why does the shuttle turn 90 degrees on take off....why not point it in the right direction in the first place

Answer 1

Fantastic question! I love any question that makes me ask myself "why didn't I wonder that before?"

This from a web site I just looked up:
As we explained in two earlier questions about max q, or maximum dynamic pressure, the Shuttle reaches a point about one minute after launch when the pressure force of the atmosphere rushing past the rapidly accelerating rocket reaches a peak. The roll maneuver is performed shortly before max q is reached because this "heads-down" orientation helps alleviate the stresses that the dynamic pressure loads cause on the vehicle's structure.

The second factor we need to consider is that for each mission, the Shuttle must launch at a certain azimuth angle in order to be inserted into the correct orbital plane. Since the launch pad (and therefore the Shuttle) sits in a fixed position, the Shuttle must perform a roll maneuver during ascent in order to orient itself to achieve the desired launch azimuth angle. If it were possible to rotate the launch pad prior to launch, the pad could simply be rotated to accomodate the launch azimuth angle, and the Shuttle could launch into a heads-down orientation while gradually pitching over during ascent.

Finally, the Shuttle orbits such that its cargo bay faces towards the Earth. The heads-down position assists in communications with the ground and allows instruments within the cargo bay to be pointed back towards Earth, which is required for many of the experiments carried within the bay. There is probably also some psychological benefit to the crew since they are given spectacular views of home rather than staring into the cold darkness of the great void of space.
- answer by Aaron Brown, 8 June 2003

Answer 2

Fantastic question. I too wonder why I didn't ask that before... and I used to be at NASA working expendable launch vehicle engineering!

Even with the answer above explaining why the shuttle needs to be in the attitude it is AFTER the manuever, it still does not explain why the shuttle must do the manuever in the first place.

I searched around and could not find the answer. I guess I will have to monitor this question and/or ask some of the old timers at NASA (retired). Might be something dumb like that's the way the launch pad was built - but I doubt it.

I will edit this post if I find anything out...
HEY, I THINK I FOUND A SIMILAR SITUATION!!!!!
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The following is from NASA-TM-108605,
"Results of the FIRST UNITED STATES MANNED ORBITAL SPACE FLIGHT FEBRUARY 20, 1962"

"Two seconds after liftoff,the roll program is initiated by onboard flight equipment. This maneuver is necessary because the launch pad is oriented so that the pitch axis of the launch vehicle is aligned on an azimuth of 115° while the Mercury spacecraft insertion head is about 75°. Therefore, the roll program has to rotate the launch vehicle approximately
30° to aline it with the Mercury spacecraft insertion heading. At 15 seconds after lift-off the roll program is complete and then the pitch program is started."

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930074071_1993074071.pdf
[Page 54 of 212 in the pdf doc, page 46 of the original doc.]

Hope this helps!

Answer 3

Then it would require MORE energy i.e. MORE fuel which is quite expensive since during take off the would have already covered some distance due to rotation around its axis.

On turning 90 deg your are effectively avoiding the wrath of FULL G-FORCE and thus end up saving a lot of fuel.
Besides this also reduces the time for which the astronauts encounter the high G-forces.

After turning the communication aerial and other stuff are easier to align and hence communication a hell of a lot easier.

ITS NOT FEASIBLE TO MAKE A LAUNCH PAD AT A PREADJUSTED ANGLE making factors like thrust ,route of escaping gases difficult to adjuct on the launch pad i mean.