Manual Shuttle Reentry

ltm_se · Jun 3, 2006

Is it possible to do a completly manual pilot controlled reentry from deorbit burn to wheel stop without the descent autopilot? Also, if it's possible has it ever happend? Is the manual procedure fully manual or semi-automatic?

blacknebula · Jun 3, 2006

Define manual, please. Are you talking about a complete computer failure, forcing astronauts to land the shuttle "deadstick"? If it is that case, I do not think it is probable, if not impossible. However, the pilot astronaut corps might disagree.

jschaef5 · Jun 3, 2006

The shuttle actually lands deadstick as there are no engines powered on during landing. Looking at a couple of the PIO that almost destroyed a couple of the orbiters, it sometimes make you think they should always land by computer.... The Russian Buran was landed completely autonomously since there was no one in it, and I remember hearing that they could land it dead on the center line even in like 30 kt crosswinds or something. I am not sure what the landing weather limitations are for the shuttle and how that factors in. <div class="Discussion_UserSignature"> </div>

henryhallam · Jun 3, 2006

I'm not sure it's even possible to fly the Orbiter completely manually. It is of course fly-by-wire and much like a lot of fighter jets I think there is always some kind of computer in the loop to translate the inputs at the control stick to movements of the appropriate control surfaces and reaction jets. This is not the same thing as the digital autopilot which can fly the reentry and landing. I believe policy nowadays is to allow the autopilot to fly the reentry and decent down to the subsonic region, though I think at least one reentry has been flown "by hand". BTW: as jschaef5 said, "deadstick" usually refers to a landing without any engines and not to lack of autopilot.

ltm_se · Jun 4, 2006

"No, a manual re-entry of the Space Shuttle Orbiter (defined as no auto pilot) is not possible due to the instability of the vehicle." So the commander cannot turn of the "reentry program" and fly using manual control. I Understand that keeping the orbiter stable would not be pleasent for a human brain but is there a semi auto/manual mode available?

vulture2 · Jun 4, 2006

The shuttle is capable of three flight modes, full manual, full autopilot, and the Control Stick Steering (CSS) mode, where the pilot's stick inputs are taken as an input by the guidance computer, which then controls the aerosurfaces. This latter is also how modern fighter aircraft are usually flown. In simulations the shuttle has been flown in the full manual mode (without CSS), but it is extremely unstable, so even the manual part of the entry is always flown in the CSS mode. Without the computer the pilot probably could not get sufficient cues to fly sucessfully. The autopilot mode (not CSS) is usually used through most of the high supersonic portion of the entry, where the Shuttle is at a very high angle of attack. Although there is an autoland system that could fly hands-off all the way to rollout, it has never been used all the way to the ground. In one early flight the CDR took over very late in the landing and could not get the "feel" of the craft, leading to "pilot induced osscilation". Since then the CDR has always taken over several minutes before landing. It would ba a shame to reach the end of the Shuttle program without ever having actually demostrated the autoland system, which may be vital for future designs. Maybe we should have a write-in campaign. OTOH, the Apollo or CEV capsule is intrinsically stable throughout entry, so could enter without a computer; occasionally Soyuz has done "ballistic" entry. Rutan's SpaceShip One similarly is intrinsically stable when the tails are angled upward and can land without autopilot. However in both cases the lift to drag ratio is very low; essentially falling like a rock. Apollo and Soyuz can get some lift but only under computer control. The SpaceShip can of course glide after the tail is moved to the normal position, but by then it is at low altitude so cannot glide far. Shuttle was designed with the objective of having high lift even at hypersonic speed, so

houston2006 · Jun 4, 2006

The shuttle can be flown manually from 90 seconds after liftoff all the way through the remainder of ascent, orbit, landing to wheels stop. Control Stick Steering (CSS) is the manual mode. There are two modes, auto and CSS. Typically, CSS is taken by the CDR below Mach 1 on entry, but it has been flown slightly above Mach 1 in the past. Early tests of auto land indicated that the shuttle would fly an uncomforatbly low approach, therefore the CDR always lands using CSS. The orbiter is fly by wire, so there is no mechanical linkage between the stick and the control surfaces, just like some modern fighter aircraft. You can not fly the vehicle without a computer just like these aircraft. As far as deadstick is concerned if you mean no engines operating then it is a, "deadstick," landing every time.

