Q&A: Mars Mission Aborts Near Mars

[Danderman]

By "return to Earth", I mean Earth orbit.

I don't think a Mars Starship would be able to return for a landing on Earth, maybe not even at the start of a mission. The different in the masses of re-entry tiles, landing prop, mass of the landing legs, etc may be sufficient to delete anything that would allow Earth landing.

It's possible that the flight crews would travel to orbit on the tankers or some other ship, so the Mars Starship could be optimized for Mars landing. Perhaps the Mars Starship would be launched virtually empty, and then another Starship would be used to fill it with consumables - in a scenario where Starship to LEO is cheap, but Starship to Mars is expensive.

[DanClemmensen]

By "return to Earth", I mean Earth orbit.

I don't think a Mars Starship would be able to return for a landing on Earth, maybe not even at the start of a mission. The different in the masses of re-entry tiles, landing prop, mass of the landing legs, etc may be sufficient to delete anything that would allow Earth landing.

It's possible that the flight crews would travel to orbit on the tankers or some other ship, so the Mars Starship could be optimized for Mars landing. Perhaps the Mars Starship would be launched virtually empty, and then another Starship would be used to fill it with consumables - in a scenario where Starship to LEO is cheap, but Starship to Mars is expensive.

This is especially true when a fleet is getting ready to go to Mars. The ships of the fleet will be launched to LEO and provisioned over a period of months, and the crews will go up as late as possible prior to the fleet leaving for Mars. Probably a single shuttle would carry crew (packed in like tourist class) for five Mars transports.

[whitelancer64]

By "return to Earth", I mean Earth orbit.

I don't think a Mars Starship would be able to return for a landing on Earth, maybe not even at the start of a mission. The different in the masses of re-entry tiles, landing prop, mass of the landing legs, etc may be sufficient to delete anything that would allow Earth landing.

It's possible that the flight crews would travel to orbit on the tankers or some other ship, so the Mars Starship could be optimized for Mars landing. Perhaps the Mars Starship would be launched virtually empty, and then another Starship would be used to fill it with consumables - in a scenario where Starship to LEO is cheap, but Starship to Mars is expensive.

Starships going to Mars are meant to eventually be refueled on Mars and return to Earth. They will be designed for both Earth entry and Mars entry.

[Jim]

By "return to Earth", I mean Earth orbit.

I don't think a Mars Starship would be able to return for a landing on Earth, maybe not even at the start of a mission. The different in the masses of re-entry tiles, landing prop, mass of the landing legs, etc may be sufficient to delete anything that would allow Earth landing.

No, earth landing.   Earth orbit requires too much propellant

[Danderman]

Since the system spec for the Mars mission does not seem to be written yet, I believe that posts here about the mission architecture are speculative. Moreover, public comments by Elon may refer to the initial mission, or a Block 10 mission 100 years from now.

So my interest in this topic is about the possibility of an abort late in the Mars trajectory, what happens if the landing prop tanks lose prop, what does the crew do?

Obviously, in a convoy, they transfer to another ship.

If the Starship is traveling alone, they would have the option to abort to LEO (going back the long way), or Mars orbit.

[dchenevert]

I imagine the first crewed starships to Mars will be a group of three, e.g. the Nano, the Pico, and the Santa Margarita

[Danderman]

What are the requirements driving the need for 3 ships?

If the probabilities of going to Mars are enhanced by reducing mission requirements,  that would be a good thing.

If Apollo 11 had to be accompanied by Apollo 12 and Apollo 13, it would have been a much greater undertaking.

I am suggesting that the real requirements are not obvious, and a lot of work must be done. I suspect the work will only be done after Super Heavy is flight proven. My feeling is that there may be virtual convoys, multiple missions launched during a launch window, but not necessarily flying close to each other.

[whitelancer64]

Since the system spec for the Mars mission does not seem to be written yet, I believe that posts here about the mission architecture are speculative. Moreover, public comments by Elon may refer to the initial mission, or a Block 10 mission 100 years from now.

So my interest in this topic is about the possibility of an abort late in the Mars trajectory, what happens if the landing prop tanks lose prop, what does the crew do?

Obviously, in a convoy, they transfer to another ship.

If the Starship is traveling alone, they would have the option to abort to LEO (going back the long way), or Mars orbit.

Starship needs around 500 m/s of dV to land on Mars, contained in the header tanks. If they lose propellant the only choice is to go on a free return orbit back to Earth reentry (they would not be able to enter Earth orbit), they probably would not have enough fuel to enter Mars orbit.

[whitelancer64]

What are the requirements driving the need for 3 ships?

If the probabilities of going to Mars are enhanced by reducing mission requirements,  that would be a good thing.

If Apollo 11 had to be accompanied by Apollo 12 and Apollo 13, it would have been a much greater undertaking.

I am suggesting that the real requirements are not obvious, and a lot of work must be done. I suspect the work will only be done after Super Heavy is flight proven. My feeling is that there may be virtual convoys, multiple missions launched during a launch window, but not necessarily flying close to each other.

