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.
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.
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?
Where is a link to the current SpaceX baseline for the initial Mars mission?Or is the baseline in Elon's mind?
The missing piece from these sources is using a swingby of Mars to support return to Earth, ie a slingshot to accelerate the spacecraft.
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, orPhase 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.
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.
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.
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.
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.
"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>
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?
Quote from: Danderman on 01/25/2024 09:57 amSince 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.
Quote from: whitelancer64 on 01/26/2024 09:12 pmQuote from: Danderman on 01/25/2024 09:57 amSince 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?
Since there isn't a real baseline for the Mars mission [...]
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.
But, there isn't a lot out there on missions using Starship.
Someone posted earlier about using Venus in a swingby maneuver to return to Earth, and someone else responded that thermal issues would preclude that.For a Starship design for both Mars and Earth re-entry, it may be the case that thermal issues may not loom so large.
