nasa pressing shuttle change amid concerns

by:Ultimate     2020-11-28
By DAVID E. SANGERSEPT.
1986 this is a digital version of an article from The Times Print Archive, before it starts online in 1996.
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The space agency is pushing ahead with the transformation of the shuttle booster rocket, and there is growing concern that it may abandon more reliable designs to save time and hundreds of millions of dollars.
The focus of criticism is on the quiet decision the agency has made in recent months to reject, at least for the time being, the design changes require the dismantling of 72 giant steel rocket shells ordered six months before the Challenger space shuttle exploded in January.
Killed seven crew members.
This decision raises serious questions about whether plans to fix rocket defects allow engineers to build within the best possible security, especially given the discovery since the Challenger disaster.
At the same time, some people involved in the redesign of the shuttle are increasingly worried about the pressure.
\"Everything is a schedule, a schedule,\" said a senior engineer at Morton tiokor . \"
Last week, the Rockets said the new idea of complaining about sealing joints on the rockets was rejected.
\"We don\'t have time to do the job well, which is very frustrating,\" the engineer, who insisted on anonymity, said . \".
There is growing concern that the agency plans to test its overhaul rocket.
Recently, the National Research Council panel, which oversees the process, warned James C.
Fletcher, chief executive of the National Aeronautics and Space Administration, the agency\'s comprehensive plan
The scale test launch before the next launch \"only meets the minimum requirements.
No one has explicitly accused the space agency of harming safety for expediency.
But many have expressed concern that it may be short-lived to find the safest design.
It was already short-circuited even before the Test started because NASA wanted to use its 72 shells, which greatly limited the possibility of overhaul.
Earlier this year, for example, a group of NASA engineers developed a plan for a completely different approach to connecting the rocket segment, a method of connecting the segments together.
While the agency is well-received internally, the plan is on hold because it will increase the weight of the vehicle and will not be able to make it from the existing rocket shell.
NASA\'s strategy of continuing to redesign the plan that started a year ago could backfire on money and time.
Chairman of the National Research Council Group H.
Guyford Stever recently said that NASA has chosen a \"more risky approach\" through gambling, thinking that it can fix the rocket\'s defects without forging a brand new rocket shell, an expensive process, shuttle flights may also be delayed for one year or more.
But he quickly added that the main risk was NASA\'s timetable for putting the space shuttle back into use, not the safety of astronauts.
\"We will never forget that NASA and Morton tiokor started this redesign before the accident, but we have not learned anything since then . \"
Stever, \"it is possible for the test to prove that it cannot work.
\"But there is a good expectation that it will work,\" said Dr.
Stever continued, \"the process will be longer if they decide to start from scratch.
\"In the past two weeks of interviews, space agency officials have insisted that their actions are very cautious.
\"Safety is the number one priority,\" said John Thomas, head of NASA\'s redesign team, who is reviewing its planned test plan and constantly weighing the benefits of alternative ways to repair the shuttle.
But he said the agency\'s second goal was to \"keep our current hardware,\" which he said was important for achieving the 1988 goal of resuming flights.
\"We are confident to use our existing stock of rocket parts to solve this problem,\" he said . \".
Nevertheless, many people involved in the redesign privately said that NASA\'s decision to deal with the existing shell indicates that there is a huge pressure within the agency to find the fastest solution, for fear that if the space shuttle is suspended for too long, congressional and public support for the space program may weaken.
At Morton tiokor, vice president Thomas Russell said \"extensive testing\" would be the right guarantee for the design of the new rocket joint.
\"If the test doesn\'t prove it works,\" he said . \"
Russell, the space shuttle is not flying.
\"Ad interviews with more than 20 engineers, investigators and external experts over the past two weeks have also produced these findings: * the space agency\'s redesign team decided not to do expensive and time-consuming work
A vertical test of the new rocket, the presidential commission investigating the accident, said the process could help reproduce key pressures when the rocket lifts off.
NASA officials said that after research, they have determined that the same stress can be detected through horizontal testing.
In contrast, the Air Force has strengthened its vertical testing program.
* The space agency\'s design team seems inclined to provide a new material for O-ring seals that failed during Challenger flight, which resulted in the destruction of the spacecraft.
