Q&A: Mars Mission Aborts Near Mars

[Danderman]

If the Mars Starship suffers a malfunction soon after Trans Mars Injection  return to Earth is simple.

My question is about return to Earth if it is determined that landing on Mars is not possible - in the final stages of Mars approach. Is it possible to swing around Mars and return to Earth?

 I realize that the Mars swingby provides all sorts of targeting opportunities, my question is whether Earth would be available for any of them.

[Robotbeat]

You’re asking if a free return is possible even after some maneuvers. Probably. Remember though that SpaceX is planning (notionally) to send two Starships together, so your contingency could be to just pile everyone in to the second Starship.

[Zed_Noir]

You’re asking if a free return is possible even after some maneuvers. Probably. Remember though that SpaceX is planning to send two Starships together, so your contingency could be to just pile everyone in to the second Starship.

It is my understanding that each SpaceX wave going to Mars included at least 2 cargo transport Starships for every crewed transport Starship. So as long as there is an intra-ship crew transfer capability, the crew from the aborted Starship will transfer over to the other Starships in the wave.

The aborted ship could probably do a Mars flyby for injection into a return to Earth trajectory with maybe supplemental propellants by buddy refueling from other Starships. Depending on the amount propellants required for the trajectory change.

[Danderman]

So far, answers about where the crew would live during an abort, but I am concerned about the orbital mechanics.

During a Mars mission, would the Earth be in position for a return in a reasonable period of time. Or, would the return period be 2 years?

My feeling is that using Mars to change Starship's trajectory would allow a return to Earth in a reasonable period of time, but I haven't crunched the numbers.

[Danderman]

Where is a link to the current SpaceX baseline for the initial Mars mission?

Or is the baseline in Elon's mind?

[Emmettvonbrown]

https://www.wired.com/2012/06/abort-from-mars-venus-missions-1970/

[tbellman]

So far, answers about where the crew would live during an abort, but I am concerned about the orbital mechanics.

During a Mars mission, would the Earth be in position for a return in a reasonable period of time. Or, would the return period be 2 years?

My feeling is that using Mars to change Starship's trajectory would allow a return to Earth in a reasonable period of time, but I haven't crunched the numbers.

Wikipedia: Free-return trajectory, the section "Earth-Mars".

If you use your favourite web search engine and search for "Mars free-return trajectory", you should find several papers exploring such trajectories.

The time for the return trip in such trajectories are indeed lengthy.  The entire aborted mission would be very roughly as long as a successful conjunction-class Mars mission.

[Danderman]

The missing piece from these sources is using a swingby of Mars to support return to Earth, ie a slingshot to accelerate the spacecraft.

Once the mission is near Mars ("Phase 3" per the wired.com article), going all the way to Mars may significant shorten the mission, compared with turning around 10 days short of Mars.

[sdsds]

Does the location of Venus within its orbit change significantly from one Mars-bound launch opportunity to another? Or Is Venus always someplace where a gravity-assist flyby there would be available for a contingency return to Earth?

[jimvela]

Does the location of Venus within its orbit change significantly from one Mars-bound launch opportunity to another? Or Is Venus always someplace where a gravity-assist flyby there would be available for a contingency return to Earth?

Not sure about the orbital dynamics part, but going IN to .7 AU will add substantial thermal management problems and may not be worth it for an abort type return.  A single starship design that can support .7 AU to 1.7 AU would be an impressive bit of kit.

[Robotbeat]

Where is a link to the current SpaceX baseline for the initial Mars mission?

Or is the baseline in Elon's mind?

🙄

You’re on this forum often enough to know that SpaceX has published this, in general terms.

(In before “but that’s 2017”: this is more recent than the previous fully detailed NASA Design Reference Architecture, DRA 5.0 and supplementary.)

[Danderman]

Concerning the printed Mars scenario, there's not a lot of detail, and nothing about multiple Starships flying to Mars together, where did that come from?

[Danderman]

The problem with invoking Venus as a requirement for an abort severely constrains the frequency and timing of Mars missions.

[Danderman]

What I am seeing from the replies is that there are 2 major phases for an abort back to Earth:

Phase 1: direct return to Earth, or

Phase 2: use Mars swingby to return to Earth.

