Nuclear Powered Space Flight#1
How about we use a nuclear reactor to power our trip to Mars?
Welcome to Fissile Material #23 — Today we take a new approach to writing blogs.
I will break down each topic into 4 parts. Each week, I write one part and keep it to 3000 characters (around 500 words). This should make it easier for new readers to grasp material — and hopefully prevent any kind of content overload. I will also link an instagram post here which contains a picture deck that explains the blog.
This blog is part 1 of our 4 part series on Nuclear Thermal Propulsion. Enjoy!
Let us engage ourselves in an interesting challenge: Interplanetary space flight. As humanity’s ambitions continue to grow, colonization of the moon and Mars becomes a real possibility.
Today, let us talk about space flight, where we stand, and an unlucky, radioactive contender.
Space is vast. The distance between the Earth and the Moon is 380,000 km. That number jumps to 5.6 million when considering Mars. Traversing these distances mandates a propulsion system: an engine and fuel.
So what do we have at our disposal?
Our “tried-and-tested” fallback is the chemical rocket. A chemical reaction generates energy in the form of hot gases, which are expelled through a nozzle and generate thrust in the opposite direction. Reliable,well-understood, but just too heavy. The Falcon 9, our current contender to reach Mars, can carry 4020 kgs to Mars. Impressive, but a pittance when we consider the Falcon’s total weight of 549,054 kgs — that’s a payload fraction of less than 1%!
Some may push for Electric Propulsion(EP) , citing its high efficiency and ability to use electricity for propulsion- which is abundant in space using solar panels. The catch is the scale. EP generates thrust on the order of small satellites. The accountant also disapproves: Xenon- the fuel used for EP- can be very expensive!
In either case,we have failed to address a serious problem: speed. Estimates for the time to Mars using conventional and electric propulsion are 347 and 245 days respectively.(1) What we need is a propulsion system that can combine the efficiency of EP and the reliability of chemical rockets: Extra points for speed!
Enter Nuclear Thermal Propulsion (NTP)
NTP is exactly what it says it is. Take uranium, fission it to generate heat, run propellant-not fuel- by the uranium which transfers the uranium’s heat to the propellant, and finally eject the heated propellant out the nozzle for thrust. Sounds complicated and rather scary, so why are we even considering this?
Simple: Speed! NASA estimates a time of just 45 days! (2) NTP also uses considerably less mass. Since the hydrogen is used as a propellant, there is no need for an oxidizer, which means less mass compared to a chemical rocket. Hydrogen is also the lightest element and is far cheaper than xenon!
These benefits — speed, lack of oxidizer, and relatively cheap propellant — also allow NPT to have economic advantages: Less time in space means fewer life support systems for astronauts en route to Mars which then means more mass for Mars missions. This ability to make the most of the rocket hasn’t gone unnoticed: NASA and ISRO — reputed space agencies — both have plans to use NTP for interplanetary missions!
So, if using Nuclear fission to power rocket engines sounds cool, do tune in next week when I go into the technicals of how it works!
Thank you for your time! (This is my first foray into concise posts — Your feedback is much appreciated)