While the new material remains flexible at low temperatures, offsetting a key flaw in the old O-rings, it also melts at relatively low temperatures, triggering a new set of concerns.
Last week, the agency said it was still evaluating the new O-rings and did not make a final decision.
* Most members of the team overseeing the redesign said NASA is usually co-operative and takes criticism.
But some members said the agency had shifted its scrutiny.
\"We don\'t usually get details, and I find that I only get general answers to specific questions,\" says Robert Watt, an expert panel member . \".
That worries me.
* A small but influential official led by NASA\'s former deputy director, Hans Mark, has something to do with the space program, who is now president of the University of Texas system, they don\'t think the shuttle needs to be redesigned immediately. Mr.
Mark insists that in the case of careful selection of components, the shuttle can launch as long as the weather is warm.
His views have aroused strong protests from members of the presidential council. Mr.
Mark, who was contacted in Texas on Friday, said, \"I didn\'t comment,\" adding that no matter what point he expressed in the \"private discussion, I didn\'t finish thinking about the position.
\"The solution to NASA\'s joint problem is the fundamental problem facing the Space Shuttle redesign team, located at the Marshall Space Flight Center in Huntsville, Alabama.
Caused by the flexibility of the shell with a diameter of 12 feet and a half inch thick.
The tremendous pressure that the rocket builds up at the time of ignition can rotate the joint of the outer shell to connect with each other, a situation that gets worse due to cold weather, triggering a series of events that destroy the challenger.
\"The way to think about these fragments is to select one of these two segments --
He said: \"Smash the coffee can and cut off the top and bottom . \"
Eugene Kerrey, a physicist at the Massachusetts Institute of Technology, served on the presidential commission.
\"Now grab the jar in your hand.
In scale, the shell of the shuttle rocket is smaller than that of the can.
To make matters worse, the latest test showed that there were only 16 differences
A few inches of the gap between the two parts of the joint can determine whether the rubber O-ring is properly sealed.
Experts say NASA\'s designers face the task of creating a joint that is not affected by cold temperatures, is not affected by joint rotation, and is more tolerant of dimensional tolerances when assembling.
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According to space agency sources, even before the presidential commission submitted its report, NASA officials decided to retain the basic design of United Airlines, in which, the tongue on a section of the rocket slid snugly into the groove on the adjacent part.
The core of the new design, by Mr.
Last month, Thomas was a \"catch feature\", an extra metal lip that limited the rotation of the joint.
The 72 new rocket shells that NASA ordered in July 1985 included 3 inch extra metal, allowing for additional capture devices, a step NASA has considered since 1981.
However, after the accident, NASA officials added other changes to the new design.
Now it is planned to \"interfere with\" between clips to help lock the capture feature.
The fine heating strip on the outside of the joint will help to protect the joint from the cold.
The redesigned joint will include a third O-ring to replenish the first two.
The channel where the O-ring is located is also widened, so that the close cooperation between the fragments does not compress too much on the O-ring to prevent them from suddenly appearing when they are subjected to pressure explosion within a few milliseconds after ignition. \'\'It\'s a layer-upon-
\"They built a layer of defense that looks good to me,\" said Edward W . \".
University of Georgia aerospace specialist price.
\"At this point, the problem has been analyzed to death.
NASA has rejected other methods, but many engineers have reservations about the new design.
Some people think that NASA\'s basic approach is correct, but are concerned that the requirement to use existing rocket components will prevent designers from building rockets within additional security.
Another smaller group thinks the tongueand-
Groove seals are inherently unpredictable and should be replaced with different designs.
People in the first camp say there is no reason to say a properly designed tongue --and-
The groove design does not provide enough sealing.
The question, said a Thiokol engineer, is whether we have enough capacity to use existing cases.
\"I\'m not sure if we do that.
\"Some members of the National Research Council group expressed similar concerns.
David Altman, a retired joint technical rocket engineer, believes that a larger shell will allow more design changes.
But the restrictions are not fatal, he added.
In a telephone interview yesterday, Edward G.
Dorsey, vice president and general manager of Morton tiokor space division, said, \"it seems to me that using the existing case section is desirable, but not mandatory.
