# How does a Star Wars X-wing fighter make it from the surface of a planet to space? [closed]

According to the Star Wars X-Wing Wikipedia page, the X-Wing has a max speed of 652 mph in atmospheric flight.

3,700 G (maximum acceleration)
1,050 km/h (652 mph; maximum atmospheric speed)
100 MGLT (megalight per hour; subluminal speed)
1.0 HCR (hyperdrive class rating; superluminal speed)

This is far below orbital velocity, so how does an X-Wing make it from the surface of a planet to space?

• "This is far below orbital velocity" — is orbital velocity planet-specific? Commented May 5 at 10:03
• At what point did anyone think Star Wars was supposed to have a sound basis in physics? Hell, none of the films even have a sound basis in a script, never mind anything else. Like every other fantasy scenario, you have to accept that it just works like that, and move on. Commented May 5 at 12:00
• @PaulD.Waite Yes. The velocity required to maintain a given circular orbit is a function of the mass of the object being orbited (and thus it’s gravitational pull) and the height of the orbit. Elliptical orbits are a bit more complicated (velocity is non-constant, and you need some trigonometry to figure out the required velocity vector at each point on the ellipse), but it’s still based at least partially on orbital height and the mass of the object being orbited. Commented May 5 at 12:32
• Aircraft here on Earth do not have a "maximum atmospheric speed." They have a maximum indicated airspeed (IAS). When an aircraft is cruising through a stationary air mass at its typical cruising altitude and, when the density of the air is typical for that altitude, then the indicated airspeed will be pretty close to the aircraft's speed over the ground. Under other conditions, especially at extreme altitudes, the IAS can be much different from the speed over the ground. (In orbit, IAS would be zero, always.) Commented May 5 at 15:43
• What the hell is “megalight per hour”? Commented May 5 at 18:15

Even without magic repulsorlift, the X-wing could make it to orbit the same way real world rockets do: climb up until the atmosphere thins out enough that it no longer slows you down too much, then accelerate sideways until you're basically in orbit.

The X-wing data sheet might show a single "maximum atmospheric speed", but in practice "atmosphere" is relative: not only do different planets have different atmospheric densities, but the atmosphere (of any planet that has one) gets thicker as you go lower and thinner as you go higher. The speed shown in the data sheet might a maximum rated speed for flight in the low atmosphere of a typical earthlike (i.e. human-habitable) planet, but as the X-wing gets higher, basic physics says it can go faster.

Besides, even if you were a really cautious pilot and really didn't want to exceed the manufacturer's rated atmospheric speed limit anywhere inside an atmosphere, you could just climb straight up at that speed1 until you get to a point where you're no longer considered to be "in an atmosphere"2 and then accelerate sideways to orbital speed.3

1 - Which, even without using repulsorlift, the X-wing's ridiculous 3700 G engine acceleration should be able to easily maintain against any planet's gravity.

2 - Of course, this is an arbitrary matter of definition; the air density drops gradually with altitude, but there's no sharp line where it would suddenly reach zero.

3 - Which, with the X-wing's still ridiculous engines, should take seconds at most.

Ps. This is actually an issue that's encountered in real world spaceflight, too. If there was no atmosphere in the way, the most efficient way to launch a rocket to orbit would be to accelerate (nearly) horizontally straight off the launch pad as quickly as possible until you reach orbital velocity (and then perform a small circularization burn at apogee to ensure that your final orbit doesn't intersect the launch pad).

However, if you tried to fly a rocket at anything even close to orbital velocity in the Earth's lower atmosphere, air pressure would flatten the rocket into a pancake and compression heating would then burn it to a crisp.

You could try to solve these problems by building a stronger rocket able to withstand more pressure and adding heat shields to protect it, but that would make the rocket a lot heavier, which is the exact opposite of what you want.4 And it still wouldn't solve the remaining problem, which is that the same air resistance that's trying to crush and burn up your rocket is also slowing it down very quickly, much faster than your engines can accelerate it.

Instead, the way real orbital rocket launches solve this problem is by first accelerating relatively slowly (almost) straight up. (Conveniently, real rockets accelerate slower at first anyway, since they're loaded down with more propellant, with their acceleration increasing as the propellant is burned and ejected and the rocket gets lighter.)

As the rocket gets higher in the atmosphere, the air gets thinner and offers less resistance. The launch trajectory of real world rockets is planned so that, as that happens, the rocket gradually turns more and more horizontal, allowing the engines to start accelerating the rocket horizontally to orbital velocity instead of just pushing it upwards against gravity.

