SCIENCE REPORTER

for centuries man's imagination has been captured by the mysteries of the universe today he stands on the threshold of a first-hand exploration beginning with a trip to the moon ironically one of the major difficulties in taking this first big step is returning the Apollo spacecraft safely to Earth in the final stages of its journey the command module enters the severa stand most dangerous lap of its mission dealing with reentry he different problems develop in their laboratories scientists have simulated this awesome environment using machines that can produce temperatures up to 5,000 degrees Fahrenheit they have experimented with hundreds of materials to find just the right protective coating for the heat shield once the spacecraft has re-entered the Earth's atmosphere the next critical step is lowering the command module with its cargo of three astronauts to a touchdown on earth Engineers have devised a sophisticated landing system with parachutes of various sizes and shapes that will be deployed in a carefully controlled sequence though the parachutes will slow the spacecraft to a 15 mile an hour touchdown still 10,000 pounds hitting the earth at this speed poses yet another serious engineering problem suspended under this gantry tower is a model of the Apollo spacecraft to simulate landing the module can be dropped on land or in a pool of water with various attitudes of pitch yaw and roll and with various vertical and horizontal velocities these tests provide valuable information about spacecraft design how scientists and engineers have solved the problems of returning three astronauts from outer space is our story today on science reporter [Music] [Applause] [Music] [Applause] [Music] hello I'm John Fitch MIT science reporter today we're at the National Aeronautics and Space administration's Langley Research Center in Hampton Virginia to learn how scientists and engineers are overcoming some of the most imposing obstacles of the Apollo mission getting the astronauts safely back through the atmosphere and down to earth it's a multi-faceted problem the first part of which is surviving the meteoric plunge into the atmosphere think for a moment of an actual meteor speeding through space as it draws near the earth the gravitational force pulls it in toward the planet at ever increasing speeds suddenly it rips into the wall of the Earth's atmosphere the friction of the meteor plowing through the denser air generates such searing heat that solid rocks are melted away and even the electrons are stripped from their atoms in a few brief moments the meteor may entirely disappear in a fiery gaseous display that we call a Utting star to find out what scientists and engineers are actually learning about techniques and materials for re-entry to protect the astronauts and their spacecraft from this extreme heat we talk first to mr. William Brooks head of the entry structures branch here at Langley when the spacecraft reaches the Earth's atmosphere by a process of compression and friction a hot layer of air is formed over the frontal part of the vehicle the temperature of this air may be as high as 20,000 degrees for the Apollo vehicle well how does 20,000 degrees compare with what we might find here mr. Fisher is three to four times as high as the temperatures created by welding torches the intense heating that is associated with this high temperature air is such that no known materials can withstand it without melting or vaporizing or decomposing in some other fashion well then what can you do about it once we accept the fact that this degradation will take place we found that class of materials called ablative plastics form very efficient heat shield what do you mean by an ablative plastic oblation is the word that we use to define the process of removing surface material by a mechanical a chemical or thermal means anti lose material actually lose material from the surface what makes a good ablative Madina bleeded plastic must have the characteristic of forming a tough Charlie which resists the scrubbing action of the hot air in addition it must generate gases which circulates out through the char and block some of the incoming heat and the final but important requirement is that these materials must be efficient thermal insulators cook the people that are inside right but what have you found makes a good plastic headline we we have been researching a material which consists of phenolic resin this material is similar to that used in fabricating countertops its function is to bind the other ingredients in to form a tough cotton surface when it alone is degraded by heat another ingredient is nylon it's a nylon they use in shirts instead of a nylon that's used in shirt and stockings except here it's an a powdered form rather than more familiar fibrous form another ingredient are these hollow micro balloons which are made out of phenolic resin it's a little spheres they are little spheres for the naked eye powder but when these are viewed under a microscope you can clearly see thin walled hollow sphere none of possible ingredient is quartz fibers which used to reinforce the composite plastic mixes all together these are all mixed together and then subjected to a molding process at temperature and the material is hardens and cures out to a plastic composite such as this but how do you know that this will work that is one of the important aspects of materials research is to distinguish how