We live in an era of renewed space exploration, in which many agencies plan to send astronauts Moon in the coming years. This will be followed in the next decade by manned missions to Mars by NASA and China, who may be joined by other countries before long.
These and other missions that will take astronauts beyond low Earth orbit (LEO) and the Earth-Moon system require new technologies, ranging from life support and radiation protection to energy and propulsion.
And when it comes to the latter, Nuclear and nuclear thermoelectric propulsion (NTP/NEP) is the best competitor!
NASA and the Soviet space program spent decades researching nuclear propulsion during the space race.
A few years ago, NASA re-ignited its nuclear programme For the purpose of developing bimodal nuclear propulsion – a two-part system consisting of an NTP and NEP element – that could enable traversal into Mars in 100 days.
as part of Advanced Innovative NASA Concepts (NIAC) for 2023, NASA selected a nuclear concept for first-stage development. This new class of bi-modal nuclear propulsion system uses “Vertigo wave cycle toppingAnd it could reduce transit times to Mars to just 45 days.
The proposal is entitledDual mode NTP/NEP with rotary wave cycle topping,” by Professor Ryan Goss, Area Chair of the Hypersonics Program at the University of Florida and member of the University of Florida Florida Applied Research in Engineering FLARE Team.
Gosse’s proposal is one of 14 selected by NAIC this year for Phase 1 development, which includes a $12,500 grant to help mature the technology and methods used. Other proposals have included sensors, tools, manufacturing technologies, innovative power systems, and more.
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Nuclear propulsion essentially comes down to two concepts, both of which are based on rigorously tested and validated technologies.
For nuclear thermal propulsion (NTP), the cycle consists of a propellant heating liquid hydrogen (LH2) of a nuclear reactor, converting it into ionized hydrogen gas (plasma) which is then funneled through nozzles to generate thrust.
Several attempts have been made to build a test of this propulsion system, incl rover projecta collaborative effort between the USAF and the Atomic Energy Commission (AEC) launched in 1955.
In 1959, NASA took over the mission from the USAF, and the program entered a new phase dedicated to spaceflight applications. This eventually led to Nuclear engine for missile vehicle application (Nerva), which is a successfully tested solid nuclear reactor.
With the closure of the Apollo Era in 1973, funding for the program was cut dramatically, leading to its cancellation before any flight tests could take place. Meanwhile, the Soviets developed their own NTP concept (RD-0410) between 1965 and 1980 and performed one ground test before the program was cancelled.
On the other hand, Nuclear Electric Propulsion (NEP) relies on a nuclear reactor to supply electricity to Hall effect motive (ion engine), which generates an electromagnetic field that ionizes and accelerates an inert gas (such as xenon) to create thrust. Attempts to develop this technology include NASA Nuclear Systems Initiative (INS) The Prometheus Project (2003 to 2005).
Both systems have significant advantages over conventional chemical propulsion, including a higher specific propulsion (Isp) rating, fuel efficiency, and virtually unlimited energy density.
While NEP concepts have the advantage of providing more than 10,000 ISp seconds, which means they can maintain thrust for nearly three hours, the level of thrust is very low compared to conventional and NTP missiles.
The need for an electrical power source also raises the issue of expelling heat into space, Gosse says — heat energy conversion is 30 to 40 percent under ideal conditions.
And while NTP NERVA designs are the preferred method for manned missions to Mars and beyond, this method also has issues with providing sufficient initial and final mass fractions for high-delta-v missions.
This is why proposals that include both payment methods (bimodal) are preferred, because they will combine the advantages of both. Gosse’s proposal calls for a bimodal design based on the solid-core NERVA reactor that would deliver an indicated impulse (Isp) of 900 seconds, twice the current performance of chemical rockets.
Gosse’s proposed cycle also includes a pressure wave supercharger – or Wave Rotor (WR) – a technology used in internal combustion engines that harnesses pressure waves created by feedback to compress the intake air.
When paired with an NTP engine, the WR uses the pressure created by the reactor heating LH2 fuel to further compress the reaction mass. As promised by Gosse, this will provide thrust levels similar to those of the NERVA-class NTP concept but with an ISP of 1400-2000s. When combined with an NEP cycle, He said Gosse, push levels are further improved:
“In combination with the NEP cycle, the ISP duty cycle can be increased (1800-4000 seconds) with minimal addition of dry mass. This bi-mode design enables rapid transfer for manned missions (45 days to Mars) and revolutionizes the deep-space exploration of our solar system” .
Based on conventional propulsion technology, a manned mission to Mars could last up to three years. These missions will launch every 26 months when Earth and Mars are at their closest point (aka Mars opposition) and will spend at least six to nine months in transit.
A 45-day (six-and-a-half-week) transit would reduce the total task time to months rather than years. This would greatly reduce major risks associated with missions to Mars, including radiation exposure, time spent in microgravity, and related health concerns.
In addition to propulsion, there are proposals for new reactor designs that would provide a stable power source for long-duration surface missions where solar and wind power are not always available.
These and other nuclear applications could one day enable manned missions to Mars and other locations in deep space, perhaps sooner than we think!