Chun Wang's Starship Mars orbital mission

[thespacecow]

Chun Wang (https://x.com/satofishi) is the guy funded and commanded the Fram2 mission.

A few days ago he posted this rather ambiguous tweet:

I wonder what is he planning...

https://x.com/satofishi/status/1976327912921104602

A Starship could generate 100+ kilograms of water per day solely from the boiled-off methane and oxygen. Rotating a 9-meter-diameter section at 9 rpm would create 0.38 g Mars-like of artificial gravity.

Imagine swimming in a vertically circular, standard 25-meter pool, where the place you just swam through is now directly above your head. That pool is not just for leisure or exercise; it offers critical protection against solar storms at Venus distance.

I don’t feel excited during a mission; I feel excited when planning one.

Now he posted a new tweet detailing a 2034 Venus-Mars orbital mission which will also visits Phobos and Deimos: https://x.com/satofishi/status/1977081065798787154

2034 Earth–Venus–Mars opportunity looks promising. 10–15 on-orbit refueling operations may be needed to make a crewed ship full. Most can be done at an altitude of 180–200 km, made possible by Starship’s size. The final refueling may be performed at a higher altitude of ~2000 km, just below the Van Allen belt.

Earth departure on 2034-08-21 from 2000 km orbit. A Trans-Venus Injection burn of ~3.7 km/s will place the ship on an Earth–Venus–Earth free-return trajectory. Venus flyby is expected on 2034-12-19, 120 days after departure. Two weeks before the encounter, if the mission proceeds as planned, a 25-m/s maneuver will shift the trajectory from Earth-return to Mars-bound. If not, the ship will free return to Earth in September 2035.

The Venus gravity assist will send the ship into another Earth free-return trajectory, with Mars flyby around 2035-06-02. One week before reaching Mars, a system health check will determine whether to commit to Mars Orbit Insertion. If it’s GO, a small 10-m/s manuever will put the ship to less than 100 km altitude periapsis. Otherwise, a Mars flyby will lead to an Earth return in May 2036.

The ship will enter the Martian atmosphere at about 9.4 km/s, performing an aerobrake to slow to 4.88 km/s and capture into a 100x140000 km, 7-day period high elliptical orbit. At apoapsis, a 50-m/s plane change will align the inclination with Mars’ equator, followed by additional aerobraking to remove about 650 m/s of velocity, placing the spacecraft in a 120x6128 km orbit. A 550-m/s burn at 6128 km altitude will then adjust the trajectory into Phobos orbit.

The ship will stay at Phobos for about 7 days. The Mars–Phobos L1 point is only about two miles above Phobos’ surface, and Mars would dominate nearly half the sky, appearing about 80 times larger than the Moon from Earth.

The ship will depart for Deimos afterward. Two burns totaling roughly 750 m/s will transfer the ship from Phobos to Deimos. And the ship will stay at Deimos for 7 days more.

From Deimos, the ship will raise its apoapsis to form a 20000x140000 km altitude, 7-day orbit, requiring about 420 m/s of delta-v. At apogee, a 50-m/s burn will adjust inclination and lower periapsis to ~500 km for final Trans-Earth Injection. If time and propellant allow, the orbit can be aligned to a polar inclination for Mars ice-cap observations before departure.

A Trans-Earth Injection burn at 500 km altitude, requiring 1.5–1.6 km/s of delta-v in early July 2035. If departure on the first days in July, Earth arrival is expected in December 2035. If missed that window, a March 2036 arrival may look more feasible.

Nominal mission duration: 490 days, with 30 days in Mars orbit and 14 days at Phobos and Deimos.

Two planets, two moons for 3.7+0.025+0.010+0.05+0.42+0.55+0.75+1.55=7.06 km/s Δv

[thespacecow]

Worth mentioning that he just posted then deleted a tweet which unfortunately I didn't screenshot, just go by my memory he said:
1. Elon told him Starship is "one way to Mars", he tried to argue back, but Elon insisted "one way to Mars"
2. He just had some discussion with SpaceX engineers at Starbase, which convinced him Starship is specifically optimized for one way to Mars, not anything else
3. But he's determined to put Starship to use for missions other than "one way to Mars" outside the Earth-Moon system.

