Are Chemical Rockets or Solar Sails Better to Return Resources from Asteroids?

One of the most important decisions to be made in the structure of any asteroid mining mission is how to get the resources back to where they came from. Chemical rockets, which we already use to get us into space in the first place, or solar sails, which don't require any fuel, will be the focus of that decision. Which method is better for these missions? Researchers at the University of Glasgow looked at two scenarios and came up with solar sails.

Limits on the answers are necessary when answering theoretical questions. Billions of asteroids exist in the solar system so it is more realistic to only look at Near Earth Asteroids. There are tens of thousands of known NEAs. Merel Vergaaij would not have been able to calculate the optimal trajectory for each of them.

The area around Earth was broken down into generalized parameters. It's easier to figure out what a general transfer orbit would look like for an asteroid in that region of space if you have those three parameters.

Calculating the cost and benefit of transferring material back from the asteroid was one of the constraints. Beyond the scope of the paper, getting the mining equipment there was considered. It was necessary to have a wait time at the asteroid so the return mission could have enough time to stock up.

The material was volatile. Volatiles, such as water, have been a focal point of asteroid mining discussions, as they form the basis of rocket fuel that would be needed to explore farther into the solar system. Chemical rockets can use volatiles as their own fuel to get back to the Earth system.

Sending the volatiles back toGEO, some assumptions about launch costs, and determining the net present value of economic studies are some of the constraints that have been put in place. NPV is the result of the solutions being judged on a number of factors. Launching cost, development cost, manufacturing cost, and operational cost are included. The revenue would be determined by the expected value of the volatiles delivered to the space station. The NPV indicates whether a mission to an asteroid in that area would be worth it if revenue surpasses cost.

The authors used a genetic method to solve the problem. The amount of volatiles returned and the orbital mechanics were some of the parameters that were given to the algorithm. It was clear from the results that solar sails have positive NPVs for a wide range of areas.

The weakness in chemical rockets was the main reason for this. They had to use some of their delivery material.

The authors suggest that future asteroid miners look at asteroids in the specific regions they call out as potentially profitable if they want to look for their first major mining site. The researchers made some modifications to their baseline missions structure, such as stopping at a lunar gateway, adding a second trip, and running a series of Monte Carlo simulations to see how profitable different schemes were.

Adding a second trip and stopping at the lunar gateway added value to each type of mission architecture. The Monte Carlo simulations showed that their profitability was consistent. Solar sails seem to be the winner between the two types of propulsion systems, as there are potentially profitable targets for each. It is up to those who want to build a mining empire to listen.

You can learn more.

Vergaaij et al. did an economic assessment of solar sail and high trajectory asteroid mining.

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