Space Shuttle ?

[JimPghPA]

OK, here are a few Space Shuttle questions that I have been wondering about.

1)a. What oil(s) are currently used for the main engine.

1)b. And what oil(s) were used in the past.

I remember a story about when NASA was looking for an oil before the first shuttle was built and someone had an oil in the back of Popular Mechanics or Popular Science with good high temperature specks. When NASA got it, it was a powder at room temp. I heard that NASA ended up using M1. If so What version of M1 was used with the first flights?

1)c What hydraulic oil(s) are used in the shuttle if any?

1)d What special preps do these oils require? Such as X amount of vacuum, exposure at Y temp. for Z amount of time to de-gas before installing, exc. such as storage, transport, time from conditioned to installation, exc

2) I remember a story about the second flight of the Shuttle having a automatic shut-down of one of the main engines well into the flight (I think it was the center engine) and they were able to get to the desired orbit by burning the other engines longer. The story was that the engine did an auto shut-down because it was LOW ON OIL. And the reason it was LOW ON OIL was that no one at NASA remembered to change the oil from the first flight. Guess it was not on ANY check list. Was this story true? If so it is high praise for the quality of the oil.

3) I heard a story that one of the early flight had all but one of the computers crash when the shuttle was in orbit, and that without the one computer that remained operating the shuttle would not have been able to re-enter. The story was that the connection (mother board or wire wrapped sockets) had a bus that was not connected for some of the slots. And that at each power down while on the ground the tecks removed the cards and then re-installed them for the next use. The problem (according to the story) was that the cards and slots were not color coded or distinguished in any way. The tecks then assumed that the back plane wiring was universal and the cards were inserted in any slot with no special order. The result is that the cards that required the wiring only had one computer that had the required cards with the required wiring in the required slots, and it was pure luck that a least one computer had one set of cards in the correct slots. The story also goes that they did not figure this out until the shuttle was back on the ground. Is this true?

4) If I remember correctly, one of the few flight that did not land in Florida had a problem with the shuttle having no breaks after it landed. If it had landed in Florida it would of not been able to stop in time and would of ran off the end on the runway and into the ocean. Is this true?

5) Finally, and this is probably opening up a real can of worms, but could be very interesting reading, can anyone list as many as possible, all of the close calls that did not result in serious damage, but could of. In other words how many (if not for pure dumb luck),close calls has the past shuttle missions gotten away with? And can you be specific? The specifics are what would be interesting reading.

 

[crinkles]

i can't answer any of your questions really, however, i suggest you read richard feynman's report on the challenger disaster.

essentially, he has estimated that a mission would fail with a 1 or 2 in 100 missions (and NASA engineers agreed to some extent). Management however believed through false science and reliability analysis that the odds where 1:100,000. THe engineers got overruled, and the challenger disaster was the result.

 

[FL_Rob]

These are some great questions,worth asking of course,however,i truly think that cloak of secrecy is just too heavy.Engineers and ground crews(also engineers)will make mistakes and theres a science behind that...quadru[le redundancy,stuff like that.Neat stuff.I guarantee nothing on the Orbiter is off the shelf.There are contracts to be filled etc.,but its not all black magic.This is heavy engineering,it still has to be welded,bonded,bolted,coated,...on..and on..So if they did{forget}
to {check the oil}there would be someone on the back of the
milk container

 

[Boomer]

I ateended the Crosby Quality College in 1981 in Florida as an Armstrong World Industries employee. Phil Crosby was a retired aviation engineer and spoke to our group. He said, and I'll never forget this in light of what happened, that the O-rings on the solid fuel rockets used on the shuttle were of a poor design and shrank when cold. He told us that several flights had shown burn marks on the main tank from high temp gas leaks from the defective seals. He said this was indicative of how the quality control systems had fallen apart at NASA and he predicted that a shuttle would blow up in the future if this was not taken care of!! Of course, he was correct.

And with all the things that have happened since, it would appear that the issue of "do it right the first time" is not being followed at NASA but rather "spend the least each time".

 

[tom slick]

I read somewhere that DuPont Krytox is used in space vehicles.

 

[MolaKule]

Right Tom.

Most of the grease is of a Krytox formulation with exotic base oils.

The type of lubricant used depends on where it is located and what mechanism it is lubricating.