Putting aside the mini-controversy wrt the one way to Mars thing, it certainly looks like he's discussing a Starship mission opportunity beyond cislunar space with SpaceX.

PS: I believe these are some of the replies to the deleted tweet: https://x.com/INiallAnderson/status/1978234642256826758, https://x.com/satofishi/status/1978235139046994420

[Oersted]

I have long advocated for a Venus-Mars flyby mission to wring out Starship on a long-duration interplanetary trajectory mission. They really should do that, and they should do it well before 2034!

It will be Apollo 8 on steroids.

[meekGee]

Well it's one way to Mars surface, for that variant (with landing-only legs for example)

But he's talking about an interplanetary non-landing ship, which is very feasible.

If I had one, I'd equip it and take it for asteroid trips, complete with "orbital insertion" and EVA visits.

What he's describing (the planet half) is best done unmanned. Martian moons are more like asteroids but I'd still focus on the main belt or NEOs.

[Vultur]

What he's describing (the planet half) is best done unmanned.

I think the point of this is to do it personally though. This isn't really a science mission, though I'm sure science would be done. It sounds more like an "explorer's first", "because it is there" sort of expedition.

This is exactly the kind of thing that is probably completely doable if you're willing to take early-Antarctic-explorer level risks, but NASA would never do.

Worth mentioning that he just posted then deleted a tweet which unfortunately I didn't screenshot, just go by my memory he said:
1. Elon told him Starship is "one way to Mars", he tried to argue back, but Elon insisted "one way to Mars"
2. He just had some discussion with SpaceX engineers at Starbase, which convinced him Starship is specifically optimized for one way to Mars, not anything else

I wish those weren't deleted, because I don't know what's meant. Surely Starship is planned to be used for several other things? (Starlink, Earth orbit satellite launch, Artemis/Moon for sure ... It's also been put in presentations as a more general Solar System vehicle.)

[meekGee]

What he's describing (the planet half) is best done unmanned.

I think the point of this is to do it personally though. This isn't really a science mission, though I'm sure science would be done. It sounds more like an "explorer's first", "because it is there" sort of expedition.

This is exactly the kind of thing that is probably completely doable if you're willing to take early-Antarctic-explorer level risks, but NASA would never do.

Worth mentioning that he just posted then deleted a tweet which unfortunately I didn't screenshot, just go by my memory he said:
1. Elon told him Starship is "one way to Mars", he tried to argue back, but Elon insisted "one way to Mars"
2. He just had some discussion with SpaceX engineers at Starbase, which convinced him Starship is specifically optimized for one way to Mars, not anything else

I wish those weren't deleted, because I don't know what's meant. Surely Starship is planned to be used for several other things? (Starlink, Earth orbit satellite launch, Artemis/Moon for sure ... It's also been put in presentations as a more general Solar System vehicle.)

Yes I got that sense too (of a personal adventure type quest.)

Works if the adventurer is paying for it, and will be cheaper once the basic Mars surface ship is fully developed.

Asteroids though, while not on the main Mars timeline, they can benefit a lot from first-hand visits by geologists, for several practical reasons, including Mars-related ones.

Plus the deltaV involved in going for a visit (not a flyby) is very manageable.

[jpo234]

Would there be enough fuel left after 1½ years for a successful landing back on Earth, especially if it first ventures to Venus? Venus receives 2611 W/m² vs. Earth's 1366.1 W/m² and Mars' 588.6 W/m² in solar irradiation.

[Comga]

Would there be enough fuel left after 1½ years for a successful landing back on Earth, especially if it first ventures to Venus? Venus receives 2611 W/m² vs. Earth's 1366.1 W/m² and Mars' 588.6 W/m² in solar irradiation.

From the OP

A Starship could generate 100+ kilograms of water per day solely from the boiled-off methane and oxygen.

The conversion of methane and oxygen to water is CH4+2*O2->CO2 + 2*H2O so water is only 45% of the output.
That means that the boiloff to convert to 100 kg of water per day is 222 kg/day.
(The shielding of the ship from the solar flux is an engineering problem, not physics, and he said "could" so maybe the amount of boiloff is other than 100 kg.)
Over 490 days this is comes to 109 tons of propellant.
Full propellant load for V3 Starship is supposed to be 2,300 tons.

