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November 30, 2008

Wheel Stop

The shuttle Endeavor completed its mission at 1:26 PM, California Time today, as it rolled to a stop at Edwards Air Force Base. Weather in Florida caused a rerouting to a California landing, where the sky was clear and the shuttle could be seen coming in from over 100 miles away by tracking cameras at Edwards. After a smooth 340-degree turn to bleed off velocity and line up on the runway, Endeavor touched down smooth as you please, a great piloting job by commander Chris Ferguson.

Allen Taylor
NSS Member

Posted by allen.taylor at 04:32 PM

November 29, 2008

Shuttle Return Home

The STS-126 crew onboard the Space Shuttle Endeavour is planning to land tomorrow at Kennedy Space Center in Florida. However, a cold front might divert them to Edwards AFB in California instead.

The first landing opportunity is at on orbit 248. The deorbit burn would occur at 11:14 AM Central time for landing at Kennedy at 12:19 PM Central time. The next opportunity is on the next orbit with the burn at 12:50 PM and landing about an hour later. If the weather is not favorable, then the crew may do their burn at 2:20 PM for a landing at Edwards at 3:25 PM. The last opportunity for the day is at 3:57 PM for landing at 5:00 PM at Edwards.

The shuttle does not stay in space because there is no gravity! It stays up there because it is traveling fast enough to balance out the pull of gravity. To return to Earth, it must slow down. To do that, the shuttle points its orbital maneuvering engines into the direction it is traveling. Then like a person on a skateboard holding a fan into the direction they are rolling, the engines are fired to slow the shuttle down. This burn is made on the opposite side of the Earth from the landing site. Each orbit is about 90 minutes, so these opportunities are about 90 minutes apart.

There is not an opportunity to land on every orbit because the Earth rotates "out from under" the shuttle as it goes around, slipping to the west a little each orbit. This is also why the Florida opportunities come before the California opportunities.

The shuttle's flight was already extended an extra day to allow time for troubleshooting the water recycling system. If conditions are not favorable at either landing location, the shuttle has enough supplies on board for another day in space. Landing at Edwards would require the shuttle to be ferried to Florida later, so a Florida landing may be worth the wait.

Returning expedition crewmember Greg Chamitoff will have the benefit of a reclined seat for entry. In freefall, blood accumulates in the upper body because its weight does not help pull it toward the feet. The body adapts by reducing the total volume of blood in the body. The heart does not have to work as hard, and shrinks in size during long stays in space. Chamitoff has been in space for six months.

When an astronaut returns to Earth, the weight of the fluid in the body once again causes it to be pulled to the feet. The weakened heart beats faster to maintain blood flow to the brain, but with less blood to pump, is not able to completely compensate. Thus, if the astronaut returns in a sitting position, they will feel light-headed and may faint.

(Fainting lowers the head relative to the heart, so increases blood flow to the brain, restoring consciousness. Note, this would not work in freefall. To revive someone in freefall, another crewmember would have to swing them around by the feet!)

Once astronauts are no longer in freefall (they "hit" the floor of the shuttle and stop falling while flying, just like on aircraft), the brain triggers the body to make more blood. Blood is mostly water, so the astronauts drink lots of water prior to entry. The heart returns to normal within a few weeks.

Wherever they land, the crew is likely to return to Houston the next day for their traditional greeting at Ellington. They will receive the thanks for a job well done in readying the space station for an increased crew next spring.

To the stars,

Marianne Dyson
Member of the NSS Board of Advisors

Posted by m_dyson at 08:31 PM

November 28, 2008

Buttoning Up and Closing the Hatch

On Thanksgiving Day, the crew of Endeavor's STS-126 mission wrapped up their duties on the International Space Station and closed the hatch that led to the Station. A lot had been accomplished. Sixteen thousand pounds of equipment and other stuff had been moved between the shuttle and the station. New stuff moved into the station and old stuff that was no longer needed was moved to the shuttle. New additions to the station included two new "bedrooms" and a second "bathroom." Also coming aboard was a new galley, complete with refrigerator, a resistance exercise device, and a water recovery unit.