houston2006 · Jun 4, 2006

The shuttle can be flown manually from 90 seconds after liftoff all the way through the remainder of ascent, orbit, landing to wheels stop. Control Stick Steering (CSS) is the manual mode. There are two modes, auto and CSS. Typically, CSS is taken by the CDR below Mach 1 on entry, but it has been flown slightly above Mach 1 in the past. Early tests of auto land indicated that the shuttle would fly an uncomforatbly low approach, therefore the CDR always lands using CSS. The orbiter is fly by wire, so there is no mechanical linkage between the stick and the control surfaces, just like some modern fighter aircraft. You can not fly the vehicle without a computer just like these aircraft. As far as deadstick is concerned if you mean no engines operating then it is a, "deadstick," landing every time.

ltm_se · Jun 4, 2006

"Typically, CSS is taken by the CDR below Mach 1 on entry, but it has been flown slightly above Mach 1 in the past." Do you know when it happend? A friend of mine said to me that he had read about one time a CDR took control very early and flew entirely manual from before the S-bank speed braking all the way to wheelstop. I guess he was talking about CSS "manual" flying of some sort but he insisted it was manualy done. Do any of you guys know if this has ever happend or is it just an imagination in his mind? <img src="/images/icons/smile.gif" />

subzero788 · Jun 5, 2006

"Typically, CSS is taken by the CDR..." Does the Pilot ever have any CSS control during landing? Or is he/she just there as a backup and flight engineer?

CalliArcale · Jun 5, 2006

I don't think the Orbiter has ever been flown on any kind of manual through the S-turns. The degree of precision required is too great. (The movie "Space Camp" is a popular fantasy, but untrue.) However, there is an entertaining description of the challenges of landing the Shuttle on the X-Plane website. (X-Plane is a flight simulator.) X-Plane: How to Fly the Space Shuttle <div class="Discussion_UserSignature"> "People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff." -- The Tenth Doctor, "Blink" </div>

earth_bound_misfit · Jun 5, 2006

Hmm, from the link Cali supplied above. <blockquote>In reply to:<hr />In the history of Shuttle missions (the 100th mission has just come to a close as I write this), the real space shuttle has been hand-flown for the entire re-entry only ONCE, by an ex-marine pilot, as I understand it, who was ready for the ultimate risk and challenge.<hr /></blockquote> So there's some conflicting information here. <div class="Discussion_UserSignature"> ----------------------------------------------------------------- Wanna see this site looking like the old SDC uplink?Go here to see how: SDC Eye saver </div>

simcosmos · Jun 5, 2006

Hello, Available here is another (hopefully) entertaining reading (full of jpg, animated gif and a small wmv) regarding a simulated manual shuttle reentry. It is called "From Earth to Earth in two hours": please have in mind that the text might have incorrections and it is also outdated in a few aspects (new simulator version + better physics are available, procedures could have been better, etc) Regarding real life, from one of the links available on the end of the above page (to be more specific, from http://orbit.m6.net/v2/read.asp?id=21709 ) mikey451wrote: (author of Shuttle Reentry / Land autopilot plugin for Orbiter Space Simulator) <blockquote>In reply to:<hr /> AFAIK, noone has actually done a manual STS re-entry yet - the corridor of energy management versus thermal and structural limitations is too narrow.<hr /></blockquote> and C3PO wrote: <blockquote>In reply to:<hr /> It HAS been flown manualy, but with computer assistance of cource: http://yarchive.net/space/shuttle/shuttle_control.html Quote from there: After the first S-turn on STS-1, the entire re-entry was hand-flown through STS-4, at which point the FCS was rewritten (and the e-seats removed). John Young took over the flying when the sideslip meter pegged and stayed pegged for several seconds, meaning that the limit had been exceeded. <hr /></blockquote> To end, a few related Links: Orbiter Space Flight Simulator: http://www.orbitersim.com New Forums at

