How Did The Shuttle Get Home Before GPS?

Hi, I'm Scott Manley. The space

shuttle

is objectively the spacecraft most capable of transporting humans. All other spaceships are capsules that will take you to and from the destination, but the space

shuttle

would carry the payload with it and could perform a precise repeat. -entry and landing which would take you halfway around the world to a runway and this final part of the flight is done without any obligation, the vehicle is a glider at all times and we have certainly discussed the challenges of maneuvering a vehicle down. a runway a plane that is not famous for its flight characteristics often described as a flying brick on good days or would it be better to fly the box it came in now in the Kerbal Space Program one of the big challenges is flying a successful space The Shuttle deorbits to land on the runway and you will often find yourself overshooting or missing.

In this case, I did a ridiculous inverted re-entry to get down into the thicker atmosphere. I exceeded about 10 G's and got myself roughly in the right spot. I finally landed it with 2/3 of the wheels and half of the wings, but on a real space shuttle it wouldn't have gotten that far, the G meter showed something like 8G for a second and the limit of the shuttle fuselage was about three. Yes, the space shuttle has a lower G tolerance than my tiny little personal plane. The space shuttle has to very carefully make its way through the upper atmosphere so that it starts at orbital speed, successfully handles re-entry through very high temperatures, and bleeds out. energy, so it arrives at the landing site with just enough energy, neither too much nor too little, and to do this you need a navigation system that can track the position and speed of the Orbiter throughout this entire regime, so I really want to cover these systems that get from orbit to landing and manage to continuously track your position and velocity throughout that regime and let's be clear today, all of this would be done with GPS.

I'm pretty sure that's what Dreamchaser uses and what the Preparing to return

home

, first of all, we need to know what orbit you are in and you. Basically do this, but use ground stations to measure, you know where it appears in the sky, the Doppler shifts and you'll also do this using the data tracking and relay satellite system that's in geostationary orbit. These spacecraft can look down. space shuttle and perform a data link and by looking at the Doppler shift they can determine how fast it is moving and from multiple sources they can derive what orbits it is in and hope to know where it will be in future orbits to get this orbital solution may take a while but it doesn't change very quickly, that is the starting point for your re-entry, so now that they have established the starting point, the team on the ground can determine when the re-entry should occur and then extrapolate back to the point where the Orbital maneuvering system should be used to slow the spacecraft down, usually to a speed of about, you know, they lose less than 200 mph when they turn on these engines, this takes about 2 and a half minutes and it sets them up. for the entry interface about 30 minutes after this, for a nominal reentry, they should reach the entry interface at about 400,000 feet within error bars of something like 20 thousand, so it's a 4C error that can be accommodate anyway for this first part.

After re-entry, the space shuttle will track its position by dead reckoning, there are three inertial measurement units on board that feed into the computer, the computer knows what orbit it was in, it can use these measurement units to detect how much the speed changed when you start the engine and then you can calculate the orbit forward to the point where you enter the atmosphere and then you can start to feel the resistance of the atmosphere, so for the first decade or so the space shuttle was equipped with a set of kt7 inertial measurement units, so they measured rotation and acceleration and by the way, the kt7 was built by a subsidiary of Singer, which is the sewing machine company, so anyway the space shuttle has to use this dead reckoning for most. of reentry for the simple reason that during reentry you have the plasma that inhibits radio communication, so there is no guarantee that you will be able to receive external signals to discover or determine your location now, of course, on subsequent flights.

In fact, they were able to get some GPS signals to input into their navigation, but the original shuttle didn't use any outside navigation sources until it was much closer to the landing site, so the inertial guidance system aboard the space shuttle would perform most of the re-entry navigation. to get it to the terminal area, so yes, once the spacecraft has passed the worst of the re-entry, there is about 10 minutes left until landing, a few hundred miles away, at that point they will turn on the tackan system which is air navigation tactic again in space. The shuttle would have three of these for redundancy reasons and they would feed into the computers, so these beacons used on the ground that could tell you the course and distance thus directed were developed in the 1950s for the US military .and they're still in use today, in fact, they appear on civil charts as Vortex, so a VR is a type of beacon that regular civilian aircraft use to get distance and, you know, heading and heading.

