NASA Considers Shuttle Launch "As Is"

Sensor Malfunction Cause Still Unknown; Earliest Next Launch Would Be Saturday

(CBS)  NASA is considering launching Atlantis despite an unsolved circuitry problem, using manual procedures to monitor the malfunctioning fuel tank sensors during ascent to prevent any potentially catastrophic problems, reports CBS News space consultant Bill Harwood.

That problem forced a delay of the space shuttle's launch on a space station assembly mission until Saturday at the earliest.

If those sensors fail to detect when the external fuel tank is empty, the engines could continue to run dry, and explode.

Based on electrical data seen during fueling Thursday, engineers believe the problem involves an open circuit in the wiring between an electronic box in the shuttle's engine compartment and the sensors at the base of the hydrogen section of the external tank. Given the shuttle's short eight-day launch window, NASA managers Thursday ruled out opening up the engine compartment to attempt any inspections of repairs.

LeRoy Cain, chairman of NASA'S Mission Management Team at the Kennedy Space Center, told reporters late Thursday engineers will meet again Friday to reconsider their options, adding they may not get comfortable with a fly-as-is rationale in time for a Saturday launch.

In the meantime, NASA managers ruled out a fueling test Friday and decided instead to top off the shuttle's onboard supply of liquid hydrogen to power the ship's electricity producing fuel cells. That would permit launch attempts Saturday and Sunday and still provide enough on-board supplies for a two-day mission extension and the addition of a fourth spacewalk.

Three spacewalks are required to connect the European Columbus research lab to the station; to replace a nitrogen coolant system pressurization tank; to install a pair of experiments on the Columbus module; and to move a failed space station gyroscope to the shuttle for return to Earth.

NASA managers want to add a fourth spacewalk if possible to permit a detailed inspection of a stalled solar array rotary joint to help engineers figure out what sort of repairs might be needed to get the joint turning smoothly again. But an additional spacewalk would require a two-day mission extension and that, in turn, is based on how much hydrogen and oxygen is available to power the ship's fuel cells.

A launch on Saturday, assuming the engine cutoff sensor problem can be resolved, would be targeted for 3:43:31 p.m., setting up a docking with the international space station around 12:56 p.m. Monday. The forecast for Saturday calls for a 60 percent chance of good weather, improving to 70 percent "go" on Sunday.

Atlantis' launch window closes Dec. 13 because of power and temperature issues related to the space station's orbit. The window reopens Dec. 30, but senior NASA managers have said launch would be delayed to at least Jan. 2 if the shuttle team misses the current window.

NASA managers had high hopes for a launching Thursday, with a forecast calling for a 90 percent chance of good weather and no technical problems of any significance at pad 39A. After a short 13-minute Mission Management Team meeting, engineers were cleared to begin loading a half-million gallons of super cold liquid oxygen and hydrogen rocket fuel into Atlantis' external tank at 7:06 a.m. A few minutes later, the engine cutoff - ECO - sensors at the base of the tank were covered with supercold propellant.

The ECO sensors are part of a backup system that ensures the shuttle's three main engines don't drain the tank in the event of other problems during the climb to space that might prevent an on-time shutdown.

The ECO sensors can indicate two possible states: wet or dry. If the sensors falsely indicated they are submerged in fuel when, in fact, the tank is dry, the engines could run out of propellant while operating at flight pressures, speeds and temperatures, suffering catastrophic failures.

Based on the logic used in the computer software that monitors the sensors during ascent, two "failed wet" sensors would have no impact. But a third sensor failing wet could trigger a premature engine shutdown to protect against the possibility of the remaining sensor failing in the dry state. Launching with two sensors in the failed wet state would leave no redundancy in the system.

Propellants flow into the tank from the bottom and shortly after the four engine cutoff sensors at the base of the hydrogen section were submerged Thursday, commands were sent to simulate dry conditions to make sure the circuitry responded properly. Voltage readings from two of the sensors immediately indicated a dry state while sensors 3 and 4 showed voltages higher than 13.5 volts, an indication of an open circuit. The readings occurred simultaneously.

"What's currently in the plan is that we'll try to put together an operational workaround plan that we can get comfortable with that will allow us to go fly on Saturday," Cain said. "And it would be with the intent of flying with one or more failures potentially in the system when we go tank up again."

A premature engine shutdown could result in a trans-Atlantic landing. An emergency landing in Spain or France would cause major disruption to the space station assembly schedule and NASA's plans to complete the outpost and retire the shuttle by 2010.

Engineers say the odds of a premature engine shutdown in this case are acceptably remote because multiple failures would be required - ECO sensor failures as well as a leak or problems elsewhere in the system that would cause the shuttle to use up its hydrogen fuel at a higher-than-expected rate.

