mission.
It performed a TLI burn, injected itself into a circular lunar polar orbit, orbited the Moon for several days, performed its TEI burn,
before slowing itself into a circular Low Earth Parking orbit.
RIFT-2 accomplished all Test goals and more. Working flawlessly, the radiation levels remained inside the design parameter and the Xenon containment issues did not flare up. The liquid hydrogen refueling operations went as expected.
After the successful LEO-LLO-LEO test, the RIFT-2 was inspected and serviced by two chemical Space Tugs.
Using newly designed Manipulator Arms over remote control, the NERVA engine core was disconnected from the propellant tank and the turbo pumps were inspected.
The Core inspection show to the ground engineers' relief that engine was in better condition than expected.
NASA officially re-designating (some would say re-christened) the stage as the Reusable Nuclear Shuttle-1 (RNS-1).
After another refuelling, it was ready for it first official Mission.
