Shuttle , Just need to know

[Dean Johnston]

Can anyone give me an explaination as to why the shuttle rolls over after take-off, is there a aerodynamic reason or is it just so the crew can see mother earth for what may be the last time.?

D.J.

Pleese excuse the spilling.

[GoneWest]

It points the communications aerials at the ground - they cannot be underneath, because there is a big tank of fuel in the way.

[Dean Johnston]

Gone West

But surely they have Sat-com on an expensive bit of kit like that.

D.J.

Pleese excuse the spilling.

[Select Zone Five]

This website gives a good answer. It seems that the manoeuver is not only for ground communication...

Why the Space Shuttle "Roll Manoeuver"? (http://www.faqs.org/faqs/space/schedule)

[Dean Johnston]

Select Zone Five

Wow, what a site, thanks for that, its been one of those things thats puzzled me for years. I just hope I dont get asked to explain that after a few pints, thanks again.

D.J.

Pleese excuse the spilling.

[Select Zone Five]

You're welcome D.J....have you seen a Shuttle launch?

If not, I HIGHLY recommend it. I saw Endeavour launch back in 1994 and although it was scrubbed for a day, because of high winds, we came back the day after and it was a fantastic experience.

The radio stations down there carry the R/T from Launch Control and the Shuttle and it sent shivers down my spine when the flight controllers gave their "go/no go" for launch. :D

[Dean Johnston]

S.Z.5.

Not in the flesh, But I will add it to my list of ' Things to do'

Thanks again.

D.J.

Pleese excuse the spilling.

[Dufwer]

I always thought that rolling onto it's back was to give gravity a chance in helping to get the fuel from the main tank to the engines on the shuttle itself.

[Hufty]

I think they're just mucking about.

Raises an interesting question - would it be as much fun doing aeros in zero G?! ;)

[Keith.Williams.]

The website certainly provides a lot of interesting information, but I'm not sure it really explains (in terms that are simple enough for my liking) why the vehicle must be inverted during its ascent.

My hypothesis goes something like this:

I think I am correct in saying that the orbiter is fixed to the fuel tank such that its nose is closer to the tank than its tail. This means that the required slightly negative (zero lift) angle of attack could be achieved without inverting the orbiter.

The solid rocket boosters are fixed to the tank, so their thrust line is probably fairly close to the drag (and inertia) line of the tank. This, together with the thrust from the main engines , will produce very little pitching moment during the initial stages of the launch.

But once the solid boosters have been used up and all thrust is being provided by the main engines, the misalignment of the drag+inertia and thrust lines will produce a large pitch down moment (towards the tank). If the inital thrust line of the main engines was parallel to its longitudinal axis, this would require a good deal of thrust vectoring to trim the vehicle (I assume they do not use ailerons at this stage). This continuous thrust vectoring would reduce the overall performance of the vehicle.

The alignment of the exhaust nozzles suggests that the thrust line of the main engines is not aligned with the longitudinal axis of the orbiter, but is angled slightly towards the front of the tank. By inverting the vehicle the drag+inertia lines of the tank and orbiter become better aligned with the thrust lines, and (when ascending inverted) with the intended direction of flight. This helps to trim out the pitching moments whilst maintaining performance.

This is of course only conjecture and was in fact (initially) constructed in the scenario you described in your previous post (in a pub over a pint).

[Dean Johnston]

Hi Keith,

Thanks for the input, by the way I have not got my results yet for instruments but your book was a fantastic help. I will let you know how I have gone on as soon as. Shown your book to lots of people at bristol, and everyone was impressed with it.

Regards

D.J.

p.s. notice the old ****** 'Standans' back at B.mouth.

Pleese excuse the spilling.

[DrSyn]

Keith's hypothesis, and the above link, explain some of the wider aspects (in some detail) rather well. I would add that another advantage of the heads-down attitude also allows an "up-and-away" separation of the boosters, keeping them clear of the Shuttle's wings.

If I might summarise the answer to Dean's original question, concerning the roll-program . . . . .

The millions of tons of concrete and steel which make up the 2 launch pads had to be fixed in one place for obvious practical reasons. Therefore, whilst on the pad, the Shuttle can only ever face in one unalterable direction.

The vector which the spacecraft has to fly in order to attain the correct orbit varies considerably according to the actual mission. One of the most important factors is the inclination of the intended orbit. This is the angle between the plane of orbit and Earth's equator. This cannot be easily altered once the craft is "up there".

As soon as the stack has cleared the tower, it has to roll in order to point it in the desired direction for its intended orbit. This is done quickly to minimise fuel and maximise use of the aerodynamic surfaces while at low speed. Thereafter she holds a steady course (relative to the equator) all the way to initial orbit, some 8 minutes later.

Hope that clarifies it, Dean.

Practical stuff: Most of the current Shuttle launches are to the Space Station which orbits at an inclination of 51.6º. The Shuttle launches when the extended ground track of the Station passes through the launch site, hence the very short launch window for these flights (5 mins±). So, after clearing the tower, the Shuttle will roll on to a "heading" of 51.6º in order to match it.

