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# Mass-Volume Stoichiometry

## Determining the amount of gas or the material needed to react with a gas in a reaction

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Practice Mass-Volume Stoichiometry

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Credit: NASA
Source: https://commons.wikimedia.org/wiki/File:Lunar_ISRU_concept.jpg

Landing a spacecraft on the moon or another planet can be fairly easy if we don’t want the vehicle back any time soon. However, if we are landing humans or want samples of material returned to earth, then we need to think about how to power the vehicle for the return trip.  Taking all the fuel needed cuts down considerably on the payload for the experiments that need to be conducted. Maybe the spacecraft could make its own fuel?

#### Why It Matters

• Getting a spacecraft back to Earth is a major technical problem. It is extremely impractical, given present technology, to expect this craft to carry all the fuel for the return voyage. Both weight and space considerations eliminate this possibility. So what is planned? NASA has developed a concept called In Situ Resource Utilisation (ISRU) to deal with the issue. This concept proposes that the fuel for the return trip be generated from materials at the landing site.
• Credit: Wikimedia
Source: http://en.wikipedia.org/wiki/File:Apollo_11_lunar_module.jpg

The Apollo 11 mission used a specialized ascent stage to leave the lunar surface. The stage was abandoned after use and crashed into the moon [Figure2]

• The feasibility of ISRU has been studied for use on the moon and on Mars. Assumptions about available resources have been made based on current data as to chemicals present on the lunar or Martian surface. Two basic needs are seen: (1) the fuel to propel the spacecraft for the return trip, and (2) oxygen and water for the humans on the spacecraft and for combustion of the propulsive fuel.
• The atmosphere on Mars is about 95% carbon dioxide. Technologies for converting the gaseous CO2 ultimately to methane and oxygen exist today. The methane would then be liquefied for storage until needed as fuel for the return trip. The two approaches both have technical problems that are currently being investigated for feasibility and yield.

#### Show What You Know

1. What is the oxygen content of the Martian atmosphere?
2. What is the pressure of the Martian atmosphere?
3. What will be used to liquefy the gases formed by the ISRU?
4. What is the Sabatier reaction?
5. How can oxygen be obtained?

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