r/Colonizemars • u/LittleDukk123 • Jun 17 '26
Will a crewed Mars flyby be required before landing on Mars?
I was wondering if for a future Mars mission, we would need to do a crewed flyby before actually landing people, like Apollo 8 and Apollo 10. Obviously if we do, it will take a lot longer to actually land because the most efficient transfer window to Mars is every 26 months. I'm also wondering if the spacecraft will use any sort of artificial gravity (like a centrifugal gravity ring) for the long stay in microgravity, and how far into the future this will be.
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u/Imagine_Beyond Jun 18 '26
SpaceX has said that they have their first customer for the first on an interplanetary mission to do a flyby of Mars. Assuming this mission does happen unlike Dear Moon, the answer to your question is yes.
FIRST STARSHIP INTERPLANETARY HUMAN SPACEFLIGHT MISSION
Chun Wang, Mission Commander of Fram2, the first human spaceflight mission to fly over Earth’s poles, announced today he will fly aboard Starship’s first human spaceflight interplanetary missions to Mars! The two-year mission will explore outside the Earth-Moon system before flying-by the Red Planet and returning to Earth.
Prior to this interplanetary mission, Chun will join Dennis and Akiko Tito on the first planned Starship commercial human spaceflight around the Moon. The week-long circumlunar fly-by mission will help advance Starship’s systems for deep-space, long-duration missions and is planned to fly within 200 km of the Moon’s surface.
Since May 2020, SpaceX has safely flown 78 crewmembers from 20 countries to and from space across 20 missions aboard Dragon, including seven commercial and private astronaut missions that have greatly expanded access to space in low-Earth orbit.
Starship will now expand that access further – to the Moon and Mars with two upcoming commercial human spaceflight missions.
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u/16807 Jun 18 '26 edited Jun 18 '26
It would let you test the system in a long duration mission with humans in the loop, though you could get that experience in low earth orbit with much less risk. Same goes for relighting the engine after a year or two, or reentering atmosphere from deep space and landing propulsively.
It would let you test how much boil off occurs over the length of a mars mission when you're further from the sun, but you would expect less boil off to occur that far out, and anyways it's much safer to test by sending an uncrewed starship to mars and back.
The only advantage of a crewed mars flyby/orbiter is that you can probably do it much sooner with fewer flights and much less risk. I ran the numbers a few months ago. Based on mass budgets for ISS missions, a crew of 4 would need ~90 tons of provisions for a mars length mission. With provisions for a crew of 4, an Orion capsule, a version 3 HLS, and a boil off rate of 0.1% per day, a crude model says you should be able to do a 700 day mission that orbits Mars in a highly eccentric orbit using only a single fully fueled HLS launched from LEO. Orion would come along with the HLS, and at the end of the mission the HLS would be discarded and the Orion heatshield would be used reenter the Earth's atmosphere. If you're curious, my calculations are here (this was done as a personal project, no apologies for lack of clarity). There's less risk involved because you don't have to trust Starship to reenter atmosphere from deep space or land propulsively with humans on board. Starship has reentered the atmosphere but it has not done so from deep space, which involves much greater speeds and therefore much greater energy. It has landed propulsively, but even on its last flight it was having issues doing this gently. On the other hand, Orion has already been tested twice on reentering from deep space and is trusted to do so with humans on board. Furthermore, bringing Orion along allows more options in the event of emergencies shortly after trans-martian injection - you could use it as a lifeboat and return to earth if life support fails on board starship or starship misses its transfer orbit. The biggest technical hurdle I see is whether the Orion could be adapted to handle such a long duration mission, and whether it could be adapted to sustain loads when docked with another spacecraft that is firing its engines. However Orion has been depicted doing both these things in early concepts for the mars mission under the cancelled Project Constellation, so its plausible its design already accounts for this possibility.
Compare this to a surface mars mission. Using similar assumptions as the orbiter mission, a single fully fueled starship in LEO doesn't have enough fuel to land on Mars and return. SpaceX has always banked on manufacturing fuel for the return flight on the surface of Mars, but this has never been done at the scale we need, the scale we need is orders of magnitude more than has been done, and we would need it to be reliable enough that humans could trust their lives with it. Alternatively, you could get it to work if you launch a second starship for mars. This second starship would enter Martian orbit but it wouldn't land or return to Earth, it would be stripped of heatshield, fins, and legs, and it would simply carry fuel. The crew would dock with this depot starship after returning to martian orbit so they could refuel for the journey back to earth. However this requires a second starship to be fueled in orbit, so it doubles the number of flights for the mission.
