This vessel (GOCE) is in orbit and maneuvers by using air similar to a plane to create lift and turn. The solar powered ion thrusters powers it continuously inside the atmosphere for years. Is this technically a plane, satellite, or a missile?

enter image description here

Source: https://space.stackexchange.com/a/33202/18879

  • $\begingroup$ I took the liberty of editing out the off-topic side question (not only because it's off-topic but also because you should only have one question per post). Feel free to roll back if you disagree. $\endgroup$ – Sanchises Apr 28 '19 at 20:42
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    $\begingroup$ By definition it's a spacecraft instead of an aircraft, because it relies on orbital velocity to stay up, not air in any form. It's a low drag satellite. $\endgroup$ – user3528438 Apr 28 '19 at 21:40

A satellite is an object in orbit. A satellite keeps a constant altitude if it is traveling at the correct orbital speed for their altitude. Otherwise it will be in an elliptical orbit where the altitude is constantly changing. In any case, satellites are (almost) in free-fall

An airplane travels at much, much lower speed than orbital speed. Airplanes keep their altitude because their wings produce lift.

Satellites in lower orbited are subject to atmospheric drag, albeit to much smaller extentd than planes. GOCE was orbiting Earth at an - for satellites - very low altitude (224 km). There is hardly any atmosphere at this altitude, but at an orbital velocity of 7.8 m/s (51337 kts), atmospheric drag is still a problem.

Therefore the structure of GOCE was particularly designed for low drag. The wings were flat without camber. They did not produce any lift. GOCE used ion thrusters to compensate the atmospheric drag and maintain orbital velocity.

enter image description here Photo: ESA

enter image description here Photo: ESA

Missiles are self-propelled guided weapons. I can assure you that GOCE was not a weapon.

[TL;DR]: GOCE was a satellite, because it orbited an astronomical body. It was not a plane, because its wings did not produce lift.

GOCE´s 20 month mission ended on November 11, 2013 with the planned destructive re-enty into the atmosphere. It measured Earth´s gravity field and acquired a precise model of the Earth geoid:

enter image description here Image: ESA

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    $\begingroup$ "The wings were flat without camber. They did not produce any lift." - What were the wings for, then? I would have thought that if a surface doesn't produce lift, then that surface is not considered a wing. $\endgroup$ – Terran Swett Apr 29 '19 at 17:14
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    $\begingroup$ @TannerSwett, They provide area for solar panels, and they stabilize the space craft. Indeed, it would be more correct to call them fins instead of wings $\endgroup$ – bogl Apr 29 '19 at 18:49

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