But not everyone agrees. Some engineers favor rolling Atlantis back to the Vehicle Assembly Building for repairs. NASA Administrator Mike Griffin participated in Thursday's Mission Management Team meeting and presumably will weigh in on how the agency proceeds this weekend.

[goldesprit]

Read "Riding Rockets" by Astronaut Mike Mulaine.

He gives an excellent wrenching account of what its like to sit on one of these shuttles on the pad, and then ride it into space. Not sugar coated.

Not for the timid.

[hissteps4u]

Leroy Cain is a Jerk to even say that. He needs to be Fired tomorrow for his comments. He would cause your child or mine needlessly to be placed in harms way for nothing and that is not right.

this is why NASA does not Have the Confidence of America and why we need to overhaul the dead weight and get some real scientists who actually give a sh-t to run NASA. this GUY is a dweeb and I can not believe he would make such a statement.

[alphaa10-2009]

downtowner97 said, "The Mars Rovers ... have outlasted their expected lives, and actually do and see something new every day... they''''re frankly more interesting than the shuttle and space station program."
---
Thank you for the interesting comments. On human vs. machine probes of space, I suspect when it becomes painfully obvious a human cargo is an insufferable burden to mission design, someone at NASA quietly will move the grandstands to a pasture somewhere, decommission most (not all) of the spacesuits, and let machines come into their own.

Machine intelligence and vision have been a long time coming, but follow the same script as the original uneasy drama between NASA astronauts and the machine which put them into orbit. As Mercury, Gemini and Apollo programs matured, each assigned machines much more of the burden of spacecraft management.

Media overplay the astronauts, and often underplay the machine missions, but considering what has been accomplished in defining our solar system and galaxy, the machines win-- probes down.

NASA always has been invaded by politics, and some suspect our shuttle losses were, at least in part, due to some impatient presidents who wanted a public fireworks display. And, of course, Apollo 13 convinced many only a human crew could save a mission. But in the main, the days of astronauts are nearing an end.

[alphaa10-2009]

rushman71 aaid, "I''''ll repeat what Demslie said,"No matter what the story, there are angry democrats screaming about something."
---
Demslie should acknowledge his own screaming. If Demslie complains about the complaints, that is not a complaint?

Those affiliating themselves with the GOP should consider carefully the mounting criticisms of Bush and his policies that seem to be everywhere.

Such criticisms are more than material for a Bush-era post-mortema-- they indict Bush for not only his incompetence and vain, destructive ambition, but extreme abuse of the political process.

[downtowner97]

The sense of apathy toward the space program is not because of peoples'' laziness, political affiliation or scientific illiteracy as Jackie states. The apathy toward the space program comes from the fact that the space program is incredibly boring.

It costs $1.5 billion to send astronauts to literally go around in circles! NASA has a dedicated TV channel, and if you''ve ever seen it, it''s the best cure for insomnia going. The people at mission control sound like they''re describing the process for cleaning a clogged drain.

The Mars Rovers have gone to Mars and send back countless pictures, have outlasted their expected lives, and actually do and see something new every day. They cost $450 million to build and launch. They don''t develop greasy hair, grin and wave at cameras, or poo into a vacuum cleaner, but they''re frankly more interesting than the shuttle and space station program.

[downtowner97]

The Alpha Magnetic Spectrometer was built at a cost of $1.5 billion and is widely hailed by scientists as the most important piece of scientific equipment ever built for the International Space Station, and it''s not going to be launched. If it was launched and antimatter was discovered, it would further call into question the creation myth. The much less controversial Columbus module will be launched instead.

[downtowner97]

There have been 121 space shuttle launches in the past. Two have killed everyone on board. That''s a 1 in 60.5 chance of being killed. The Russian launch vehicles that have been used since the Space Shuttle came into service in 1981 have had 58 missions with no crew killed.

The cost of a single space shuttle launch taking into consideration the cost to build the shuttle and launch facilities, and the expected end of the program in 2010 is $1.5 billion. The cost of a Soyuz launch including construction and facility costs is $50 million, or 1/30 the cost of a shuttle launch.

The problem of debris shedding from the main fuel tank of the shuttle has NOT been resolved, so it''s more a matter of blind luck if there is no damage to the landing vehicle. The Soyuz does not have this problem and is therefore much less likely to kill astronauts in the future.

Soyuz is much simpler, and can be launched with far less preparation than a shuttle. The Russians think nothing of selling extra seats to offset launch costs.

Very few new discoveries are coming from the space station since the Soviets logged so much time in orbit already.

[fitedafuture]

so basically NASA considers all their astronauts expendable?...NASA should stand for Not Another Seven Astronauts.!!.

[denn034]

If it''s serviceable, then, why not? Go for it, NASA!

[tburzio]

The space station is a make-work program for Russian scientists so that they won''t make a bomb for Al Queida. Not a bad return, considering the alternative. Who knows, we may even learn something in the bargain.