The Space Shuttle is the only manned winged vehicle to fly hypersonically. I have seen it fly almost directly overhead at Mach 15 – extraordinarily impressive. No other flying machine comes close. But the price to fly at hypersonic speeds is the subsonic L/D, near landing approaches the aerodynamics of the common brick (L/D is the ratio of lift to drag, one of the most important properties of any flying machine). Which is to say, the shuttle comes down fast; its glideslope on final approach is 7 times steeper than a commercial airliner. Think dive bomber. And the pilot only gets one chance to get it right. No go-around capability.
The number one job of the Entry Flight Director is to make sure the Commander has the very best situation for landing. No, that’s not right; if we were to wait for the very best situation the flights would have to be a lot longer than they are. No, the number one job of the Entry Flight Director is to make sure the Commander has an adequate situation for final approach and landing. Defining the dividing line between an unacceptable situation and marginally adequate situation takes about 25 pages of Flight Rules. The worst part about this whole thing is it revolves around the weather. Or more precisely – and even worse – the weather forecast.
The law of conservation of energy means that all the energy that went into getting the shuttle from the launch pad to earth orbit must be removed to get the shuttle from earth orbit to wheelstop on the runway. 99.8 % of the energy is taken out by air friction – which is why it gets really hot during re-entry. Any glider pilot will tell you that making a good landing is all about energy management. Energy management on the shuttle is particularly complex. Stay with me now. This is rocket science.
After deorbit and throughout entry you always want to keep just a tad more energy than you need to get to the runway, but not too much or you will overshoot the runway and plop down in the middle of nowhere without a runway in sight – considered to be poor form.
The band between too much energy and not enough energy gets tighter and tighter as the shuttle approaches the runway. Like baby bear, you want don’t want to be too hot or too cold, but just right. The tail of the shuttle acts as a conventional rudder but also splits down the middle to make what is called a “speed brake” or in pilot speak: the “boards.” As the speed brake opens up, the shuttle will slow down faster and faster. The minimum (closed) is 15% — don’t ask why, it’s a long story. At settings of the “boards” about 60%, the handling qualities for the pilot degrade.
Periodically before the predicted landing time, balloons are launched near the runway and tracked up to 50,000 feet altitude or so. This gives a profile of wind speed and direction. This information is fed into a computer program which assumes the shuttle is flown perfectly and it computes all kinds of interesting results. Among the most important results are predicted speedbrake setting on final approach and the predicted touchdown location on the runway. The touchdown target is 2,500 feet past the painted threshold stripe on the runway.
The shuttle touches more than twice as fast as a commercial airliner, 205 knots for heavy weight returns and 195 knots for lighter weight returns when the payload bay is empty. Only slightly faster and the tires will come apart. Not very much slower and the tail will drag before the wheels touch down.
So there I was, the rookie Entry Flight Director, in charge on my very first shuttle entry. Watching the weather, sweating, over-caffinated, about to be sick to my stomach, but radiating calm confidence to my team. In other words, it was just like every other time I was in charge at the Flight Director console.
I had studied all the previous shuttle entries, knew all the procedures by heart, had all the rules memorized, and had watched several previous landings sitting right beside an experienced Entry Flight Director. The secret is, of course, that no two landings are alike, and I was about to learn that the hard way.
It was a windy day at Edwards AFB. All real test pilots like to fly early in the morning before the winds build up. Shuttle landing times are determined by orbital mechanics and this was going to be an afternoon landing. Stiff winds started blowing hours before landing and the forecast for surface wind speed was just below the limit. No other runway would do, only the big concrete runway that runs in a southwesterly direction, straight into the prevailing winds.
The onboard computed guidance which the Commander would be following would try to get the shuttle to a landing 2,500 feet down the runway at 195 knots; the speedbrake would be automatically adjusted accordingly. With the winds that were measured aloft, the computer model predicted that even with the speedbrake closed (15% — not dissipating any excess energy) would come up short on the minimum distance past the threshold allowed by the rules, 1000 ft. Now, at the very end game, a pilot can trade airspeed for lift and thus distance down the runway. The rule of thumb is 10 knots of airspeed difference results in around 1000 ft of distance along the runway. If you land 10 knots too fast, touchdown will be short by 1/5 mile. If the pilot stretches the landing by holding off until the airspeed reads 10 knots lower, the tires will hit the pavement about 1/5 mile farther down.
