How NASA Learned To Fly The Space Shuttle Like A Glider

hello it's scott manley here this is the space shuttle enterprise making what is the worst landing of its career and many would argue the worst landing by any space shuttle piloted by fred hayes and gordon fullerton this would be the final flight of the approach and landing test program and the first landing of the space shuttle on a hard concrete runway and they did it in front of assembled dignitaries from around the world including prince charles of the united kingdom what happens is there's a bit of a wobble and then a bounce and they're back in the air a little more wobbling back and forth before it finally settles down and lands a little skew with on the runway despite all these shenanigans they still managed to put the shuttle down with only 7 000 feet of runway they had been allotted 10 000 for this demonstration the program was considered a success and there would be no more purely atmospheric test flights this would be the last flight of the space shuttle enterprise the first space shuttle to fly was revealed in 1976 given that this was the 200th anniversary of the declaration of independence it was thought that this would be called the constitution but a letter writing campaign by fans of star trek got the name changed to enterprise to reflect the spacecraft from the tv show and there were members of the cast at the rollout ironically however space shuttle enterprise would be the one space shuttle that didn't go to space enterprise was built as a test vehicle it had all the correct structural elements in place it had roughly the right mass distribution it had working wheels and wings and control surfaces but its first job was going to be to verify the aerodynamic behavior of the space shuttle and for that it didn't need to have working engines it didn't need the reaction control thrusters or a fully kitted out payload bay and it also didn't need a working thermal protection system the tiles which are on enterprise are made of polyurethane foam they're roughly the right density in the right dimensions but they certainly wouldn't help you through re-entry enterprise did have one feature that was missing from the other shuttles this long aerodynamic probe which extended out beyond the nose this was because it was a test vehicle and they were needing to calibrate the onboard aerodynamic instruments and to do that you have a sensor which sticks out beyond the front of the aircraft before the air gets messed up by the airflow around the vehicle enterprise would also be the only shuttle to actually fly with the aerodynamic tail cone attached but long before the space shuttle could take flight or even finish its design they were testing models of the shuttle in wind tunnels some as large as one-third the size of the real thing they tested it across all sorts of speed ranges even up into hypersonic speeds and of course they had to test the vehicle when it was mated to its external tank and boosters enterprise would of course never fly with the external tank and boosters but it would fly on top of the shuttle carrier aircraft and they needed to know that this would work the shuttle carrier aircraft was a converted 747 it had dorsal mounting points allowing a space shuttle to be carried on its back and because the air flow from the shuttle would interfere with the operation of the regular tail plane it had an extra wide horizontal stabilizer with extra fins on it to allow the vehicle to actually control itself the carrier aircraft was going to be an integral part of the space shuttle program because they needed the carrier to be able to move the space shuttle between its landing sites which might be on the west coast to a launch site that might be on the east coast and initially it was very much an experimental aircraft in its own right they performed a lot of tests just to make sure that the 747 was safe to fly with this extra aircraft riding piggyback on its structure this test program with enterprise was carried out in 1977 at edwards air force base and after demonstrating that they could taxi and roll down the runway at speed they eventually took to flight and they carried out a series of five cold tests where the space shuttle was inert and its control surfaces locked into place now this showed them a lot about the vehicle in particular it showed that there was a decent amount of turbulence due to the air shedding off of the space shuttle on top of the 747 having demonstrated the airworthiness of the shuttle carrier with an inert shuttle they proceeded to the captive active phase where there would be astronauts on board and the shuttle systems would be running generating power and cooling including the power that's needed for the all-important flight computers because the space shuttle was very much a fly-by-wire vehicle that had five computers on board it had four that would work by voting each other out and it had a final backup computer which you would be able to perform if they had lost everything else the space shuttle wasn't passively stable so it needed a flyby wire system to keep it stable and controllable by astronauts during the descent the astronaut test pilots would also train in shuttle training aircraft aircraft that had been modified to give them similar performance to the space shuttle they took a gulfstream 2 jet they added extra drag surfaces and then put the engines into reverse and that turned a high performance business jet into a flying manhole cover the left side pilot seat was modified to have the same controls as the space shuttle whereas the right co-pilot site maintained the original controls in case there was some situation that required them they also had a simulator that they could train on before they flew the real thing and of course since this was the mid 1970s the cockpit views were generated by a camera moving over a model of the terrain surrounding edwards air force base since they didn't have the computer graphic capabilities in that era so with all this preparation under their belt the first free flight of the space shuttle enterprise was to be on august 12th 1977. the test pilots for the first flight would be fred hayes who had previously flown on apollo 13 and gordon fullerton who would go on to fly on sts-3 a critical part of this test was where this two aircraft had to separate now this would be initiated by the carrier aircraft beginning to go into a dive and picking up enough speed that the enterprise could get lift but if you think about it the enterprise had very small wings whereas the carrier aircraft had much larger wings so to achieve separation they needed to have very different angles of attack and that's why the forward pylons were about two meters longer compared to when the carrier aircraft was used for transporting