these perform in a re-entry environment mr. Wilson is will prepare this for test and we will show that test later on the facility that we're using to test this material is based on the principle of using an electric arc to heat the Airstream in this facility we have three electrodes they each consists of two concentric water-cooled copper rings an arc is struck between the two rings and is caused to rotate very rapidly by a magnetic field air is introduced through at the base of the electrode and passes up between the Rings and is heated by this rapidly spinning on the individual streams are squeezed down into one stream at a temperature of about 70,000 degrees Fahrenheit and this stream envelops the test model now actually the model is knotted on an L shape inserter outside of the stream the instrumentation leads there are connected and when the model is position the facility is started when the proper flow has been established the model has been swung into place over the exit of the facility now the facility is actually controlled from central control room which I'd like to show you this is our control we operate several Aki to gas facilities from this room here we have instrumentation and controls which deal with facility parameters such as gas flow rates water flow rates water temperatures and pressures here are the controls and instrumentation which involve the power applied to the facility for the particular run that we're making with this type of facility we can put upwards of 5 million watts into this heater during the course of the test the overhead monitor is used to determine the progress of the test and we have a digital clock here on which has recorded the test time the equipment in the senator room is for programming and controlling very precisely the air flow or the flow of other gases used over here are the data collecting instrumentation the data is collected in the form of electrical signals which represents temperatures pressures flow rates and so forth this data is transmitted by wire to a central computing station where it is reduced some of the reduced data is displayed on these charts for control purposes the crew has been preparing for a test and are ready to commence mr. Wilson reacted set flow rate dead buta said take data dr. Jack I mean addition to the type of data that I described that is temperature pressures and so forth we also take closeup motion pictures to permit us to observe the details of the test let's go back into the other room and an exam in one of those motion pictures finds the facility is being spied in the flow being established the specimen is swung into place and starts to ablate immediately why does the air seem to glow even before it hits the object this is because the air is heated to very high temperatures before it comes out of the facility and radiates energy note also that along the sides of the specimen there is illumination of at a lower level which is caused by the gases produced by ablation I think that's what the astronauts actually see out the window nothing yes note that the ablation is uniform over the surface except a slight rounding at the corners where the test conditions are somewhat more severe lights please very dramatic piece of film this is a typical tested specimen you'll note that a char has been formed over the entire surface just such as this we measure the surface recession the surface temperatures and internal temperatures the specimen is then sectioned and the chart thickness is measured and other characteristics determined this test a good simulation of what actually happens it is not an exact duplication of the reentry environment we cannot produce these environments in the laboratory but then tests such as these we get the data which can be used with theoretical procedures and can predict what will happen in an excellent in reentry that is will this material make a good heat shield [Music] the ablative heat shields for the Apollo command module are manufactured at the research and advanced development division of Affco corporation in Lowell Massachusetts the outer shell of the spacecraft arrives here in four separate pieces the blunt end of the cabin which takes the brunt of the heating is mounted upside down on its cradle and has already been partly covered with its heat shield this section fits on the bottom of the crew compartment in which the astronauts will arrive above that is the forward equipment and parachute section and finally a small nose cap because of the tremendous heat of reentry all surfaces must be protected to learn about the processes involved we talked with mr. Edward often parks director of half chose Apollo operation the heat shield that we've developed at Avco consists of a honeycomb matrix to which we add an ablative material now what is the purpose of this honeycomb actually it serves two purposes one it gives us additional mechanical strength and the other it assures us that we can have a good bond between the ablator and the steel well how do you actually fasten the honeycomb onto the steel we start with the steel and we have to clean it and incidentally that's the reason for the white gloves it's a clean area and we cover the clean steel then with a tape which is sticky on both sides we lay it on top and then we take some preformed sections of the calm and we put them on top to hold it down and that really fastens it on tight well not quite we have to go through a cure operation which