The current TurboPump bearings are not lubricated, so there can be no low oil shutdown. There can be a shutdown due to the sensors showing too low or too high a pressure either in exhaust or feed, or incorrect temps.

As of last count, SKYDROL or a variation of it was used in the hydraulics.

Quote:
What special preps do these oils require? Such as X amount of vacuum, exposure at Y temp. for Z amount of time to de-gas before installing, exc. such as storage, transport, time from conditioned to installation, exc



The lubes have a vapor pressure spec as well as other specs such as viscosity index, viscosity at temps, flame point, ignition temp, etc, much as automotive lubes.

 

[postjeeprcr]

Originally Posted By: MolaKule
Right Tom.

Most of the grease is of a Krytox formulation with exotic base oils.

The type of lubricant used depends on where it is located and what mechanism it is lubricating.

The current TurboPump bearings are not lubricated, so there can be no low oil shutdown. There can be a shutdown due to the sensors showing too low or too high a pressure either in exhaust or feed, or incorrect temps.

As of last count, SKYDROL or a variation of it was used in the hydraulics.

Quote:
What special preps do these oils require? Such as X amount of vacuum, exposure at Y temp. for Z amount of time to de-gas before installing, exc. such as storage, transport, time from conditioned to installation, exc



The lubes have a vapor pressure spec as well as other specs such as viscosity index, viscosity at temps, flame point, ignition temp, etc, much as automotive lubes.


Interesting

 

[Kestas]

I've done some reading on lubrication and space. Basically, designs are favored to have as few moving parts as possible for space application.

Here on Earth metal surfaces have what is called and "adsorbed air layer", which prevents two metal surfaces from cold-welding to each other and provides minimal lubrication. If you recall, Sputnik was a satellite designed to do little more than send a simple beeping signal with a transmistter. There was a relay to make the signal go "beep-beep-beep". The relay failed shortly after deployment because the contacts cold-welded to each other and the signal became one long "beeeeeeeeeep".

Moly disulfide is a favored lubricant for moving surfaces in space. It's a solid lubricant that will not gas off.

I'm not familiar with Krytox, except that it is a perfluorinated polyether similar to Teflon, and I've heard that it is used in space application. It must have low gassing properties. And any outgassing must not compromise nearby parts.

I imagine that much of the life of satellites depends on the life of the lubed parts.

 

[JimPghPA]

Thanks for the information everyone.

Just thought that when it comes to extreme lubricants the Shuttle would be one of the worst / best applications to learn about lubricants from.

Also it would be very interesting to review engineering details about any close calls.

One very good engineer I once worked with pointed out that if you were to look at the statistics regarding possible critical failures and the number of critical components in a modern computer you would be amazed that they are able to work for more than a few hours.

 

[Greggy_D]

Originally Posted By: JimPghPA

2) I remember a story about the second flight of the Shuttle having a automatic shut-down of one of the main engines well into the flight (I think it was the center engine) and they were able to get to the desired orbit by burning the other engines longer. The story was that the engine did an auto shut-down because it was LOW ON OIL. And the reason it was LOW ON OIL was that no one at NASA remembered to change the oil from the first flight. Guess it was not on ANY check list. Was this story true? If so it is high praise for the quality of the oil.

3) I heard a story that one of the early flight had all but one of the computers crash when the shuttle was in orbit, and that without the one computer that remained operating the shuttle would not have been able to re-enter. The story was that the connection (mother board or wire wrapped sockets) had a bus that was not connected for some of the slots. And that at each power down while on the ground the tecks removed the cards and then re-installed them for the next use. The problem (according to the story) was that the cards and slots were not color coded or distinguished in any way. The tecks then assumed that the back plane wiring was universal and the cards were inserted in any slot with no special order. The result is that the cards that required the wiring only had one computer that had the required cards with the required wiring in the required slots, and it was pure luck that a least one computer had one set of cards in the correct slots. The story also goes that they did not figure this out until the shuttle was back on the ground. Is this true?

4) If I remember correctly, one of the few flight that did not land in Florida had a problem with the shuttle having no breaks after it landed. If it had landed in Florida it would of not been able to stop in time and would of ran off the end on the runway and into the ocean. Is this true?

5) Finally, and this is probably opening up a real can of worms, but could be very interesting reading, can anyone list as many as possible, all of the close calls that did not result in serious damage, but could of. In other words how many (if not for pure dumb luck),close calls has the past shuttle missions gotten away with? And can you be specific? The specifics are what would be interesting reading.





