skywalker@dino.qci.bioch.bcm.tmc.edu (Timothy B. Reynolds) (06/05/90)
On all the shuttle flights @ around 50 + MET into
the flight, Houston gives the command to go at throttle up
to 104%. My question is how can you throttle up past 100% ???
ALso what is MAX-Q
Someone please explain....
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Timothy B. Reynolds : VAX Systems Manager
Howard Hughes Medical Institute : Structural Biology Laboratory
Baylor College of Medicine : Houston, Texas
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Disclaimer: My opinions are my own, not HHMI's or Baylor College of Medicine
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Quote: I used to hate obnoxious people, but now Im their leader...
------------------------------------------------------------------------------henry@utzoo.uucp (Henry Spencer) (06/05/90)
In article <990@gazette.bcm.tmc.edu> skywalker@dino.qci.bioch.bcm.tmc.edu (Timothy B. Reynolds) writes: >On all the shuttle flights @ around 50 + MET into >the flight, Houston gives the command to go at throttle up >to 104%. My question is how can you throttle up past 100% ??? The percentages are with respect to the original nominal thrust of the engines, not to what they are rated for today. I believe 104% is the highest power currently cleared for flight, although in pre-Challenger days NASA was hoping to operate at 109% routinely by now. >ALso what is MAX-Q Maximum aerodynamic pressure. As a rocket climbs, it is picking up speed (increasing the aerodynamic forces on it) but the air density is also falling off with altitude (decreasing the forces). In general there is a specific point, fairly early in flight, where aerodynamic forces hit a maximum, and this is one of the worst-case design points for the rocket. The shutttle throttles back some, early in flight, to avoid building up too much speed early on while the air is still thick and worsening Max Q. -- As a user I'll take speed over| Henry Spencer at U of Toronto Zoology features any day. -A.Tanenbaum| uunet!attcan!utzoo!henry henry@zoo.toronto.edu
gwh@monsoon.Berkeley.EDU (George William Herbert) (06/05/90)
In article <990@gazette.bcm.tmc.edu> skywalker@dino.qci.bioch.bcm.tmc.edu (Timothy B. Reynolds) writes: >On all the shuttle flights @ around 50 + MET into >the flight, Houston gives the command to go at throttle up >to 104%. My question is how can you throttle up past 100% ??? >ALso what is MAX-Q The thrust of 104% is expressed relative to a theoretical max thrust that was determined before the SSME's were acutally tested thoroughly. When they found that they could safely be flown to 104% of the estimated max thrust they didn't want to change the thrust ratings they'd already specified... Max-Q is the point where the aerodynamic forces from passing through the atmosphere are highest. (Maximum-Q; Q=aerodynamic drag force) ******************************************************************************* George William Herbert JOAT For Hire: Anything, Anywhere: My Price UCB Naval Architecture undergrad: Engineering with a Bouyant Attitude :-) ------------------------------------------------------------------------------- "Who?" the man managed. Whip me, Beat Me, Make me learn C... "The Rastafarian Navy," Case said, ++++++++++++++ gwh@ocf.berkeley.edu "...and all we want is a jack into your ============= gwh@soda.berkeley.edu custodial system." -neuromancer """""""" maniac@garnet.berkeley.edu
alan@merch.TANDY.COM (Alan Caldera) (06/05/90)
In article <990@gazette.bcm.tmc.edu>, skywalker@dino.qci.bioch.bcm.tmc.edu (Timothy B. Reynolds) writes: > On all the shuttle flights @ around 50 + MET into > the flight, Houston gives the command to go at throttle up > to 104%. My question is how can you throttle up past 100% ??? Throttling up the engines above 100% typically indicates that the engines are being throttled up to 4% above original design specs for those engines. > ALso what is MAX-Q > MAX-Q is the area of maximum dynamic pressure exerted on the spacecraft, the engines are throttled down to 65% to keep the shuttle from breaking apart. Hope this clears up your confusion. Sorry about the lack of engineering detail, I design software not spacecraft. --------------------------------------------------------------------------- Alan Caldera System Engineer Computer Support Services Tandy Corporation alan@merch.TANDY.COM #include <std.employer.disclaimer>
petej@phred.UUCP (Pete Jarvis) (06/06/90)
In article <990@gazette.bcm.tmc.edu> skywalker@dino.qci.bioch.bcm.tmc.edu (Timothy B. Reynolds) writes: >On all the shuttle flights @ around 50 + MET into >the flight, Houston gives the command to go at throttle up >to 104%. My question is how can you throttle up past 100% ??? >ALso what is MAX-Q The engines were designed to operate at 109% of nominal thrust. Nominal thrust being 100%. They operate at 104% of nominal, but 5% below max rated thrust for saftey factor. MAX-Q is maximum dynamic pressure on the vehicle during ascent where you have the highest amount of forces on the vehicle for the speed it is doing. Peter Jarvis......
richard@hpfcdc.HP.COM (Richard Artz) (06/06/90)
Timothy writes: > On all the shuttle flights @ around 50 + MET into > the flight, Houston gives the command to go at throttle up > to 104%. My question is how can you throttle up past 100% ??? > ALso what is MAX-Q > Someone please explain.... As I heard, the first engines were built for some X thrust-value, later improvements allowed 104% to be *nominal*. Of course engineers should have rescaled this back to 100%, but the instruments were already labeled. I think the MAX-Q was the max aerodynamical stress point. It can be seen on the videos. It's the point where their speed is "too fast" relative to the thickness of the air (which thins out as they get higher). I know others can explain this better, hope I didn't mess it up to badly. Richard Artz / 303-229-2036 / richard@hpfcww.fc.hp.com
umapu02@sund.cc.ic.ac.uk (D.A.G. Gillies Supvsr Dr K.J. Bignell) (06/08/90)
In article <990@gazette.bcm.tmc.edu> skywalker@dino.qci.bioch.bcm.tmc.edu (Timothy B. Reynolds) writes: >On all the shuttle flights @ around 50 + MET into >the flight, Houston gives the command to go at throttle up >to 104%. My question is how can you throttle up past 100% ??? >ALso what is MAX-Q > >Someone please explain.... Dunno what MAX-Q is (hip-hop singer ?),but 100% is the nominal rated working thrust beyond which it's not a good idea to go for too long.However pushing it hard (ie >100%) for a while doesn't hurt.It's a bit like the reheat on a jet airplane - that gives more thrust than rated nominal.I think it's silly terminology though. David Gillies (umapu02@cc.ic.ac.uk)