then puts and guarantees the run it ends up like this we have a rigid attachment when you have a honeycomb firmly bonded to the steel then do you fill these up with the ablative material well not quite as you know the heating varies around the vehicle and for example we have a higher heating here than we do up toward the top so you want more heat shield right we want the thickness to be greater here than it is toward the middle and incidentally it's non-uniform the heating also varies in the other direction as well so we define the thicknesses in going around the vehicle in such a way so that we can provide the required protection and achieve the weight that is needed to do the job well how do you do this trimming operation well it is something that we have to accomplish with a machine and we do that next door in order to machine compartments of this size we required the use of a 16 foot vertical boring mill because of the motions of the tool that we needed we converted this machine to an electronically controlled tape which enables the tool to the program so that we can cut the ablator and fix the thicknesses as we require around the vehicle after machining we have to get the ablator into the honeycomb matrix we do this by gunning and what you see over here is a nose and forward compartment when the process initially of being done it's actually squirting the ablative material into the hole that's right what we do is mix the ablator itself it's a plastic we have additives fibers micro balloons to get the correct density unloaded into cartridges which we can store for later use when we get a cartridge we load it in a gun and it's heated as you can pretty well tell here there's well we have a nozzle at the end and if you'll hold this I'll try and see if I can duplicate what he's doing here and you can see that the material guys come out so they get air mixed in with it right the air actually entrains the material in the cylinder and lows the material from the base up so like warm putty with fibers in it it's pretty much they can you didn't see the material and he goes around and fills every one of the holes right we have quite a few on the vehicle how many altogether there are 400,000 that need filling and one is as important as the other well then how can you be sure that you've got every single one filled we have an x-ray technique which enables us to tell follow me what we do is x-ray the entire vehicle and we have trained technicians who can read and interpret the x-rays what you see here is something that's been called out for repair looks like those are holes punched right through the film that's right first we identify the flaw and then the x-ray is put back on to that part of the vehicle where the floor occurs and by punching the hole we pick up that cell which requires repair we do the right one we just dig that out and fills that one again great we do this until we have the completed section assuming that you've got every hole properly filled and what would be the next step in the process we have to then go through the oven cure or the setup of it the ablator the hardening process each compartment is roll into the oven in order to enable it to undergo or cure which results in hardening the ablative how long is it stay in the other it generally stays in the oven for better than half a day and incidentally the temperatures that we keep it at are greater than 200 degrees we in addition require a bagging operation what's the bag for well we have to do the cure in an inert atmosphere so that we can drive off any volatile gases generated during the cycle after the compartment comes out of the oven the ablator sets up hard and takes on this overall appearance see ya we then go through a kiss with the machine to achieve a smooth surface and then we apply a combination moisture barrier paint which gives us this overall finished product why do you need a moisture barrier and the material itself is of a low density and it would absorb moisture we would prefer that it wouldn't so it's a preventative maintenance aspect that we're concerned with here I noticed this crew compartment seems to have a lot of openings cut into it all the way around what's the purpose event well at assembly there are many detailed further connections and work that must be done so this provides access the doors that fit in here are identical to the ablator as shown here and what we have are the frames are gaskets to provide the seals thank you very much for dropping arms as efficient as the ablation process may seem it isn't the total answer to apollo's reentry problem to control the heating and the extreme stresses of deceleration the command module will enter what's called a double pulse first a shallow dive into the upper atmosphere followed by a skip back up to a higher altitude to cool off then the final descent to earth the Apollo command module returning from the moon must enter the Earth's atmosphere through a precisely defined re-entry corridor if it enters too steeply and drops below the corridor the astronauts will be subjected to excessive heat and g-forces above the corridor the spacecraft might not be slowed by the atmosphere and missed the earth completely the center of gravity of the command module has been offset from the center line so that the spacecraft travels at an angle as a result a small lifting force is provided by the air in addition to the drag the direction of this aerodynamic lift can be