An Airship is a lighter then air craft that is streamlined and possesses engines. It has more control over its position then a balloon, which is at the mercy of the currents.
History of Airships
The 1930s was a golden age of airships on Earth. Rigid airships were common. However, the Hindenburg disaster meant that airships fell out of favor. Non-rigid airships, called blimps, which were inflated with helium instead of flammable hydrogen found a niche in advertising, surveillance and sightseeing trips. Plans have come and gone for large airships to rival the Hindenburg, but these plans have lost funding and have never materialized.
Airships on Mars
An airship might be useful for transport on Mars.
The payload on Mars will be the difference in density of hydrogen versus CO2 at the martian atmospheric pressure, minus the mass of the airship. Martian atmospheric density is 0,02 kg/m3, while the density of hydrogen is about 0,0005 kg/m3 (need to check). So the airship needs to mass less than 0,02 kg/m3 to fly. For a 5m sphere, with a volume of 32 m3, the mass of the airship would need to be no more than 0,02 x 32 = 0,6 kg, so it would need to be extremely thin to carry any practical payload. For a much larger 100 m diameter airship, the displacement is much larger, almost 10 000 kg, while the surface has not grown as fast (to the square rather than to the cube), and is about 30,000 m2. So the material of the airship could mass up to 0,3 kg/m2. Using flexible high tensile fibers such as Kevlar with a thickness of about 1mm yields a fabric massing 0,15 kg/m2. Such an airship, with a 1mm thick skin, could lift about 5 tonnes of payload and other structure.
The main limitation is the strength of the structural materials that can be used on Mars. Another problem is the very large size that would make the vehicle difficult to control.
- Hydrogen is a more effective lifting gas in the CO2 rich Martian atmosphere
- Hydrogen is not flammable in the Martian atmosphere
- The stronger radiation damages the hull faster than on Earth.
- Due to the thin atmosphere the airship must be several times the size, reducing the efficiency heavily.
- The large surface of the airship would results in strong forces during dust storms.
Other cargo systems
- Large rovers: have to traverse rough terrain
- Balloons: at the mercy of the wind
- Railways: Need thousands of miles of track
- Aircraft: Need more fuel then airships