Primary, backup, backup for the backup. Triple redundancy is common (where it's possible) in engineering something that absolutely has to function. Crew vehicles launched in the same synod would probably intentionally be close enough to dock and rescue another crew if something went horribly wrong in transit.

[Danderman]

"Starship needs around 500 m/s of dV to land on Mars, contained in the header tanks. If they lose propellant the only choice is to go on a free return orbit back to Earth reentry (they would not be able to enter Earth orbit), they probably would not have enough fuel to enter Mars orbit."

Mars Starship *should* have an RCS sufficient for midcourse maneuvers, ship to ship rescue, and late course correction for landings. If so, the RCS should be able to maneuver Starship for aero-braking into Mars orbit.

I admit I am handwaving here, not knowing the final spec for Mars Starship.

[Danderman]

"Crew vehicles launched in the same synod would probably intentionally be close enough to dock and rescue another crew if something went horribly wrong in transit."

The question is whether rescuing a crew without their consumables is going to help them much. Or how much "extra" mass Mars Starship can deliver to the surface of Mars.

Someone would probably offer the suggestion that additional supplies could be pre-positioned on the surface of Mars, but what if Starship lands off-course? This implies a requirement for a cargo Starship to be stored in Mars orbit. Which would solve a lot of problems for late aborts.

[Zed_Noir]

"Crew vehicles launched in the same synod would probably intentionally be close enough to dock and rescue another crew if something went horribly wrong in transit."

The question is whether rescuing a crew without their consumables is going to help them much. Or how much "extra" mass Mars Starship can deliver to the surface of Mars.
<snip>

On the basis of a Mars bound wave of Starships will have both crewed and uncrewed cargo Starships.

AIUI all the initial Mars bound Starship transports are essentially the same. So it would be sensible to loaded each Starship with enough extra consumables for the transit and about 6 weeks on Mars for one crew. Presuming the initial Mars crew size will be at the most 12 persons per Starship. The extra consumables will be transfer later to the crewed Starships to replenished their consumables stock as needed and also act as emergency consumables caches.

The above consumable requirement also permit the the use of any Starship in a wave to return crew back to Earth without having to transfer large quantities of consumables between Starships.

[stilrz]

So my idea of the only practical way to get to Mars *alive and in condition to work/explore* is in a space station. One that attempts to rotate and has a full ability to regenerate food and O2. (at least algae, duckweed and likely fish))  For this audience it would be at least 2 habitat starships, 2-3 mars landers and 2-4 fuel tankers. Fuel tanks would work as backup landers and likely there would be a lander fueled on Mars, 1-2 habitat SS and lots of robots.  At least one fueled starship in
orbit around Mars.  So the space station would simply  loop around Mars over a 1-3 month period -- NOT orbit. As it approaches the planet the lander leaves, lands near spare return vehicle and exploration begins. The only way to survive and be useful in space for nine months is to at least have some rotational resistance to their muscles -- rotation is required. ISS astronauts spend huge amounts of every day exercising and still take a month or more to recover.  Of course waldos are bad solution.

Back on topic: So the lander leaves the station and as it power descends it would have the ability to power abort. The distance and delta-V outside the atmosphere should be doable by a second set of engines and fuel tanks. Once in atmo it is likely committed to landing. So if lander fails then landing near a prepositioned launcher gets them back up. Then the "launch" distance is not to earth just "near mars". Further a emergency launcher could be small enough just to send crew up and survive for a week or so. The station would have spares to rescue anything that can make mars orbit too.  So the main mass of the station never slows down and needs only a small amount of power to maneuver and return.

Oh the lander can act as a isolated bio-lab to detect life in the tons of material brought from planet -- While in space.

[Danderman]

Since there isn't a real baseline for the Mars mission, people are jumping in with their own architectures, which inevitably add more requirements to the mission.

I really don't know what Elon is thinking; in the past, he has mentioned one way trips.
 If return to Earth is in the mix for every mission, that would really complicate things. For example, it's not going to be a few weeks on Mars, it's going to be 18+ weeks before return to Earth is feasible.

But this topic is about aborts in the later phase of a flight to Mars. So far, the suggestions are:

Return to Earth, no matter how long it takes, or

Transfer to a second ship.

I will spend some time on these alternatives a bit later.

[Danderman]

A requirement for multiple Starships per Mars missions implies all sorts of requirements - if 10(?) tankers per Starship in LEO are required for propellant loading, then 2 Starships are double that.

On the other hand, abort to Mars orbit could require just one "safe haven" in orbit. That safe haven could be an uncrewed Starship with propellant to land on Mars.

So, are there failure modes where ship to ship rescue is possible, but abort to Mars orbit is not?

[Jim]

A requirement for multiple Starships per Mars missions implies all sorts of requirements - if 10(?) tankers per Starship in LEO are required for propellant loading, then 2 Starships are double that.

