NASA
Getting people to Mars and back is quite difficult. In fact insanely difficult. NASA and other prospective Mars pioneers face many challenges when planning missions to the red planet, but among other things is the amount of propellant needed.
During the Apollo program 50 years ago, humans went to the moon using chemical propulsion, that is, rocket engines that burn liquid oxygen and hydrogen in a combustion chamber. It has its advantages, such as giving NASA the ability to quickly start and stop an engine, and the technology was then the mature one for space travel. Since then, some new propulsion techniques in space have been devised. But no one is better or faster for humans than chemical propulsion.
This is a problem. NASA has some base missions to send four or more astronauts to Mars, but relying on chemical propulsion to venture beyond the Moon is unlikely to cut it. The main reason is that a lot of rocket fuel is needed to send supplies and astronauts to Mars. Even in favorable scenarios where Earth and Mars are in line every 26 months, a human-to-Mars mission still requires 1,000 to 4,000 tons of propellant.
Consider this if it is difficult to visualize. After NASA’s Space Launch System rocket is upgraded to its Block 1B configuration, it will have a carrying capacity of 105 tons to a low Earth orbit. NASA expects to launch this rocket once a year, and its cost is likely to be around $ 2 billion for flights. To get enough fuel in orbit for a Mars mission, it will take at least ten launches of the SLS rocket, or about a decade and $ 20 billion. Just for the fuel.
The bottom line: if we’re going to Mars, we’ll probably have to think of other ways to do it.
Go core
A new report from the National Academies of Sciences, Engineering, and Medicine provides answers on two such ways. A broad committee of experts was conducted at the request of NASA to assess the viability of two propellants – nuclear energy and nuclear energy – for a human mission to Mars in 2039.
“One of the key takeaways from the report is that if we want to send humans to Mars, and we want to do it repeatedly and in a sustainable way, nuclear space is on the way,” said Bobby Braun, director of planetary science said. at the Jet Propulsion Laboratory and co-chair of the committee that wrote the report, in an interview.
The committee was not asked to recommend a specific technology, each relying on nuclear reactions but working differently. Nuclear thermal propulsion (NTP) involves a rocket engine in which a nuclear reactor replaces the combustion chamber and burns liquid hydrogen as fuel. Nuclear electric propulsion (NEP) converts heat from a fission reactor into electrical power, such as a power station on earth, and then uses this energy to produce propulsion by accelerating an ionized propellant, such as xenon.
“If you look at the recommendations of the NTP committee, we felt that an aggressive program, built on the fundamental work recently achieved, could get us there,” Braun said of the March 2039 target. For NEP, we felt it was unclear whether such a program could get us there, but we did not conclude that it could not get us there. “
Nuclear propulsion requires significantly less fuel than chemical propulsion, often less than 500 tons. This will be useful for a Mars mission that will include several pre-missions to increase cargo on the red planet in advance. The fuel consumption of nuclear power is also more in line with the launch opportunities offered by the orbits of Earth and Mars. During some conjunctions, which occur approximately every 26 months, the propellant required to complete a Mars mission with chemical propellants is so high that it is simply not feasible.
A plan for NASA
If NASA wants to use nuclear propulsion in human missions during the 2030s, it must start developing technology immediately, the report said. So far, the agency has been somewhat reluctant to proceed quickly with nuclear power. This may be due in part to the fact that the space agency has invested so much in the Space Launch System rocket and chemical propulsion required for the Artemis Moon program.
In recent years, therefore, NASA has not asked for funding for nuclear power. In any case, Congress has allocated money for the effort. In the budget account for the fiscal year 2021, NASA received $ 110 million for the development of nuclear power.
Braun said it would cost significantly more – at least an order of magnitude – for NASA to work with the Department of Energy and other parts of the government to develop this technology and launch cargo flights to Mars in the mid-2030s. However, he said that this is the kind of project that NASA would be well positioned to tackle.
“This is the kind of technological challenge that NASA is built for, and this is the kind of technological challenge that our country expects NASA to overcome,” Braun said. ‘You know, that’s the kind of thing NASA was created for all the way back to the Apollo program. So, I guess they could do that. ‘
Starship
And what about the Starship concept that SpaceX is building to send humans to Mars? The project seeks to address the problem of the need for many chemical propellants by developing an inexpensive, reusable launch system. SpaceX engineers know that it will take a lot of fuel to reach Mars, but they believe the problem can be solved if Starship can be built to fly regularly and for relatively little money. The basic concept is to launch a Starship to orbit empty tanks and transfer fuel launched by other Starships into a low-Earth orbit before a single vehicle flies to Mars.
Braun said SpaceX is developing a plan to send humans to Mars with assumptions other than NASA. “I think there’s a fundamental difference in the assumptions that NASA tends to make for what kind of infrastructure is needed at Mars,” he said.
This is not to say that Starship cannot work. However, it illustrates the challenge of setting up a mission to Mars using only chemical propulsion. To use traditional propulsion, one has to limit the limits of reuse and heavy lift rockets to the extreme – this is exactly what SpaceX is trying to do with its fully reusable launch system.