Aside from the deliveries, shuttle spacewalkers repaired the starboard Solar Alpha Rotry Joint (SARJ) and performed preventive maintenance on the port SARJ. A total of 26 hours and 41 minutes of spacewalks were performed. The station is finally configured to support its design complement of six crew members. The STS-126 crew can be proud of a very successful mission.

Allen Taylor
NSS Member

Posted by allen.taylor at 12:07 AM

November 26, 2008

Thankful in Space

The STS-126 crew have much to be thankful for this Thanksgiving. All the primary objectives have been met: the new expedition crewmember has been delivered (Sandy Magnus replaces Greg Chamitoff), the four spacewalks resulted in a working solar alpha rotary joint, and the new water recycling system is now up and running.

On Monday, the spacewalkers finished replacing the last of twelve trundle bearings in the giant joints that allow the solar arrays to spin like paddle wheels. Starting Tuesday, the array successfully tracked the sun for the first time in a year.

For those of us looking forward to future solar power satellites to collect sunshine and beam it to Earth, the spacewalks on STS-126 provided valuable confirmation that solar power systems can be repaired and maintained in space. The failure and repair of the joint will also lead to improved future designs.

The urine processing assembly is another victory for in-space engineers. ISS Commander Mike Fincke and STS-126 Mission Specialist Don Pettit were able to stabilize the centrifuge and get it working smoothly. It completed a second full test run on Tuesday and another one today without shutting down. Having the ability to reclaim all that water is crucial to increasing the crew size next spring.

Because there were no problems with the other "home improvements," not much has been said about them in the news. In looking over the specs for the new "bedrooms" that were added, I noticed that they are planned to be used as radiation safe havens. These two closet-sized "rooms" were installed in the Harmony node, the one between Columbus and Kibo. About the size of the lavatories on a commercial jet, these rooms have no window to the outside. But the padded rooms are quiet and dark and are "wired" for laptops. They have ventilation and temperature controls and "cupboard" space for personal belongings. Best of all, the room is in freefall, so the occupant can actually easily access every cubic inch of the room.

Though space station crews have the benefit of protection from Earth's magnetic field, if these new "cabins" work well, they could easily be adapted for stations at lunar distances. So this safe haven "home improvement" is also an important new capability to test prior to building stations on the Moon or sending humans to Mars.

All the supplies and new equipment were brought to space inside Leonardo. After emptying it out, the crew loaded it up with 3,500 pounds of "returnables." The crew then plucked Leonardo off its perch today and placed it back in the shuttle's payload bay for return to Earth.

The capability to bring back lots of equipment is something unique to the shuttle. The Russian progress ships bring up supplies and take the trash out. But they burn up in the atmosphere. The Soyuz are primarily for crew exchange and only have room for about a suitcase in addition to three crewmembers. The Orion will have some return cargo capability, but not nearly the carrying capacity of the shuttle. So it is important that the shuttle haul away as much of the reusable equipment as possible before retirement in 2010.

The shuttle crew will share Thanksgiving dinner with the expedition crew and then undock on Friday. Progress 31 launched today and will arrive at the station on Sunday. The Progress is bringing up holiday gifts and foods for the three crewmembers including Fincke, Magnus, and Yury Lonchakov.

The shuttle is scheduled to land at Kennedy Space Center on Sunday after a job well done. We should all be grateful for their hard work that will allow people to live and work in space more comfortably and affordably in future years.

Thankful in Houston,

Marianne Dyson
Member of NSS Board of Advisors

Posted by m_dyson at 08:48 PM

November 22, 2008

Working in Freefall

The National Space Society's vision is of "People living and working in thriving communities beyond the Earth." The astronauts of STS-126 and Expedition 18 are making major progress this week toward making that vision come true.

