3
$\begingroup$

I just created a Modelica Model of a rocket landing in vacuum. Now I attempt to verify it against reality. However, I have a hard time to figure out some plausible initial parameters. Apollo 11's Eagle had a Periapsis of 15km. But what was its initial speed?

I assume that everyone does one deorbit burn and later attempts to get as close to a suicide burn as reasonable. So I modeled my experiment after a falling mass under retrograde thrust in a cartesian coordinate system. Obviosuly, this model has a hard time when it comes to very long landing approaches (since the cartesian coordinates to not take into account the curvature of the target body), so lowering the periapsis to 0 is not an option right now (although probably the most efficient approach). I arbitrarily choose an initial surface velocity of 1km/s which gave me a landing at 140km.

So what is a plausible surface speed after the deorbit burn?

Improve this question
$\endgroup$
1
  • 4
    $\begingroup$ Start from the end: Model a launch from the Lunar surface, to the orbit. Of course you'll have to tweak fuel usage to be negative ;) Once you achieve the orbit, you have your "initial" parameters, just replay the whole thing backwards. $\endgroup$
    – SF.
    Commented Jun 24, 2016 at 15:15

1 Answer 1

Reset to default
6
$\begingroup$

This document provides the Apollo 11 LM velocity at the start of powered descent as 5564.9 ft/s.

Improve this answer
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.