He added that it is mandatory to obtain a section that has been reviewed by NASA and external reviewers.
But he admits that all the options for the shell that Thiokol ordered before the accident were sought for use.
Engineers have raised other concerns about the special joint projects NASA and Thiokol are working on.
They point out that \"interference devices\" that counter the rotation of the joints also make it harder to assemble the joints.
When the joints are not properly installed, the Kennedy Space Center staff must combine these parts, which some experts believe led to the failure of the Challenger seals.
Professor Price of the Research Committee said in describing the new timing, the tolerance is very close.
\"It bothers everyone, so we have to look at it.
Other experts say they still don\'t know how the trend of expansion of space shuttle components after each use will affect new joints, a phenomenon found in the accident investigation.
However, Thiokol engineers say they are most concerned about promising options such as metal high pressure seals and springs
Due to time constraints, the load O-rings that constantly exert pressure are briefly screamed.
\"If it hasn\'t flown before, no one here wants to hear it,\" said an engineer . \".
In response, Morton tiokor insisted that it was still \"reviewing the possibilities \".
Other options for the space agency some engineers, mainly engineers other than NASA and Thiokol, maintain that the basic joint design used on the shuttle should be completely discarded to support seamless rockets or inherently non-rotating joints.
NASA responded that it might do so when the agency purchases a new solid rocket booster that will be delivered in 1990s.
At the same time, however, the agency officials acknowledged that they did not want to try a brand new design except as a last resort.
However, within NASA, many engineers were disappointed that a particular alternative was put on hold: the Lanley research center proposed a simple design this summer to connect the various parts together, attach them along the two horizontal flanges embedded in the rocket\'s outer niche.
\"The advantage is that the joints are not susceptible to radial movement,\" said Robert T . \"
Wingate, deputy director of systems engineering at Lanley, said, \"it is not susceptible to assembly problems because the original design seems to be like this.
The Lanley proposal also addresses key issues with existing O-ring seals, experts say.
Seals used in Challenger flight and seals in NASA\'s improved joints must both pop up in place in the event of a pressure explosion, and if they are not in place properly, hot gas can escape.
In contrast, the sealing in the bolt connection is always under pressure, which makes its performance more predictable. Mr.
Thomas insisted that Lanley\'s proposal was \"not completely rejected\", but said, \"using our existing shell does not meet our secondary goals if we can . \".
In addition, he said it would increase the weight of the shuttle and reduce its payload capacity. At Langley, Mr.
Wingate said he did not think the decision to abandon the team\'s plan was unreasonable.
\"Without money and time constraints, you can sit down and develop something that you will almost certainly succeed,\" he said . \".
But I don\'t think the country is that extravagant.
We need a way back to space as soon as possible.
The debate about the space shuttle\'s solid rocket engine was tested in the medium term for the first design
NASA and Morton Thiokol conducted extensive tests on them in 1970s.
Seven of these tests were \"comprehensive\", which meant that the actual version of the rocket was launched and then double-checked for tens of millions of dollars.
However, officials from the space agency and Thiokol did not have any evidence in the testimony before the commission of the seriousness of the problem, which ultimately doomed the fate of the challenger.
Now, critics say there are only four complete
Scale test, no one will ensure that the sealing problem has been solved. But Dr.
Stever pointed out, \"big, all
He added, \"While we would like to have more tests, it seems at this point in time to go beyond the scope of economics.
NASA itself said
Scale testing is only part of the process.
The agency has developed a complex sub-matrix. scale and full-
Diameter test, lower price.
\'I think that\'s enough,\' he said. Thomas.
Some members of the presidential panel investigating the accident did not agree, saying that the four tests may not reveal potential problems.
Engineers inside and outside NASA are concerned that the agency did not fully replicate the pressure applied to the engine during takeoff, especially from the pillars connected to the external fuel tank and the shuttle itself.
The advertisement \"they have to convince us not only \".
Speaking about the testing process, supervisory committee member Watt said.
\"They have to convince the public this time.
This is not entirely NASA\'s decision.
\"A version of this article appears on page A00001, national edition, September 23, 1986, with the title: NASA pressing the shuttle change in its concerns.
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