Woo boy......here we go:

2) STS-51-F (the eighth flight of Challenger and the 19th shuttle flight overall) had the center engine shutdown 5 minutes and 45 seconds after launch. This was due to a faulty high temp sensor. Nothing wrong with the engine itself. This is the only flight that had a main engine shutdown during flight.

3) No...this story is not true. 5 GPCs are on each shuttle. Shuttle flights have had a single GPC go out, but there are spares on-board. When the shuttle arrives in space, the crew reconfigures the computers for orbital operations. Two GPCs run the on-orbit program, and one GPC is dedicated to payload operations. One GPC is powered down but has the landing program loaded in case an emergency requires the crew to return in a hurry. The final GPC is powered down until needed.

If one GPC fails in orbit (or even two), the mission won't necessarily be aborted if the problem isn't expected to affect the other GPCs. In theory, any of the five computers has the capability to land the shuttle safely. During reentry and landing, all five GPCs operate together again.

4) Just the opposite. On STS-51-D, the brakes locked up during landing at KSC. The shuttle blew a tire during rollout. All landings from that point on were to take place at Edwards until the brakes could be redesigned and the nose-wheel steering was implemented. The same problem, although to a lesser degree, happened 2 months later on STS-51-G.

STS-49 (the first flight of Endeavour) featured the first time a drag chute was used after WOW (weight-on-wheels).

5) There were two really big ones. STS-27 (the second flight after the Challenger disaster) had insulation from the right SRB nose cone come off and strike Atlantis 85 seconds into the flight. Unbeknownst to the crew, hundreds of tiles were damaged or missing. What compounded the problem was the fact this was a DoD mission. All communication and video transmissions had to be encrypted. When the crew sent a video downlink of the damage to Mission Control, the resolution was so poor that exact damage estimates could not be made. The crew honestly did not know if they would make it or not. After Atlantis landed successfully at Edwards, the crew basically [censored] in their pants when they saw the damage.

STS-93 was probably a bit scarier. Five seconds after Columbia lifted off, an electrical short disabled one primary and one secondary controller on two of the three main engines. The engines automatically switched to their backup controllers. The short was later discovered to have been caused by poorly routed wiring which had rubbed on an exposed screw head. Concurrently, an oxidizer post, which had been intentionally plugged, came loose inside one of the main engine's main injector and impacted the engine nozzle inner surface rupturing a hydrogen cooling line allowing a small leak. Because of the leak, the engine's controller saw an increase in use rate of hydrogen. The controller assumed the extra hydrogen was being burned in the engine (rather than being leaked overboard as it actually was) and increased the oxidizer flow to maintain the presumptive mixture ratio, resulting in a premature engine shutdown near the end of the projected burn due to low liquid oxygen level. Despite the premature shutdown, the vehicle safely achieved a slightly lower orbit and was able to complete the mission as planned.

Coincidentally, Columbia was also carrying the heaviest payload to date, the Chandra X-ray Observatory. If two out of three main engines had shut down after lift-off, Columbia would have fallen right out of the sky with absolutely no hope of an emergency landing. The orbiter and crew would have perished upon hitting the Atlantic Ocean.

As we all know with Challenger, there were MANY flights that had erosion/blow-by of the primary O-ring seal on the SRBs, but the secondaries were not breeched until 51-L.

 

[JimPghPA]

Thanks Greggy D.

Someday if NASA ever retires the Shuttle and declassifies material, photos and stories about details would make a great engineering book that would probably be a best seller.

I know hind sight is 20-20 and it is hard to insure that all people who should be up to date on any given project are, epically when there are many people involved. I am not in any way trying to criticize NASA. The Shuttle is probably one of the most complex machines ever made by man. And it probably has more individual items required to build one than any other machine ever. That makes it a testament to mans ability to work together on a project. The engineering involved to maintain the require organization and scheduling of tasks, deliveries, and when each item was required would be an interesting chapter or more in any book regarding the engineering involved with the designing and building of a Shuttle. Just think of the total man hours really involved in making all of the items, and then assembling those into larger items.

The thought and engineering that goes into some items alone could make up a good one hour TV documentary, or a good engineering book. I saw one about the runway the Shuttle uses once. Probably the longest flattest piece of real-estate known. It actually follows the contour of the curvature of the earth.

