Pilots and amateur aviation enthusiasts alike use desktop flight simulators like Laminar Research‘s X-Plane to polish their skills and fly new aircraft in different places—we’ve used it to design our own fantasy plane. As long as you’re piloting from your desktop, why not fly in some very far-out places?
A conventional desktop flight simulator uses a matrix of aerodynamic and performance data to determine how each aircraft responds to the pilot’s actions. In real flight, the aircraft’s geometry interacts constantly with the surrounding air in more complex ways. To simulate this, developer Austin Meyer designed X-Plane to perform aerodynamic calculations for each component of an aircraft 30 times a second. Changing the variables to fit another world will allow a plane to respond naturally to getting less lift in a atmosphere or experiencing easier flight in lower gravity than Earth’s.
Results vary from planet to planet. Mercury has no atmosphere, and Jupiter’s gravity is too strong to overcome with lift. The skies on Venus are about 800 degrees Farenheit, streaked with clouds of sulfuric acid, and torn by 200-mile-an-hour winds. Fortunately, two of the most hospitable places in our solar system are also two of the most interesting: Mars and Titan.
Icy Wings on Titan
Beyond Earth, Saturn’s moon Titan offers the solar system’s best environment for flight. Its largely nitrogen atmosphere is four times as dense as Earth’s at the surface. A denser atmosphere makes flight easier, since more air moving over the airplane’s wings creates more lift. And that extra lift helps out a lot on Titan, where gravity is only one-seventh as strong as on Earth.
You don’t need much speed to generate lift on Titan. Technically, strapping artificial wings to your arms and flapping briskly will provide enough thrust to fly, but the weather on Titan makes that a really bad idea.
One important variable: Other than Earth, Titan is the only known place in the solar system with stable bodies of surface liquid, and its surface shows evidence of erosion by rivers and rain. It rains methane on Titan, in big drops that fall slowly in the moon’s low gravity.
The presence of liquid on Titan poses a challenge for flight, because Titan’s atmosphere is also very cold — about -290 degrees F at the surface. Methane freezes at -296.5 degrees, which makes methane ice a potential problem at flight altitudes. Ice on an aircraft’s wings will increase weight and drag and decrease lift, which is why passenger jets on Earth de-ice before flight. In the X-Plane’s simulator, its developers say, a plane will ice up if the conditions are right.
To replicate Titan’s environment in X-Plane, try the following parameters:
•Gravity = 1.352 m/s2
•Mass = 1.3452×1023 kg
•Radius = 2,575 km
•Temperature at Sea Level = -291.1 F
•Pressure at Sea Level = 146,700 pascals
•Density of Air at Sea Level = 5.4765 kg/m3
Titan’s scenery is not pre-loaded on X-Plane, but with a little programming skill you could render your own. An icy coastal area on Earth may also provide a decent approximation.
Thin Air on Mars
Mars has a thin atmosphere composed mainly of carbon dioxide. The atmospheric pressure on Mars at ground level is 6.36 millibars, about the same as Earth’s atmosphere at 100,000 feet above sea level. Since aircraft depend on the flow of air over their wings to produce lift, flight in such a thin atmosphere presents major design challenges.
“You could not use a reciprocating propeller engine to try to take off on Mars because the thrust is so small,” says Randy Witt, X-Plane co-owner. The flight simulator includes a rocket and a jet that Meyers designed for Mars.
Real-world engineers agree. Unconnected with X-Plane, a group of engineers at NASA’s Langley Research Center actually designed a Martian airplane. From the curvature of its 21-foot wingspan to its rocket engine, the 17-foot-long Aerial Regional-scale Environmental Survey of Mars, or ARES, was specifically designed for flight in the thin Martian atmosphere. Its large airfoil and powerful thrust would maximize lift to achieve controlled flight.
Controlled does not necessarily mean maneuverable, however, especially at the speeds necessary to maintain lift on Mars. Joel S. Levine, principal investigator on the project, says it would take ARES about 10 miles to execute a 180-degree turn because of the speed the rocket must maintain to stay aloft.
Because the distance between Earth and Mars causes a 10- to 15-minute lag in communications, the unmanned airplane cannot be flown remotely. Its trajectory would be programmed in advance, although researchers could modify the plan up to two days before reaching Mars. ARES would drop into the Martian atmosphere in a heat-shielded “aeroshell,” which then falls away, allowing the plane to unfold into flight.
Why build a Mars plane? Levine says an aerial survey is the best way to survey the southern hemisphere of the planet, where the rugged terrain is inhospitable to landers and rovers but contains some of Mars’ most scientifically interesting features. The team is currently preparing a proposal for NASA’s next announced opportunity for a planetary mission.
If you want to be a Martian aviator now, X-Plane 9 lets users simply set the planet to Mars—no coefficients or planetary radii required. The setting includes a Martian scenery package that Laminar Research claims is “accurate from the surface up to orbit.”
The newest version, X-Plane 10, doesn’t offer a pre-loaded Mars setting, but users can modify gravity and atmosphere in the “Environment Properties” dialog, and user-generated Martian scenery can be found through the online X-Plane community.
Try these parameters:
•Mu = 0.04283 x106
•Radius = 3,389.5 km
•Temperature at Sea Level = -89 to -31 C
•Pressure at Sea Level = 636 pascals
•Density of Air at Sea Level = 0.020 kg/m3
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