the shuttles across the country so separation occurred at an altitude of about 25 000 feet and a speed of about 310 miles per hour or 500 kilometers per hour the separation is performed by explosive bolts and as soon as that was triggered the vehicles began to move apart however the shock of the exploding bolts caused a glitch in one of the computers which had bad soldering that was computer number two but of course computers 1 3 and 4 voted off the line and the vehicle continues to fly so while that was a bit of a black mark against the computer hardware it was definitely a big plus demonstrating the redundancy of the system immediately after the separation the plan was the shuttle would turn to the right and the carrier aircraft would turn to the left and after that the pilots were had a job of basically performing their test flight they only had a few minutes before they would land because the shuttle was not a great glider but they were able to run their control through various uh configurations you know sweep their attitudes and their control surfaces orientations and then they set the thing up for an automatic landing because they were testing an automatic landing system the computer was supposed to handle this and put it down on the runway their job was just just to make sure that it flew correctly and of course to push the button to drop the landing gear as it descended towards the lake bed at edwards air force base so that was the first of five successful approach in landing tests three of the tests would be carried out by fred hayes and gordon fullerton and two would be carried out by joe engel and dick truly so for test three they dropped the speed a bit and then for test four they removed the cone off the back to increase the aerodynamic drag and as a result of that the separation speed was lower which is why they tested with the lower speed on number three but test number five that was the one where they were aiming to show that they could actually hit a concrete runway and the flight went very well right up until a few seconds before touchdown and you can actually listen to the on-board audio [Applause] 210 200 real good space ah here we're about to catch it let the stick go hold it jesus oh far down speed breaks out we're 1 30 getting the hose on okay we're indirect so yeah a lot of you are hearing the salty language there because the pilot was having a fairly hard time keeping things under control this is a perfect example of a pilot-induced oscillation but it wasn't entirely the pilot's fault the computer was getting behind and and the immediate solution to the problem was a co-pilot's suggestion to just let the state go let the computer catch up stabilize things but after the landing yet they spent a lot of time analyzing this and optimizing the computer and understanding that there were problems for example unlike many aircraft the space shuttle had a set of elevons and these would control pitch and roll the fly-by-wire system placed a higher priority on pitch control over roll control so when there was a lot of control inputs coming in the pitch would end up getting rate limited and delayed and that changed the vehicle behavior over what the pilots had learned and that served to amplify or exaggerate the pilot-induced oscillation to refine the flyby wire system they used the digital fly-by-wire project which was an f8 crusader which had been converted in its flight system replaced with a fly-by-wire system that used the apollo guidance computer you can actually see the diskey display there in the side of the aircraft neil armstrong was a huge fan of this project and promoted it so they were able to adjust the control laws between flights so that they could introduce delays or rate limits and see how the pilots responded they were able to model the conditions or determine the conditions under which pilots were most likely to introduce the oscillations and figure out ways of adding dampening which would also allow rapid control response the software was rebuilt and tested on this test vehicle without the shuttle being needed so the next time that a computer with this software flew on a shuttle was sts-1 when colombia made its maiden voyage to space and there were many technical problems on that flight but the flight software for the landing was not one of them but the space shuttle was still very much an experimental vehicle at this point and its fly-by-wire system did continue to evolve on sts-3 there was a rather dramatic landing the automatic landing system was still very much in development at this point and they left it on longer partly because they were interested in finding out the bugs in it but it ended up like messing around with the speed brake opening and closing it more than it should they brought the landing gear the front nose gear down and then moments later decided no we're actually going too fast and they raised the nose gear back up before then finally putting it down on the runway charles bolden who had worked on the auto landing system said that this saved the shuttle and while the test program with colombia continued enterprise the shuttle named after a fictional spaceship never got the chance to go to space the original plan had been to send it back to the factory strip it down and then rebuild it into a fully functioning orbiter but that never happened because it was very quickly realized that there was a structural test article which could be just have the stuff added instead of having to strip it down first so enterprise became the shuttle that was moved around and used for fit checks it was taken out to vandenberg and they verified that a shuttle could move down the road that they had uh graded and cut out of the hillside they put it on side of rockets to make you know make sure that it could fit on the booster stack to make sure that the handling tools were all there but then in 1986 after the challenger disaster nasa was looking for another shuttle and there was a serious loop given to upgrading enterprise again but once again it was realized that there were spare parts that would be a lot faster and easier to use so enterprise continued to be this uh non-flying space shuttle it was put on display at the smithsonian and then after the space shuttle program ended it was replaced by discovery and enterprise moved to the intrepid in new york and that's where it is today but remember all those other actual space shuttles they were able to land because of enterprise because enterprise had gone to places in the flight envelope that no shuttle had gone before i'm scott manley fly safe [Music] you

Channel: Scott Manley

Views: 1,028,002

Keywords: aviation, wind tunnels, nasa, fly by wire, space shuttle, test pilot

Id: pfNQW4jToHE

Length: 14min 51sec (891 seconds)

Published: Thu Oct 07 2021