Difference between revisions of "Space electric propulsion"
| Line 40: | Line 40: | ||
==Morphological Tradespace== | ==Morphological Tradespace== | ||
We can see the tradeoffs that each mission was forced to make to achieve its objectives. Clearly, as discussed above, the biggest tradeoff is with respect to Thrust-to-Power and Specific Impulse | We can see the tradeoffs that each mission was forced to make to achieve its objectives. Clearly, as discussed above, the biggest tradeoff is with respect to Thrust-to-Power and Specific Impulse | ||
[[File: | [[File:morphological_tradespace_SEP.png|||centre||500x500px|Figures of Merit for electric propulsion system]] | ||
Revision as of 16:57, 2 November 2023
Electric Propulsion in Space
Roadmap Overview
Spacecraft electric propulsion uses electrostatic or electromagnetic fields to accelerate mass to high speed and thus generate thrust to modify the velocity of a spacecraft in orbit. This method leverages the charge/mass ratio of propellants, with relatively small potential differences potentially generating high exhaust velocities. This reduces the amount of reaction mass or propellant required, but increases the amount of specific power required compared to chemical rockets.
Electric thrusters typically use much less propellant than chemical rockets because they operate at a higher specific impulse than chemical rockets. Due to limited electric power the thrust is much weaker compared to chemical rockets, but electric propulsion can provide thrust for a longer time.
Design Structure Matrix (DSM) Allocation
Below we can see the DSM Allocation for the electric propulsion system. Sub components have been classified by tier and colour for ease of understanding (for instance, electrons and electric field are related to anode and cathode and thus highlighted in green). Cells shaded in yellow indicate that the corresponding components interact with each other during the operation of the propulsion system.
Roadmap Model using OPM
Figures of Merit
Relevant figures of merit can be seen in the table below.
Strategic Drivers
The key strategic drivers are electrical efficiency of the thruster system, and input power available to the thruster. These directly relate to increasing the product of specific impulse and thrust-to-power, which we know to be directly proportional to thruster efficiency. This is to say that increasing thrust efficiency pushes out the pareto frontier and will enable a more diverse range of space missions with longer lives. Additionally, increasing power available to the system will result in higher output thrust available.
Comparison with Competitors and FOMs
Given that thruster parameters vary widely by mission purpose and orbit, we consider 'competitors' to be rival space missions. For station keeping applications, we assume that our company is trying to improve on the Telstar 401 mission launched by the US in 1993. Similarly, for deep space missions, we would aim to build upon the progress achieved by the Dawn mission launched by NASA in 2007.
We look at the FOMs of Thrust-to-Power versus Specific Impulse to compare ourselves to our competitors. As can be seen, we have chosen to compare four electric propulsion technologies that were used to power four missions - Resistojet, Arcjet, Hall Effect, and Grid Ion. For each of these technologies, we have selected missions that have achieved results that are closest to the Pareto frontier (i.e. with the highest product of Thrust-to-Power and specific impulse). With regards to improvement in FOMs, we have assumed that our 2030 target is to see a 20% improvement for both parameters. This is purely to visualize how the Pareto front is likely to move with time - there are scenarios where we may want to trade off Thrust-to-Power for a higher specific impulse, and vice versa. This will likely be determined by the scope of mission, type of thruster chosen, and choice of propellant.
Morphological Tradespace
We can see the tradeoffs that each mission was forced to make to achieve its objectives. Clearly, as discussed above, the biggest tradeoff is with respect to Thrust-to-Power and Specific Impulse
