Flying the SMS

I flew down to Houston last weekend (4/30/10) for some simulator training. Most pilots probably don't really look forward to sim flying but in this case I lucked into an opportunity to fly one that just about any pilot in the world would go way out of the way to fly. We are in the last few months of NASA manned space flight so I feel very lucky to have been given the opportunity to fly the SMS (Space Shuttle Motion Simulator). Our small group was warned that the motion portion of the simulator was inoperative due to a problem with a hydraulic accumulator and was unlikely to be restored during our visit. OK, it would have been fun to have motion, but who is going to complain?




Early Link simulator


I took the first turn. There are a really lot of buttons, lights, switches and displays but it is greatly simplified for us. The computer is completely able to land the Shuttle but the normal thing is to allow the commander (left seater) to take part of the tasks and in our case the pilot (right seater) handled jobs such as gear lowering and drag chute deployment, as well as prodigious coaching for the newbies. It really came down to matching up a couple of symbols on the head-up-display that lead you through the approach. It had a video game feel and it was said the gamers do well. Let me go over some of that again; the pilot is the commander and the copilot is the pilot, got it?





We first did an ascent but it didn't seem like much as we were just sitting there level in chairs. For the landing we started over the runway at over Mach 1 and shortly entered a continuous steep left turn until time to roll out on final. We are following the computer flight guidance and the computer is controlling the speed at about 300 knots with the split rudder speed brake. It is NOT a stabilized approach. You are aiming steeply down at a point way short of the runway so when you are not far out on final you make a pretty radical pitch up maneuver (pre flare) to about a .5º final glideslope. From that glideslope only a mild flair is necessary when over the runway. The biggest problem I had was underestimating the aggressiveness of that pull-up which is around 2.5 gs in real life. Paul helped me on the first one.


Louise Hose photo

Making the course reversal to final



Louise Hose photo

After the preflare, the view on final is pretty normal looking


After my flight we got a call saying that the crew might be able to get motion back. Ok, that sounds great, so we looked at some of the non-motion simulator stuff including the robot arm (video display) and the toilet. Yep, the training is thorough.








Non-motion simulator


When we got back they were testing the motion on the SMS by running everything to the stops in every direction. This includes tilting the whole cockpit area 90º up.



Testing the Link. Yep, this one is also a Link designed simulator




Commander Randy


Randy took the next hop. The ascent was more fun this time. First, you are lying on your back. You feel the main engine start, see the tower going by and feel the vibration during the whole engine run portion. When the solid rockets separate you feel that and see the flash. I got a kick out of watching the mach number and the EAS (think indicated airspeed). As we are going hypersonic the airspeed is dropping and dropping. From RV speeds down to 100 knots, 50 knots and 5 knots. When that part of the simulation ended the airspeed was 1 knot as we are going 15 thousand miles an hour or so. In these realms the speed thing gets pretty confusing though. The EAS part makes sense, although Paul said some of that is derived since you can't put the probes out when things are too hot. What about Mach? Usually that means the speed of sound where you are but not here. You are going into space where there is essentially no air so no true Mach number. They picked 1,000 feet/second as the value for Mach 1. But 1,000 fps relative to what? I didn't find out. It must not be relative to the surface as that doesn't matter as far as reaching orbital speed. I'm guessing that most of the time it is relative to a model of the surface of the Earth where the Earth is not rotating. On the way to the moon, that doesn't make sense so maybe in that case it is relative to a tangent to the surface of the Earth? *

When my turn came up again I found that there had been some learning. I was better and knew what to expect. Originally I thought I would like to do an approach where I would also do the speed control with the air-brake, but I think that would best wait a bit until things were more familiar. The graphics are pretty primitive and in fact the computer can't drive the window displays for all the windows at once so you don't have all the visual cues you would want. I guess it comes though. Paul talked about a case where a first timer was too aggressive on the stick and got the Shuttle upside down at the top of a loop. He was able to take over, half roll, and make a successful approach to the other end of the runway. He didn't have guidance because there wasn't time to reconfigure the electronics.

