pre-alpha v39: Simple patched conics estimator for refueling flights, lunar-surface payload, and early fueled-HLS-in-LLO placement cases.

Basic Instructions: The simplest use is to explore pre-selected missions under "Mission Profile" and then customize those missions by adjusting either payload and clicking "Calc fuel" or fuel load and clicking "Calc max payload".

This is all EOR, not LOR. So not the Artemis plan, which is LOR. For the return cases you can see why: they almost all come up short. Previous versions had a data bug in the dV needed for Earth capture on return. Interestingly, the aerocapture case holds out a thread of hope, but it requires keeping the heavy shield and flaps. It's interesting to try things you know won't work and see how badly they fail. One-way missions from LEO are still a go.

There are always two types of Starships involved: the Lunar HLS and the Refueling Tanker. Their specifications can be adjusted in dedicated panels below. Note that tankers can be either expendable or reusable. Expendable cuts the total number of refueling flights significantly at the cost of 6 very expensive Raptor engines. There is no separate propellant depot because my suspicion is that at the beginning HLS will be the propellant depot, and that Orion or Dragon will fly up to dock with it. Supposedly a basic white-painted HLS can achieve <0.2%/day of boiloff in LEO, for a semi-constant daily loss rate of 3.2t/day. I suspect Elon will want to do 4 refueling flights per day, but settle for 2 initially. My belief is they'll want to launch out of LEO in less than a week, so < 22.4 tons lost total (probably less than 6 from last top off). Boiloff is a future to-do.

All models are as simple as possible with the goal of giving a qualitative feel for tradeoffs without being numerically dependable. There are too many assumptions, estimations, and outright SWAGs for this tool to do that. Expect real payloads to be less and refueling flights at least one greater in number

Mission payload and fuel

Mission profile

Mission summary

Mission Starship — Moon-bound vehicle

Refueling Starship — tanker fleet specs

Super Heavy — separation context

Orion Capsule

Δv budgets

Propulsion and logistics

Applied to lunar mission burn legs only; tanker insertion uses the Super Heavy gravity + steering loss field.
# Leg Engine Δv Docked Orion Mission Starship mass before Minimum prop before Prop used Minimum prop after

Mission payload vs refueling flights

Flights Fuel available Initial HLS propellant Max surface payload Required fuel Margin inside tier

Logistics snapshot

Notes

  1. Model limitations. This is a first-order rocket-equation planner: tanker LEO insertion now includes an explicit gravity/steering-loss term, but the lunar mission legs still omit gravity losses, plane changes, boiloff, cooldown, settling, residuals, thermal limits, and operational reserves unless the user adds them through Δv or margin inputs. Gateway is treated as LLO-equivalent; Orion is passive docked mass when attached.
  2. Mass accounting. The lunar-only Mission Starship default dry mass is now treated as the no-heat-shield/no-flaps baseline. Mission 1 is the baseline LEO-return lunar sortie and carries neither Earth-return hardware nor terminal landing fuel. Mission 1a is the Earth-surface-return case and carries heat shield, flaps, landing legs (+25 t dry mass) plus +20 t terminal landing fuel, for +45 t total. Mission 5 carries the +25 t aerobrake/Earth-entry hardware but not the +20 t landing fuel; other fuel savings are calculated by the selected burn sequence.
  3. Stubby tankage. The Stubby model assumes the vehicle keeps Starship's 9 m diameter and is shortened by deleting tank barrel length. Using a 52.1 m public Starship height reference and roughly 28.5 m equivalent tank length, the default 0.8-height vehicle keeps only the remaining tank barrel length rather than scaling propellant linearly. Dry mass is still a planner assumption.
  4. Payload cap versus physics. The uncapped rocket-equation payload check shows what the selected fuel and trajectory could lift if structural, volume, interface, and operations limits were ignored. The actual mission solver still caps delivered cargo at the Mission Starship payload cap.
  5. Refueling tanker accounting. Tanker flights are modeled as zero-cargo launches. The planner separately computes reusable residual propellant in LEO and expendable residual propellant in LEO using the selected ground-relative staging velocity plus eastward launch-site rotation, staging altitude, dry mass, propellant load, Raptor Isp, and explicit gravity/steering loss. Reusable mode then subtracts the landing reserve; expendable mode uses the lower dry mass and has no landing reserve subtraction. Ullage allowances are not included unless the user adds margin.
  6. Versions prior to v37 had a bug in the data section where the dV needed for LEO capture was 1.2kps instead of the correct 3.2kps. I missed it, ChatGPT missed, Grok missed it but Claude found it. Go Claude!
Lunar cargo minimum targets