Answer · confidence: partial
How fast must a spacecraft go to stay up, and why won't it fall?
Research question: What speed does a spacecraft need to stay in low Earth orbit, and why doesn't it fall back down?
The records show the ISS, which orbits at roughly 410–420 km, travels at about 7.66 km/s, fast enough to circle the Earth in about 92 minutes 41. The facts give no general speed for low Earth orbit and do not explain why a craft stays up, though the first cosmic velocity is named without a numerical value 910. What the records do show is that atmospheric drag steadily lowers the ISS by about 50–100 metres per day, so reboosts are needed 6. Drag rises exponentially closer to Earth, and orbits below about 450 km need propulsion bursts or continuous thrust to counteract it 57, and vehicles there stay up only until their propulsion runs out or they are resupplied 8. The newest dated fact is from November 1957 11, and the ISS figures carry no date, so the records cannot confirm how current they are as of October 2026 14.
Checked 2026-10-20. Only documented and supported facts are used.
Dig deeper on this questionSources
[1] supported
The ISS travels at about 7.66 km/s, which is fast enough to circle the entire Earth in about 92 minutes.
"The ISS travels at 7.66 km/s — 27,600 km/h (17,150 mph) — fast enough to circle the entire Earth in just 92 minutes."ISS Tracker — Live Map & Visible Passes Tonight
[2] supported
Very low Earth orbit is defined as orbits whose lowest point (perigee) is below 400 km.
"Very low Earth orbit ( VLEO ) is a range of geocentric orbits with lowest altitudes (at perigee ) below 400 km (250 mi) ."Very low Earth orbit
[3] supported
The lowest medium Earth orbit, a circular orbit at that altitude, has a minimum orbital period of about 2 hours, showing that orbital period depends on altitude.
"All satellites in MEO have an orbital period of less than 24 hours, with the minimum period (for a circular orbit at the lowest MEO altitude) about 2 hours."Medium Earth orbit
[4] supported
The ISS orbits at roughly 410–420 km above Earth's surface in Low Earth Orbit.
"The International Space Station currently orbits at approximately 410–420 km above Earth's surface in Low Earth Orbit (LEO)."ISS Tracker — Live Map & Visible Passes Tonight
[5] supported
Air drag, and therefore fuel consumption, rises exponentially the closer an orbit is to Earth.
"Air drag and therefore fuel consumption increase exponentially the closer to Earth the orbit is."Very low Earth orbit
[6] supported
Atmospheric drag steadily lowers the station's altitude by about 50–100 metres per day, and reboosts from spacecraft or the station's own thrusters are needed to restore it.
"Atmospheric drag continuously lowers the station's altitude by roughly 50–100 metres per day, and periodic reboosts from visiting spacecraft or the station's own thrusters restore it."ISS Tracker — Live Map & Visible Passes Tonight
[7] supported
Orbits below about 450 km need special measures such as frequent propulsion bursts or continuous propulsion to counteract atmospheric drag.
"Orbits below about 450 km (280 mi) require the use of novel technologies for satellites to operate in, such as frequent bursts of propulsion, or even continuous propulsion (e.g., GOCE), to counteract the atmospheric drag."Very low Earth orbit
[8] supported
Because drag is stronger in VLEO, vehicles there stay in orbit only until their propulsion runs out or they are resupplied with fuel.
"Because atmospheric drag is greater in VLEO than in higher orbits, vehicles in VLEO will remain there until either their propulsion runs out, or they are resupplied with fuel."Very low Earth orbit
[9] supported
The document names the first cosmic velocity (Erste Kosmische Geschwindigkeit) as the speed at which a rocket's path stops being ballistic and becomes like a satellite orbit, but it does not state the numerical value.
"Erreicht die Rakete auf ihrer Flugbahn die Erste Kosmische Geschwindigkeit, so wird die Flugbahn nicht mehr „ballistisch“ genannt, sondern verläuft ähnlich einer Satellitenbahn."Ballistische Rakete
[10] supported
The page lists 'v1' as the first cosmic velocity (erste kosmische Geschwindigkeit), a term tied to circular orbit speed, and points readers to the orbital-velocity section of the spaceflight escape velocity article.
"v 1 , erste kosmische Geschwindigkeit, siehe Fluchtgeschwindigkeit (Raumfahrt) #Kreisbahngeschwindigkeit"V1
[11] documented
Sputnik II orbited the Earth once every 103.7 minutes at a speed of 17,840 miles an hour.
"Radio reports from the orbiting satellite indicated that Curly was alive and in good condition as Sputnik II shot round the world once every 103.7 minutes at 17,840 miles an hour."Image 1 of The Key West citizen (Key West, Fla.), November 4, 1957
[12] documented
Sputnik I was still circling the Earth on a lower and faster orbit, and its batteries had died about three weeks after launch.
"Sputnik I — the 184-pound pi pioneer - oneer pioneer earth satellite the Reds sent into space Oct 4 — still is circling the earth on a lower and faster orbit The batteries in the original satellite died about three weeks after it went up."Image 1 of The Key West citizen (Key West, Fla.), November 4, 1957