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Turbojets On "White Knight"  
User currently offlineTimz From United States of America, joined Sep 1999, 6873 posts, RR: 7
Posted (9 years 11 months 3 weeks 1 day 16 hours ago) and read 1686 times:

http://www.scaled.com/projects/tierone/data_sheets/html/white_knight.htm

It says the Spaceship One carrier uses J85s to climb to 53,000 ft. Did they choose turbojets (instead of fans) because of better high-altitude performance? If so, is it just the afterburner that makes it perform better, or does the J85 itself outperform a comparable fan?

2 replies: All unread, jump to last
 
User currently offlineWidebodyphotog From United States of America, joined Jun 1999, 917 posts, RR: 67
Reply 1, posted (9 years 11 months 3 weeks 1 day 15 hours ago) and read 1672 times:

I believe the J85-GE-5's were chosen because they were available and they could get them at a very low price. A comparable turbofan would be something like A TF-731 or a PWC PW-300, both vastly more expensive engines even on the used market, and much heavier as well. I do remember watching the documentary and seeing an F-5 or T-38 trainer in the background sans engines, so I it's possible they were removed to that aircraft and transplanted to White Knight. The all up weight for White Knight and Spaceship One was about 17,000lbs giving a thrust to weight ratio of 2.2:1, and without Spaceship One close to unity. The J85's thrust would be behind those turbofans I mentioned at altitudes below 10,000 feet or so but after that the J85 would leave them far behind as far as thrust is concerned.

-widebodyphotog



If you know what's really going on then you'll know what to do
User currently offlineGigneil From United States of America, joined Nov 2002, 16347 posts, RR: 85
Reply 2, posted (9 years 11 months 3 weeks 1 day 15 hours ago) and read 1637 times:

Turbojets do performa a lot better at altitude, yes.

N


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