Rotating a 9-meter-diameter section at 9 rpm would create 0.38 g Mars-like of artificial gravity.

One possible problem with this is that a 5 meter long torus of water 1 meter deep on the inside of a 9 meter cylinder would have a mass of 503 tons. 
I don't know how much water would be needed for radiation shielding but 1 m would be some kind of minimum for swimming.
So that's around 600 tons of extra mass that would need to be put through that 3.7 km/sec Trans Venus Injection and not much less for all the subsequent burns.
(Can't double book it by using the generated water as shielding because it would be needed early in the 120 day leg "down" to the Venus fly-by.)
Somebody else can do the rocket equation calculations backwards from the Trans-Earth injection, with the target empty mass of Starship and some nominal habitat mass, but tracking this much shielding and unreturned boiloff mass back to the TVI might not work.  It might require a reduction in the dimensions of the shielding "swimming pool" and increase the rotation rate required to get Mars gravity level acceleration.

[MickQ]

And 9 rpm sounds too fast to be practical.  Less than 7 seconds per rotation.  On returning to earth the crew wouldn’t walk straight for a year.

[Vultur]

And 9 rpm sounds too fast to be practical.  Less than 7 seconds per rotation.  On returning to earth the crew wouldn’t walk straight for a year.

9 rpm is stretching it. I'm not sure if highly selected people can adapt to that or not; it's definitely not in the safe range

[thespacecow]

Worth mentioning that he just posted then deleted a tweet which unfortunately I didn't screenshot, just go by my memory he said:
1. Elon told him Starship is "one way to Mars", he tried to argue back, but Elon insisted "one way to Mars"
2. He just had some discussion with SpaceX engineers at Starbase, which convinced him Starship is specifically optimized for one way to Mars, not anything else

I wish those weren't deleted, because I don't know what's meant. Surely Starship is planned to be used for several other things? (Starlink, Earth orbit satellite launch, Artemis/Moon for sure ... It's also been put in presentations as a more general Solar System vehicle.)

I agree, I think this part of the tweet is poorly written and lack proper context, which is probably why he deleted it.

My guess of what he meant is that the Mars Starship is optimized for one way to Mars, i.e. SpaceX is not planning on bring anyone back any time soon. This would obviously be a problem for him if he wants to charter one of the ship to Mars, I think that's why he came up with the idea of Mars orbital mission which can bring him back to Earth in less than 2 years.

[Oersted]

Well it's one way to Mars surface, for that variant (with landing-only legs for example)

If you are referring to my post then I was talking about a Venus and Mars flyby mission, which is eminently doable on one Starship tank of gas and oxidizer (preventing boil-off).

Starship can depart from Earth, slingshot by Venus and Mars and return to Earth on one tank load.

I really think they should do it while preparing for crewed Mars landings.

Such a mission would be a grand adventure and would help qualify the ship for interplanetary space ops.

Risky, yes, a bit, but with a small crew they can easily bring the supplies needed, water and oxygen in abundance, even if the regen systems fail.

[meekGee]

Well it's one way to Mars surface, for that variant (with landing-only legs for example)

If you are referring to my post then I was talking about a Venus and Mars flyby mission, which is eminently doable on one Starship tank of gas and oxidizer (preventing boil-off).

Starship can depart from Earth, slingshot by Venus and Mars and return to Earth on one tank load.

I really think they should do it while preparing for crewed Mars landings.

Such a mission would be a grand adventure and would help qualify the ship for interplanetary space ops.

Risky, yes, a bit, but with a small crew they can easily bring the supplies needed, water and oxygen in abundance, even if the regen systems fail.

I was contextualizing Musk response to Chin's plan, that Starship is one-way to Mars (only)

[jstrotha0975]

Finally, a manned Venus flyby.

[thespacecow]

https://x.com/satofishi/status/1978953142034141654

This is something I never understand: When people say they dream to go to space, what they really mean is that they want to travel to Earth orbit.

But no one says they dream to go to Mars orbit. And when I say I want to go to Mars orbit, they respond, “What? No landing? Why not go down and land?” 🤔