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Martian Aircraft

written by Steven Wintergerst on July 31, 2005 | contact me
number of views: 74732 |   printable version (text) (PDF)

A blimp on Mars.
A blimp on Mars.
Credit: Jason Archer
Transportation on Mars will be a troublesome issue for quite some time. No one has ever traveled on the surface of Mars. I believe that most people do not realize the importance of this fact.

On earth, virtually all road systems follow the paths of old trails. Old trails follow the paths of older trails, which follow the paths of animals, or natural stream beds, or the wanderings of near insane explorers who just ambled across a desert thinking “Well, I guess there must be something else thataway…”

Mars has no animal life, and therefore, roads must either follow the winding course of dry riverbeds, or the wild guesswork of near-insane explorers. Everything will be a destination off the beaten path.

Robert Zubrin has made some very useful descriptions of early motors for cars, but the fact is that Mars also has some of the most enormous differences in altitude in the solar system. Riding a mars buggy to the bottom of Valles Marineris will be difficult.

Ballistic travel, as by rockets, or some sort of catapult will be less accurate than on the moon, and the thin atmosphere makes planes somewhat dangerous. A plane on Mars must have an enormous wing span, a massively long runway, and some really powerful engines. Propellers would be virtually useless on Mars, so that most planes would probably need rocket, or at least jet propulsion.

Flying about like this is not much different from Ballistic travel in the first place, and maneuverability is poor at best. There isn’t much wind resistance to use for turning. Going by at the rapid pace needed to sustain such flight, with trouble steering, and low gravity would also make crashing very horrific. You’d have quite a bit of inertia to plough along with.

Of course, Mars has been thoroughly investigated by vehicles traveling at ballistic, and near ballistic courses: Orbital satellites have taken a myriad of pictures. What is really needed is a slower paced travel, with human observers to get a discerning look at the ground truth. Mars buggies are one way to do this, but the lack of extensive trails could be a problem.

On Earth, helicopters would be the next logical solution, but the thin gravity would require helicopters to have enormous blades, that would need to spin at an unbelievable speed. Even on earth, helicopters are not fuel efficient. Some people say that helicopters do not fly, but rather, they just beat the air into submission. It is certainly an energy intensive process.

What is needed is a fuel efficient way to get slightly above the ground, and not move around too fast. Slow speed travel close to the ground is generally safer anyway, and it will allow humans more time to use their discerning eyes.

One possibility would be a lighter-than air craft. There are three basic types of lighter than air crafts: Balloons, blimps, and dirigibles. A fourth type, the zeppelin is sort of a cross between a blimp and a dirigible, and I do not feel the need to describe it here.

Balloons are shapeless, un-powered craft, capable of going only up, down, and where the wind blows them. While unmanned balloons may be very useful for random surveying, it would be somewhat unsafe to have a manned balloon on Mars at this time, unless it was capable of lofting both the balloon, and the mars buggy to take the crew back to the base.

Blimps are unsupported lighter-than air crafts with some form of powered flight. The balloon may be designed so that it takes on some basic form when inflated, as for aerodynamic reasons. On earth, blimps are generally powered by propellers, but on Mars, jet, or rocket engines might be needed.

Dirigibles are powered lighter than air crafts, with solid supports inside them. I believe that a dirigible holds the best chance of providing reliable air transportation on Mars.

A dirigible could be shaped so that it is more or less an enormous floating rudder. This would make steering in the thin Martian atmosphere much easier. Such a shape would also be fairly aerodynamic, and a powerful jet engine could then be strapped to the underside, near the Gondola.

Most of the materials needed to build a blimp will also be useful for other applications on Mars. The main component of blimps is a special fabric, which is also used in space suit manufacture. If there are any colonists on Mars, I am sure they would greatly enjoy being able to manufacture repair parts for their space suits, if not entirely new space suits altogether at some point. If this sort of material proves inappropriate for Martian blimps, it is likely that Martians will be producing thin sheets of Kevlar for greenhouses, and specially lightweight sections of these might also serve the purpose.

Jet engine components, such as turbines would also probably be useful on Mars, for production of energy, or pumping materials around, and most any material useful in constructing a Hab would also be more or less applicable in building the gondola, although lightweight materials would be preferable, so that marsbuggy equipment might be more appropriate.

Blimps are composed of only a few simple components, the bag, the rudder, the two engines, the gondola, internal supports, and a pair of balloonets, which are small bags placed inside the main bag, and filled with air for ballasting to rise, and dive.

In designing a lighter than air craft, we must consider the buoyant force. For such a craft to rise, it must have a weight that is less than the weight of an equal volume of the air it is to rise through. Since weight is a measure of acceleration caused by gravity, the truth of the matter is simply that the total average density of the craft must be less than the total average density of the atmosphere it is in.

Since the atmosphere of Mars is very thin, any lighter than air vehicle will have to be absolutely enormous before it can loft any real payload. The atmosphere of the earth is about 100 times denser than the atmosphere of Mars, so a Martian blimp would have to be about 100 times bigger than an earth blimp in order to lift the same mass.

This is a rather serious drawback to using blimps on Mars, but it is no show stopper. In fact, the requirements placed on the engines needed to move such a blimp may be the more critical issue. The reason for this is that beyond the payload of the gondola, the blimp itself could be used to transport useful goods.

On Mars, the atmosphere is virtually all CO2, at a very low density. This low density is good, because it means we can fill the bag to a far lower pressure than on Earth, and still loft. Most of the mass of an earth blimp is actually in the gas placed in the bag, so a Martian blimp, although it needs an enormous bag, probably does not need much more gas than an earth blimp. Since it is the gas that gets lost anyway, this should help the maintenance costs to be more equal, especially since Martian blimps do not have birds, and other flying debris (except dust) to worry about.

Since CO2 is a rather heavy gas, there are a lot more choices for lofting gasses on Mars. Along with Helium, and Hydrogen, it should be possible to loft blimps using nitrogen, and Oxygen. Also, since CO2 is not an oxidizer, using hydrogen would be much safer on Mars.

One might wonder, since we can use Hydrogen, the best lofting gas, without any risk, why would we want to loft a blimp using anything else. I have a very simple answer. The fact of the matter is that Oxygen, and yes, even Nitrogen are commodities on Mars, and it may be useful to transport these commodities.

By using these commodities as lofting gasses in blimps, you will have a sizable reduction in shipping costs, especially if you are traveling with the wind. Certainly, there will be a bit of loss in the shipping process, but it may be possible to make up for this by the added speed of air travel, which is straight, rather than the bumpy, winding routes necessarily taken by overland mars buggies. By converting the payload into a lofting gas, it is also possible to take added payload on as cargo, although most of this would probably have to be lightweight materials, or personnel.

It may be possible to design blimps that can transport these commodities, and then be deflated, and shipped back via rover, or converted from blimps into greenhouses, or some other useful device.

Alternately, and dangerously, it could be possible to make a longer range blimp, with two compartments in the bag, one for hydrogen, and one for oxygen. In this case, the lofting gasses could also be used as the jet engine fuel, making a vehicle of considerably lighter weight, since the fuel is also used as the lofting gas. For such a vehicle to be effective, it might be best for it to be shaped more like an aircraft than a blimp though.

While such a vehicle sounds extremely dangerous, I should remind you that most rockets sent from Earth will have used hydrogen, and oxygen in a more or less uncontrolled burn behind them, a process that uses the same fuels in a much more demanding, and dangerous fashion. No, colonists using a hydrogen-oxygen blimp jet would not be in any more danger than they were on their way to Mars.

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