Louise's turn in the "box"


The motion adds a bunch to the experience. You can tell how your landing is by feel. Most of the landings felt like a typical airliner landing. On my second try I had a low descent rate when I touched but was too fast and it skipped just a bit. I knew exactly what was happening and it felt just like what I have felt many times as a Boeing passenger. On roll out you feel the drag chute deploy and then you feel it unreef. On the initiation of turns it did feel like there was some adverse yaw. I don't know, that might have been a simulator artifact as the rudder pedals don't do anything in the air and coordination is automatic. The pedals are just for ground steering and crosswinds are handled by landing in a crab.

The simulator reportedly simulates the handling of the Space Shuttle very well but I don't think anyone would ever come back and say "isn't she a sweet handling bird" because she isn't. Maybe it is much like some of the modern airliners, I don't really know. Only the stick grip area moves and after you move it there is delay until something happens. It is rate based so if things are going good they pretty much stay going good if you don't do anything, until something needs to change. Oh, and there is zero tactile feedback to the person doing the flying. All in all, it made me long for the feeling of my RV with the stick connected solidly to the elevator through a stiff pushrod where the air pushes back to me and tells me important things. The Shuttle system seems to do the job though and when you are dealing with problems such as wanting things to work the same all the time, from a vacuum down through hypersonic speeds to the landing speed area of 200 to 300 knots there probably isn't a better solution.




Note the stick at right. Immovable box with movable grip at the top.


There are other differences from an RV. We all know that in a tricycle gear RV you hold the nose off after landing. The Shuttle is bizarro world by comparison. The drag chute is mounted high on the tail so that tends to hold the nose up. You don't want the nose up too long though because if it comes crashing down things would be really bad and you also want it down for wheel braking, so you positively lower the nose with forward stick. After the chute is completely out you put in forward stick and the nose starts down and then down and some more down. Now you seem to be about level, but that is not good enough--more forward stick until that nose finally touches at a way negative angle of attack. Quite unnatural feeling!

Terrific, terrific experience which I will never forget, nor will I ever throw away the data sheets they give you for each one of your flights. I feel very lucky to have been able to do this!



After the simulator flights Paul gave us a tour through the control rooms of Apollo, the Shuttle and the International Space Station. Things have really changed a lot over the years. A lot of the Apollo stuff is just incredibly low tech by todays standards. Paul mentioned a lot of people on tours don't even know what those round things with the holes are, that are by the phones. The display panels used a television technology where the proper label slide for the task needed to be pulled and superimposed with the data. The computers couldn't handle the job of showing the labels and the data.




Shuttle Control Center





International Space Station Control Center live

A tiny part of the massive Saturn V


It is really sad to see the end of this era. Commercial space flight would seem to be a real good thing but there is not enough money to be capable of what NASA has been capable of, in the private sector. Maybe there isn't enough money in the public sector either. I just hope the eight year olds of today find inspiration somewhere as the Homer Hickams and  Paul Dyes and Neil Armstrongs did at that age.




Paul with Randy and Katie at the ISS Control Room




Paul and Louise, I owe you forever for this and thank you much for all the hospitality!



* Paul answered some of my speed questions in an e-mail

On your question of “Speed relative to what?”, well, the answer is complicated. When you are an air vehicle, you are truly measuring speed relative to the air, so long as you’re getting air data. If you don’t have air data, the speed is relative to the earth, where we assume that the air is still (hence, the potential for Nav errors if you have significant upper air winds). When you are in orbit, we use an inertial reference frame – a reference stable to the stars. In that frame, the earth is rotating and moving, so the equations get complicated. But since those are just large, non-intuitive numbers, we think in terms of gaining or losing velocity relative to an earth-centered frame – essentially, we are in a big ellipse about the center of mass of the earth, and we gain or lose sped along the ellipse – or sometimes radially (and sometimes out of plane, but only a little).


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