Related tools
- Julian Date ConverterConvert between calendar dates, Julian Date, Modified Julian Date and Unix time, with sidereal time and Delta T.
- Moon Phase CalculatorThe moon's phase, illumination, age and distance for any date, with the next four phases and moonrise for your location.
- Planet Positions and Rise TimesWhere the sun, the moon and the naked eye planets are for any place and date, with rise and set times, brightness and whether you can see them.
- Magnitude CalculatorConvert between apparent and absolute magnitude using the distance modulus, and work out flux ratios, combined magnitudes and surface brightness.
What it does
Runs two body Keplerian orbital mechanics: circular and elliptical orbit speed from the vis-viva equation, orbital period from Kepler's third law, escape velocity, the geostationary or synchronous orbit altitude, and the two burn Hohmann transfer delta-v and transfer time between a starting and a destination orbit. Presets carry the gravitational parameter, radius and rotation period for the Sun, every planet, the Moon, Ceres and Pluto, or you can supply a custom GM and radius.
How to use it
Write one field per line, such as "body: Earth", "altitude: 400 km" and "to: 35786 km" for a transfer, or just type a body name on its own to see its escape velocity and geostationary orbit. Lengths, speeds, times and angles all accept a unit after the number (km, AU, mi, m/s, mph, hours, days, degrees), and a bare number is read in the field's natural unit.
Why this one
Most orbital mechanics calculators online handle one equation at a time and make you look up GM yourself. This one carries the constants for every body in the solar system, chains vis-viva, Kepler's third law and the Hohmann transfer into one readable report, and is upfront that it is idealized two body, impulsive burn mechanics with no drag, oblateness or launch cost, rather than pretending to be a mission planner. It runs entirely in your browser, so your inputs never leave your device.
FAQ
- How much delta-v does a transfer from low Earth orbit to geostationary really take?
- About 3.9 km/s total for the two Hohmann burns, from a 300 km parking orbit: roughly 2.43 km/s to leave the circular orbit onto the transfer ellipse, and 1.47 km/s to circularize at geostationary altitude. That excludes the delta-v to reach the parking orbit from the ground and any plane change.
- Why is the geostationary altitude 35,786 km and not the orbit radius?
- 35,786 km is the altitude above Earth's equatorial surface; the orbit radius, which is what the vis-viva and Kepler equations actually use, is about 42,164 km, measured from Earth's center. The calculator reports both so neither number gets mixed up with the other.
- Does this account for atmospheric drag or launch losses?
- No. Every result is two body, point mass, impulsive burn mechanics: no drag, no oblateness, no third body pull, no finite burn or gravity losses, and no cost to reach the starting orbit from the ground. Real mission delta-v budgets run higher than these numbers, which is stated on every result.
Keyboard shortcuts: press ? anywhere on this page to see them.