The crew is ready to return, all the other parameters are GO, just that pesky wind and short touchdown prediction. I checked with the weather man; conditions were predicted to be worse later in the day and unacceptable tomorrow.
Time to go to the coffee pot and think this over. It is a myth to believe that all the important decisions are made at the Flight Director console or maybe in some conference room down the hall. All the really important decisions in Mission Control are made by the coffee pot in the hall right outside. Lots of ex-Flight Directors and other management types seem to show up when the Flight Director on duty stops by for a cup. Lots of good advice can be had there. On this particular day, the place was deserted. Nobody to help. Well, back to the console, the clock is ticking.
The Flight Dynamics Officer points out that there is an exception in the rules; for a lightweight orbiter, landing at 10 knots slower – at 185 rather than 195 knots – with a predicted touchdown at 1000 or more feet past the threshold is considered adequate. By making that adjustment in the computer model, with the balloon measured winds, the prediction is touchdown at 1100 feet with 185 knots and CLOSED SPEEDBRAKE. No energy reserves other than that 1100 feet back to the start of the runway. Any EXPERIENCED Entry Flight Director would have seen warning flags all over this!
But, I was a rookie. All the flight rule criteria is met – GO FOR DEORBIT!
During the hour between the deorbit burn (no turning back now) and landing, the winds got stronger. They got stronger on the surface and the balloons showed the winds increasing aloft. There was nothing we could do about it but tell the Cmmander. He did not sound happy when he acknowledged the call. The Capcom stopped making eye contact with me.
The landing looked great on TV. You can’t tell on the video where the touchdown spot was. A good landing and the crew was healthy. I was feeling good about life. The tag line on all the news reports was that the shuttle landed safely. As far as the public knew it was all routine and there had been no danger. My stomach stopped doing flip flops.
A couple of hours later, I got THE PHONE CALL. The commander was NOT HAPPY. As I’ve told you before, it is never a good thing to have a commander who is NOT HAPPY. He thought he wasn’t going to make it to the runway. He really had to stretch to make it over the threshold. Just what did I think I had been doing to put him in that situation? I had a low moment.
The next day the official numbers came in. The rubber marks where the main gear tires kissed the runway were 1176 feet past the threshold. Yeah! That is OK! But wait, further down the form, the speed of touchdown was 176 knots. Oh no! Not 195 knots which is the standard target or even the 185 knots special exception, the shuttle touched down at 176 knots! The Commander really did have to stretch it out. The computer models did the math: if touchdown had been at the target speed of 195 knots, the wheels would have hit the ground 130 feet BEFORE THE RUNWAY THRESHOLD. Not good.
There are a lot of things in space flight that can kill you. Having a rookie Flight Director is one of them. If you ever get assigned to a space flight, check to see who is sitting in the big chair in mission control before you agree to go. If it’s their first flight, or maybe even their third, you may want to ask for a ticket on another flight.
Oh, and that wasn’t the worst thing that I ever did to a commander on landing. But that’s another story for another day.
There was 1 severe roll oscillation & overshoot in the 80’s. It’ll all be a bad dream when we go back to capsules & water landings, budget permitting. Don’t let the rookies pack the parachutes.
Hi Wayne,
That was all at once insightful, hilarious, and brings back some old – but still to a degree – vivid memories…. Thanks.
It’s wonderful that you are sharing your past with us like that. Of course I knew your job (genericly speaking – a Flight Directors job) was – no – could be difficult. Very-very difficult. I know that the possibilities for problems were endless. I hope you don’t have to rely on antacids after all the ascents and entrys you presided over all those years on console.
Speaking of MCC coffee-based stories, I have one for you (and those out there…). As you know (and others will now) – I was a member of the INCO Section (Instrumentation and Communications Group – which Mr. Hale here was Section Head at one point in his career folks). One of the most important responsibilities of the group – was of all things, keeping the coffee pots going – 24/7 throughout a mission (and simulations as well). We charged a dime back in the early 90’s – and ALL the profit-monies went to charities and the like. Coffee is – and probably will always be the ‘life-blood’, the ‘food’ – of Mission Control. Fireballs were the desert…
Anyway – to the story; this tale is about when President Clinton visited the MCC during what I believe was first MIR/Shuttle combined docking mission. Before he entered Mission Control proper, we had to ‘power-down’ the coffee pots, and close AND pad-lock the cabinet that housed the coffee makers (BUNN – 4 pot type). I wonder if that was a first… The Secret Service in their infinite wisdom somehow saw this cabinet as a threat to security (?) – so we had perform the unthinkable, the unimaginable!!! – lock it up!!! The announcement was made over the loops (no doubt FD-1) – and I think even the crew on board the orbiter was informed ( I don’t recall the exact words – but it seemed the CDR’s comments were to the affect of a simple “uh-oh!!” response.