Ironically, more progress is often made when things go wrong than when they go perfectly. During a spacewalk last week, an expensive tool kit got away from Heide Stefanyshyn-Piper. This padded white box contained tools, including a grease gun, important to the repair of the solar alpha rotary joint that turns the solar arrays like a paddlewheel to track the sun. Fortunately, they had more than one set of these tools, though they now have to conserve the use of grease.

To rescue the box, Piper could have used her SAFER backpack to fly after it. But those backpacks are not reusable, and therefore are reserved only for life-threatening situations. The loss of a tool box is unfortunate, but not life-threatening.

The lesson here for long-term working in space is that care must be taken to provide backups for everything. Accidents happen. If that tool box had been the only one, the repair would have to wait until a logistics flight could bring up a new one. If the station were on its way to Mars, that might not be possible. If the repair were critical to survival, Piper would have had to use the backpack to go after those tools. This repair was not that critical, and there was also another set of tools. So Piper made the right decision in not going after it.

But how did this loss occur? It was NOT because there is no gravity in space. If you stood on a bathroom scale tower as tall as the station is high, you would weight 90 percent of what you weigh on the surface of Earth. You weigh less because you are farther from the center of mass, but certainly not zero.

The reason that things are weightless and appear to float in space is because they are all falling at the same rate. The effects of falling can be felt on Earth, but only until the falling object or person hits the ground.

NASA's "vomit comet" aircraft falls about 10,000 feet in the sky so that astronauts and scientists can run tests during about 25 seconds of being weightless. (Put a heavy object on a bathroom scale and drop it over a bed to see for yourself that the scale goes to zero while falling.)

So the astronauts and their tools and the space station are floating because they are falling. The correct term for this environment is FREEFALL.

NSS members: Please do not contribute to the extreme science illiteracy in this country by repeating misleading phrases such as "Because there is no gravity in space..." and "In zero-g..." this or that happens. I have discovered through my speaking engagements that at least 95 percent of school children (and their teachers!) believe that there is no gravity in space. NASA's not helping. On a diagram of the new water recycling system that NASA provided to the press this week (and that was published in the Houston Chronicle) it said, "because of the lack of gravity in space..." PLEASE use the term FREEFALL instead!

But if everything is falling together, how did the box get away? Basics physics: objects move in the direction of the force applied to them. Imagine jumping off a diving board while holding a box. You and the box will hit the water at the same time. But while you are falling, if you push that box sideways, it will move away from you until you both hit the water. If you push it down, it will hit before you. If you push it up, it will hit after you. The same thing happens in space, only the astronaut and box never hit the water--they continue to fall in a big circle around the Earth without hitting the ground, and the box continues to move away (without even air to slow it down).

Why don't spacecraft hit the ground? Not because there isn't any gravity! They stay in orbit because they are going fast enough to balance out the pull of gravity. If they went even faster, they could escape (to fall in a big circle around the sun--so they'd still be weightless). It may be helpful to think of twirling a stick (the spaceship) on a string (the pull of gravity). If the spin is too slow, the stick falls. As long as it moves fast, it keeps going around.

Learning to work in the FREEFALL environment is tricky. Small forces that are usually damped out or inconsequential when not falling become very important. The experience the astronauts and ground teams have developed and continue to develop, lost equipment and all, is providing just the lessons we need to realize our vision of people living and working in space.

And the troubleshooting on the water recycling system is another great example of working in space. The motor in the centrifuge that is used to separate contaminants from water in urine is not working correctly. Addressing this problem involves understanding what sensors are needed to diagnose the problem, what tools are required to fix it, and what spares our future lunar and Martian travelers will need to have with them.

The public may not understand what FREEFALL is all about, but hopefully, they will have the opportunity to experience it for themselves in the future thanks to the work of shuttle and station astronauts.

To the stars,

Marianne Dyson
Member of the NSS Board of Advisors

Posted by m_dyson at 02:25 PM

November 19, 2008

Moving Moving Day

Things were really moving up in space today. While spacewalkers Heide Stefanyshyn-Piper and Steve Bowen moved a nitrogen tank and greased up the Solar Alpha Rotary Joint to get it moving again, other members of the crew moved equipment and supplies from the Leonardo module to the Destiny lab. Sandra Magnus, now a member of the Expedition crew, and Don Pettit operated the robotic arm for the spacewalkers.