Happily (for some!) this means that around 20 mins after launch she must pass over southern UK (Lat 51º). In favourable conditions, just after sunset or just before sunrise, you can actually watch the Shuttle and its separated tank passing overhead, like a couple of fast moving stars. This is even more enjoyable if you have just watched the launch on TV.

CNN and Sky News usually cover the final moments of launch but you can find a suitable NASA TV streaming video to watch on your PC from here (http://www.nasa.gov/multimedia/nasatv/index.html). If you have Broadband and WM, I recommend this site (http://playlist.broadcast.com/makeplaylist.dll?id=139072&segment=) to save in your bookmarks/favourites. NTV broadcasts throughout each mission and covers all major events. Fascinating stuff if you are interested in the Space Program.

Those looking for fairly detailed technical info on the Shuttle should look here (http://spaceflight.nasa.gov/shuttle/reference/index.html). For up-to-date info on upcoming missions, etc, I recommend Space.com (http://www.space.com/shuttlemissions/), plus of course NASA's own site at http://spaceflight.nasa.gov/. There are many more!

I hope this proves interesting to some of you.

(Edit to update links)

[Select Zone Five]

Excellent post DrSyn, thanks very much.

Your comments reminded me of getting back to KSC shortly after watching the launch and hearing the commentary saying Endeavour was already on her 3rd of 4th orbit! Amazing. (I don't remember exactly how many orbits but I remember being amazed! :D

[Dean Johnston]

DrSyn

didnt think anyone could give a different angle, well done. If only this was a pub and not a website.

can anyone add to this?

D.J.

Pleese excuse the spilling.

[scroggs]

This is all good stuff, and very interesting, but absolutely not what 'Wannabes' is for. Off to 'Questions' with you.

Sorry Chas!

[Ace Rimmer]

Couple of years back Mrs R and I were in FL on our winter golf break when we heard on the radio that a Shuttle launch was planned for that night. So leeged it over to the Merritt Island causeway very cool, cept a weird thing the noise never reached us (we would have been about seven or so miles from the pad). Many moons ago (‘bout 360 of em) I was fortunate enough to be abole to attend the launch of Apollo 17 (the last moon launch and the only night launch of a Saturn 5) Let me tell you, that was IMPRESSIVE and the noise ‘kin ell…every fibre of your being was rattled (although this was from much closer almost alongside the VAB). Apparently the glow of the launch was visble from as far away as Virginia.

[DrSyn]

Distances can be very deceptive in the Cape area, Ace. If you were indeed on the MI causeway you were actually 17+ miles from the pad, although I am surprised that you heard nothing at that range. At 7 miles you can hear it loud and clear. For anyone interested, the closest off-base viewing point is along the waterfront at Titusville. At around 11 miles, it is the place to be if one has no pass.

A further bit of trivia. The closest any person is allowed to be during (Shuttle) launch is 3 miles, which is at the VAB/LCC area. Inside 2 miles the shock waves can cause internal damage, and inside 1 mile it may kill you --- so goes the standard spiel. I am assured by ground crew friends that rabbits are found hopping around the pad, shortly after launch, although the subsequent acuity of their hearing has never been tested. On at least one occasion I know of, an hour after launch, a pad crew found a rat crawling along one of the gantry arms, half way up the tower, singed, disorientated but still alive. Also, no doubt, profoundly deaf!

Ace, my first ever experience of a launch and the start of my lifelong friendship with the Cape was also Apollo 17 and up at the LCC area. Were you "journoing" then, or part of a certain crew? Drop me a line!

[InFinRetirement]

Very glad you enjoyed Dr Syn's very lucid descriptions. He certainly is a whizz at it. Fortunately for me, he is a very close friend and I have to "put up with this all the time" :D And I love it! He is an avid space nut who has seen many launches, has many friends who work at Cape Canaveral and has a book of stories to tell. And........he drives a B767 for a living.

PPRuNe you see, has so much talent in aviation, you cannot fail to be fully informed.

:cool:

[DrSyn]

Nut, IFR? I would prefer afficionado as I don't wear an anorak ;)

[Ace Rimmer]

Dr Syn
Nope I was but a pup in those days, in fact Uncle Rimmer was at the time working in Flight planning at JSC (it had just changed over from being MSC to JSC or pehaps that was a year or two later) and had decided to score some nephew points by allowing me to go with him to the launch on one of his tickets.
At the time Casa Rimmer was in Barbuda Lane in Nassau Bay and Gene from down the street was driving the beast.
He came to give a talk to my class at school after the mission (his daughter Tracy was in the same class) he brought along various bits of his EVA suit along, while most of the kids were scrambling to try on the helmet, I played with the outer glove when I put it down there was a graphite-like substance on my fingers. Cernan noticing this said yep that's the moon you have there. Still make the hairs on the back of my neck stand up. Turned a kid interested in space into an "afficionado" in no time flat.

Funny thing, I ran into him at an airline conference a few years back, he was still very pumped about the whole astronaut thing (BTW he had a book I guess it's still in print "the Last Man on the Moon quite a good read)and in the course of our chat He recalled the incident said that he'd never seen a kids eyes get that big that quickly.