Of course aborts require Starship to be able to safely return to Earth, ie either survive Earth re-entry and landing, or abort to Earth orbit.

The nature of the circumstances forcing the abort are key: perhaps Starship's landing legs are damaged, or the landing propellant has been lost - in that case, aborting to Earth orbit may be necessary. There may be scenarios where landing is impossible, but so is return to Earth.

Of course, much later on (when Mars has been colonized), abort to Mars orbit may be possible.

The question is when Phase 2 begins.

[Danderman]

Different people are posting different architectures for Mars missions. Where are these concepts coming from? Presentations at conferences? Offhand comments from Elon?

[Jim]

The missing piece from these sources is using a swingby of Mars to support return to Earth, ie a slingshot to accelerate the spacecraft.

Doesn't really help, still have to go around the sun

[Emmettvonbrown]

Random thoughts
-During the Apollo 13 crisis they could have turned back and returned faster, but  a lunar flyby was found to be a far better and logical idea. Ok ok, I know, Moon ain't Mars and Apollo 13 had its own pros and cons there.
...
-About Mars aborts: there are no easy ways to quickly return Earth. Orbital mechanics are absolutely unforgiving.
-Using Venus is not an answer, as it makes the return trip even longer
- A matter of heliocentric orbits, as Jim said
- What I mean: a rather vexing and uncomfortable fact is, when travelling between Earth and Mars, most of the trip happens in a heliocentric orbit - and there is no easy abort out of this. The Solar System is vast, and the Sun is massive.

Bottom line: the only viable abort option on the way to Mars is... *convoy*. A few ships on the same trajectory mutually supporting each others.

-This is exactly what Musk suggested (above links and picture) but he invented nothing.

-Multiple spaceships bound to MArs in convoy, supporting each others - was a stapple of Von Braun & Co Mars plans, all the way from 1953 (Colliers) to 1969 (STG). Same from Boeing IMIS, 1968.  The NERVA was more than an engine module: it was to be a multipurpose nuclear space tug (RNS: Reusable Nuclear Shuttle, that was the REAL name)  hence build in certain numbers. And from there, they would use multiple RNS to build a couple or trio of Mars stacks - that would fly to Mars in convoy just in case something went wrong.

-(Hello, For All Mankind season 3 - with the multiple ships helping each others rather than racing).

- Note that it is only because NASA was so cash strapped about Mars architectures that they featured just one  ship (1969-1989, before Mars Direct).

- Obviously Mars Direct and the DRM tried a different approach with pre-positioned hardware and propellant manufacturing send ahead of the manned ship. No idea whether it helps with aborts when in heliocentric orbit between Earth and Mars ?

[Danderman]

In the event that it's discovered that landing on Mars is impossible, then maybe the best alternative is abort to Mars orbit, and wait until rescue is possible.

However, for early missions, it may be a long wait.

Someone is going to suggest a base camp in Mars orbit, but I'm not sure that it would be accessible to all missions to Mars.

This also raises the question of aborts during early phases of the mission, ie immediately after TransMars injection. Is return to Earth going to be feasible at all, even assuming that the damaged Starship has a functional engine and prop? Can it survive a dip in the atmosphere to enter LEO?

[Danderman]

My feeling after reading replies here is that much of the Mars mission remains TBD, ie Elon plans to get serious about the mission after Super Heavy is flight proven.

[whitelancer64]

What I am seeing from the replies is that there are 2 major phases for an abort back to Earth:

Phase 1: direct return to Earth, or

Phase 2: use Mars swingby to return to Earth.

Of course aborts require Starship to be able to safely return to Earth, ie either survive Earth re-entry and landing, or abort to Earth orbit.

The nature of the circumstances forcing the abort are key: perhaps Starship's landing legs are damaged, or the landing propellant has been lost - in that case, aborting to Earth orbit may be necessary. There may be scenarios where landing is impossible, but so is return to Earth.

Of course, much later on (when Mars has been colonized), abort to Mars orbit may be possible.

The question is when Phase 2 begins.

"Phase 1" is really only valid prior to TMI. After that, there's not enough fuel  to flip around and return to Earth, they're committed to either going to Mars or orbiting around the Sun to return to Earth.

What scenario are you imagining where landing is impossible but so is return to Earth?