# Would a fighter jet be able to go into orbit from Mars surface?

Says a F22 with full tank is trying to break through the thin layer of Martian atmosphere and almost moon like gravity(alright that's probably too exaggerated) anyway say there is a runway stretching all the way to the highest peak on the planet, would it be able to orbit Mars? For the purpose of this question assume the pilot can survive on Mars without special apparatus but the same cannot be applied anywhere else including the plane.

• Very good explanation of what would happen to a plane on all the planets here: what-if.xkcd.com/30 (okay, so it's a using a Cesna as a model rather than a jet plane, but I suspect the effect would be much the same in terms of flight performance. – Simba Oct 10 '16 at 14:11
• @MichaelKjörling That depends on the OP's definition of "orbit". Nevertheless, the question is moot as the F22 won't work on Mars. – Snow Oct 10 '16 at 14:42
• How is this question "unclear"? It's a yes/no question and the answer looks like a fairly straightforward "no". Any parts of the question that could be better specified don't really seem to have much bearing on the answer. – type_outcast Oct 10 '16 at 17:26
• No. Orbital Mechanics 101: Your orbit includes the point where you shut down your engines. Since you're dealing with an air-breathing powerplant the engine will shut down in atmosphere and thus your periapsis is in atmosphere. You'll soon re-enter. To reach a stable orbit your last burn must be in space, period. – Loren Pechtel Oct 10 '16 at 19:31
• I agree with @type_outcast; this question may be any number of things, but it certainly isn't unclear. The simple fact that it accumulated three answers all reaching the same conclusion (from different perspectives) before being put on hold pretty much demonstrates how it is not unclear. It might have been either unclear or too broad had each answer reached a different conclusion. – a CVn Oct 11 '16 at 8:28

An f-22 would not operate on Mars at all.

The engines require oxygen.

The engines require much higher air pressure.

The wings are designed for much higher air pressure.

• At only a third the gravity of Earth, maybe an F-22 would not need as much air pressure under its wings, or could even lift off vertically, rocket-style. – user8976 Oct 10 '16 at 12:39
• Also, the storms on Mars seem to be very powerful, so maybe the F-22 could lift off against one of those storms? A storm might even create enough density for the engines to work – user8976 Oct 10 '16 at 12:40
• @what Nope. Storms on Mars aren't powerful at all. At most 60mph with a density 0.6% of that of earth. It's the major part of "The Martian" that wasn't true. Please read here for more info of Martian storms. – Snow Oct 10 '16 at 12:43
• “The highest atmospheric density on Mars is equal to that found 35 km (22 mi) above Earth's surface.” that’s thiner than you realize. – JDługosz Oct 10 '16 at 12:43
• @JDługosz Okay, and since the F-22 can only fly about 20km high on Earth, that's a no for OP then, I guess. – user8976 Oct 10 '16 at 12:45

# No, it will not, no matter the changes done while keeping it a F-22

Wikipedia gives the data for the F-22 as empty weight 19,700 kg and a maximum take-off weight (MTOW) of 38,000 kg. That gives a mass ratio of about 0.52 if it lands on fuel vapors in the tank. While exact specifications will obviously vary, I suspect that this is relatively representative of this class of aircraft.

We can approximate the F-22 in this case as a single stage to orbit (SSTO), because it lacks any meaningful staging capabilities. (No, ditching extra tanks doesn't really count for much, because the mass of those tanks when empty is likely negligible.)

The rocket equation describes how a single stage rocket can change its velocity (delta-v or $\Delta v$) as a function of the mass ratio and exhaust velocity ($v_e$):

$$\Delta v = v_e \times \ln\left(\frac{m_i}{m_f}\right)$$

where $m_i$ is the initial mass and $m_f$ is the final mass. Plugging in the above numbers, and assuming an exhaust velocity of 2,000 m/s (this is probably way higher than the actual F-22, so the calculation becomes very optimistic), and ignoring that a rocket needs to bring its own oxidizer as well as fuel and propellant, we get

$$\Delta v = 2\,000~\text{m/s} \times \ln\left(\frac{38\,000~\text{kg}}{19\,700~\text{kg}}\right) \approx 1\,300~\text{m/s}$$

The escape velocity of Mars is 5.03 km/s. We can approximate the mean orbital speed as $$v_o \approx \frac{v_e}{\sqrt{2}} \approx \frac{5\,030~\text{m/s}}{\sqrt{2}} \approx 3\,560~\text{m/s}$$

None of this is exact, but that doesn't really matter because our F-22 comes up about 2/3 short based on publicly available data, optimistic guesses and a highly improbable scenario (not needing to bring any oxidizer or propellant, only fuel). Because of the exponential nature of the rocket equation, the remaining two thirds are far harder than they would appear to be simply looking at the velocity change figures.

