Category: space shuttle

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Space Shuttle

space shuttleI thought its time to write a bit about the space shuttle itself. As many say, it is the world’s most complex machine ever built.

The space shuttle made its maiden flight on April, 12th 1981 and will, based on current plans, be retired in 2010 after completing the construction of the international space station, its current primary target.

The space shuttle was developed as a replacement for the Apollo spacecrafts. Contrary to Apollo, it can reach low earth orbit, only. It is not capable to go to the moon.

The space shuttle’s major components are the boosters, external tank and the orbiter. The orbiter is the airplane-shaped white “ship” that is commonly called “the shuttle”, though it is only part of it. The reddish external tank contains ascent fuel. And the white booster rockets on the sides of the external tank provide the main propulsion for the initial flight phase after launch.

Its main feature was reusability of most parts. Only the external tank is lost on launch, the boosters glide back to earth on parachutes after separation from the craft. The initial design called for huge savings from that fact – something the space shuttle could not life up to. Some sources quote that NASA expected to have as much as one flight per week and the shuttle to replace all other launch vehicles. In practice, only a few launches per year were achievable and each of them being much more expensive than initially thought.

The space shuttle program was compromised by budget cuts in its early design phase. Initially, it was planned to have the actual orbiter sitting on top of the external tank and boosters. There would obviously be a different design for the main engines in this concept, too. The then-chosen configuration with the orbiter being mounted to the side of these components is a trouble source until today. It exposes the shuttle to launch debris, for example parts of the external tanks foam isolation that fall off during launch.

Launch debris is very hard to avoid. On launch, each spacecraft is shaken quite well. So chances are great something will go off. With all designs but the space shuttle, this poses no problem, because no vital system can be hit by such debris. If you look at Apollo-days Saturn V launches, you will see lots of ice falling off, but the crew capsule and their support system sat well protected above the debris source. Consequently, NASA’s new constellation moon program designs an Apollo-like craft with the vital systems again sitting on top of the launch propulsion system.

In my personal opinion, the space shuttle is a good example why budget constrains should not overrule engineering decisions. NASA paid badly for the initial savings…

Besides that problem, the space shuttle is an incredible and fascinating machine. Among its many great achievements is the delivery and continued servicing of the Hubble Space Telescope. Also, construction of the international space station ISS depends on space shuttles doing the heavy hauling. The space shuttle is also the only spacecraft ever capable to capture massive satellites in orbit and deliver them back to earth.

The space shuttle is also very inspiring. Viewing a space shuttle launch is a special experience.

space shuttle launch

Astronauts also praise the space shuttle for its roominess and the smooth ascent and descent, which puts very low G-forces on the crew.

NASA’s future constellation space program borrows heavily both at the space shuttle and Apollo programs. It is expected to get the best of two worlds. For example, Ares rockets will fly modified space shuttle boosters.

So while the space shuttle has some weaknesses, it is a very successful craft that not only contributed significantly to science, but will also help pave the way to the Moon, Mars and beyond. In my personal opinion, even the weaknesses were kind of success: they proved which things needed to be done differently. And, of course, a lot of issues were already fixed during the lifetime of the space shuttle program.

Currently, the shuttle fleet is set to retire in 2010. This is a political decision not backed by hard technical fact. In my personal opinion, I would like to see the space shuttle flying at least once a year until the Ares I and Orion vehicles are ready to launch. Of course, I do not know exactly what this requires, but I am a bit hesitant to leave access to the international space station just to the Russians. I also doubt that there will really be a “just” six-year inability of carrying humans into space – the Constellation program already has some of its schedule’s slipping. And with an endeavor as complex Constellation, it would be wise to count on some more schedule slips. I wouldn’t be surprised if the first Ares manned flight will not happen before 2018…

The space shuttle has received numerous fixes both in procedures and technology. It is more capable than ever before. It is safer than ever before. Wouldn’t it be wise to count on it as long as its successor is not ready?

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Why is the external tank not painted?

I found a student web site with a lot of interesting data of the space shuttle’s external tank. While the site was set up as a think-tank for the student project, it provides generally useful information.

