Topic: Report Blames Shoddy Work on Shuttle Foam Replacement Project  (Read 5339 times)

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Offline prometheus

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Re: Report Blames Shoddy Work on Shuttle Foam Replacement Project
« Reply #20 on: October 25, 2005, 04:14:26 am »
well i just did the math ;).  (should have warned ya... its a bit long ;))

Ok here is the intial tangental velocity an vehicle would have at the equator

Vlaunch site = R * angular velocityof earth

Where R is the radius from the spin axis (radius to the center of the earth)

Vlaunch site = 6378.137 (km)* .0000729212 (rad/s)

Vlaunch site = .4651 (km/s)

ok now for the tangental velocity at the geo sync orbit

Vcircular orbit = Sqrt(mu/R)

Where mu is earths gravitational constant, 3.986*10^5 and R is the radius of the orbit to the center of the earth (altitude (km) + 6378.137(km)

Vcircular orbit = Sqrt(3.986*105(km3/sec2)/42158(km))

Vcircular orbit = Sqrt(9.4549(km2/sec2)

Vcircular orbit = 3.074 km/sec


so as you can see you would not be able to maintain a circular orbit. 


ok now to prove that it will burn up ;)

first we must find the specfic mechanical energy which is always negative for elliptacl orbits, 0 for parabolic, and positive for hyperbolic (which makes sense as it takes more energy than what it take sto just take a parabolic orbit)

SME=V2/2 - mu/R

where R is the radius of the orbit, and v is the velocity at that orbit

SME=.4651(km/s)2/2-3.986*105(km3/sec2/42158(km)

SME = -9.23855 (km2/s2)

from here we can calculate the semi major axis

a = - mu/(2*SME)
a = - 3.986*105(km3/(2*-9.23855)
a = 21572.76 km

and now to determine the radius at perogee (closet to earth)

a=(Ra + Rp)/2

we know the Ra (radius at apogee) is 42158 as this is the furthest distance from earth

21572.76(km)=(42158 (km)+ Rp)/2

Rp = 987 (km)  <  6378.137(km)  and thus will make contact w/ earth. 

to prove it has a highly elliptical orbit we must check it eccentricity (e).  when e=0 the orbit is circular, 0<e<1, the orbit is elliptical with values closer to one becoming more elliptical, e=1 the orbit is prabolic (leaving earth), e>1 the orbit is hyperbolic (leaving earth, used for interplanatary travel)

e = (Ra - Rp) / (Ra + Rp)
e = (42158(km) - 987(km)) / (42158(km) + 987(km))
e = .95 (unitless)

i would tell you the time it would take but that takes shyt load of time ;)

hope that helps (that took alot of time to type arg lol)





I'll need to go through this later on when I'm more awake, but I can see what Ken Mattingly meant when he said "I don't know how to do 90% of this mission."

I would hate to be the poor sod who has to translate this into roll and pitch angles and burn durations...

Anyway, thanks for taking the time out for that, I appreciate it and will go through it step by step when I'm fully awake in a couple of hours... :)


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Offline prometheus

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Re: Report Blames Shoddy Work on Shuttle Foam Replacement Project
« Reply #21 on: October 25, 2005, 04:58:35 am »
a rough estimate on the time till impact once in orbit,

4 hours till impact (half of the period) (rough because at perigee is already under ground and finding the actual time is alot of derivatives and stuff i dont' want to do lol)

Yeah, I can see the proof in it now that I've followed the maths through...  You were right and I was wrong...


To make an apple pie from scratch, you must first create the Universe!