Mission Δv Budget Ladder (2D)

Engine

Spacecraft Mass

Initial wet mass 3200 kg

Payload / dry mass 1000 kg

Mission Legs

Mid-course correction (0.10 km/s) Surface descent & landing (0.80 km/s)

Contingency margin 10%

Δv Ladder

Live Readouts

Total Δv budget

0.00 km/s

Propellant burned

0 kg

Final mass margin vs payload

0 kg

How it works

Every burn obeys Tsiolkovsky's rocket equation. Rearranged for the mass left after a maneuver of size Δv:

Δv = Isp · g0 · ln(m0/mf)
mf = m0 · exp(−Δv / (Isp · g0))
propellant used = m0 − mf

A real mission is not one burn — it is a ladder of them. The mass left over after burn 1 becomes the starting mass m0 for burn 2, so each leg's propellant cost compounds on a lighter (or, if margin is too thin, an already-starved) vehicle. This 2D map chains the same four legs as the 3D version — departure injection, an optional mid-course correction, orbit insertion, and an optional landing burn — plus a contingency reserve added as a percentage of the baseline total, exactly the way mission designers pad a Δv budget for navigation errors and off-nominal burns.

Engine — chemical propulsion trades a low specific impulse (Isp) for high thrust; ion propulsion needs far less propellant per unit Δv (higher Isp) but the mass savings only matter if the vehicle can afford the longer burn time.
Wet / dry mass — dry mass is the payload that must still exist after every burn. If the ladder's cumulative propellant use eats past (wet − dry), the margin readout goes negative: the mission is not flyable with this propellant budget.
Contingency margin — real missions never fly the bare-minimum Δv; a 5–15% reserve absorbs launch dispersions, navigation error and off-nominal burns.

The fuel bar beside the transfer map is a physical bar chart: each block is one increment of remaining propellant, and blocks disappear from the top as the ship burns down the ladder — a stalled or empty column mid-ladder is the visual signature of an infeasible mission. Drag the map to pan and scroll (or pinch) to zoom the transfer orbit.

Earth Mars Burn marker Propellant remaining

drag to pan · scroll to zoom