OHM Gemini semi-optical rendezvous tutorial (v 0.3)

[OrbitHangar]

This is a tutorial and Orbiter scenario demonstrating semi-optical (angle measurement plus radar data) navigation and piloting techniques similar to those developed for rendezvous in Projects Gemini and Apollo. The "coelliptic orbit," the basis for rendezvous from Gemini through mid-Apollo, is introduced and explained. An Orbiter scenario is included in which two Delta Gliders serve as proxies for the real life Gemini spacecraft and Agena target. The scenario begins with the Gemini in coelliptic orbit with the Agena, ready for rendezvous maneuvers, a few minutes prior to making the initial burn to intercept the Agena. The tutorial guides the reader to accomplishing the rendezvous, using only data and techniques similar to those the real Gemini pilots had available and would have used for this mode of rendezvous. The technique assumes no equipment failures, but also assumes no "updates from Mission Control" during the rendezvous regarding position, trajectory, etc. For those who are interested, some further commentary on the mathematics is presented; however, this is not necessary to perform the rendezvous.

More...

 

[Sam]

That was the summary; here are the prerequisites

Prerequisites

System requirements: None beyond the base Orbiter package.

No particular modules need to be activated. In the “Parameters” tab of Orbiter Launchpad, “Stars/Count” should be set as high as your PC will comfortably allow for maximum “eye candy” value. If you do the rendezvous properly and if you don't vary the magnification or direction of the field of view (e.g., external views, use of alt-arrow), you should never have anything in the field of view other than stars and the rendezvous target craft, so high resolution textures are irrelevant.

Orbiter skill level required: Minimal.

I assume you're familiar with basic Orbiter terms like "RCS LIN," "Surface HUD," etc. and with the Delta Glider's controls and displays. Specifically, you'll need to read angles off the Surface and Orbit HUDs, use RCS in both translational and rotational modes, and read distance values from the Docking MFD. You'll sometimes have to switch quickly between RCS LIN and RCS ROT. I'd say that if you've ever successfully rendezvoused and docked with anything, you're ready to do this.

Math skills required: Basic arithmetic.

The only two equations you'll use are of the forms A = B - C, and D = (A * E) / 2.

Orbital mechanics knowledge required: None to simply do the rendezvous.

To understand the rendezvous plan you need to know that spacecraft in lower orbits move faster than those in higher orbits, but that's about it.

Additional equipment required: A stopwatch or some other timing device capable of displaying elapsed time to the nearest second.

In a pinch you could use the clock in the upper right hand corner of the Orbiter display, but having a separate timer is easier. A calculator is highly recommended but not required; you could probably just estimate the results of the two equations and do just as well.

Time to run the simulation: About 50 minutes.

 

[Frin63]

And it works just fine (after some practice ;-) )
Very nice piece of work! I saw a lot of references to coelliptical orbit rendezvous when reflying Gemini and early Apollo missions, this makes it all a lot clearer. I hope to incorporate some of it in the AMSO Apollo 9 scenario pack I'm working on. Will need to create another table for that since the initial burn is different.

 

[Sam]

And it works just fine (after some practice ;-) )
Very nice piece of work! I saw a lot of references to coelliptical orbit rendezvous when reflying Gemini and early Apollo missions, this makes it all a lot clearer. I hope to incorporate some of it in the AMSO Apollo 9 scenario pack I'm working on. Will need to create another table for that since the initial burn is different.

Thanks! If you've looked at the thread in the "Flights and Challenges" section, a few of us are discussing it over there and I've been convinced to move away from the "start making MCCs and keep making 'em" model to a two-MCC model. I've found a few NASA sources that imply that they did two MCCs between the terminal phase initiation (TPI) burn and the rendezvous, but nothing more than that. Since the rendezvous trajectory ends up being about 32 minutes, and that's largely invariant to changes in orbital parameters, for now I'm just arbitrarily putting the MCCs at 10 minutes and 20 minutes after TPI (2 minute timing intervals from 9-11 and from 19-21 minutes). I'm hoping to come up with something fairly simple that can be used across a wide variety of LEO situations.

If while putting together your AMSO material you've come across any more specific information on the how they did MCCs for real, I'd appreciate anything you could give me. As for the table, if you need one for a specific configuration (target and active craft SMas), I've already got the code written to do that so it would be easy to do.

SAM

 

[boogabooga]

It's a cool concept, thank you.