The mad rush was on – and I recall having to go out the backroom there in the middle of Ops, and fill up the pots so everyone had a chance to fill up their cups before the temporory ‘Prohibition’ took place. That lasted for the hour or so while the President was in the Flight Control Room. Needless to say – it was a long hour.
To highlight the air of and level of security , we were in the back-room, and heard Mr.Clinton right outside our doorway to the hallway – this afer he had talked to the crew and was done in the MCC. Myself and a few others – with our 20 foot headset cords stretched to the limits, opened the door to see what was going on. Well we certainly surprised the agent who was leaning up against – guarding the door!! “We’re only Conrollers!!!!!” we nervously blurted out – we were as surprised as the agent.. Little did the lady know what and whom was behid that door… Luckily – Mr. Clinton interviened – shook our hands – exchanged fast pleasantries – until a woman (who will remain anonymous – but I knew – and remember who she is – and so would you Wayne) – blurted out ver loudly from the end of the hallway: “HEY BILL – COME HERE!!!”. Mr. Clinton did a fast right-face, and scurried – and I will say very quickly – down the hallway to the owner of that unmistakable voice….. Totally hilarious.
Anyway, I certainly too – don’t entirely miss the stomach-churning – adrenilin pumping ‘adventures’ there in the MCC (eh – I still have those ‘scenarious’ occasionally happen up here in Ottawa these days) – but I certainly miss the comradship, leadership and professionality of those I was so lucky to work with. And of course (and you know this) you sir are one of them.
One of these days I’ll have to tell you (and others here IF you allow it) about my Command Console ascent/entry certification run (6-7 of them in 6 hrs) – that my then-mentor Ellen Porter (Hillis) put me through – on console – alone. Yes – alone. One of those deals where afterwords I went home, drank a 6-pack of Corona (I think in an hr)afterwords just to calm down the nerves. And no – I didn’t feel any affects of that 6 pack – none. And of course I passed my ‘exam’. My teacher was the best.
Ah yes, the make the call stories. I imagine there are a few. Thank you for taking the time to do this. It is appreciated by many.
Best regards,
Testing
Yesterday, I got an error code when I tried to send a missive…
Wayne, perhaps you didn’t know it then, but you do now: everything NASA does is predicated upon trust.
If I ever was assigned to a space flight, say STS-144 (check it out), I would implicitly trust everyone assigned to that mission, rookie or not…just as you and my crewmates would trust me to perform my assigned tasks to the best of my abilities.
Hi,
that is fun to read!
But there is something I am wondering about: I am a glider pilot and if I know that there is a strong headwind in final approach I would shorten my pattern (in this case the HAC) to come in higher. I think there is a way to switch the SPEC50 display to a low energy HAC. Wasn’t that appropriate? Or was is already an approach “direct in” (without flying the HAC)? If so, I know how it feels. I had some x-country flights in a glider coming home this way. Modern gliders are outfitted with GPS and glideslope calculaters and if it says you are “just” on glidepath and the field is still 20 miles away and there are no more thermals to catch, it gets a little “tight”. I just brought it over the fence of the airfield and some friends had to loosen my hand from the stick… 😉
Greetings from Germany!
Hi,
that is fun to read!
But there is something I am wondering about: I am a glider pilot and if I know that there is a strong headwind in final approach I would shorten my pattern (in this case the HAC) to come in higher. I think there is a way to switch the SPEC50 display to a low energy HAC. Wasn’t that appropriate? Or was is already an approach “direct in” (without flying the HAC)? If so, I know how it feels. I had some x-country flights in a glider coming home this way. Modern gliders are outfitted with GPS and glideslope calculaters and if it says you are “just” on glidepath and the field is still 20 miles away and there are no more thermals to catch, it gets a little “tight”. I just brought it over the fence of the airfield and some friends had to loosen my hand from the stick… 😉
Greetings from Germany!
Hi,
that is fun to read!
