some questions (1 Viewer)

[abdooooo!!!]

i need to make sure my answers are all correct for my assignment... so help me.

1. When the space shuttle is launched into orbit, it will have an approximate altitude of 250 km above the Earths surface and an orbital velocity of 7756 m.s-1

a. Identify and describe the types of energy possessed by the shuttle when it is in orbit
b. Briefly analyse the energy changes that have occurred, during the launch, to achieve this orbit.

for this question i wrote about kinetic and potential adding up to mechanical energy. is that right?

and when the rocket launches the kinetic increases, potential increase and mechanical also increase. am i right?

2. The acceleration of the space shuttle during launch is not constant. Briefly explain why this is so in terms of the structure and mass of the launch vehicle. Analyse the changing acceleration during launch in terms of the Law of Conservation of Momentum.

what does this question mean by 'structure'? is the structure the amount of fuel it holds?

3. State the optimum angle for re-entry into the Earths atmosphere and discuss the consequences of failing to achieve this angle. Your answer should examine angles that are greater than and less than the optimum angle.

what is the optimum angle for re-entry? isn't it always different depending on various things?

and if you have time please check my workings for calculations in the other thread (http://www.boredofstudies.org/community/showthread.php?s=&threadid=20113) if someone hasn't already done so.

thanks

 

[Dash]

Ok... this is off the top of my head, so elaborate on this...

Originally posted by abdooooo!!!
1. When the space shuttle is launched into orbit, it will have an approximate altitude of 250 km above the Earths surface and an orbital velocity of 7756 m.s-1

a. Identify and describe the types of energy possessed by the shuttle when it is in orbit
b. Briefly analyse the energy changes that have occurred, during the launch, to achieve this orbit.

for this question i wrote about kinetic and potential adding up to mechanical energy. is that right?

and when the rocket launches the kinetic increases, potential increase and mechanical also increase. am i right?

What you described I guess is ok. But then again, I'm not sure what else to include. I suggest putting detailed explanations in what you already have down.

Originally posted by abdooooo!!!
2. The acceleration of the space shuttle during launch is not constant. Briefly explain why this is so in terms of the structure and mass of the launch vehicle. Analyse the changing acceleration during launch in terms of the Law of Conservation of Momentum.

what does this question mean by 'structure'? is the structure the amount of fuel it holds?

This question is answered in this thread: http://www.boredofstudies.org/community/showthread.php?s=&threadid=20206
The 'structure' is referring to the shuttle, and the 'mass' being the fuel carried by the rocket.

Originally posted by abdooooo!!!
3. State the optimum angle for re-entry into the Earths atmosphere and discuss the consequences of failing to achieve this angle. Your answer should examine angles that are greater than and less than the optimum angle.

what is the optimum angle for re-entry? isn't it always different depending on various things?

The optimum angle of re-entry is between 5.2 and 7.2 degrees to the horizontal of the Earth's atmosphere.
Too steep and the astronauts inside the shuttle will experience extreme g forces and be crushed under the immense pressure.
Also, the heat buildup will be too great for the insulation and ceramic tiles to handle.
The shuttle will disintegrate as a result under the extreme temps.
Too shallow and the shuttle can bounce off the atmosphere, sending it back into space.

 

[zeropoint]

Originally posted by abdooooo!!!
i need to make sure my answers are all correct for my assignment... so help me.

1. When the space shuttle is launched into orbit, it will have an approximate altitude of 250 km above the Earths surface and an orbital velocity of 7756 m.s-1

a. Identify and describe the types of energy possessed by the shuttle when it is in orbit
b. Briefly analyse the energy changes that have occurred, during the launch, to achieve this orbit.

A rocket on the launch pad possesses gravitational potential energy U_gi, initial kinetic energy K_i = 0 and initial chemical potential energy U_ci. Conservation of energy implies

K_f − K_i + U_gf − U_gi + U_cf − U_ci = 0

That is, the change in kinetic energy plus the change in gravitational potential energy plus the change in chemical potential energy remains constant over time. The above expression can be simplified to

K_f − 0 + U_gf − U_gi + 0 − U_ci = 0

U_ci = K_f + Delta U_g

In other words, the inital chemical energy is transformed into the final kinetic energy plus the change in gravitational potential energy.

 

[abdooooo!!!]

Originally posted by Dash
The 'structure' is referring to the shuttle, and the 'mass' being the fuel carried by the rocket.

umm... so is this right: because the shuttle is structured so that fuel can constitute up to 90% of its mass...

Originally posted by zeropoint
A rocket on the launch pad possesses gravitational potential energy U_gi, initial kinetic energy K_i = 0 and initial chemical potential energy U_ci. Conservation of energy implies

what the, what the hell is chemical potential energy

but i think i can see your point... so will include this chemical energy concept in my answer, thanks

 

[Ragerunner]

It's not that it's structured so that 90% of it's mass is fuel, but that it HAS to be like that in order to be able to leave the earth - high fuel requirements.

Then as fuel is being used, it is jettison'd to lose some of the mass and accelerates more.

For the one on the law of conservation of momentum, you'd want to put appropriate equations to back up your answers.

 

[abdooooo!!!]

Originally posted by Ragerunner
It's not that it's structured so that 90% of it's mass is fuel, but that it HAS to be like that in order to be able to leave the earth - high fuel requirements.

oh no... whats going on

then how am i suppose to answer the part - Briefly explain why this is so in terms of the structure...

 

[zeropoint]

Originally posted by abdooooo!!!
oh no... whats going on

then how am i suppose to answer the part - Briefly explain why this is so in terms of the structure...

Recall Newton's second law; the acceleration of a body is directly proportional to the net force acting on it and inversely proportional to its mass.

a = F/m

During launch, the net force consists of the force of gravity and the thrust produced by the engines. Therefore the net force F remains relatively constant. However, since the rocket is ejecting fuel to produce thrust, the mass m of the rocket is decreasing with time. It follows that the acceleration a of the rocket is increasing over time

 

[Ragerunner]

In terms of structure, it's built in different stages so when stage 1 of the fuel usage has been used, it is jettison'd to remove the un-needed mass off the rocket.

That's all I know about the structure. No idea what else to say.

 

[abdooooo!!!]

Originally posted by Ragerunner
In terms of structure, it's built in different stages so when stage 1 of the fuel usage has been used, it is jettison'd to remove the un-needed mass off the rocket.

oops, forgot about that. thankyou

the calculation thing is killing me... can't think straight

 

[Dash]

LOL.... ahhh I miss the tension..... *somewhat*

Good luck

 

[abdooooo!!!]

Originally posted by Dash
LOL.... ahhh I miss the tension..... *somewhat*

Good luck

lol... its this 'tension' that makes studying a subject like physics whorthwhile...

i need a lot of luck...