Delta-v Map
How much change in speed it takes to move between Earth, orbit, the Moon, Mars and the asteroids.
ESO/S. Guisard (www.eso.org/~sguisard) (CC BY 4.0)
Delta-v Map
What is this? A map of space trips. Each line is one leg of a journey, and its number says how much a spacecraft must change its speed to fly that leg. Add up the legs and you get the trip's fuel budget.
How to use it: Choose a start and a destination: tap two dots on the map, use the From and To menus, or press one of the trip buttons. The route lights up and the fuel budget bar adds up each leg.
Fuel budget for this trip
Total delta-v
Swipe sideways to see the whole map.
Values are one-way, ideal impulsive manoeuvres unless marked typical. Real missions add losses and plane changes.
Try this
- Press "To orbit" to go from Earth's surface to low Earth orbit.Notice: That first step costs 9.4 km/s. Going on from orbit all the way to the Moon's surface costs only about 5.6 km/s more.
- Press "To the Moon", then "To Mars", and compare the totals.Notice: They are almost the same: about 15.0 and 15.1 km/s, even though Mars is always more than a hundred times farther away than the Moon. Mars has air to brake with when you land; the Moon has none, so every bit of slowing down costs fuel.
- Plan a trip from Mars surface back to Earth surface.Notice: The last leg, down to Earth's surface, costs 0 km/s: Earth's air and a heat shield do the braking, as they did for every Apollo crew. Climbing off Mars still costs about 4.1 km/s.
- Press "To geostationary orbit" and compare it with going from low Earth orbit to low lunar orbit.Notice: Reaching the high orbit where TV and weather satellites sit costs about the same as reaching orbit around the Moon: about 3.9 km/s from low Earth orbit in both cases.
The ideas behind it
What is delta-v?
Think of a road trip. Add up every time you speed up and every time you brake: that total is your delta-v. In space there is no road to push against and no brakes, so every change of speed, up or down, has to come from the rocket engine, and every bit of it costs fuel.
Why is getting to orbit the hardest step?
Being in orbit is not about being high up. It is about going sideways so fast that you keep falling around Earth instead of into it. Just above the air that means about 7.8 km/s (about 28,000 km/h), once round the planet in about 90 minutes. On the way up a rocket also loses roughly 1.5 to 2 km/s fighting gravity and air drag (Earth's spin gives a little back), so this one step costs about 9.4 km/s.
Why is landing on Mars cheaper than landing on the Moon?
Mars has a thin atmosphere. A lander hits that air at high speed and its heat shield turns the speed into heat; parachutes and a short rocket burn at the end do the rest. So the map counts 0 km/s of rocket fuel for landing on Mars, but 1.63 km/s for the airless Moon, where engines must do all the braking. Leaving Mars is another story: climbing back up to orbit costs about 4.1 km/s.
What is aerobraking?
Using a planet's air as a free brake. A spacecraft dips into the thin top of the atmosphere, drag slows it, and it saves fuel it would otherwise burn. In 2006 NASA's Mars Reconnaissance Orbiter shrank its orbit this way, with hundreds of dips through Mars's upper air over about five months.
Why does each km/s matter so much?
A rocket has to carry its own fuel, and that fuel has to be pushed along too. So each extra km/s needs more fuel than the one before. That is why the Saturn V that sent astronauts to the Moon weighed nearly 3,000 tonnes at launch, most of it propellant.
Sources: computed legs use standard two-body orbit formulas with NASA/JPL planet data (scripts/build-deltav.mjs); typical legs from the Delta-v budget article on Wikipedia and its cited references. Saturn V launch mass: NASA. Mars Reconnaissance Orbiter aerobraking: NASA/JPL.
Say "delta vee". It means "change in speed": how much a spacecraft must speed up, slow down or change direction. It works like a fuel budget for a trip, measured in kilometres per second (km/s).
More in the glossary →The path of something that keeps falling around a planet or star without ever hitting it, because it is moving sideways fast enough.
