Will SpaceX Make Nuclear Rockets In The Future?

NASA, SpaceX, and other aspiring Mars pioneers face numerous obstacles in preparing for their trips. The requirement for enormous quantities of propellant or fuel has been a challenge for all such initiatives.

Early spacecraft, such as those employed in the Apollo programme fifty years ago, utilised chemical propulsion, which involved the combustion of liquid oxygen and hydrogen in a combustion chamber.

The use of such technology enabled the astronauts controlling them to instantly start and stop an engine. Numerous new space propulsion mechanisms have been imagined or prototyped, but none of them has proven to be as dependable and user-friendly as the traditional chemical propulsion technology.

nuclear rocket

NASA has many mission scenarios for taking four or more humans into space safely, but none of them can take them beyond the moon due to the limitations of the chemical propulsion system.

Even when the two planets are aligned every 26 months, it takes between 1,000 and 4,000 tonnes of propellant to launch a rocket from Earth to Mars. NASA's SLS rocket and all of SpaceX's existing rocket designs currently carry several hundred tonnes of propellant.

If anyone wishes to get to Mars, they will need to discover an alternative method. Recent discussions and research have focused on the practicality of employing nuclear fuel for space launch rocket systems.

In response to a request from NASA, the National Academies of Sciences, Engineering, and Medicine have analysed it.

Although their findings have not yet been made public, it is known that they discussed two types of nuclear propulsion systems: nuclear thermal propulsion (NTP) and nuclear electric propulsion (NEP).

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In nuclear thermal propulsion, a nuclear reactor operates in place of a combustion chamber in a rocket engine. The nuclear reactor continues to power an ignition mechanism that uses liquid hydrogen as a fuel.

In contrast, nuclear electric propulsion turns heat from a fission reactor into electrical power and then uses this energy to produce thrust through the acceleration of an ionised propellant.

Typically, xenon is the ionised propellant in this instance. A little less than 500 metric tonnes of fuel would be needed for a voyage to Mars using any of the two nuclear propulsion technologies.

Fuel consumption is also more consistent with the orbital characteristics of both Earth and Mars, as well as the particular manner in which these orbits shape prospective launch windows.

Experts such as Bobby Braun, head of planetary science at the Jet Propulsion Laboratory and co-chair of the group that conducted the research, stated, "We did not conclude that such a programme could not bring us there."

NASA and other international space organisations have not yet requested financing for nuclear propulsion technology from their respective governments or legislatures. In view of the escalating US-China space conflict, Congress has appropriated funds for the effort notwithstanding.

In the budget bill for fiscal year 2021, NASA was allocated $110 million for nuclear thermal propulsion research.

According to Braun, it would be significantly more expensive for NASA to collaborate with the Department of Energy, SpaceX, and other US government agencies to develop this technology and launch regular cargo trips to Mars by the mid-2030s.

It was the type of aerospace technology problem for which NASA was designed, and it is the type of technology NASA is anticipated to be able to implement in the next few years.

This is where SpaceX comes into play with its Starship concept spacecraft, which is being constructed with the eventual objective of flying Mars missions. The project aims to solve the issue of requiring large quantities of chemical propellant by building a low-cost, reusable launch system.

Engineers at SpaceX are also aware that it will require a substantial amount of fuel for any spaceship to reach Mars. However, they believe the issue can be resolved if starships can be constructed often and at a low cost.

Concepts include putting a spacecraft into orbit with empty tanks and transferring fuel from other spacecraft in low-Earth orbit before reaching Mars. Elon Musk, on the other hand, has proposed SpaceX for 2019.

He emphasised how the alternative to rocket fuel could facilitate faster travel beyond the solar system, a topic of considerable interest to the Starship project. To be clear, Musk declared on Twitter, "To be clear: fine for in-space transit, but not advised for Earth to orbit."

Others had expressed concern about the risk of radiation hurting astronauts and the Earth's atmosphere, so he elaborated on his justification of nuclear reactors being used to accelerate spaceships with nuclear power.

SpaceX's ambitious objectives may necessitate the development and implementation of nuclear propulsion technology for its spacecraft. As of August 2021, SpaceX is on track to develop their starship prototypes according to plan, with no discussion or movement toward introducing nuclear propulsion into the design.

Given SpaceX's tight relationship with NASA and their extensive history of collaboration, it seems likely that SpaceX may eventually request NASA's assistance in developing a nuclear propulsion system for the Starship or other spacecraft designs.

This leads us to the primary obstacle preventing SpaceX and NASA from developing nuclear propulsion technology. While shorter mission durations might reduce the crew's exposure to space radiation, there is still significant concern regarding the radiation emitted by the spacecraft's nuclear reactor throughout the lengthy journey to Mars.

NASA engineers have suggested that the presence of liquid propellants between the engine and the crew compartment would block radioactive particles, mitigating the effects of reactor radiation. As a radiation shield, it is said to be quite effective.

At opposite ends, they have also envisioned configurations in which the distance between the crew and the reactor is maximised. Concerning the safety of the planet and its inhabitants, the spacecraft would not launch immediately from Earth using its nuclear-powered engine.

A conventional chemical propulsion rocket would first propel the spacecraft into orbit before activating its nuclear reactor. It remains to be seen what the engineers want to do regarding the prospect of a catastrophe resulting in the dismantling of the reactor.

Failure of an atmospheric or orbital rocket could result in the release of radioactive material into the atmosphere. The fissile material's confinement could be compromised by a collision with orbital debris, material failure owing to uncontrolled fission, material faults or fatigue, or human design mistakes.

Such a catastrophic breakdown in flight might disperse radioactive material over a vast and unpredictable area of the Earth.

The amount of contamination would depend on the size of the nuclear thermal rocket engine, while the zone and concentration of contamination would depend on the prevailing weather and orbital characteristics at the time of re-entry.

Nuclear-powered rockets will be the key to opening the solar system to humanity in the next decades, but their widespread deployment will not occur for at least two decades due to the potential for disaster and risk.

Before a crew could be dispatched to Mars on a nuclear-powered rocket, numerous demonstrations and experiments would need to be conducted.

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