But there is something I am wondering about: I am a glider pilot and if I know that there is a strong headwind in final approach I would shorten my pattern (in this case the HAC) to come in higher. I think there is a way to switch the SPEC50 display to a low energy HAC. Wasn’t that appropriate? Or was is already an approach “direct in” (without flying the HAC)? If so, I know how it feels. I had some x-country flights in a glider coming home this way. Modern gliders are outfitted with GPS and glideslope calculaters and if it says you are “just” on glidepath and the field is still 20 miles away and there are no more thermals to catch, it gets a little “tight”. I just brought it over the fence of the airfield and some friends had to loosen my hand from the stick… 😉
Greetings from Germany!
Rainer
Wayne: This was a gripping narrative… thanks for sharing it!
My curiosity has been aroused, though, and I’m lusting for more details! How, exactly, did the crew “stretch it out” and reduce their airspeed on this particular flight? A HAC shrink? A straight-in? An alpha adjustment? Some combination of these?
Interesting, I wonder if during STS-118, that when Endeavour Flew over Hurricane Dean, did they get any winds? I mean, a Category 5 Hurricane certainly has a lot of winds.
Great story. I too am curious now about what went on in the cockpit as they squeezed out that last ounce of energy to make it over the threshold.
Is the heat generated during re-entry really from air friction? I had read somewhere that it was caused by something else…knocking the electrons off the air molecules or some such ‘plasma’ thing.
Hurricane Dean wouldn’t have affected Endeavour; when they passed near it, they were probably 200,000 feet in altitude.. they only encounter weather about the time they reach the HAC at 60,000′ or so..
Wayne – was this STS-37? No, can’t be.. I’m remembering now that landed on a lakebed runway. Hmm.. which flight was it then?
On Bob Mahoney’s post:
The kinetic energy partly changes into another form of energy: heat. But as the shuttle slams through the molecules of the atmosphere, it knocks indeed electrons out of their orbitals around the nucleus. For this, there is also energy necessary. By filling up the empty position with electrons, energy of the same amount that was needed to knock them out is released now. And that is what we see: light.
It’s quite similar to what is going on in neon tubes.
The knocking off of electrons creating a plasma would be caused by air friction. Friction is just some molecules in the shuttle bashing up against some molecules in the air. When they get bashed hard enough their electrons pop out and create light, and the original molecule is still very very hot. So you get the fiery hot plasma.
why can`t they slow the shuttle in space so it doesn`t heat up so much on reentry.
Hi, Wayne, I was wondering because I want to fly something like the Suttle, what degreese from colledge, and high school should I go for if I want to be an astronaut. Also I have alergies, and I take Zertec, but would i be accepted in the astronaut program with alergies? Your friend Cole.
Experience is the only way we can build memories that we later use to make decisions. And the best experience is when decisions turn out to have undesirable consequences (some might call these errors, but I am convinced that the term error should never be used-but that’s another whole blog).
I think experience can be acquired in 3 ways (in order of preference):
1. Survive an event (or a simulated event).
2. Share the memory of an event with the survivor.
3. Read about the event.
I once read a comment from an NFL quarterback, reflecting on the difference between his rookie year and 10 years of experience. When the ball is snapped the QB has about 7-10 seconds before the first lineman hits him. In that 7-10 seconds he has to see the defense, see his receivers, decide if the receiver is going to be open, and throw the ball. As a rookie he was just barely able to get the ball away. As a 10 year veteran, 7-10 seconds was all the time in the world.
STS-37 is known for landing short (about 600 feet) due to incorrect given wind speeds. But I understand, this one landed behind the threshold. This low touch down speed means probably that the body flap was (very) close to scratch the runway…
But on the other hand: Auto speed brake setting is calculated at 3000ft altitude to hit the runway at 2500ft behind the threshold. 1176 feet is still short… 🙂
Here’s a nice story about STS-37:
http://sci.tech-archive.net/Archive/sci.space.shuttle/2007-06/msg00059.html
a
glider like landing what a pitty not having some thrust engine to make shuttle more like plane
b
is there any other solution for landing
perhaps on sea surface
c
to much risk not without blame for engineers who are comfortable sitting and watching pilots in shuttle like rodeo cowboys
that is all falk
drale savic, md
serbia
pancevo city
Wayne,
I can’t thank you enough for sharing these stories. It really is an extrodinary team effort by imperfect humans and imperfect flying machines that allows us to explore space.
We appreciate your insight, with great respect.
How can the shuttle go at mach 15 without a sharp pionty nose like most supersonic air/spacecraft? Also I heard that a small, tiny hole can cuse the shuttle blow up when re-entering, I think that that is an easy target for terrorists.