How any of them can get any work done with the view of Earth swirling by and the sunlight and shadows playing across the golden arrays of the station never ceases to amaze me. Even having the view up in a little window on my computer monitor is enough to distract me from my work (oh that sunrise is gorgeous!). If you can stand a little distraction, live coverage of STS-126 events is available at:

Speaking of moving, Don Pettit sent down a video that is posted on YouTube. After his tour on Expedition 6, he spoke to the JSC Astronomy Club about how he learned to track the ground with his camera to prevent blurring of the images. He captured amazingly clear photos of meteors burning up in the atmosphere, and also of auroras. With this video, Pettit shows that he is the master of aurora photography. Watch this and try to remember to breathe: Pettit's Aurora

Wednesday will be devoted to installation of the new environmental systems needed to prepare for doubling the crew size come spring. This equipment includes 3 racks containing the water recycling system. Two racks are for processing urine, and one for recovering water (sweat and humidity) from the air. Each crewmember requires about one gallon of water per day, so this system will make a huge difference to how much water has to be lifted to the station on future flights.

The next spacewalk will be on Thursday with Piper and Shane Kimbrough moving the cart along the truss and putting up a new GPS antenna.

Thursday, November 20, 2008 is the 10th anniversary of the International Space Station. For ten years, there have been 2 to 13 people in space going around the Earth at about 17,000 mph, making one orbit every 90 minutes. That's the key to staying in space--keep on moving!

To the stars,

Marianne Dyson
NSS member

Posted by m_dyson at 02:07 AM

November 16, 2008

Docking with a Star

Astronauts make it look so easy. All the shuttle has to do is loop around in big circles on that orbital "racetrack" until they "catch up" with the International Space Station (ISS). Then they do a fancy dance including a few flips for the ISS cameras (to photograph the shuttle's belly), and let their airlocks kiss each other hello. This process is called rendezvous and docking.

But it is anything but simple or easy--especially when the space shuttle's Ku-band radar system is on the fritz. The antenna is having trouble staying locked onto the tracking data relay satellites that handle high-speed communications and two-way television. The ground can take over some of the functions, but the system may not be reliable for use during rendezvous. A work-around procedure using small telescopes called "star trackers" was used once before (on STS-92 in 2000) when there was a radar failure, and the astronauts are trained to use this procedure.

Using the star trackers for this tricky rendezvous is the equivalent of an airplane pilot finding Houston at night using the North Star and the Moon to find the direction, radio with the airport tower to decide when to descend, and then looking out the window to spot the runway lights.

However, the ISS does not hold still like an airport, and does not have any "runway" lights. It is zipping around the Earth at about 17,000 mph. And though NASA has called the ISS "a new star on the horizon" in promotional literature, it is obviously not a star. Like the Moon, it shines by reflected sunlight. (This is why those of us on the Earth's surface can only see it pass overhead when it is near sunrise or sunset and the arrays reflect the light).

The shuttle's star trackers are designed to look for stars. They use triangulation to determine what direction the orbiter is pointing. The plan is to use the star trackers to "sight" on the ISS (and some other guide stars) to determine its direction. This sighting will obviously have to occur when the ISS is in sunlight and at the right angle for the shuttle to see it. But a direct look at the sun will blind the star trackers, and the orbiter must be maneuvered so one of the telescopes is looking at a very tiny spot in space.

The orbiter will have to execute a very precise maneuver to get into the right "attitude" for the star tracker to pick up the ISS "star." The position in Mission Control in charge of that tricky little calculation is called "Pointing." They work in the support room of the Flight Activities Officer (a position I held during the early shuttle program).

But the star trackers don't provide any distance or speed information. It is almost impossible to judge speed and distances in space by looking out the window because there is no horizon or stable landmark. (I think the astronauts have a hand-held device they can use once they are close enough to see the ISS.) Fortunately, Mission Control can track both vehicles very precisely and provide additional navigational help.

