Rainer Gerhards, Author at Rainer Gerhards

2007-10-11

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.

2007-10-10

More on Discovery’s heat shield problem.

Unfortunately, the rumors on space shuttle Discovery’s heat shield problem are no longer just rumors. Today, nasaspaceflight.com carries a story with details. While NASA has not yet confirmed the story, it also has not declined it. So it must be well rooted.

The story confirms what I have written yesterday. However, it adds a subtle but important detail: there is no way to detect the suspected type of damage once in orbit. So should the situation worsen during the launch, there is no way to find out before reentry. This is indeed a scary scenario. However, the story also tells:

However, given the data appears to point to worst case scenarios, and that flight experience has seen such issues before, shuttle managers may decide that the risk is no greater than they’ve previously flown with, allowing the launch to proceed on track.

So there still seems to be hope. Of course, my firm opinion is that no missing should be flown when there is unacceptable risk. But face it: spaceflight is a risky business. The astronauts know that and everyone else in the shuttle program does. So what is now important is an in-depth technical analysis, and a good risk analysis based on that. Then, decisions can be made. And these decisions should neither be driven by the urge to fly in any case nor by over-cautiousness. I believe that the NASA folks will have the standing to do the right thing. They should not let them move too much by public (uninformed) opinion. But while I trust them, I still hope the situation is not as bad as it looks.

Source: http://www.nasaspaceflight.com/content/?cid=5249

2007-10-09

Astronauts practice countdown…

Besides the bad news about Discovery’s heat shield issue, launch preparations continue at Kennedy Space Center. The Astronauts have begun practicing launch procedures. Among others, this includes fitting of launch suites as well as emergency procedures. The so-called “terminal count down test” is an important milestone towards launch. As far as I know, the emphasis is on emergency procedure, which includes a ride in the emergency escape basket system.

Future Orion astronauts will possibly enjoy a roller coaster ride during the emergency drill. The current basket escape system is somewhat more basic, but obviously quite thrilling.

If everything goes well, the astronauts head back for a brief stay to Houston. They will return to Kennedy Space Center shortly before launch.

2007-10-09

Heat Shield Trouble looks worse…

The more I read about space shuttle Discovery’s heat shield trouble, the worse it looks. News not yet generally available yet points to a potentially serious issue, which could actually make a launch in the October/November time frame impossible. Thankfully, nothing is finalized yet and there still is hope the situation is not as bad as it currently looks.

As far as my travel plans are concerned: While it is too early to panic, I have begun to think about fall back scenarios. I am right now checking what I can cancel and at what cost. From the cost perspective, it looks frightening, too. Is this really supposed to be the end of my launch viewing trip, at least for this launch window…?

I’ll post updates as soon as I get more news…

2007-10-09

Trouble with space shuttle heat shield?

There is been some rumor about trouble with Discovery’s heat shield for a while now. Nothing is yet confirmed, but at the public raumfahrer.net forum a message popped up that there may actually be trouble.

This is the first public posting on the problem. If it really exists, that would probably be extremely bad: if some of the so called RCC (reinforced carbon carbon) elements would be damaged, the repair would probably be very time consuming. That could cause not just a slight delay but in worst case make a launch of STS-120 in the set launch window impossible. Of course, this would be extremely bad news for me personally, too.

The RCC (Reinforced Carbon-Carbon) panels are a vital part of the space shuttle’s thermal protection system. They gained notoriety as the cause of the Columbia disaster. During Columbia’s STS-107 launch, a RCC panel was damaged by foam debris falling from the external tank. On re-entry, that lead to ultra-hot gases entering the orbiters inside, which in turn lead to melting and break up of the space ship. All crew members lost their lives in this accident.

So problems with the RCC panels are to be taken seriously. And I am sure NASA will. What gives me hope is that so far no official word from NASA is out. So, hopefully, these rumors are exactly that: rumors. I hope to get better information in the next few hours. Actually, I am very eager about any news: after all, it would more then depress me if I needed to cancel my launch viewing trip at this stage – especially as so far everything went exceptionally well…

2007-10-09

malloc/free anomaly cleared

Peter Vrabec provided very helpful information on the anomaly I experienced with malloc/free under mudflap instrumentation. See his report:

$ gcc -lmudflapth -lpthread -fmudflapth mud.c .........---------- mud.c: In function ‘main’: mud.c:27: warning: return type of ‘main’ is not ‘int’ ./a.out alloc p in thread: 0ea72530 alloc p in main thread: 0ea72460 freeing p from thread: 0ea72530 free done! freeing p from main thread: 0ea72460 free done! main thread exiting

gcc -lpthread -fmudflapth mud.c -lmudflapth ................................---------- mud.c: In function ‘main’: mud.c:27: warning: return type of ‘main’ is not ‘int’ $ ./a.out alloc p in thread: 1bffe3f0 alloc p in main thread: 1bffe440 freeing p from thread: 1bffe3f0 free done! freeing p from main thread: 1bffe440 *** glibc detected *** ./a.out: double free or corruption (out): 0x000000001bffe440 *** ======= Backtrace: ========= /lib64/libc.so.6[0x32bde6e8a0] /lib64/libc.so.6(cfree+0x8c)[0x32bde71fbc] ./a.out(__wrap_main+0x174)[0x400924] /lib64/libpthread.so.0[0x32bea061b5] /lib64/libc.so.6(clone+0x6d)[0x32bdecd39d] ======= Memory map: ======== bla bla bla
Note the position of the -lmudflapth argument. So, as it looks, the problem was really one of the instrumentation and not of rsyslogd itself. So, bad as it is, we are still back to hunting a bug that is hiding well. But hopefully we’ll get somewhat closer when mudflap is now actually active… I’ll see and post news as soon as I have them.

2007-10-08

Discovery Crew arrives at Kennedy Space Center

On Sunday, space shuttle Discovery’s crew has arrived at Kennedy Space Center. This is a major step in launch preparations. This week, the crew and technicals will participate in the so-called terminal countdown demonstration test (TCDT) in which launch and emergency procedures are being practiced.

2007-10-08

launch “on time” stats

I was pointed to this interesting article today:

http://cbs4.com/topstories/topstories_story_219064717.html

According to it, only 40% of the space shuttle launches are on time. Interestingly, the number one reason for delays are technical issues. They are to blame for about half of the launch delays. The weather, which I thought to be number one, is actually the second-most reason. About a third of all launches are delayed due to bad weather.

2007-10-08

work-around for malloc/free issue created

I have now created a work-around for the malloc/free threading issue which creates an extra thread for the mainloop. The startup thread then simply waits for it to be finished. As such, there is never memory allocated in the “main” thread. At least for me, it works now with mudflap. I am still in doubt if that was the segfault issue (or just a bug in mudflap), but at least we can give it a try.

I will now see that I get some feedback. The next thing is change the packaging back to a single source tarball (by popular request ;)).

2007-10-08

A fire alert near the VAB

According to many news source, a fire alert happened last Friday on Kennedy Space Center property. The Launch Control Center and possibly also the VAB had been evacuated. NASA sources tell that the alert was not a drill, but it was a false alert. So, it was real, but the fire sensor didn’t work correctly and detected fire where none was.

To the best of my knowledge, work at the launch pad was not (seriously) affected by the fire alert. However, all traffic, including tour buses, was stopped.

But now think about launch day: if such an alert happens then, the launch will be scrubbed for sure. I hope this will not happen while I am on my launch viewing trip.