On the other hand, abort to Mars orbit could require just one "safe haven" in orbit. That safe haven could be an uncrewed Starship with propellant to land on Mars.

So, are there failure modes where ship to ship rescue is possible, but abort to Mars orbit is not?

Starships are not going into Mars orbit.  Don't have the delta V for it.

[laszlo]

Since the system spec for the Mars mission does not seem to be written yet, I believe that posts here about the mission architecture are speculative. Moreover, public comments by Elon may refer to the initial mission, or a Block 10 mission 100 years from now.

So my interest in this topic is about the possibility of an abort late in the Mars trajectory, what happens if the landing prop tanks lose prop, what does the crew do?

Obviously, in a convoy, they transfer to another ship.

If the Starship is traveling alone, they would have the option to abort to LEO (going back the long way), or Mars orbit.

Starship needs around 500 m/s of dV to land on Mars, contained in the header tanks. If they lose propellant the only choice is to go on a free return orbit back to Earth reentry (they would not be able to enter Earth orbit), they probably would not have enough fuel to enter Mars orbit.

So they've used up the header tanks to return to Earth, survived entry into the atmosphere and are falling horizontally towards the ground. What next?

[whitelancer64]

Since the system spec for the Mars mission does not seem to be written yet, I believe that posts here about the mission architecture are speculative. Moreover, public comments by Elon may refer to the initial mission, or a Block 10 mission 100 years from now.

So my interest in this topic is about the possibility of an abort late in the Mars trajectory, what happens if the landing prop tanks lose prop, what does the crew do?

Obviously, in a convoy, they transfer to another ship.

If the Starship is traveling alone, they would have the option to abort to LEO (going back the long way), or Mars orbit.

Starship needs around 500 m/s of dV to land on Mars, contained in the header tanks. If they lose propellant the only choice is to go on a free return orbit back to Earth reentry (they would not be able to enter Earth orbit), they probably would not have enough fuel to enter Mars orbit.

So they've used up the header tanks to return to Earth, survived entry into the atmosphere and are falling horizontally towards the ground. What next?

Why would they have used up the header tanks to return to Earth? A few minor adjustments would need to be made to the orbit, but not all of the reserve fuel. Starship only needs about ~150 m/s dV to land on Earth.

[sdsds]

Since there isn't a real baseline for the Mars mission [...]

You mean the Starship-based mission, right? Because

M. A. Rucker et al., "NASA's Strategic Analysis Cycle 2021 (SAC21) Human Mars Architecture," 2022 IEEE Aerospace Conference (AERO), Big Sky, MT, USA, 2022, pp. 1-10,
http://dx.doi.org/10.1109/AERO53065.2022.9843237

might be worth a look. Or there might even be one published more recently than 2022.

Abstract:
The National Aeronautics and Space Administration's (NASA) Mars Architecture Team (MAT) was challenged to develop a mission architecture capable of transporting humans to the surface of Mars and back as fast-and as soon-as practical. This challenge represented a significant departure from previous approaches that minimized Earth-launched mass and maximized in-space transportation efficiency, often resulting in roundtrip missions of three years or more in duration. In the interest of crew health, MAT's cross-Agency team of subject matter experts was challenged to develop an architecture capable of shortening crew time away from Earth to about two years. MAT was given specific mission constraints, such as number of crew, as well as mandates to minimize surface infrastructure as much as possible and to incorporate nuclear transportation options. The resulting MAT-developed concept, referred to here as the Strategic Analysis Cycle 2021 (SAC21) architecture, leverages Artemis elements and emerging commercial capabilities for cargo and logistics launches, and features a hybrid Nuclear Electric Propulsion (NEP)/Chemical transportation system able to complete the 1.8 billion kilometer round-trip journey to Mars and back in 760 to 850 days transit time for the 2039 Earth departure opportunity. Three Mars Descent Systems (MDS), each capable of landing about 25 metric tons of useful cargo on the surface of Mars, would be pre-deployed in advance of crew departure from Earth; two of these MDS's would deliver a partially fueled Mars Ascent Vehicle (MAV), a fission power system, surface mobility, and additional MAV propellant. To minimize surface infrastructure, only two of the four Mars crew would descend and live in an MDS-landed pressurized rover, exploring the martian surface for 30 martian days, or sols, before returning to Mars orbit aboard their MAV and rejoining the other two crew on the Deep Space Transport for the Earth return voyage. Specifics of many of these architecture elements are detailed in separate technical publications; this paper outlines the end-to-end integrated architecture performance and concept of operations, including synergies with Artemis lunar architecture elements. It is important to note that NASA does not have a formal human Mars program and no decisions have been made; the architecture described here is intended to fill in an often-overlooked corner of the trade space, helping to complete the menu of options available to decision-makers as they chart the course for humans to Mars.

[Danderman]

No lack of NASA studies of Mars missions.

But, there isn't a lot out there on missions using Starship.