gandalf@pro-canaveral.cts.com (Ken Hollis) (11/17/90)
Greetings and Salutations: >From: lydick@freezer.it.udel.edu (William Lydick) >In article <1990Nov9.184955.279@news.arc.nasa.gov> yee@trident.arc.nasa.gov (Pet >er E. Yee) writes: >> [Stuff deleted] >> A hot fire of auxiliary power unit number 1 is planned >Mon- >What, exactly, is meant by "A hot fire..."? Is it the obvious conclusion, or is >it just a little bit more subtle that that? The APU (Auxiliary Power Units) is a hydrazine-fueled (N2H4), turbine driven power unit that generates mechanical shaft power to drive a hydraulic pump that produces pressure for the orbiters hydraulic system. There are three separate APUs, three hydraulic pumps, and three hydraulic systems. When the APU is changed out on a bird, the retest is to "Hot-fire" the APU, thus verifying the functionality of it. Each APU has it's own fuel tank, and is loaded with approximately 325 pounds for launch. Another subject : >>In article <kNuDs2w163w@ehpcb.WLK.COM>, ehopper@ehpcb.WLK.COM (Ed Hopper) writes ... >>There has been some discussion here regarding hydrazine. A friend of >>mine, who works for a NASA contractor, once told me that hydrazine is a >>major concern when working on a satellite during EVA. Hydrazine is highly >>toxic. Contact with the skin can be fatal. ....... Contact with the skin is not fatal. HOWEVER EXPOSURE IS NOT GOOD ! The Hydrazine reacts with the water in your skin to form Nitric acid (among other nasty things). If you breathe it in, and it forms Nitric acid in your lungs, guess what happens... Please note that the APUs also use Hydrazine. Ken Hollis ProLine: gandalf@pro-canaveral Internet: gandalf@pro-canaveral.cts.com UUCP: crash!pro-canaveral!gandalf