I’d like to quote one section that I found especially interesting:

Why doesn’t NASA apply paint, a cover, or net over the tank? One might remember that we painted the first couple of External Tanks with white paint in the early 1980’s. In both cases, we had a significant amount of foam loss during ascent. Although at face value applying a net or some other foam entrapping method to the External Tank sounds easy, it is not without concern. After careful examination of this approach, NASA’s conclusion is that portions of the net could become in itself an undesirable debris source. Depending on the material used (Kevlar, aluminum, etc.), the density of the netting material would present a more critical debris source than foam to the Orbiter Thermal Protection System. Through a rigid certification process, we would also have to understand if and when the netting material could come off and in what quantities or mass that the netting material could present. Our assessment is that the process of certifying a netting material for flight would take several years and would not be available until late in the Space Shuttle Program life. NASA’s goal remains to eliminate the potential for critical debris from all sources, including the External Tank foam.

At Kennedy Space Center, I was always told to the weight of the paint was the reason that the tank is no longer painted. That sounded logical to me (and for sure is part of the reason). It was so logical that I never thought about it any further. It now makes perfectly sense to me that paint can also be a major source of debris – it may hold loose parts together, forming an even greater lump that could come off.

Thanks to Nicole Sharp for putting this all together.

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Atlantis still set for December, 6th launch…

The ISS' Columbus module is moved into space shuttle AtlantisI just found this nice picture of the Columbus module being moved into Atlantis’ cargo bay on the NASA shuttle home page. It was taken some days ago. I thought it is worth sharing.
Processing flow on Atlantis is still going smooth, the launch is so far on-schedule for December, 6th. This is confirmed by NASA’s latest statement on the home page:

Space shuttle Atlantis will be the stage for the countdown dress rehearsal next week as preparations for mission STS-122 continue toward a targeted Dec. 6 launch. The rehearsal is known as the Terminal Countdown Demonstration Test or TCDT.

The seven astronauts who will fly the mission are due to arrive at NASA’s Kennedy Space Center over the weekend for several days of in-depth training.

A practice countdown that includes all the normal launch day activities except the liftoff itself will be conducted on the last day of the crew’s visit. Afterward, the crew will return to Houston.

A program-level review of Atlantis and the European-built Columbus module it will carry was conducted Tuesday. A poll taken at the end of the session called for processing to continue. A second review will be held Nov. 30, and NASA will formally select a launch date.

Please note that “formal selection of the launch date” is NASA speak and in this case most probably means sticking with the originally scheduled December 6th date.

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Discovery still set for October 23rd launch

Space Shuttle Discovery is still set for a launch on October 23rd. Launch pad processing for the STS-120 mission is continuing very well. However, there is no longer any contingency left in the processing flow. If now there is any unexpected problem, the launch date will most probably be delayed. Except, of course, the Wizards at NASA manage to make up for lost time once again (they have done it numerous times, for example on the shuttle landing gear strut repair). But: don’t let’s even think about delays and remain optimistic.

The next big action to come is todays Flight Readiness Review (FRR). This is an agency-level FRR, which means that the senior level meets and finds final decisions. Most importantly, it will be decided if Discovery needs to be rolled back due to anticipated problems with the wing leading edge heat shield. From what can be read on forums and the NASA homepage, this is unlikely but still a possibility. Let’s hope the problem is not that bad and the FRR able to give a go for the launch. If they do, we will also receive final word on the actual target launch date. It is still anticipated to be October, 23rd. Even if it slips, it will only be a day or two if they do not need to rollback.

So it will be a very important day today. There is a news conference scheduled after the FRR. It will be held no earlier than 3pm EDT (7pm GMT). Depending on how late it actually is, I may miss it and get the news only tomorrow morning.

Stay tuned …

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Movie of Rotating Service Structure re-attached to Shuttle

The mobile launcher platform at the pad, waiting for the RSS to be attached.Yesterday, I captured NASA public webcam images and created a small animation from them. It shows how the rotating service structure (RSS) is being reattached to space shuttle Discovery.

The RSS had to be rolled back to carry out the APU hotfire test, which was postponed to yesterday due to bad weather. I have not yet heard of any test results, but assume all went well.

The video is the ground-level MLP view, the actual space shuttle can not be seen. When the video starts, watch the shadows. You will see the RSS shadow before you see the RSS itself.

