General Question shuttle HAC info

[caningo]

Hi everyone,

I was wondering where on the web can I find a detailed explanation of how the HAC is performed once the Shuttle is in the vicinity of the base. I am more interested in a diagram that explains on what heading the HAC must be intercepted depending on what your initial approach heading is...

HOpe I made sense.... :lol:

 

[garyw]

This site might be of some use -> http://www.nasa.gov/centers/johnson/news/flightdatafiles/index.html

 

[Urwumpe]

Which HAC is selected depends on the wind conditions and cross-range error (remaining reentry energy at HAC). The exact algorithm is not known to me, but I suspect it contains a lot of experience rather than science.

 

[Andy44]

but I suspect it contains a lot of experience rather than science.

I think there is definitely a pilot's seat-of-the-pants aspect to it. The HAC, from what I've read, is the STS version of the landing procedures used by various test vehicles back in the 50s-70s, lifting bodies and such. According to my history book, the pilots entered a "high key", circled around to the "low key", and then circled around once more to final approach. The shuttle orbiter does a similar thing, except there is only one circle, which is sufficient for energy managment.

If you've ever done any pilot training, you learn how to something similar in an engine-out emergency when you have to manage your energy in a glide to reach a chosen landing point, such as a cornfield or a road. For any given airframe, there is a glide ratio, a best glide speed, and a known vertical speed, and you can quickly work out in your head, taking wind into account, when you need to turn to make your field. Capt. Sullenberger did this when he landed his jetliner in the Hudson River last winter.

Of course, the HAC is much more scientific, as all of this is predictable and can be automated through software. As long as you always carry a little extra energy, their will be some margin for correction.