We are now living in a time of renewed space exploration, in which numerous companies are planning to send astronauts to the Moon in the upcoming years. China and NASA are likely to follow suit in the following decade with crewed missions to Mars, which could be joined by other nations soon enough.
These as well as other missions which will take astronauts past the low Earth Orbit (The Earth-Moon and leo) system will need new technologies which range from life support as well as radiation shielding to propulsion and power.
And with regards to the second, Nuclear Thermal as well as Nuclear Electric Propulsion (NTP/NEP) is a premier contender!
Throughout the space Race, the Soviet Union as well as the NASA spent decades studying nuclear propulsion.
A couple of years ago, NASA reinited its nuclear program for the purpose of creating bimodal nuclear propulsion – a two-part program comprising of a NEP and NTP component – which can allow transits to Mars in 100 days.
Within NASA Innovative Advanced Concepts (NIAC) plan for 2023, NASA chose a nuclear idea for Phase I development. This innovative bimodal nuclear propulsion system utilizes a “wave rotor topping cycle” and may lessen transit times to Mars out of just forty five days.
The idea, titled “Bimodal NTP/NEP with a Wave Rotor Topping Cycle,” was put forward by Prof. Ryan Gosse, the Hypersonics Program Area Lead at the University of Florida along with a member of the Florida Applied Research in Engineering (FLARE) staff.
Gosse’s idea is among fourteen selected by the NAIC this year for Phase I development, which includes a US12,500 grant to help in maturing the science as well as strategies involved. Additional suggestions included innovative sensors, instruments, manufacturing methods, power systems and more.
Essentially, nuclear propulsion is dependent on two ideas, which are based on technologies which have been extensively tested and validated.
For nuclear thermal Propulsion (NTP) the cycle consists of a nuclear reactor that heats liquid hydrogen (LH2) propellant and transforms it into ionized hydrogen gas (plasma) which is then channeled through nozzles to create thrust.
A number of attempts were put there to create a test of this propulsion system, such as Project Rover, a joint venture between the Atomic Energy Commission as well as the US Air Force, launched in 1955.
NASA had taken over from the USAF in 1959 and also the system entered a new stage, devoted to space applications. This eventually resulted in the creation of the nuclear Engine for Rocket Vehicle Applications (NERVA), a solid core Nuclear reactor successfully analyzed.
With the closing of the Apollo Era in 1973, the program’s funding was considerably lowered, resulting in its cancellation before any flight tests could be carried out. In the meantime, between 1965 and 1980, the Soviets developed their own NTP concept (RD 0410) and carried out a single field test just before the demise of the system.
Nuclear-Electric Propulsion (NEP), on the other hand, banks on a nuclear reactor to supply energy to a Hall-Effect thruster (ion engine), which generates an electromagnetic field that ionizes and accelerates an inert gas (like xenon) to create thrust. Attempts to produce the technology include NASA’s Nuclear Systems Initiative (NSI) Project Prometheus (2003 to 2005).
Both propulsion systems possess substantial advantages over conventional chemic drives, including higher specific impulse (Isp) ratings, better fuel efficiency and practically unlimited power density.
Even though the NEP ideas are distinguished by providing much more than 10,000 seconds of Isp, which means they’re able to keep thrust for close to 3 hours, the thrust quantity is quite low compared to conventional rockets and NTP.
Gosse additionally mentions the need for an electric power source in addition raises the issue of heat rejection in space, where thermal energy conversion is 30-40% in ideal circumstances.
Even though NTP NERVA designs are the preferred technique for crewed missions to Mars as well as beyond, this method also has issues providing adequate initial and final mass fractions for high delta-V missions.
This is exactly exactly why proposals are preferred including both bimodal propulsion methods, because they will incorporate the advantages of both. The idea by Gosse calls for a bimodal design based on a solid core NERVA reactor that would supply a specific impulse (Isp) of 900 secs, twice the current performance of chemical rockets.
Gosse suggested cycle also contains a pressure wave supercharger – or Wave Rotor (WR) – a technology utilized in internal combustion engines that utilizes the pressure waves created by reactions to compress intake air.
When coupled with an NTP motor, the WR would further compress the reaction mass by utilizing the pressure generated by the heating of the LH2 gas by the reactor. This particular device can deliver thrust levels similar to that of a NERVA-class NTP idea, but with an Isp of 1400-2000 seconds, as Gosse promises. Gosse pointed out that thrust amounts are even further improved when combined with a NEP cycle.
The duty cycle Isp may be increased with minimal addition of dried up mass, combined with an NEP cycle (1,800-4,000 seconds). This bimodal design enables fast transit of human missions (45 days to Mars) and revolutionizes deep space exploration of our Solar system.
A crewed mission to Mars could last as much as 3 years, based on standard propulsion technologies. These missions will start every twenty six weeks if Earth as well as Mars happen to be at the nearest point (aka a Mars opposition) and spend at least 6 to 9 weeks in transit.
A transit of 6 and a half weeks (forty five days) will lessen the entire mission time to weeks instead of years. This will considerably lessen the main risks related to missions to Mars, which includes radiation exposure, time spent in microgravity as well as health issues.
Additionally there are proposals for new reactor designs that would supply a constant source of power for long-duration area missions, where sun and wind power aren’t often available.
Some examples are NASA’s Kilopower Reactor Using Sterling Technology (The hybrid and krusty) fission / fusion Reactor chosen through NASA for Phase I creation by the NAIC 2023 selection.
These along with other nuclear applications might allow crewed missions to deep space to Mars along with other places, possibly sooner than we think.
This article was originally published by Universe Today. Read the original article.