controlled by rolling the spacecraft with small Jets this permits the flight path to be controlled up and down or sideways much like a high-speed airplane under normal conditions the automatic guidance system controls this flight down the re-entry corridor to avoid excessive deceleration and heating the system is programmed to bring the spacecraft into the atmosphere in two separate stages first a shallow dive followed by a steeper path with a cooling-off period in the upper atmosphere in between the pilot continuously monitors the entry trajectory if the guidance and navigation system places the spacecraft in danger of encountering excessive g-forces or of skipping out of the atmosphere with super circular velocity that is a speed that would take it out into space in a new orbit the pilot would take over control and complete the entry manually when the spacecraft begins to descend for the second time the atmosphere slows the command module - less than the speed of sound at 25,000 feet small drogue parachutes are deployed to further slow the spacecraft at 10,000 feet pilot chutes bring out the main parachutes which float the command module to its journey's end though parachutes will certainly help in slowing down the Apollo command module its landing will be by no means gentle when it finally hits the water some 10,000 pounds will be going almost 20 miles an hour over here in this building various command module shapes have been tested to see if they'll withstand the impact this is Langley's impacting structures facility an 1,800 foot towing tank built before World War two to test various amphibious planes we talked with an aerospace technologist mr. sandy Stubbs the facility here is used for water impact we also can get land landings here we have done tests on the mercury project mercury the Gemini and currently a running tests on the Apollo vehicle as you see here this is a quarter scale model inside it we have accelerometers and pressure pick ups to measure the deceleration and water pressures on impact the signals from the accelerometers and pressure pickups are fed through the cable here to the recording equipment over on the beach we also have cameras located along the beach to record the dynamic motions of the model when it impacts the water now we can raise this up a bit and run a test as you see it's on a pendulum a simple pendulum which were used to obtain the desired horizontal velocity the model is released about here in the necessary vertical velocity is the same of the freefall well now what will be the conditions in this particular test that you're going to run the vertical velocity will simulate parachute letdown of about 20 miles an hour vertical and 20 miles an hour horizontal right the bottle will impact the water in a positive pitch attitude with the heat shield contacting the water is that a realistic landing pretty much that's a nominal landing and what anything special we should watch for would inhibit the there will be a pretty big splash and a violent pitching Mercia and then the model will remain upright and i come to rest and an upright flirting position okay you ready want to pull the sash board back up just a bit alright I get to wear okay let it go there's quite a splash well I see it stayed upright so I assume the astronauts are all right on the inside yes it's a dramatic impact but it sounds pretty good we can show you a film next that'll show the same R on the hand and let you get another view of it these tests show an earlier version of the Apollo spacecraft known this configuration see the landings were made in in water simulating paraglider let down and you'll see that the horizontal Asti is much higher than the vertical velocity in this case oh I see because a paraglider be coming in at a much higher horizontal velocity than a parachute would that's right mm-hmm this is it a much higher velocity simulating a smaller paraglider oh look at that what that wasn't a very good landing the next group of landings will simulate a hard surface or runway type landing in which the vehicle skids and rocks along the runway is this also with coming into the paraglider this is also as a paraglider landing speed I think this was proposed at one time this is the view of configuration a which was the early proposal the first proposal the accelerations on this vehicle were a little on the high side and we tried to cut them down with configuration B which had a a better acceleration bottom shape mm-hmm don't get quite so much of a shock Oh those understatement to try it again so that we went from here to configuration C with the same bottom shape as shown here but with an extension of the diameter to a little bit larger diameter here we got a very good acceleration false and the stability was acceptable what do you use all this information that you've measured for the data that we obtained from the model is quickly analyzed here at Langley and then shipped to the users in the case of Apollo 2 manned spacecraft Center in Houston and then on to the prime contractor of the Apollo spacecraft they in turn use the data for the basic design of the heat shield structure the excel the instrumentation mounts and other important structural parts of the spacecraft thank you very much our guests today have been mr. William Brooks and mr. sandy Stubbs of Langley Research Center and mr. Edward often hearts of Avco Research and Development Corporation I'm John Fitch MIT science reporter [Music]