When I stop and think about all the calculations and communications and piloting requirements for a successful rendezvous in space, I can't help but be a little in awe of the astronauts and ground team who make it look so easy to dock with a star.

Marianne Dyson
NSS member

Posted by m_dyson at 02:17 PM

November 09, 2008

STS-126: Extreme Home Improvements

The Space Shuttle Endeavour is scheduled to launch Friday, Nov. 14, 2008. The press kit subtitles this STS-126 mission, "Extreme Home Improvements." The nickname is appropriate for a flight that will deliver a new water recycling system, toilet, sleeping quarters and exercise equipment. These "home improvements" are needed to support the planned expansion of the International Space Station crew from 3 to 6 beginning in the spring of 2009.

The commander is Navy Captain Chris Ferguson, who admitted that he spent a few sleepless nights wondering if there were anything that he hadn't thought of, but who has total confidence in his crew and expects the flight to "go entirely perfect!"

The pilot is rookie Eric Boe who said he is looking forward to the "awesome view" from orbit that the veteran astronauts have raved about. He will get his chance in between helping with the complex logistics of this flight and supporting the space walks.

The lead mission specialist on this flight is Don Pettit, former Expedition 6 crewmember famous for spending his off-duty time doing "Saturday morning science" demonstrations. With this flight crowded with four spacewalks and installation and testing of so much new hardware, he said he expects any "free" time will be spent "catching up on sleep." But Sandra Magnus, the replacement for current expedition crewmember Greg Chamitoff, said she had plans to do some educational videos during her Expedition 18 tour. She will join Expedition Commander Mike Fincke and Russian Flight Engineer Yury Lonchakov who have been on station since mid October.

The other three mission specialists are all assigned spacewalk duties. The purpose of the four spacewalks is to "grease" the stuck Solar Alpha Rotary Joints (SARJ) that allow the station's solar arrays to track the sun and generate power for operations and science. The spacewalks are scheduled for flight days 5, 7, 9, and 11. If launch is on Friday, the first spacewalk will be the following Tuesday, and the others will be every other day after that.

Heide Stefanyshyn-Piper, wearing the red stripe on her suit, will go out with rookie spacewalker Steve Bowen on the first Extravehicular Activity (EVA). Their job is to remove and replace a tank of nitrogen and remove a cover from the Japanese Kibo ("Hope") module to prepare it for STS-127 that will install the exposed facility (sometimes called the porch).

Piper will be joined by Shane Kimbrough for the second EVA that will relocate two Crew Equipment Translation Aids (CETA) carts. This move is in preparation for the moving of an external stowage platform. The spacewalkers will also "grease" the end effector of the station's robotic arm. The end effector consists of two nested cylinders that grab onto objects by rotating to wrap cables around doorknob-shaped grapple fixtures. The astronauts will end their EVA by lubricating a bearing on the SARJ.

Piper's third spacewalk will be with Bowen and focus entirely on greasing up the SARJ.

The fourth spacewalk, by Bowen and Kimbrough, will remove insulation from Kibo and add a Global Positioning System antenna and TV camera. Kimbrough will also complete the servicing of the SARJ.

The spacewalks are a vital part of the space station assembly and maintenance, but the work going on inside: installing the new recycling system, has the greater potential for long-lasting impact to the future of humans in space.

The ability to recycle waste water is absolutely necessary for trips of more than a few weeks duration beyond low-Earth orbit. These systems will allow the crew size to double without doubling the supply flights--especially shuttle flights that deliver much of the fresh water needed by the current expedition crews. The shakeout and testing of these new systems during Expedition 18 may not make headlines, but they will provide the foundation upon which to build the space-faring civilization that NSS members envision. Extending the human presence beyond the old homestead of Earth certainly qualifies as an Extreme Home Improvement!


Marianne Dyson
NSS member
Former NASA flight controller

Posted by m_dyson at 12:54 PM


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