Tag: mars

Mars Propellant Production for Starship

Making Rocket Fuel on Mars

When humans get to Mars, Elon said the first order of business is propellant production. This means producing liquid methane and oxygen, Starship’s fuel, using only the resources and raw material gathered on Mars.

Why produce propellant on Mars?

The ability to produce rocket fuel without importing it from Earth is critical if humans want to successfully build a self sustaining base on Mars:

  • To ensure humans have consistent fuel supply on the red planet for return missions.
  • To reduce weight by minimizing the amount of fuel carried onboard Starship. Carrying less, we reduce launch mass and enable more efficient flights.

“In-situ propellant-production is critical to the space architecture needed for a long-term human presence on Mars, future interplanetary transport, and eventually, multi-planet colonization.”

– NASA

How does rocket propellant work?

Rocket propellant needed to launch rockets from the surface of a planet into orbit and beyond. Starship uses chemical fuel like methane and oxygen, in contrast to satellites and deep space probes which use electrical propulsion such as ion thrusters.

There are a few different types of chemical based rocket fuel, but they all have a few things in common.

Rocket fuel works similarly to the way gasoline in a car works, via combustion. For any combustion reaction, you need two things: a fuel source, and an oxidizer. The oxidizer accepts electrons. Because oxygen has 6 electrons in its outer shell, it accepts 2 electrons to create 8, a full outer valence shell.

For a combustion reaction, you really just need oxygen and a fuel source. The fuel could be liquid, like gasoline, or solid, like gunpowder. Rocket fuel is complicated – over the years, chemical engineers have tried different combinations of fuels and oxidizers to try to find the optimal rocket propellant:

  • Liquid Hydrogen, for example, is the most efficient. The problem with hydrogen fuel for Mars missions is that it has a boiling point of -423 degrees F, which presents a challenge keeping it in liquid state during long trips and during the friction-intensive high temperature entry burns.
  • RP-1 is another type of rocket fuel similar to kerosene, but is not suitable for SpaceX’s goal of having rapidly reusable rockets because it leaves a large amount of soot residue after use, which requires extensive effort to clean.
Chemical structure of methane. source: science.org.au

There are a few differences between gasoline and rocket fuel: In the case of an automobile, oxygen is readily available in the environment to be used as an oxidizer. In a rocket travelling through outer space, the oxidizer must be carried along with the fuel in a separate tank. Space travel means moving through a vacuum, where you don’t have the luxury of an endless supply oxidizer in the surrounding space.

To get to and from Mars, methane and liquid oxygen will be used. Although Mars doesn’t have an abundance of liquid Methane like Saturn’s moon Titan, the good news is that methane can be readily made on Mars from material that is available in the ground and atmosphere.

Key Requirements for Mars Fuel

It will be in our best interest to implement the following items into the propellant production process:

  • Minimize electrical power needs because all electric power will need to come from batteries, solar power, or nuclear power. There is no way of knowing whether or not Mars will have fossil fuels beneath the surface, and we cannot rely on this.
  • The propellant production process will be heavily dependent on chemical engineering and the ability to complete multiple chemical reactions and separations sequentially. In addition to the desired products of Hydrogen and Methane, the process will produce by-products, many of which are useable for other endeavors on Mars.
    • Nitrogen is one byproduct that is specifically useful because it is inert and non-reactive. The gas can be used used for flushing of tanks and lines through which other gases pass since it is reactive neutral.
    • Oxygen and water byproducts are both potentially valuable feedstock for making propellant oxidizer or for life support/drinking. For this reason, Mars engineers will need to consider options, means, and costs in any facility design with business analysts to determine the costs to market value of any manufacturing byproducts.

Efficiency: one metric ton of propellant per 17 megawatt-hours energy input. Starship needs 240 tons of fuel – which will require 4.1 gigawatt hours of energy input.

How long does propellant production take?

How much time does it take to make enough fuel for launching Starship.

This brings us to outlining the process of creating fuel. There are 4 key steps.

Chemical Reactions to make Methane Rocket Fuel:

Pre-Requisites to fuel creation:

Gathering CO2

Carbon dioxide is highly available in Mars’ atmosphere, 20 times as much as on Earth. We would likely use a type of air pump to gather the CO2.

Separation and removing contaminants

To obtain pure CO2, dust filtration will be important in this step of the process as well as removing the small amounts of ambient gasses including nitrogen, argon, neon, and krypton. Carbon molecular sieves (CMS) will be used to separate the carbon dioxide from the nitrogen, and a Vortex Swirl particle separator will use used as well.

As the reaction proceeds and produces methane and water, a separator will be used to remove the water vapor, leaving pure methane. This will be done by simply allowing the products to cool, so that water goes through the process of condensation then stored in tanks.

An important consideration is: How do we make sure no contaminant gasses are present with additional harmful byproducts?

The diagram below shows the reactions that will be required for producing propellant on Mars.

spaceX mars propellant production
source: SpaceX

The reactions get complicated, and while I started covering them below, I found this super helpful video on YouTube that covers the chemical reactions as well as a lot of other information about making rocket fuel on Mars.

1. Electrolysis of Water

Hydrogen is the critical component that is hard to get, which we must separate from water. We need to pump water from underground wells, use robotic vehicles to mine raw water ore.

– Robotic vehicles, such as the NASA KSC Regolith Advanced Surface Systems Operations Robot (RASSOR) prototype or the OffWorld Inc.5 smart robots, are likely candidates for mining the raw “water ore”.

