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UPDATE # 128 - July 19, 2000 PART 1: What's Cooking at NASA Quest WHAT'S COOKING AT NASA QUEST
In the category of what to expect this fall, watch for a new website look. We really think you'll like our face lift and will find it easier to get around our many projects. Your bookmarked addresses should still work, but we hope to keep you better informed about the total NASA Quest offerings at a glance. We're working hard to open the new site in September. One of the new "kids" around NASA Quest will be Solar System Online. In this developing center you'll be able to find areas of study and, as usual, enthusiastic experts ready to share more about the planets and the sun. Aerospace Team Online will bring you Regimes of Flight, a project where you can learn about flight at different speeds! On Space Team Online, we will continue to focus on human space exploration, opening the year with a new version of our Space Shuttle Countdown: Landing to Launch series. The October 5 launch of STS-92 marks the100th Shuttle Flight and happens to be during World Space Week! We are planning to celebrate that week with a return of the popular Classroom Today week in cooperation with Classroom Connect. That's just a taste. As you can see, though we're not as "active" during the summer months, there's still a lot going on at NASA Quest. Stay tuned, Linda Conrad lindac@quest.nasa.gov UPCOMING EVENTS:
Note: Most chats require pre-registration, so please plan ahead. If you need some help with how to chat, see the NASA QuestChat Information Center at: http://quest.nasa.gov/qchats/ Chats may be accessed from: http://quest.nasa.gov/common/events.cgi?prj_sto ->Tuesday, July 25,12noon-1pm PDT (3-4pm EDT, 7-8pm GMT) WebCast Tour of the ISS Mockup and Training Facility Find out where astronauts train to live and work in space, and aboard the International Space Station (ISS). Visit the ISS mockup at Johnson Space Center. Join us from http://quest.arc.nasa.gov/space/events/iss/ ->Tuesday, July 25, 1 PM - 2 pm PDT (4-5pm EDT, 8-9pm GMT) QuestChat with Grant Palmer When a spacecraft such as the Space Shuttle returns to Earth from space, the friction caused by the air rushing past the surface of the vehicle causes it to heat up. Grant Palmer writes computer programs that predict how hot these vehicle surfaces will get. See Grant's profile at: http://quest.nasa.gov/aero/team/palmer.html Register from http://quest.nasa.gov/common/events.cgi?prj_sto [Editor's note: William Boyd is the deputy chief of the propulsion and fluid systems branch of the engineering department at JSC. Propulsion is what is often referred to as "rocket science." As an engineer, he is responsible for taking what the scientists come up with and making it work in real-life applications like the Space Shuttle.] SHUTTLE UPGRADES -- CHANGING AUXILIARY POWER UNITS http://quest.nasa.gov/space/team/boyd.html July 12, 2000 Interviewer: Lori Keith I have been quite busy, since my last journal, working on many projects. Several of them involve shuttle upgrades. We've been using our shuttles for about 20 years, and hope to use them for 20 more. To do this, we must make investments in our vehicles to keep them operational and safe. One of the Shuttle upgrades we're involved with is the electric auxiliary power units (EAPU), to replace the auxiliary power units (APU) we currently use. An APU is like another rocket engine on the Shuttle that is used to provide power for running things inside the vehicle. It runs during launch and landing, and we want to change it from a rocket type of engine to an electric type of engine. I'll explain more later, as we go. There are key parameters that must be met concerning any shuttle upgrade. First, and foremost, is always safety. Then we must think about supportability - will the replacement hardware be available when a repair is needed. Of course, cost effectiveness is always a major concern. Performance is the next major parameter we look at - will it work well and meet mission requirements. These are not the only things we look for, but they are the major ideas that everything is built around. Currently, the APUs are used to raise and lower the landing gear, move the rudder surfaces or body flap, use the speed brake, and a few other things inside the vehicle. The APUs we use now operate a pumping system using hydraulic fluid. An example of how this technology works can be found on a car - the brakes and power steering systems are basically hydraulic systems/pumps. On the shuttle, a signal is sent to actuators (via computer), and these actuators tell the landing gear to lower. The work is then done by the hydraulic fluid, in enclosed fluid lines which push on the pistons and surfaces, which in turn cause the landing gear to lower, or the body flap to move or the rudder speed brake to separate and slow the vehicle down. The pump is generally always running keeping the fluid under pressure during launch and reentry /landing, but not on orbit. On a car, the engine turns causing a belt to run on pulleys, which runs the hydraulic system. On the shuttle, the force that turns the hydraulic pump is a turbine. A turbine is kind of like a windmill - wind blows past and causes it to turn. The turbines on the shuttle turn when high-pressure gas blows against it. This high-pressure gas is actually a combustion process like in a rocket engine. We take a fuel and cause it to energetically decompose, or react, making a hot gas. This hot gas comes out under pressure and blows on the turbine wheel, which then turns the pump. The pump turning keeps the fluid at a high pressure. The fuel we use is a liquid called hydrazine, stored in tanks on the shuttle. Hydrazine is a common propellant for rocket engines and reacts readily with just about anything. When it reacts, it