Tan is the military version of that, so it's pretty common for these systems. to be positioned to have a v tan or VOR Tac, so first of all, for range measurement, what you do is send a ping to the station with some magic code and then it sends it back and tells it how far away it is for the angular measurement its heading relative to the station what it does is emit two different signals, one is a kind of rotating heart shaped uh signal called Lemon and that's the pattern that it basically emits as this thing rotates 360° from where the signal goes from strong to weak to strong to weak, basically this is a sine wave based on the amplitude of the signal and then it has a reference burst that is sent omnidirectionally when the pattern is oriented in the predetermined direction , can indicate its relative heading. to the station within about 2° and that's similar to how civilian VR works, but the military wants greater precision so they add a second oscillation to their signal, it oscillates like nine times faster, which means that can get nine times better accuracy, so the accuracy of a tan is like 2 ninths of a degree, which is less than 1/3 of a degree, so it is used to increase the accuracy of the inertial system as they get closer more and more, but normally you would find that errors would have been introduced and The initial plan is not exactly the same as what you are seeing, so this is one of the screens that would be shown in Mission Control.

The green line is the trajectory they expected. The yellow line is where the guide on board thinks she is. es and the red line is where the ground tracking radar actually knows the spacecraft is also those pink triangles are airports with long enough runways that could handle the shuttle if it were really off course so now the shuttle It is a glider and what is really important in the end is how much energy it has as they approach the landing site they have to figure out if they have the right amount of energy, they have too much, they have too little and therefore their state of energy right at the end it says it.

They explain how they are going to fly the final approach to land on the runway. Ideally, the shuttle should arrive with enough power to be able to spiral around what is called a heading alignment cone, and when it reaches about 10,000 feet, it should roll in line with the runway. and make the final stretch so that these heading alignment cones are not actually cone shaped, but are close enough to show where the Spire will be when the shuttle descends losing energy in doing so, you should be able to open the air brake to lose excess energy if necessary, but if the shuttle arrives with less energy if it is too low and too slow, there are other roots it can take, so essentially it can join any of these four cones and there are two that are closer , in which they are used for the minimum energy approach, this is all known as terminal area energy management and you will find a lot of documentation on how the shuttle handles this, anyway, once the shuttle is in the final area, You can also pick up another one.

The navigation aid called the microwave scanning beam landing system, so it is based on a technology that first appeared in the 1970s and was supposed to replace the older instrument landing system that used higher frequencies. high and therefore smaller antennas, and by using active scanning they were able to cover a much wider area and support many more types of aircraft approaches, unfortunately the microwave landing system which was designed for regular use of civil aircraft never got stuck, so to speak, because GPS came along and airports could define an instrument approach without installing any hardware, so anyway at this point the space shuttle was able to use this to do a full autoland , but it never did because the crew would normally take control during these final downward spirals and the reason is that if something went wrong, you didn't want the astronaut who had never touched the lever to suddenly have to grab the lever, you know, seconds before landing and figuring out how to fly it again, they wanted to get a feel for the plane again during that final. spiral but the crew member is following the computer's guidance.

However, there is a set of old visual age that uses lights to help them know if they are on the glide slope. First, there is a precision approach path indicator that indicates a 20° path is located approximately where the speed vector on this HUD is pointing and displays up to four lights; you want to have two white and two red and that will show that you are on the glide slope. I use these on my airplane, except they are not set for a 20° glide slope, now you will notice these bars appear on the right and tell them to start burning.

You see just below, that's where daddy was now as he lifts the area. lights to the left of the runway that you are now going to pay attention to, this is the ball bar indicator, they are going from a 20 Dee glide to a 1 and 1/2 degree glide, so there is a white light outside in front of a row of red lights and the pilot is supposed to keep them aligned to make sure they are on that glide slope. Now one thing to notice on the right is that they are a bit like a flat shaped thing at the bottom that shows the speed. but on top of it there is a cross which is where the nose is pointing, so during this final flash the nose is pointing up and the speed vector is barely pointing down and now the commander just has to lower the nose, they have to do it at 180 knots , uh, if they do it too soon then the extra speed will overload the landing gear as the L wings push down and of course if they take too long they will run out of airspeed and the nose wheel will drop too quickly and also. about the stress itself, while the space shuttle was shielded against re-entry forces, it was a pretty fragile vehicle, so yes, long story short, they started with an orbital solution, used Imus and computers to track the orbit, once they arrived at 200 miles, they were able to use the tackan for navigation and yes, at some point there they can also deploy the air data system, the static PTO tubes that will read the air and give them the altitude and air speed, once they get very close, they will be able to pick up the microwave landing system. terminal radar can decide which heading alignment cylinder, uh, sorry, cone to follow on their final approach, the crew will fly down manually once they reach final, they are using the air brake to control their speed, they are looking the landing lights, the daddy and the vazi and the ball on the bar so they can place this on the runway in an orderly manner and yes, one last nuance that a shuttle commander told me is that it doesn't matter if you land the shuttle in Cent Off The Runway as long as during the rollout you make sure it ends in the center of the runway because that's where the publicity photos are going to be taken.

I'm Scott Manley, fly safe.