morse@leadsv.UUCP (Terry Morse) (01/31/86)
I remember hearing that the main engine compressors have worn out much
faster than had been predicted. Does anybody know how they are designed ?
More specifically:
Are they axial or centrifugal ?
What is their power source ?
Why are they wearing out so fast ?
Do they pump the fuel as a liquid or gas ?
What is their design pressure ?
It has been speculated that a compressor failure could have caused a breach
of the external tank, but I doubt that.
With resolve for the continuation of the shuttle program,
--
Terry Morse (408)743-1487
{ hplabs!cae780 } | { ihnp4!sun!sunncal } !leadsv!morsehenry@utzoo.UUCP (Henry Spencer) (02/03/86)
> I remember hearing that the main engine compressors have worn out much > faster than had been predicted... Actually, they're pumps rather than compressors. They're pumping liquids rather than compressing gases. At the pressures they work at, mind you, the distinction is sometimes a little fuzzy... > Are they axial or centrifugal ? Axial, I believe. > What is their power source ? The full fuel flow plus some of the oxidizer are "pre-burned" and the moderately-hot gases from that run the pumps. The gases then go into the main combustion chamber where the rest of the oxidizer arrives to complete the burn process. This is unusual; earlier engines generally used only a small fraction of the incoming propellants to run their pumps. The SSMEs run at such high pressure that they need a lot of pump power to get the propellants in, hence the odd approach. > Why are they wearing out so fast ? Because they work very hard in a very harsh environment. There was little experience with reusable large rocket engines, and practically none with ultra-high-pressure engines like this, to guide the engineers. So their estimates of lifetime etc. were a little, uh, optimistic. > What is their design pressure ? Don't have the exact numbers on hand; something like 2000-3000 psi. (This is roughly the same pressure as a big laboratory compressed-gas cylinder at full pressure, and those pumps are pushing several tons of propellant *per second* in against that pressure!) > It has been speculated that a compressor failure could have caused a breach > of the external tank, but I doubt that. It probably would have caused other types of havoc first. -- Henry Spencer @ U of Toronto Zoology {allegra,ihnp4,linus,decvax}!utzoo!henry