Homework Help: Physics

Posted by Rory on Wednesday, December 28, 2011 at 10:59pm.

The De-orbit Burn

The Shuttle must reduce its velocity at a pre-calculated point in its orbit in order to return to Earth. In order to reduce the velocity and change the orbit of the Shuttle, a maneuver called the de-orbit burn is performed. For this maneuver, the Shuttle is turned in a direction such that the Orbital Maneuvering System (OMS) nozzles point in the direction of the Shuttle's velocity back toward Earth. The OMS engines fire and give the Shuttle a velocity in the opposite direction, thus slowing the spacecraft.

The Shuttle must perform the de-orbit burn to change its orbit so that the perigee, the point in the orbit closest to Earth, is inside of Earth's atmosphere. De-orbit maneuvers are done to lower the perigee of the orbit to 60 miles (or less). An altitude of 60 miles is important because this is where the orbiting spacecraft is recaptured by Earth’s gravity and re-enters Earth’s atmosphere.

Calculate the minimum change in velocity (delta V or ∆V) required for the Space Shuttle to decrease its altitude to 60 miles if it’s orbiting with an apogee of 236 miles and a perigee of 205 miles above the surface of Earth.

Use the rule of thumb that below an altitude of 500 miles, for every 2 feet per second (ft/s) change in the orbiting space craft’s velocity its altitude will change by 1 mile.

and I have to answer in feet per second

Physics - bobpursley, Wednesday, December 28, 2011 at 11:04pm
change of altitude: 205-60=145

rule of thumb: deletV=145mile*2/sec.mile

290ft/sec
Physics - Lafonda, Friday, December 30, 2011 at 1:55pm
I see that someone else is in the VASTS program that didn't understand this problem...
Physics - Lafonda, Friday, December 30, 2011 at 2:00pm
But I might add that that would be the necessary velocity to do it, but the question asks for the CHANGE in velocity. The change in velocity would be 290ft/sec - (the initial) 2ft/sec, so 288 ft/sec.
Physics - sam, Monday, January 2, 2012 at 9:34pm
isn't that wrong because of the units?

you would have to convert 145 mi to 765,600 ft.

then divide by 2 (because its 2 ft/s) and get 382,800.

then subtract 2 ft/s to get the change, so 382,798.

is that right or did i do something wrong?
Physics - Brooke, Wednesday, January 4, 2012 at 2:18pm
I too am in VASTS... that's what I thought. The units would have to be converted first to feet to get an answer in ft/sec.
Physics - Levi, Thursday, January 5, 2012 at 5:21pm
I am also in the program, but I was wondering did you guys use the program to help you at all?
Physics - Brooke, Thursday, January 5, 2012 at 5:45pm
My computer is really slow and I've only been able to get it to work once...
Physics - Raequan, Thursday, January 5, 2012 at 11:59pm
Some hard stuff homie.
Physics - Poop, Friday, January 6, 2012 at 12:23am
How can you find Delta V without having the initial Velocity?
Physics - Rory, Friday, January 6, 2012 at 1:04am
Thank you all for your help, but I'm still confused, I converted miles to feet
145 miles= 765600 feet
then what?
Physics - Brooke, Friday, January 6, 2012 at 7:29am
If you divide 765600 by 2 ft/sec you're going to still have a huge number. I don't think that's right somehow. I'm going to get a teacher's help today.
Physics - Anonymous, Friday, January 6, 2012 at 11:22am
1
Physics - Anonymous, Friday, January 6, 2012 at 11:22am
1
Physics - Anonymous, Friday, January 6, 2012 at 11:22am
if you take 1 and at the answer minus 1 it is correct
Physics - Anonymous, Friday, January 6, 2012 at 11:23am
*add
Physics - Anonymous, Friday, January 6, 2012 at 11:25am
or did i mean subtract?
Physics - Anonymous, Friday, January 6, 2012 at 11:25am
ok im leaving now hahahahaha bye
Physics - Brooke, Friday, January 6, 2012 at 2:11pm
The first one I believe is right except for the units. Since 2 ft/sec is just rule of thumb, it wouldn't count towards the change. That's just the information given so that 2ft/sec = 1 mile. If you have 145 miles, for every mile you're going 2 ft/sec. So you would multiply 145 times 2.
Physics - Levi B., Friday, January 6, 2012 at 5:26pm
what is the initial velocity? how can you find the Delta v without the initial
Physics - Kayla, Friday, January 6, 2012 at 9:26pm
I'm so glad I'm not the only one lost in VASTS. What a relief!
Physics - T, Friday, January 6, 2012 at 11:32pm
Eh, from what it looks like, it should just be the change in height that you need to do, which will be in units of miles right? and then you multiply that by the ratio of delta V to altitude change, which I believe is in units of (ft/s)/(change in miles)
Physics - Joey, Saturday, January 7, 2012 at 6:48pm
Ughhh this is confusing. - In the VASTS program. I'm just glad I'm not the only one having trouble :P
Physics - Muhammad, Friday, January 4, 2013 at 9:18pm
I am also in the VASTS program.My data is different, but they have the same concept.
Physics - Muhammad, Friday, January 4, 2013 at 9:19pm
I am also in the VASTS program.My data is different, but they have the same concept.
Physics - Muhammad, Friday, January 4, 2013 at 9:22pm
I am also in the VASTS program.My data is different, but they have the same concept.
Physics - Monika, Monday, January 21, 2013 at 5:00pm
this is the same question that HAS is useing. im happy that im not the only one who needs help with it
Physics - Monika, Monday, January 21, 2013 at 5:00pm
this is the same question that HAS is useing. im happy that im not the only one who needs help with it
Physics - swaggy, Monday, January 21, 2013 at 11:53pm
this is a retarded question, nasa thinks we're geniuses.
Physics - swaggy, Monday, January 21, 2013 at 11:53pm
illuminati
Physics - red, Wednesday, March 6, 2013 at 4:24pm
u guys area bunch of cheaters

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