5
$\begingroup$

This is the question that I should have asked here. The space shuttle and the two solid rocket boosters (SRBs) are mechanically attached to the giant tank.

SRB's, shuttle, and tank all experience forces due to drag, and due to gravity. SRBs and shuttle also experience forces due to thrust.

There are also mechanical forces between the SRBs and tank, and between shuttle and tank. My question here is about these forces.

While under flight, the SRBs are lifting the tank, so the forces of the SRBs on the tank are positive. Near the end of their propulsive flight, they separate from the tank - are they still lifting at this moment?

The shuttle's three main engines burn LOX & LH2 from the tank. The shuttle sometimes carries a very heavy payload, but sometimes it does not - meaning the gravitational force on the shuttle can vary substantially from one flight to the next. The shuttle's main engines support the weight of the shuttle. But do they always share in the lifting of the tank? Or when the shuttle has a very heavy payload, is the tank (+SRBs) actually pulling the shuttle?

Ideally, I'd like to see if there is a plot of SRB-tank, and shuttle-tank force (magnitude and sign) as a function of time, for small payload mass and maximum payload mass (Hubble?).

Basically what-pushes-what vs time?

enter image description here above: STS-79 (NASA) from here

enter image description here above: STS-51f - Spacelab (NASA) from here

enter image description here above: STS-132 (NASA) from here

enter image description here above: STS-117 (NASA) from here

$\endgroup$
6
$\begingroup$

The three SSMEs provide 568 tons of thrust, the Orbiter has a weight in the region of 100 tons incl payload. The Orbiter always exerts a positive force on the tank from liftoff to MECO, no matter what the payload (0-16 tons in practice).

The SRBs are jettisoned when their thrust drops to 100,000 lbf/45 tons, so by then their thrust/weight ratio is below 1 and they are being pulled along by the Orbiter. Thrust dropoff is very rapid, so this occurs for just a few seconds.

$\endgroup$
  • $\begingroup$ OK this is really helpful! Somewhere out there, there must be some kind of plot of these vs time. $\endgroup$ – uhoh Jul 10 '16 at 8:22
  • $\begingroup$ @uhoh -- Somewhere out there is a plot of force vs time. Click on Hobbes' link, and there it is. $\endgroup$ – David Hammen Jul 10 '16 at 9:35
  • $\begingroup$ @DavidHammen there is a plot of something, but not what I've asked for. Please read my question again. "Ideally I'd like to see if there is a plot of SRB-tank, and shuttle-tank force (magnitude and sign) as a function of time, for small payload mass and maximum payload mass (Hubble?)" $\endgroup$ – uhoh Jul 10 '16 at 10:13

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.