CalliArcale · Jun 5, 2006

<blockquote>In reply to:<hr />So there's some conflicting information here.<hr /></blockquote> Yes. I've heard conflicting information elsewhere as well. From what I've heard, that brief mention at X-Plane is apocryphal, although note simcosmos' post. <div class="Discussion_UserSignature"> "People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff." -- The Tenth Doctor, "Blink" </div>

houston2006 · Jun 5, 2006

The pilot is really the copilot and flies at the discretion of the CDR and within the scope of the flight rules. Currently permitting pilot flying for short periods (20 seconds) when subsonic.

houston2006 · Jun 5, 2006

Flying the orbiter through the, "S-turns," is no different than flying an instrument approach in an airplane. You fly the needles. Of course, if you were to miss a turn reversal you can quickly degrade your energy state.

simcosmos · Jun 5, 2006

Just a few more notes about what I wrote above: a) The "From Earth to Earth in Two Hours" mission report is about the simulation of a clearly non-typical STS mission where there are less roll reversals than what usually happens and where the full crossrange of the Orbiter has a nice simulated test. Just to make it clear I have my doubts that something like that mission would be possible in real life, at least without additional risk... b) However, the basic concepts of a shuttle reentry expressed on that virtual report are correct, in particular: b.1) utilization of bank angle – for a given AOA - to control lift (more bank = less lift = faster descent rate; less bank = more lift = slower descent rate / flight altitude stabilization, etc) b.2) utilization of roll reversals to keep the flight trajectory on target, manage temperature, etc c) Also: on that report I simply followed a table with mach and altitude as function of range to target. This is one way of doing things given certain initial conditions for the deorbit burn but it is not the right way of doing it. d) And the correct way is to use the GPC MFD just like in real shuttles: the MFD shows a little representation of the shuttle and all what we have to do, if flying manually, is to keep it inside the reentry corridor by controlling the descent rate as previously mentioned. Then, when near the intended landing zone, we pay more attention to the MFD showing the Horizontal Situation Display, fly the HAC and finally follow the ILS, like in real life, like in any airplane... just with the "little" exception that the Orbiter is descending faster and with an AOA that would scare the passengers on a common flight... at least until the pre-flare procedure <img src="/images/icons/smile.gif" /> To give a better idea about what I'm writing about (MFD), will

vulture2 · Jun 5, 2006

"Early tests of auto land indicated that the shuttle would fly an uncomforatbly low approach, therefore the CDR always lands using CSS." So rather than correct a minor error in the code they've flown by hand for 20 years? Let's be honest. The reason the landing is always flown by hand is that no pilot would wait so long for a chance and then not take the stick. Unfortunately this means the autoland system has never been flight-tested, which means if the weather does go bad after deorbit they won't use it.

CalliArcale · Jun 6, 2006

<blockquote>In reply to:<hr />Flying the orbiter through the, "S-turns," is no different than flying an instrument approach in an airplane.<hr /></blockquote> Well, no different from flying an instrument approach in a hypersonic brick with stubby little wings, a combination of control surfaces and RCS (which will shift to completely control surfaces at computer-determined intervals, as the air pressure increases), in a flight regime where a slight deviation is not only detrimental to crossrange but actually lethal.... ...but otherwise, yeah, just the same. <img src="/images/icons/wink.gif" /> The main difference between handflying the Orbiter and handflying a Cessna is that the consequences for error are vastly larger with the Orbiter -- and the tolerance for error is extremely thin. Roll too far, slip outside that envelope, and aerodynamic forces will tear the vehicle apart instantly. <div class="Discussion_UserSignature"> "People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff." -- The Tenth Doctor, "Blink" </div>

Manual Shuttle Reentry

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