# Survey on Unmanned Aerial Vehicle for Mars Exploration: Deployment Use Case
## 3 Preliminary Studies
### Different Types of UAVs in Space
#### 3.2.1 Airships and Balloons  
An airship or balloon is an aircraft carrier that requires no external power to navigate [71]. The balloon is a straightforward technology that requires no power to maintain altitude. Power is only required for instruments and payloads. However, balloons face many difficulties in changing the altitude and location. For example, it cannot stay in the Sun. Balloons also face difficulty in station keeping them, concluding that they are not flexible enough in atmospheric science. However, airships are challenging to place and deploy at a low speed [72]. There are three different kinds of balloons capable of planetary exploration, including super pressure balloons, standard helium balloons, and Montgolfiere balloons. Super balloons: With no open ducts, these ULDBs are completely sealed. Carbon does not escape from the balloon and, as the gas expands, pressure builds up. Super pressure balloons can travel for a longer duration because of the reduced leakage of the gas inside the balloon. Due to their form, they are also known as the Pumpkin. A Super Pressure Balloon is considered a balloon that often holds a positive inner pressure compared to the atmosphere in which it is floating. Super Pressure Balloons consist of a particular volume of estimated helium lifting gas. Specific altitude and a well-known mass of a payload hanging from a balloon are explicitly planned. The quantity of helium initially inserted into the balloon is determined by how much it is required to lift the whole flight mechanism and have an upward force of some additional helium. When the float height is reached, this excess helium is adequate to pressurise the balloon evenly. It has a greater internal pressure as the Sun heats the balloon during the day and at night when it cools down to have much lighter differential pressure. The differential pressure is above the atmospheric pressure. Helium Balloon: Standard helium balloons are capable of space discovery, but relative to super-pressure balloons, they have a significantly shorter lifespan. The continual  
Figure 1: Type of UAVs for planetary investigation. process of solar heating that takes place every day allows typical helium balloons to last as little as a few days [48]. * Montgolfiere balloons: A Montgolfiere works exceptionally well for the climate at low temperatures. Thus, making its place in exploring space. Instead of using helium gas, this balloon uses the planet's natural ambience to explore the spatial body [48]. Balloons are considered explicitly for exploring the surface of Venus. This is because of the noteworthy benefit of Venus' carbon dioxide atmosphere that enables a far wider variety of balloon-lifting gases (not just the hydrogen or helium commonly used by terrestrial balloons). In reality, oxygen and nitrogen are gas lifters in the atmosphere of Venus. Two other lifting gases at the altitudes considered are water and ammonia. In 1985, the Russian 'VEGA' experiment successfully demonstrated ballooning in the atmosphere of Venus, the first space mission to float in the atmosphere of a planet other than Earth to date. The Russian Halley's Comet probe delivered the two VEGA balloons (along with the help of two surface landers) while it executed a Venus gravity-slingshot technique. Two balloons were launched into the atmosphere and floated at about 54 km for 48 hrs [73]. Aside from Venus, balloons have been considered to explore several other planets (such as Mars' surface and Titans' moon). The viability of balloon missions on other planets and celestial bodies have continued to be explored by NASA centres and private enterprise. NASA's latest missions of concern are directed at Mars, Venus, and Titan. In situ observations at various altitudes, which are not possible for other platforms, such as satellites and rovers, can be made possible by balloons [74]. To spearhead future, more-ambitious efforts in Mars exploration through balloons, NASA Jet Propulsions Laboratory started an experiment known as MABTEX.