To watch the video, please go to my personal site – it is too big to fit into this blog’s theme. The link is:

RSS being re-attached to mobile launcher platform

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Official Word from NASA: Discovery wing edge does not delay launch!

Space Shuttle Discovery at the launch pad is ready to goAs of the NASA shuttle program home page, the heat shield issue seems no longer to be a show stopper:

One of the topics discussed before the conclusion of the program review Wednesday involved the reinforced carbon carbon, or RCC, on Discovery’s wing leading edge panels. In the past, there have been post-flight indications that the edges of a couple of panels have lost small amounts of their upper-level coating. Thermography, or thermal imagery, has been used to inspect the panels in order to identify any internal defects that could lead to coating loss.

The NASA Engineering and Safety Center (NESC) has been working with shuttle engineers to better understand the potential causes of coating loss. At Wednesday’s meeting, NESC recommended replacing three of Discovery’s 44 panels.

Discovery has flown at least twice with these panels in the current condition, and with no indications of degradation based on thermography. At this point, the Space Shuttle Program has determined that Discovery’s astronauts can safely carry out their mission without having to replace the panels.

That sounds to me as clear indication that NASA intends to launch Discovery as is. I speculated about this solution this morning and I am glad to read it now seems to be official policy. Of course, that does not mean Discovery will launch under all circumstances. Space flight is far too risky and something may happen at any instant. After all, we have nearly two weeks of pre-launch activities before us. But it now sounds likely again that there will be a launch — even on-time. So I stop thinking about how to cancel my trip … ;)

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APU hotfire test about to begin

The Rotating Service Structure at launch pad 39A is now in parking positionThe APU hotfire test seems to be carried out right now. The rotating service structure (RSS) has just moved to parking position. The hotfire test was originally scheduled for immediately after space shuttle Discovery’s rollout to the pad, but had to be postponed due to bad weather at Kennedy Space Center. It was re-scheduled post FRR, which is today.

There was some discussion whether or not NASA would do this test (there seems to be no hard requirement), but it now seems to be done.

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An Alternative to Shuttle and Constellation? ;)

While browsing the web, I found an interesting blog entry on the “space elevator”. In short, it is an elevator-like concept that is promised to deliver people and material at a much lower cost into orbit — with a real elevator-like system. It sounds much like a curiosity, but has received serious consideration, even in scientific circles. However the latest scientific news I read (don’t remember where) is that no current material is strong enough to withstand the forces. The conclusion there was that it could not be done…

You might find this blog post an interesting read:

Good by Space Shuttle. Hello Space Elevator.

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News on Discovery’s wing leading edge problem

The problem with Discovery’s wing leading edge is now being reported by mainstream media (the issue was first reported by nasaspaceflight.com). So it is definitely no rumor any longer and it also has been confirmed by NASA.

The good new, though, is that this issue is unlikely to actually defer the launch. According to Yahoo News, space shuttle program manager Wayne Hale said that space shuttle Discovery’s launch later this month should not be delayed to replace three possibly defective heat shields. He “will recommend to his NASA bosses that Discovery go ahead with its planned October 23 liftoff”.

This statement was made on Wednsday after a program level flight readiness review (FRR). However, Hale has ordered to gather more data on the wing leading edge problem. A final decision is expected after next weeks agency level flight readiness review.

The reason a go ahead seems likely is that only one body inside NASA (the NESC) has recommended replacement. Other teams have already assessed the issue and found the risk to be acceptable. Discovery has been in orbit twice with the heat shield in its current state and there were no indications that the problem has worsened during the flight. Thus, the majority of NASA teams do not anticipate any real problem over here.

The current situations resembles somewhat the tile issue that came up during STS-118 earlier this year. There, a problem with the tiles was detected and one NASA group voted to fix this in orbit. All other groups concluded that it would be safe to fly as is. After some controversy, no fix was applied and the reentry was perfectly well, just as expected.

It is important to note that NASA groups should voice even the slightest concern. It is then the responsibility of the team as whole to decide whether or not the issue is a real show stopper. As it right now looks, the wing leading edge problem seems unlikely to be one. In any case, I trust NASA management to do the right thing.

With that said, I hope for an October, 23rd launch and a great and problem-free mission.