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#1
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Question on shuttle fuel usage on liftoff.
I was puzzled by this passage on a web site describing the shuttle:
The Ascent Stage of a Space Shuttle Mission Profile by Jim Cornish. "It takes five seconds for the shuttle to clear the 85 metre (247 feet) tower and its 30 metre (100 foot) lightning rod. By the end of the eighth second, the shuttle has traveled only twice its own length in distance has already accelerated to 161 kilometers per hour (100 mph.) During this short time, the orbiter's three main engines and two solid rocket boosters have consumed more than 680,000 kilograms (1.5 million pounds) of fuel, about half of its total fuel supply." http://www.cdli.ca/CITE/sts_ascent.htm This amount of fuel usage after only 8 seconds does not seem right to me. On this page I found the fuel usage of the two SRB's together is about 10,000 kg per second: Shuttle Fun Facts "Each of the Shuttle's solid rocket motors burns 5 tons (4,536 kilograms) of propellant per second, a total of 1.1 million pounds (498,952 kilograms) in 120 seconds." http://www-pao.ksc.nasa.gov/kscpao/f...s/funfacts.htm So after 8 seconds this would amount to about 80,000 kg. And this page allows you compute the fuel usage of the shuttle main engines: EXTERNAL TANK. "The 17-inch-diameter feed line permits liquid oxygen to flow at approximately 2,787 pounds per second with the SSMEs operating at 104 percent or permits a maximum flow of 17,592 gallons per minute." .... "The liquid hydrogen feed line flow rate is 465 pounds per second with the SSMEs at 104 percent or a maximum flow of 47,365 gallons per minute." http://science.ksc.nasa.gov/shuttle/...ewsref/et.html This gives a hydrogen/oxygen burn rate of 1471 kilograms per second, so after 8 seconds would be 11,768 kg. I know the shuttle remains latched to the launch pad after the main engines are started for 6 to 7 seconds to get the main engines up nearly to full power, but even this would still be less than 7*1471 = 10,297 kg. So the total fuel usage 8 seconds after launch should be less than 80,000 + 11,768 + 10,297 = 102,065 kg, not the 680,000 kg claimed. Is it correct the shuttle uses only about 100,000 kg total of fuel during the first 8 seconds after launch? Bob Clark |
#3
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In article . com,
wrote: During this short time, the orbiter's three main engines and two solid rocket boosters have consumed more than 680,000 kilograms (1.5 million pounds) of fuel, about half of its total fuel supply." This amount of fuel usage after only 8 seconds does not seem right to me. Especially since it would mean that the shuttle would run out of fuel roughly another 8 seconds later. -- "Think outside the box -- the box isn't our friend." | Henry Spencer -- George Herbert | |
#4
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Henry Spencer wrote:
In article . com, wrote: During this short time, the orbiter's three main engines and two solid rocket boosters have consumed more than 680,000 kilograms (1.5 million pounds) of fuel, about half of its total fuel supply." This amount of fuel usage after only 8 seconds does not seem right to me. Especially since it would mean that the shuttle would run out of fuel roughly another 8 seconds later. Assuming it wasn't a cloud of debris by then due to the acceleration loads! - Ed Kyle |
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