Then, the water will go through electrolysis to break water into components Oxygen and Hydrogen.

Once this is done, we can use the hydrogen and CO2 from the atmosphere to run the Sabatier methanation reaction.

Note, we will have to do the electrolysis of water twice throughout.

2. Sabatier Reaction: Carbon Dioxide and Hydrogen to create Methane gas and Water.

The Sabatier methanation reaction has been recommended by many of the top researchers as the most likely basis for an ISRU propellant production processing plant on Mars.

This reaction leverages the abundance of CO2 in the Martian atmosphere to create both the methane fuel and water. CO2 is taken from the atmosphere by either freezing the gas into a solid, mechanical compression, and absorption pumping. Freezing will purify the gas, and may be advantageous.

Nickel or aluminum oxide transition metal catalyst is required (why?)

The reaction has to be carried out at high temperatures (why doesn’t it happen at low temp?) There is a principle in chemistry that describes the effect of temperature on reaction speed.
“Higher temperatures mean faster reaction rates; as molecules move about more quickly, reactant molecules are more likely to interact, forming products…” – sciencing.com
Since mars is cold, the reaction has to take place in an insulated container. The good news is that the reaction is exothermic, so once it starts, there isn’t much energy required to keep it going at temperature.

This is used today on the international space station to form water for astronauts to use.

3. Carbon Dioxide solid oxide electrolysis to create Oxygen and CO byproduct.

4. RWGS (reverse water gas shift)

A way to supplement producing methane and oxygen from hydrogen and carbon dioxide.

Sources:

Mars Perseverance Rover 2021 Update

Purpose of the Mars Perseverance Rover

NASA’s Mars Perverance rover is on the way to Mars to find out if life ever existed there.

Perseverance will collect samples to try to find fossils, organic material, and more.

What will Perseverance Rover do?

The rover will land on Mars on February 18, 2021.

Landing in Jezero crater, an ancient lake the size of Lake Tahoe, Perseverance rover will explore riverbeds which appear to have provided inflow and outflow of the lake, as well as delta deposits.

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The Jezero crater is of particular interest because it represents the possibility that Mars had water about 4 billion years ago.

Perseverance rover 60-second summary:

NASA also has a website dedicated to the official updates for Perseverance Rover.

What technology does Perseverance have?

  • The stage that brings it to Mars uses hypergolic chemical propellants
  • Perseverance has 23 cameras with 20 megapixel color, 2 microphones, UV laser, Xray spectrometer
    • This is the first time we will have audio data (via the microphones) from a celestial object.
  • During descent a camera will scan the terrain and heat shields will protect it from friction temperatures of 2100 deg. C
  • After landing the sky crane will fly away but crash into the surface nearby
  • Self driving 200 meters per day, perseverance will run for 14 years, powering itself on a 45kg Radio-isotopic thermal electric generator, converting heat from plutonium-238 into electricity.
  • Perseverance rover carries a system to test oxygen production on Mars, called MOXIE. Oxygen production on Mars is an important part of in-situ resource utilization, which humans must take on if we are to ever colonize the red planet.
  • Perseverance also has a 4 pound drone helicopter and coring drill to search for microbial fossils.
  • NASA redesigned the wheels from Curiosity to avoid getting stuck, featuring a wider diameter and smaller tread-width.

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sources:

  • mars.nasa.gov/mars2020/
  • additional info: mars.nasa.gov/mars2020/timeline/landing/

SpaceX Starship Overview 2021

Starship Rocket Overview

Important Breakthroughs

  • Propellant production in Boca Chica will be important to optimize the supply chain.
  • Rapidly reusable rockets – like air travel or car travel, you don’t get a new car every time you take a trip.
    • Re-usability will allow flying the booster 20 times per day, and the ship 3-4 times per day. Reason ships can only be used a few times a day: since ship goes to orbit, the track of a satellite is sinusoidal (unless it is equatorial or san-synchronous). you have to wait for the ground path to sync up with the launch site. It takes like 6 hours to sync up.
  • Satellite Delivery: Currently, the company uses Falcon to deliver satellites for Starlink. Starship will be able to deliver satellites further and at a lower marginal cost per launch, as Startship has a much greater payload..
  • SpaceX created the Raptor engine, which has a very high specific impulse. Because Earth’s gravity is quite high, we are just on the cusp of reusable rockets being physically possible. Raptor engine (it will have 6 engines) uses mostly oxygen per unit of fuel (3.5 tons of oxygen for every 1 ton of fuel).
  • Making it to orbit was tough… landing the rocket was tougher, and SpaceX was the first to do so.

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Reducing Launch Mass

  • Steel: the rocket it made of steel. It has the perfect combination of strength and heat resistance. Because of this, the rocket will be able to have a smaller heat shield, and only need a heat shield on 1 side of the ship. This will reduce launch mass.
  • Orbital re-fueling: Starship attaches to another rocket containing fuel while in orbit, making it pace.

Starship Demographics

Image
Raptor Engine. Source: @brandondeyoung_ twitter

SpaceX has published a quite succinct user guide with detailed information.

  • Engine: Raptor
  • Fuel: Methane and Liquid Oxygen (CH4 and LOX)
  • Length: 72 meters
  • Diameter: 9 meters
  • Material: Stainless Steel
  • Payload: 100 tons
  • Nomenclature: SN9 stands for “Serial Number 9”

Starship flights:

Starship performed its first test flight on July 26, 2019 and has so far performed 6 orbital test flights.

Starship SN8 flight recap

Sources: