In addition to the US and Russia, both China and India have joined the space race in the last twenty years, with lunar probes that landed on the Moon, orbiters around Mars and even a separate space station in Earth orbit. Now, 50 years after the first Apollo mission, we are more poised than ever to return to the Moon and reach Mars within the next two decades.

Challenges of Space Exploration

That said, there still exist many major obstacles in the way of a potential manned mission to Mars and beyond, with the most significant limitation being the amount of time astronauts can spend in space. The human body is not designed to function in the microgravity of space. Time spent in such an environment leads to the degeneration of our muscles and bones and damage to our immune systems.

There is also the factor of psychological issues that can arise from being confined to a small space-faring capsule for long periods of time. In the case of a journey to Mars, astronauts will have to spend a minimum of 14 months in space for a two-way journey, assuming the fastest speeds achievable with our current chemical propulsion technology.

It stands to reason that the best way to remedy the issue of time is to make spacecraft that can travel faster. This is where nuclear powered engines come into play.

The Promise of Nuclear Engines

The human conquest of space is currently stuck in second gear due to our reliance on chemical propulsion systems. Chemical rocket engines work by combusting a liquid fuel and oxidizer (most often liquid oxygen) together, then shooting the resulting hot gas out of a nozzle. This emission pushes the rocket in the opposite direction, by Newton’s Third Law of action-reaction.

The speeds that can be achieved with chemical propulsion systems are limited by how much energy can be generated from a given mass of fuel. The operational efficiency of a rocket engine is indicated by a metric known as the “specific impulse”. Where the fuel efficiency of a car can be gauged in litres per kilometer, a rocket engine’s specific impulse measures how long a kilogram of fuel can last while providing a constant thrust of one Newton. Conventional chemical rocket engines can usually generate impulses up to 460 seconds.

Nuclear thermal engines are not too different in that they also work by expelling hot gas to generate thrust. The difference here lies in the type of fuel used. In nuclear engines, a type of gas, like hydrogen, flows over a nuclear reactor operating on fissile material like uranium-235 or plutonium. The process generates extreme heat (in the range of 2000 to 4000 degrees Kelvin), expanding the hydrogen gas and expelling it out of the engine’s nozzle at extremely high pressure, propelling the engine forward.

Because of the incredibly high temperatures achievable in a nuclear reaction, nuclear fuel engines can generate a higher specific impulse than any chemical combustion rocket. Nuclear engines are theoretically able to reach specific impulses of between 850 and 1000 seconds, which is twice the highest impulse attainable by a chemical rocket engine. Additionally, the pure hydrogen gas ejected from nuclear thermal engines is pure hydrogen, which is much lighter in mass per molecule than the waste generated by chemical engines, meaning it can achieve higher velocities – and by Newton’s Third Law, the higher the velocity of the ejected material, the higher the velocity that would be reached by the rocket.

The high energy density of nuclear fuel also means that less fuel needs to be carried by a nuclear-powered spacecraft compared to a chemically propelled one. This enables more efficient mass budgets and, in turn, faster travel times for future interplanetary missions. Reaching Mars on a nuclear spacecraft could take two weeks instead of the current seven months. Journeying to Jupiter, which could take up to ten years with a chemical propulsion system, could theoretically be done in only two with a nuclear rocket, which would finally put the gas giant within humanity’s reach.

Past and Future Prospects

Several nuclear rocket engines have already been tested so far. Between 1959 and 1973, a total of 23 engine tests were performed by the United States. The U.S. Department of Defense took the lead with its NERVA program (Nuclear Engines for Rocket Vehicle Applications). Researchers in the program were able to develop an engine which sustained a maximum impulse of 850 seconds for 90 minutes and achieved a maximum temperature of 2750 K. The NERVA program had a total cost of around 2 billion USD (about $6 per person in the U.S. at the time).

Newer projects for nuclear thermal engines, such as a 2023 DARPA-NASA joint contract and another independent endeavor by Lockheed Martin, are already under way. The costs for these projects are estimated to be between 10 and 20 billion USD (about $62 per person in the US). Despite the seemingly high price tags, investing in nuclear rockets could actually pay off in the long run in the form of reduced travel times for interplanetary journeys and reduced costs for the transport of materials to and from the Earth, such as shipments to the Moon for the construction of a future lunar base. 

At present, there are still several challenges standing in the way of building commercially viable nuclear engines. Building an engine able to withstand the extreme heat of a nuclear fission reaction, for instance, is a major challenge. The materials used to build Earth-bound nuclear reactors are difficult to transport and would be hard to use in space. This is compounded by the necessity of using chemical rockets to transport building materials into space, as igniting a nuclear engine on the Earth’s surface would be extremely dangerous.