I suspect that, in order to be able to attain orbit around Mars, an F-22 which has been modified to work in that environment would need a mass ratio of less than 0.1 (bringing about ten times its own final mass in fuel). Keeping one of the values fixed, this corresponds to a MTOW of around 200,000 kg or an empty weight of less than 4,000 kg. If the exhaust velocity is lower (which is probable), this becomes even worse. Given that it can only carry its own weight in fuel (a mass ratio of 0.5 is pushing it), this is clearly not feasible.

And of course, the person flying it might want to get back down, too, which having attained a stable (even short-term) orbit requires either waiting for orbital decay (for example due to atmospheric drag, such as that experienced by the ISS), or a deorbit burn. While the deorbit burn can require shedding only a small fraction of the orbital velocity, you still need the fuel for that.

• This is beautiful! By pushing the F-22 into an absolute best case solution it demonstrates its sheer infeasibility. Actually assuming an exhaust velocity of 4 km/s as if the F-22 was a rocket and the velocities attained still don't meet the criteria for orbital or escape velocities. Although the pilot only has to step out & parachute back to the surface of Mars. :) – a4android Oct 11 '16 at 3:23
• @a4android No need to step out, even; the plane will get back down to the surface in short order. I make no guarantees about the landing attitude, however; you'd have to ask Lockheed Martin for data on that. :-) – a CVn Oct 11 '16 at 8:19
• @a4android Even assuming 5050 m/s $v_e$ (lithium-hydrogen-flourine, which would require some serious engine retrofitting on the F-22 and is right among the most energetic rocket fuels by mass), ignoring losses, you still only get to about 3300 m/s. Close, but no silver medals in spaceflight, and I'm pretty sure the resultant craft would not qualify as an F-22 under any reasonable definition. See space.stackexchange.com/a/18577/415 and comments. – a CVn Oct 11 '16 at 17:54
• All the fun is in working what might make it work, assuming it could, with plausible ways of doing so. You'd already converted a F-22 into SSTO rocket, any further conversions only illustrate its impossibility. Very nicely argued though. – a4android Oct 12 '16 at 3:54

The engine will not even start. There is almost no oxygen, and extremely low atmospheric pressure. The f-22 engine uses an air compressor to start the engine rotating, so that will fail. The fuel would likely freeze solid in the tank, since the average temperature on Mars is below the freezing point of kerosene..and if it doesn't, it will boil away as soon as it's injected into the engine due to the very low pressure.. Some parts may burst due to the unexpectedly low pressure.

On earth, we do not have planes (jet or otherwise) which can go into orbit, even if designed to do so, and operating in much, much thicker air. Even replacing the engines with rocket engines isn't really enough. If you could somehow fly yur fighter plane up and out of the atmosphere, you then face the much harder task of speeding up to orbital speed. And if you somehow have magic engines to accelerate you, then how are you supposed to steer? Aircraft turn by using the flow of air over the vehicle control surfaces. The fighter will just tumble out of control (and experience malfunctions due to extreme cold and lack of pressure). On Mars, you will have control surface problems while still on the ground. Even with giant rocket engines strapped to the plane it wouldn't lift off the runway since raising the planes nose requires a substantial airflow over the elevators.

With specially designed, high speed, extreme wingspan glider type aircraft powered by rocket engines flight on Mars is theoretically possible. It's been modeled in xplane and others. But if you put an unmodded F22 on Mars it'll handle and fly as well as a 20ton rock.

• Parts of Mars have almost Earth-like temperatures. I think the record temperature is something like +15 to +20 deg C, near the equator in the summer. The extremely thin atmosphere (just barely thick enough to present difficulties from being there) and the high level of CO$_2$ just add icing to the cake. – a CVn Oct 10 '16 at 14:42
• The average martian temperature is -55C, below the freezing point of kerosene, the primary ingredient in f-22 fuel. However, good observation, and liquid kerosene is plausable. But if the fuel doesn't freeze in the tank, it will boil off as soon as it's injected into the engine due to the very low pressure. – Innovine Oct 10 '16 at 14:51
• Ok, edited to include new data on fuel temps – Innovine Oct 10 '16 at 15:00
• Anyone want to calculate if the 12tons of kerosene (thats with extra fuel tanks) is anywhere near enough to orbit the f22? Instinct says absolutely not but I'm too lazy to work this one out :p – Innovine Oct 10 '16 at 15:07
• Wikipedia says the F-22 has an empty weight of 19,700 kg and a MTOW of 38,000 kg, giving approximately a 0.52 mass ratio. We can approximate the F-22 in this case as a SSTO. As per the rocket equation and with an exhaust velocity of 2 km/s (which is probably really high), its theoretical $\Delta v$ capability if used as a rocket would be about 1300 m/s. I don't know off the top of my head what Mars' orbital velocities are, but I highly suspect that 1.3 km/s is not enough. For comparison, on Earth we need about 7.5 km/s for low orbit. – a CVn Oct 10 '16 at 15:16