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#1 Yesterday 18:44:35
- SpaceNut
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- From: New Hampshire
- Registered: 2004-07-22
- Posts: 30,388
Block 3 starship first mission
The information on the web indicates that 4 cargo with 2 crewed are thought to be there with fuel to return already waiting but that means those ships needed a dedicated mission to create fuel.
It might look like this with the ships on mars surface.
But what if the mission was a half payload delivery where man setup a system from the cargo and ships that they arrive in.
Ai indicates that
[center][size=150]Starship Block 3 – Fuel Remaining on Mars (50 t Payload)[/size][/center]
Scenario: Block 3 Starship is fully refueled in LEO (≈1200–1250 t propellant) and departs for Mars carrying 50 t of payload.
With a lighter payload than the “maxed out” case, Starship needs slightly less Δv from its tanks, so it arrives with a bit more residual propellant margin—but it still lands effectively “dry” from an operational standpoint.
[hr]
[size=120]Propellant Usage Breakdown (50 t Payload)[/size]
Trans-Mars Injection (TMI): ~850–900 t
Course Corrections: ~10–20 t
Mars EDL + Landing Burn: ~80–120 t
Total Used: ~940–1,040 t
Initial Load: ~1200–1250 t[hr]
[size=120]Estimated Remaining Propellant on Mars[/size]
Remaining = 1200–1250 t - (940–1040 t) Remaining ≈ 160–310 t (in main tanks, gross)However, this “remaining” is not clean, usable ascent propellant:
Main tanks: Largely reserved as performance margin, residuals, and non-usable slosh.
Header tanks: Provide the controlled landing propellant and are nearly empty after touchdown.
Practical, controllable post-landing propellant:
[size=120]Still only a few percent of total capacity, effectively negligible for ascent.[/size]The lighter payload improves margin and robustness, not the fundamental architecture: Starship is still intended to rely on ISRU for any departure from Mars.
[hr]
[size=120]Operational Conclusion (50 t Payload Case)[/size]
Starship lands with more margin than a heavier-payload mission, but still not enough for ascent.
Mission design still assumes full ISRU refueling (~1200 t CH₄/LOX) on Mars for return.
For base planning, you should continue to treat each landed Starship as operationally “empty”.
[center]Even with only 50 t of payload, Starship’s Mars architecture is still: arrive nearly dry, refuel on the surface.[/center]
Seems like something is off as a full payload is expected to be next to nothing but with less payload it should be quite a bit remaining.
Seems that AI gets confused....
Why “Less Payload” Doesn’t Automatically Mean “More Fuel Left on Mars”
1. The landing burn dominates the fuel budget — not the payload mass
On Mars, Starship performs:A long supersonic retro propulsive deceleration
A flip maneuver
A final landing burn
These burns require a minimum fixed amount of delta‑V, regardless of payload.
Even if you remove 50 tons of cargo, the landing sequence still costs almost the same amount of propellant.Payload mass changes the burn slightly, but not enough to leave a meaningful surplus.
Think of it like braking a car from 80 mph to 0 mph — removing passengers doesn’t change the braking distance much.
2. Starship uses header tanks for landing — and they are sized for safety, not efficiency
The landing fuel comes from:CH₄ header tank
LOX header tank
These tanks are:
Small
Fixed‑volume
Filled before EDL
Designed to guarantee a safe landing even in worst‑case conditions
If payload is lighter, the header tanks don’t magically shrink or adjust.
They still contain the same amount of fuel, and Starship still burns most of it to land safely.So the “extra” fuel isn’t in the main tanks — it’s in the header tanks, and it gets used anyway.
3. Mars atmosphere is thin — so payload mass barely affects drag
On Earth, a lighter vehicle slows down more easily.
On Mars, the atmosphere is so thin that drag is weak, so mass doesn’t change the deceleration profile much.Starship still needs nearly the same:
Heat shield performance
Retropropulsive braking
Landing thrust
Thus, fuel savings from reduced payload are tiny.
4. The landing burn must maintain a minimum thrust level
Raptor engines cannot throttle arbitrarily low.
Even if the ship is lighter:The engines must stay above minimum throttle
That means extra thrust
Which means extra fuel burned
This cancels out much of the theoretical savings from reduced mass.
5. Propellant gauging in low gravity is inaccurate
As we discussed earlier:Slosh
Low gravity
Thermal gradients
Pressure transients
All cause fuel readings to fluctuate, making it look like payload changes fuel remaining when it’s really just sensor noise.
The short version
Reducing payload does help a little, but Starship’s Mars landing fuel requirement is dominated by:Fixed landing maneuvers
Header tank sizing
Minimum engine throttle
Weak atmospheric drag
So the leftover fuel doesn’t scale with payload the way intuition suggests.
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#2 Yesterday 19:05:59
- SpaceNut
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- From: New Hampshire
- Registered: 2004-07-22
- Posts: 30,388
Re: Block 3 starship first mission
This is what Mars Society has in its planning
what we know for harvesting the atmosphere
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#3 Yesterday 19:22:12
- SpaceNut
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- From: New Hampshire
- Registered: 2004-07-22
- Posts: 30,388
Re: Block 3 starship first mission
Our engineered atmosphere is 0.5 bar for internal use starting from mars air which is 0.006 bar Composition: 95% CO2, 2.85% Nitrogen, 0.17% Oxygen.
Normal earth air is o2 at 21% for 1.0 bar containing N2 which makes up almost the remaining % of the 14.7 psi.
Of course one of the issues is the quantity of air we need to the volumes that we are living with in and the other is the fuel levels to get back home are huge which makes the power demand high.
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