# Optimal Propulsion Strategy for a Mars Mission

I am designing a mission to Mars for a class project aimed at studying Mars' space weather. The mission is constrained to use a single Vega-C launch.

I need to determine whether using a propulsion module would allow for a greater payload. The Vega-C injection orbit is elliptical with a perigee of 250 km, an apogee of 5700 km, and an injection mass of 1580 kg. The Delta-V required to move from this orbit to a transfer orbit towards Mars is 3.1846 km/s, while the Delta-V required to enter a 250x7500 km Mars orbit is 1.2505 km/s.

The goal is putting around 30kg of instruments in mars orbit, ideally splitted in two spacecrafts, a spacecraft containing a 10kg radio occultation instrument in a 250km x 10000 km orbit, and another larger spacecraft in a 250km x 7500 km orbit containing another20kg of instruments.

The transfer phase shouldn't be longer than 5 years. Cost is also a constraint as the whole mission shouldn't cost more than 200M euros.

I am considering two approaches:

1. Use a propulsion module for the first manoeuvre and the large satellite's engine for the second. Use the large satellite's engine for both manoeuvres. How can I determine which option allows for a greater payload?

Understanding how the payload-to-dry-mass ratio correlates to Delta-V for interplanetary missions might help. Additionally, I am open to suggestions for solutions that maximize payload mass, such as using an electric propulsion module, or the use of aerobraking.

• There are a number of things that need to be defined. Does it matter how long the trip takes? If it does not then some form of ion propulsion might work. If it does then the travel time limits need to be known. other options might include some form of sling shot using the Moon, Earth and possibly Venus. But such opportunities are infrequent and could be lengthy. Commented May 6 at 17:47
• I asked a similar question not too long ago - it's not the same as this question, but it generated some really interesting technical answers. Studying those answers and watching the video linked in the question will help you understand some of the relevant problem-solving techniques. Commented May 7 at 5:20
• Vega C? I wasn't expecting that. Commented May 7 at 21:04
• is understanding which of those options allows for a greater payload not one of the objectives of your class? Shouldn't you do your own class project? Commented May 8 at 4:05
• I know, VEGA-C is indeed a serious constraint, but it's present in the Statement of Work for my Team, so it's not something I can change. Electric propulsion is also an option, for example I found this thesis very intresting link. Anyway for me a Chemical Propulsion strategy would give me more confidence on eventual caclulations as it's something I am more familiar with. Commented May 8 at 21:00

I'm going to answer even though I think the question is a little broad or even opinion based.

It all depends on the demand. Let me explain with an example: we could do a minimum cost for development model, where we use almost entirely flybys of other celestial bodies such as Venus, Earth, etc. This would imply however, that we either do not have the funding, or do not have a time constraint that would make flybys unreasonable.

The second model is that of a direct journey: Burn for longest possible time to accelerate and decelerate at each end with the highest efficiency possible, whilst maintaining meaningful thrust.

Neither of these are the options you would be likely to use, though I would note that the flyby option is more feasible in terms of cost, engineering, etc.

If your mission required use of a VegaC, then you are assuming that you have reason to: maybe it's available for a mission at a lower cost than other options for some reason...
However you might wish to consider: what is the purpose of the satellite or probe, what is the mass of a probe with or without propulsion for full manoeuvrers, what is the lifting capacity to the orbit needed for the transfer of either option, and so on and so on.

Essentially: your question lacks important information and other constraints to narrow down your options.
Once you have done this, you should run trade studies for the science, technology, economy, spacelaunch opportunities, and so on. This would give you a good idea of what option to choose.

• I tried to add some more clarifications in the text of the question. I would love to have some more ideas on how to increase the payload mass considering the constraint I put in the question text :) Commented May 11 at 19:01