Former House Commute Program Supervisor Wayne Hale has posted a correction to NASA’s historical past of STS-109, which he claims “is a lie” – even if that can be a slight exaggeration.
STS-109, introduced in 2002, used to be the final undertaking of Columbia sooner than the STS-107 crisis. Throughout the undertaking, the group carried out a chain of 5 spacewalks to provider the Hubble House Telescope.
It used to be an enormous good fortune. Hubble won new sun arrays and a substitute for the unique energy keep an eye on unit, amongst different upgrades. Alternatively, it’s the ultimate paragraph of the historical past with which Hale took factor.
NASA’s abstract reads: “After a a success release, flight controllers in Undertaking Regulate spotted a degraded drift fee in one among two Freon cooling loops that lend a hand to burn up warmth from the orbiter. After reviewing the loop’s efficiency, undertaking managers gave the group a ‘move’ to continue with customary operations. The issue had no have an effect on on any of the group’s actions. Each cooling loops carried out most often on de-orbit and touchdown.”
In keeping with Hale, it wasn’t fairly so simple as that. The House Commute had two Freon Coolant Loops (FCLs). Those have been vital items of apparatus liable for cooling the orbiter’s electronics. Dropping one will require touchdown the orbiter on the subsequent to be had alternative. Dropping two would cause a complete emergency since temperatures would breach the specification operational limits of the Gasoline Cells after 50 mins, and conserving the gasoline cells going after 75 mins can be “questionable.”
The House Commute will depend on electrical energy. No gasoline cells, no electrical energy.
Throughout this system, the House Commute by no means misplaced each FCLs. Had it completed so, the group would have needed to energy down a lot of {the electrical} apparatus at the orbiter sooner than carrying out an emergency touchdown. “The tick list used to be extraordinarily complicated, time eating, and – worst of all – makes an attempt to validate it have been unsuccessful,” Hale mentioned.
As such, the likelihood of dropping each car and group used to be prime.
Sooner than the orbiter used to be given a “opt for orbit ops” (after the payload doorways have been opened and Freon loop cooling throughout the radiator used to be established, however sooner than the group may get out in their release/access drive fits and turn on the bathroom), the EECOM (Environmental Electric, Consumables Supervisor) spoke up.
“The flowmeter in Freon Coolant Loop #1 used to be appearing a drift of most effective 200 lbs/hour.”
In keeping with the Flight Regulations, failure used to be the rest lower than 211 lbs/hour. Subsequently, the loop must be regarded as failed, and the House Commute must go back to Earth.
In addition to a First Day PLS (Deliberate Touchdown) at Edwards Air Pressure Base, which required the whole thing to be in position for a retrofire in roughly 90 mins, the principles supposed the group must additionally get cracking at the procedures for dropping one FCL, and turn off a lot of the House Commute’s redundant electric apparatus. That, in fact, would depart the car open to different dangers.
So what to do? Generally, the Undertaking Control Crew (MMT) can be consulted because the MMT used to be the one part in a position to authorize a metamorphosis to the Flight Regulations. However the MMT used to be now not there. With the release whole, a minimum of so far as Primary Engine Reduce Off (MECO), the MMT had departed for flights again to their more than a few NASA facilities and may now not be simply contacted.
The staff regarded as the issue. The group used to be prompt to check the procedures however now not do the rest but. The query used to be a easy one – had it failed or now not? If the great FCL additionally failed, would the “failed” FCL supply sufficient cooling to steer clear of the scary two-FCL failure state of affairs?
After all, the NASA staff made up our minds to proceed with the undertaking. The MMT used to be steered and an terrible lot of engineering research came about.
Hale noticed: “FCL #1 by no means regained complete drift right through flight. Such a lot for ‘Each cooling loops carried out most often on de-orbit and touchdown.'”
That mentioned, the Flight Regulations have been revised after the undertaking. After the engineering research have been finished and reviewed, the brand new failure restrict used to be diminished to 163 lbs/hour. A lot later, the principles have been modified to require the MMT to stick on station till after the “opt for orbit ops” used to be given.
Alternatively, there is not any getting round the truth that even if the verdict became out to be proper, a Flight Rule used to be damaged by means of people.
In keeping with Hale, John Shannon used to be the Ascent Flight Director for the undertaking. Hale quoted a up to date remark from Shannon: “This may be a excellent case for why you will have a flight keep an eye on staff as a substitute of simply programming the flight laws into a pc.
“Human judgment and possibility trades are vital to spaceflight operations.” ®