Thanks again.

 

[kd5byb]

Hi fellas,

I spent 5 year early in my engineering career in the Shuttle and Space Station programs. This was post-Challenger, pre-Columbia.

The Shuttle is both wonderful and highly flawed.

The redundancy of the design is fantastic - from the 4 Primary flight control computers and the logic rules in place to make sure all 4 agree on guidance, control, and navigation - plus a 5th running a Backup Flight System by a different vendor in case the 4 GPC's running the primary system encountered an unsolvable set-split, to the three engines with each engine having two controllers, each controller fed with two different power buses - it's all fantastically redundant.

Yet highly flawed, as the thermal protection system (the tiles) had absolutely ZERO redundancy as we saw with Columbia. Plus, I'd argue that the management structure of NASA and it turning over operations to a profit and schedule motivated contractor, United Space Alliance, also resulted in ZERO redundancy.

I worked for USA at one point and LEFT partially based on my personal concerns that another accident was not an if, but a when. I personally consider United Space Alliance to have blood on its corporate hands for the Columbia disaster. FWIW, I trained all six US astronauts who died on Columbia, and worked closely with Laurel Clark and Mike Anderson for a long time. When I saw Columbia come apart, I bawled like a child and STILL have a hard time watching her break up. I also spent days reading the entire Columbia Accident Investigation Board report and it still resides on my computer today, as sort of a morbid tribute to those who perished.

So while the vehicle is from an engineering point of view beautiful, it's also highly flawed.

Some specific comments:

Lubricants. Shuttle and Station have very strict requirements for flammability and off-gassing performance of lubricants for inside the cabin use. I specified a lot of Krytox 240AC lubricated bearings (at about $300 for a half pound jar) and remember others specifying Braycote PTFE-based greases and oils. A favorite trick of ours was to use specialized coatings, like those by General Magnaplate, to reduce or eliminate the need for any lubrication. Dry film lube was also commonly used - believe I recall Molykote 321 used frequently.

Engines - my recollection is that the engine turbopumps use LOX and H2 as not just the fluids/gases being pumped, but also as lubricants. Lots of fancy ceramic bearings. But I'll note that that I was not an engine guy, but was a systems guy who specialized in electrical power generation, distribution, hydraulic power generation, distribution and control, plus environmental control and life support systems.

Classification. Nothing on the base shuttle was or is classified. Yes, the Shuttle did conduct DOD missions where the payload and mission was classified, but the in-flight anomaly logs, the design, and all relevant things of that nature were not classified. As a new employee, the first thing plopped on my desk was a Space Shuttle Systems Handbook (basically the design of the shuttle) and an In-Flight Anomalies log with all past problems noted in flight. At this point, I had had no background investigations of any type.

I could type many more pages - but it's been a long day and I'm growing tired. More tomorrow.

later,
b

 

[kd5byb]

Originally Posted By: Greggy_D

If one GPC fails in orbit (or even two), the mission won't necessarily be aborted if the problem isn't expected to affect the other GPCs. In theory, any of the five computers has the capability to land the shuttle safely. During reentry and landing, all five GPCs operate together again.


Not quite correct - four of the GPC's run the primary system, with the fifth running the Backup Flight System.

From:

http://spaceflight.nasa.gov/shuttle/reference/shutref/orbiter/avionics/dps/bfs.html>

Even though the four primary avionics software system GPCs control all GN&C; functions during the critical phases of the mission, there is always a possibility that a generic failure could cause loss of vehicle control. Thus, the fifth GPC is loaded with different software created by a different company than the PASS developer. This different software is the backup flight system. To take over control of the vehicle, the BFS monitors the PASS GPCs to keep track of the current state of the vehicle. If required, the BFS can take over control of the vehicle upon the press of a button. The BFS also performs the systems management functions during ascent and entry because the PASS GPCs are operating in GN&C.; BFS software is always loaded into GPC 5 before flight, but any of the five GPCs could be made the BFS GPC if necessary.

Even after hearing it a thousand times in simulations, I still shudder when I hear the ground call: ATLANTIS (or whatever other shuttle), HOUSTON, ENGAGE! ENGAGE! ENGAGE!

Because if you hear this, it means the [censored] has hit the fan.

later,
b

 

[crinkles]

kd5byb, thanks for your insights. man, we have some learned folks on this board.