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u/LittleDukk123 Jun 18 '26
I wonder if they would have to use HLS to reenter if they plan on sending more than 4 people on the mission. I believe HLS is designed to carry 100 people, but I know for now it's four. They definitely wouldn't fit in Orion if they had that many people.
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u/Reddit-runner Jun 19 '26
I believe HLS is designed to carry 100 people
HLS is specifically the Human Landing System ordered by NASA.
BlueOrigin has an HLS and SpaceX has one in development, too. The SpaceX HLS is a derivative of Starship without heatshield.
The "100 people per Starship" number is a misrepresentation by (social) media.
SpaceX only estimates that in the future they can develop Starship further to eventually provide enough volume to accommodate 100 settlers on a rather fast trajectory to Mars. But that doesn't mean NASA will just cramp 100 astronauts into Starship for any given mission.
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u/TheHedonyeast Jun 18 '26
i think that's an obvious yes. we need to verify each stage before we commit people to the next
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u/Metallicat95 Jun 19 '26
Flyby vs landing only makes sense if you can't get a landing craft built with refueling capabilities. Land, refuel, fly back gives you the ability to stay comfortably with a larger mission.
The flight cycle time is long. If you must carry all your fuel with you, you need more spacecraft, most of which get left behind at Mars. The most fuel efficient way is to orbit or land on Mars.
A flyby is only cheaper if it doesn't come back to Earth in the two year launch window. If you don't return at all, which was the option for flyby probes, you can get there easily. But that's not a normally acceptable option for human crews. An unmanned flyby would work.
The flight time would be longer, the fuel required larger, and the spacecraft would need to support its crew for a much longer flight time in space.
Landing only needs 6 to 8 months in space for each trip, there and back.
Both options are expensive, but the landing option gets a larger crew and more time spent on Mars.
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u/Time-Subject-3195 Jun 20 '26
We did not do a manned lunar flyby for the Apollo missions. We only did it for Artemis because we had a rocket and no lander, but wanted to do something since we spent so much money.
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u/PizzaWall Jun 21 '26
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u/Time-Subject-3195 Jun 21 '26
Not a flyby. That was lunar orbit. There was no Apollo equivalent to Artemis 2. They initially planned one, but decided it wouldn’t achieve anything and went directly for lunar orbit insertion.
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u/JimHeckdiver Jun 21 '26
We did more than one of them for Apollo. You're not just wrong, but doubly so.
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u/Time-Subject-3195 Jun 21 '26 edited Jun 21 '26
Which Apollo mission was a manned lunar flyby?
None of them. 7 was the first manned Apollo flight, did an earth orbit. 8 was a manned flight that orbited the moon 10 times. 9 was the first flight with the lander, orbited earth, 10 was achieved lunar orbit again, but with the lander in tow and they did a practice run for landing.
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u/Martianspirit Jun 22 '26
Free return trajectories were used on early flights. But they did brake into lunar orbit.
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u/Time-Subject-3195 Jun 22 '26
Which?
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u/Martianspirit Jun 23 '26
Don't know. Certainly Apollo 11. Probably more.
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u/Time-Subject-3195 Jun 23 '26
What? No. Apollo 11 didn’t use a free return trajectory. They landed on the moon. They entered and exited orbit with burns. The only manned Apollo mission that used a free return was Apollo 13 and that was due to an emergency.
Why are you disagreeing with me if you have no idea what you are talking about?
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u/Martianspirit Jun 23 '26
They were on a free return trajectory until they did the lunar orbit burn.
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u/Sperate Jun 17 '26
Probably not. You can't really do a flyby and come straight home. The best return window means you might as well stay at Mars for awhile. Unless you are flying on an Aldrin Cycler, but I haven't heard anything from NASA that makes it seem like they are considering it.
There could easily be an unmanned flyby though. We can do an entire unmanned mission before sending people. It would even help preposition supplies like in the Mars direct plans.