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Noiredd / PEGAS

Powered Explicit Guidance Ascent System - a KSP & RO autopilot using the Space Shuttle guidance algorithm, UPFG
http://forum.kerbalspaceprogram.com/index.php?/topic/142213-pegas-powered-explicit-guidance-ascent-system-devlog
MIT License
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True/Mean Anomaly Targeting #16

Closed mferrie closed 6 years ago

mferrie commented 6 years ago

Is it possible to pull off true or mean anomaly targeting? If so, how?

Noiredd commented 6 years ago

In the current version of PEGAS - it is not possible. The underlying guidance algorithm, UPFG, in the standard ascent mode (which PEGAS implements) leaves this element free. It is possible that other modes would allow something like that - ascent to coast reference trajectory looks particularly promising. But even if this is possible to implement, it's not something that would happen anytime soon.

Is there any mission where you need to do this at ascent? Shuttle could do stuff like launch, intercept a satellite and land within a single orbit - but other than doing something that spectacular, is there any real need to be able to target anomaly? Maybe we could work around it within the limits of PEGAS?

mferrie commented 6 years ago

I was thinking something like launching a GPS or iridium satellite directly into its intended orbital "slot", e.g. Ω = 45, ω = 90, ν = 15.

Noiredd commented 6 years ago

Generally, UPFG is good at plane angles and velocity vector - when it comes to phase-related stuff (AoP, anomaly), it just does not feel like the right tool for the job. I spoke more on similar things here.
Realistically speaking though, are GPS satellites launched directly into their anomaly-constrained orbits, or rather to some intermediate parking orbits from which they get to their final ones on their own?