If you watch a video of a rocket launch (which we have plenty of these days), one of the moments likely called out in the video is "max Q", or the point of maximum aerodynamic pressure. Basically that's the point where the rocket is high enough that the atmospheric density starts dropping faster than the rocket's speed increases. It's also the point where the rocket experiences the heaviest loads on its structure, and thus the point where the rocket is most likely to break if you didn't build it strong enough. (That used to be a serious risk with early space launches. Fortunately we've gotten pretty good at rocket engineering, and that almost never happens anymore.)

Some rockets will even temporarily throttle down their engines before max Q to deliberately keep the rocket's speed from getting too fast and the aerodynamic pressure from getting too high. Once the rocket is past max Q and the air is thin enough for the aerodynamic pressure to start dropping, they'll throttle the engines back up again and start building up orbital velocity for real.

4 - Real world rockets don't have anything like the magic engines of Star Wars and struggle to even accelerate their own mass — not to mention any satellite or other useful payload — to orbital speed. In the real world, we still don't even have a practical single stage to orbit rocket, and have only recently figured out how to squeeze enough performance out of lower rocket stages to make it practical to safely land and reuse them instead of just letting them crash into the ocean after doing their job. In practice, what that means is that every gram of mass you can shave off a rocket, especially in the upper stage(s), is precious because it directly translates to more payload mass you can launch.

• "then accelerate sideways until you're basically in orbit" - or skip that part and embark on the interstellar part of your voyage right away. Why bother with reaching orbital velocity if you might not want to stay next to the planet you've just left anyway? Commented May 5 at 9:01
• @O.R.Mapper: That, too. With real rockets, there are often good reasons to go into orbit first even if you're going to another planet, since that's a convenient "halfway point" where you can stay for a moment while you run systems checks and plan the transfer burn and wait for the optimal moment to execute it. But with engines like in Star Wars, none of that really matters — just point the nose where you want to go and light them up. Commented May 5 at 17:32
• Tsiolkovsky is a big meanie-head. Commented May 6 at 18:50

You've fundamentally misunderstood the principle of 'escape velocity' which is a measure of how fast an object fired like a bullet from a gun would need to be going at ground level in order to leave the gravitational pull of its starting planet, assuming no other forces were applied to it (e.g. either acceleration or wind-resistance)

In celestial mechanics, escape velocity or escape speed is the minimum speed needed for an object to escape from contact with or orbit of a primary body, assuming ... no other forces are acting on the object, including propulsion and friction

This number can essentially be ignored in Star Wars because ships possess a magical technology known as repulsorlift, which can lift a ship into space without the obvious expenditure of reaction mass to get there. This means that they can travel from the ground into space without needing to move especially fast, merely by applying continuous lift rather than large amounts of rocket-like acceleration.

An X-Wing (with a maximum in-atmosphere speed of 652mph) would be in space within a few minutes, provided it can achieve this speed continuously.

• Ignoring gravity also means you can do cool stuff like this; qph.cf2.quoracdn.net/… Commented May 4 at 22:05
• To really drive home the point about escape velocity: imagine there were giant stairs built from the surface into space. Then you could just climb to space with your own two feet, not coming anywhere near escape velocity. The whole escape velocity business only matters to objects that are accelerated once, and then continue moving with nothing but their inertia. But if you have some other means of continuing to move upwards (like a rocket strapped to your butt), then it doesn't matter how fast you go - you'll get there eventually. Commented May 5 at 9:52
• @Vilx- I'm afraid that's not allowed Commented May 5 at 9:55
• Also note that it is one thing to just "get to space" (aka far enough from the surface) and another thing entirely to "get into orbit" (aka circle around the planet without using any extra energy). The latter doesn't automatically happen when you achieve the former. For that you also need to move sideways REALLY fast. And again - if you have another means of counteracting gravity then you don't need to move fast sideways. You can just hover up there as you please. But it will cost you extra energy all the time. Commented May 5 at 9:58
• @Vilx- Read the sign. "No Stairway To Heaven" :-) Commented May 5 at 10:03

Ilmari Karonen explained perfectly why a spacecraft capable of 100 MGLT (cough) would be limited to much less in atmospheric conditions.

But there is another point to make:

Orbital velocity is how fast you need to go "sideways" to "keep missing the planet" when you go into freefall, to counteract the 1g of pull without expending more fuel.

But Star Wars craft don't need to go into freefall, because their fuel is not limited (at least in this regard; we see the X-Wings refuelling at the end of Ep. IV, but obviously launching from Hoth, landing on Dagobah, launching from Dagobah, and flying to Bespin at least is well within their capabilities).

If your engines can just keep accelerating you at >1g (or whatever the gravity of the planet you're launching from), you don't have to bother with orbital velocity, or escape velocity. You can just keep going straight ahead. Stick to the atmospheric max. speed while you're still in atmosphere, then power up once you're high enough.