decomposes forming a high-pressure gas very rapidly, and is hard to contain. We use chambers to contain it. When a command is sent out for an APU to run and turn the hydraulic pump, hydrazine is injected in a chamber. In the chamber is a catalyst (or an aide) waiting to react with the hydrazine, causing it to decompose. The catalyst never gets used up because once the hydrazine begins to decompose it feeds on itself, no longer needing the catalyst. The catalyst is strictly an initiator. The resulting gas is primarily an ammonia type gas. This gas blows the turbine. Though this system has been used for years, hydrazine is a very hazardous fluid to people. Besides being very reactive, it is also toxic. If the right conditions exist, hydrazine can be quite problematic. A leak could cause components around it to decay. We must also store hydrazine on the ground to be used on the orbiter. Any contamination in the system could cause a reaction, like an explosion. While considering shuttle upgrades, a lot of concern has been expressed about this system. Though we have flown using it for 20 years with no major problems, there have been a few minor ones. There have been no major problems because a lot of experienced people are always working on this system. Since safety is NASA's number one concern, it was decided to look at other ways to run the APUs, doing away with the hydrazine. We looked at other fluids to drive the turbine, but none were suitable. We then began thinking about getting rid of the turbine. Condensed sequence of events: hydrazine being stored, flowing into reactor, reactor making the gas, the gas blowing on the turbine, the turbine turning the pump. If we could get rid of everything from the turbine back, and use an electric motor to turn the pump, it would be safer and much simpler to operate. There would be no hydrazine, no combustion process and no worry of turbine failure. Upon looking over these considerations, NASA's Shuttle Program decided to develop and implement EAPUs within the next five years. This brought about new considerations - will the systems be robust enough to keep the pressure up where it's needed to cover demand during launch and reentry/landing; and what about redundancy, what NASA calls its back-up systems? What types of failures can be expected and how would these failures be worked around? Currently, the orbiter uses three APUs. If one fails, we can maintain our objectives using only two. If two APUs have failures, we have limited use of the last one to maintain our objectives, and landing may become a bit more hazardous. The main objective is always crew and vehicle safety. My team's part in this is to set up the testing area and test this new EAPU hardware. The test will include a pump and an electric motor, which we will put through the paces to see how well this system will do its job.The tests we do will prove how reliable this system will be, how we will provide redundancies, and the amount of power and robust performance we are able to achieve. Reliability really comes from time, and many hours (upon hours) will be spent testing this new system. Another thing we are looking into is the power needed to run this new motor, and it will take a lot of power. Currently, there is not enough excess/extra power to run this motor with the fuel cells we use now. Until new fuel cells are developed, this new motor's power will be generated with batteries. Of course, it will take many large batteries (about 2000 pounds worth), so storage space and weight on the shuttle become a concern. NASA is researching the use of lithium ion batteries, as they are smaller, lightweight, and longer lasting than conventional batteries. The concern is whether or not the lithium ion batteries would generate the power capacity we need. Once our testing is done here, this new system will need to be put through the paces with integrated simulated testing - putting the new system into the shuttle environment including changing atmospheric pressures to the vacuum of space, and differing thermal environments. Other tests performed will go through the eight and a half minute launch profile and the 30 minutes from orbit to landing. We will begin testing in April 2001, with a projected date of 2005 for full implementation. This seems like a long time off, but it really isn't. Once all testing is done, prototypes made, and operating procedures/simulations worked through; it could take six to eight months to modify each shuttle with this new system. With summer here, my son is home from college co-oping at Union Carbide. My daughter is involved in a very rigorous softball program, which keeps her quite busy. My wife, Susan, and I enjoy spending a lot of time going to softball games and tournaments. STATUS OF ORBITER PROCESSING
MISSION: STS-106, 4th ISS Flight scheduled for launch September 8 Technicians completed Shuttle main engine installation on July 7. Orbiter Atlantis' engine heat shields were installed yesterday, and integrated hydraulic testing begins Thursday. This week, workers are checking the orbiter's water spray boiler and servicing the drinking water system. The orbiter's maneuvering system and reaction control system will undergo flight control testing this week as well. Next weekend, the flight crew will conduct the crew equipment interface test. MISSION: STS-92, 100th Shuttle Mission scheduled for launch 10/5 The pressurized mating adapter (PMA-3) was installed inside Discovery's payload bay on July 6. Last week, the flight crew came to KSC to complete the crew equipment interface test. The visit culminated with crew inspections of the orbiter payload bay and crew module. PMA-3 interface verification testing is under way this week. Workers are also performing orbiter maneuvering system pod checks.
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