More in the glossary →An orbit just above the air, a few hundred kilometres up. The International Space Station flies there, going once round Earth in about 90 minutes.
A high orbit, 35,786 km above the equator, where one trip round Earth takes as long as one turn of Earth (just under 24 hours). A satellite there seems to hang still in the sky, which is why TV and weather satellites use it.
A stretched orbit used to get from one place to another, like a motorway slip road. You only pass along it; you do not stay there.
Using a planet's air as a free brake. The spacecraft dips into the thin top of the atmosphere and air drag slows it down, saving fuel. The price is heat, so it needs a heat shield or many gentle passes.
The most fuel-saving way to move between two circular orbits: one push to start an oval path that just touches the new orbit, and a second push when you get there.
More in the glossary →Data table (text alternative)
| From | To | → | ← | How it was worked out |
|---|---|---|---|---|
| Earth surface | Low Earth orbit (200 km) | 9.4 km/s | 0 km/s (can use aerobraking) | typical (published): Delta-v budget (Wikipedia, with its cited references), typical values including lossesLaunch to orbit: about 7.8 km/s of orbital speed plus losses to gravity and air drag. |
| Low Earth orbit (200 km) | Geostationary transfer orbit | 2.45 km/s | 2.45 km/s (can use aerobraking) | computed (ideal): Hohmann perigee burn, 200 km to 35,786 km altitude, equatorial |
| Geostationary transfer orbit | Geostationary orbit | 1.48 km/s | 1.48 km/s | computed (ideal): Hohmann apogee burn, no plane changeFrom a launch site away from the equator, also changing the orbit's tilt adds a few hundred metres per second. |
| Low Earth orbit (200 km) | Earth escape | 3.22 km/s | 3.22 km/s (can use aerobraking) | computed (ideal): Escape speed minus circular speed at 200 km |
| Low Earth orbit (200 km) | Transfer to the Moon | 3.13 km/s | 3.13 km/s (can use aerobraking) | computed (ideal): Raise apogee to the Moon's mean distance |
| Transfer to the Moon | Low lunar orbit (100 km) | 0.82 km/s | 0.82 km/s | computed (ideal): Patched conic capture into a 100 km lunar orbit |
| Low lunar orbit (100 km) | Moon surface | 1.63 km/s | 1.63 km/s | computed (ideal): Circular speed at 100 km (ideal, no gravity losses; real landings need more) |
| Low Earth orbit (200 km) | Transfer to Mars | 3.61 km/s | 3.61 km/s (can use aerobraking) | computed (ideal): Earth-Mars Hohmann departure from 200 km, Oberth effect included |
| Transfer to Mars | Low Mars orbit (300 km) | 2.09 km/s (can use aerobraking) | 2.09 km/s | computed (ideal): Capture into a 300 km circular Mars orbit |
| Low Mars orbit (300 km) | Mars surface | 0 km/s (can use aerobraking) | 4.1 km/s | typical (published): Delta-v budget (Wikipedia, with its cited references), typical values including lossesLanding mostly uses the atmosphere (heat shield and parachutes); the ascent back to orbit is the published typical value. |
| Low Earth orbit (200 km) | Near-Earth asteroid (Bennu) | 4.11 km/s | 4.11 km/s (can use aerobraking) | computed (ideal): Heliocentric Hohmann 1 au to Bennu's semi-major axis, coplanar (ignores its 6 degree inclination and its eccentricity); departure from 200 km LEO |
| Low Earth orbit (200 km) | Ceres orbit | 9.48 km/s | 9.48 km/s (can use aerobraking) | computed (ideal): Heliocentric Hohmann 1 au to Ceres, coplanar (ignores its 10.6 degree inclination); departure from 200 km LEO, capture into a 200 km Ceres orbit |
Tools and lessons use simplified models for learning only. They must not be used for navigation, mission planning or any operational decision. Certificates are free and non-accredited. Read the educational content disclaimer