Any nuclear spacecraft would also require extensive shielding to protect astronauts and electrical instruments on board from the nuclear radiation, adding to its mass budget. There is also the problem of public opinion around the idea of a nuclear reactor in orbit above our heads – nuclear accidents over the years (such as Chernobyl and Fukushima) have cast a pall of fear over the use of nuclear power which would undoubtedly carry on to the public perception of new nuclear-powered spacecraft.

Nonetheless, nuclear engines hold great potential for a new generation of spacecraft. Despite the current logistical challenges that persist, the technology to build nuclear- powered spacecraft is already well within our reach. The relevant engineering hurdles are expected to be overcome in the next 10 to 20 years. Thorough testing by reliable organizations and a strong enforcement of safety standards may be able to sway public opinion and interest in the use of nuclear energy in space. Nuclear propulsion could be vital for our forays into deep space, and I, for one, am excited for the engineering marvels we are likely to witness in the coming decades.

The post The New Frontier to Space? appeared first on The McGill Daily.

Suddenly your morning trip to Starbucks is a lot less ordinary. Everyone, from the cashier to the bus driver to the receptionist and your boss, are all talking about what they believe the aliens from planet Xorg look like. Finding life outside of Earth has always been one of the most captivating pursuits in science. As a space scientist myself, I can attest to the fact that the question of alien life will come up without fail in any given public talk related to astronomy.

Recently, it seemed as though internet publications had beaten scientists to the punch with announcements that evidence of life had been found in the Exoplanet K2-18 b. This came as quite a surprise to the scientists who had published their findings about this planet but had no recollection of telling the media that they had confirmed the existence of extra terrestrials.

What happened was that some of the conclusions of their published findings were spun into very misleading headlines. They did, however, prove to be quite effective in terms of how many people clicked on those articles online.

Such misrepresentations of science in the media, especially online media, have been happening more frequently in the last ten years. The business model of high engagement equals higher profits has created an online media ecosystem that thrives on sensationalizing scientific findings. By sensationalizing I mean that a lot of facts are distorted to attract more readers.

For context, what exactly is this planet K2-18 b? It is a planet that is two and a half times as wide and eight times as massive as Earth. It orbits a small red dwarf star at a distance of 124 light years from our solar system. K2-18 b has half the Earth’s density, suggesting the existence of light material such as water and ice on the planet. Furthermore, the planet was found to orbit near the habitable zone of the system, which fuelled speculation on whether K2-18 b could harbour life. Discoveries such as the evidence of water vapour and hydrogen gas in its atmosphere by the Hubble Space Telescope presented this world as a Hycean world candidate (a planet with a hydrogen atmosphere and a global ocean).

This wasn’t the first time that planet K2-18 b made an appearance in the media as a flag bearer for fake alien life. The same happened when this planet was discovered in 2015 and several online publications described it as a planet with a global ocean. While the idea that K2-18 b could potentially have water was proposed based on the density of the planet, the astronomers who studied this world simply mentioned it as one of many possible conclusions to their observations.

Similarly, in September of this year, spectral data from the NIRISS instrument of the James Webb Space Telescope showed evidence of methane, carbon dioxide, and hints of dimethyl sulfide (DMS) on K2-18 b. Among these, DMS was predicted to be a potential biomarker, but the data was not strong enough to say that the DMS came from life. The conclusions of the paper on these findings, which appeared as a letter in the Astrophysical Journal, were that DMS might be present in the atmosphere of K2-18 b but that it would require much more data to confirm. While the possibility of the origin of DMS being biological was brought up, considering it a certainty would have been scientific malpractice.

Several news outlets, however, spun these findings in a different light. USA Today led with the headline “NASA says Exoplanet named K2-18 b could harbor life.” CNET had the headline “Webb finds potentially habitable planet might be an ocean world,” while The Guardian sounded off the headline “NASA says distant Exoplanet could have rare water ocean and possible hints of life.” Many of these articles cherry-picked findings from these studies while omitting the researchers’ words of caution. One might argue that sensationalizing science will get more engagement from the public. But researchers would say that they still observe strong public engagement without having to exaggerate scientific results. When it comes to news, simply announcing findings as they are is the best course of action.

Over time, media exaggeration of science erodes the public trust in science and scientific institutions. It is the collective responsibility of researchers and the media to ensure clear communication between science and the public.

The post Science Sensationalism in the Media Damages Trust appeared first on The McGill Daily.