Author Topic: Possible ammonia leak inside the ISS - January 14th 2015 (Read 71861 times)

ThereIWas3 · « **Reply #60 on:** 01/14/2015 02:02 pm »

An "instrumentation failure" is still a failure. It isn't supposed to give false alarms.
It will be interesting to see what this turns out to be, so they can prevent it happening again.

asmi · « **Reply #61 on:** 01/14/2015 02:25 pm »

File Photo from NK

Joey S-IVB · « **Reply #62 on:** 01/14/2015 03:03 pm »

Space Station Live, Michael Sufferendi interviewed. He mentions that at 4 a.m. the systems indicated that there were four measurements that were off scale. The time didn't know what the cause was. The cumelator level was the issue. He mentioned the ammonia system as part of the cooling system and heat exchangers that go between the water loop and the heat exchange loop. There was a possible path for the ammonia to leak into the water. If the accumulator was filling up, that would indicate a leak. The team then discussed if it was a real leak or not. They immediately safed the crew and segment.

Joey S-IVB · « **Reply #63 on:** 01/14/2015 03:06 pm »

The crew moved to the Russian segment and then take tests of the atmosphere. Confusing things, included increase cabin pressure, which might indicate an ammonia leak.

They've checked the environment twice, and no leak found. Crew allowed back in the US lab. Pressure went up again, and the crew donned masks and moved back to the Russian segment.

WindnWar · « **Reply #64 on:** 01/14/2015 03:09 pm »

Would like to get the crew back into the US segment by tonight. Looks to be tied to an MDM failure.

Joey S-IVB · « **Reply #65 on:** 01/14/2015 03:10 pm »

Seems to be an electronic card that contains sensors is the problem. They think everything is good. They have the water loop up. Have done data dumps. Powering up systems, external loop B is being integrated, which takes time.

Steps.
1) Powerup
2) Get insight into the accumolator to make sure it is tight to get crew back in the USA segment

Trying to get crew back in the US segment tonight. Crew hanging out in the Russian segment.

Impacts to Science were Micro5 was delayed. Fruit flys were the other experiment that was affected, they needed to be fed, but they will be alright. They didn't lose any research.

JimO · « **Reply #66 on:** 01/14/2015 03:12 pm »

Mike says there's a chip in an MDM that, if failed, could account for the funny readings. The MDM's memory was dumped and is now being checked. Once the MDM is cleared, its power will be recycled to try to get the chip working again. Mike says they want to check accumulator level to verify there is nothing leaking into the water. Only then will they clear the crew to return.

Space Pete · « **Reply #67 on:** 01/14/2015 03:15 pm »

Mike Suffredini:

Ground detected increased pressure in water loop via increased accumulator quantity.

So ground shut down loop B PM, thus requiring equipment powerdowns. Meanwhile crew closed Node 1 Aft hatch and took shelter in RS.

Then detected increased pressure in cabin - believe this could be a result of powerdowns, so not necessarily related to increased pressure in water loop.

Some pressure measurements lost due to some cards inside an MDM going down.

Crew re-entered USOS when cabin pressure begain to lower, however when pressure began to climb again the crew were re-isolated in RS again.

Team does not believe any ammonia leak has occurred.

Now looking to get loop B back up, get internal water loop back up, do MDM data dump and power cycle suspect cards, then re-power equipment and let crew back into USOS - hope to get this done tonight. They want to take a look at the water loop accumulator quantity before letting crew back in, but need MDM to be back up for that.

WindnWar · « **Reply #68 on:** 01/14/2015 03:16 pm »

Pressure build up that was detected they believe may be tied to the shutdown procedures done in that segment, they are looking at the data to understand it. Says everyone performed the steps of the plan very well. Data points to it not likely being an ammonia leak, but rather a faulty sensor or computer.

JimO · « **Reply #69 on:** 01/14/2015 03:23 pm »

In the big picture, here's an interesting take by Susan Helms from ten years ago about how the bipolar design accidentally provided enhanced robustness: http://www.nbcnews.com/id/7763702/#.VLaWi8J0xjo

SkipMorrow · « **Reply #70 on:** 01/14/2015 03:34 pm »

How do they detect an increase in the US side cabin pressure? Would the cabin pressure be the same throughout the ISS, including the Russian side?

robertross · « **Reply #71 on:** 01/14/2015 03:43 pm »

Quote from: SkipMorrow on 01/14/2015 03:34 pm

How do they detect an increase in the US side cabin pressure? Would the cabin pressure be the same throughout the ISS, including the Russian side?

From a Fluid Power standpoint, it would be due to air flow through the cabin.

With an exhaust fan on in a segment, the air passes through the hatch openings from one segment to another. This pressure drop can be read, and it would be highest at the origin, dropping along the way until it is sucked up by an air intake fan.

SkipMorrow · « **Reply #72 on:** 01/14/2015 03:59 pm »

Oh, wow, that seems like the cabin pressure sensors would have to be pretty accurate, but not beyond the realm of possibility.

So, if I am understanding all of this, they noticed a drop in ammonia pressure at the same time as an increase in cabin pressure. And maybe even some fire alarms? That does seem like a lot of simultaneous things using independent sensors, which sure would make me think this was the real deal. Talk about pucker factor...

But if there is a chip on an MDM that feeds all of these, and failure of that chip could lead to such erroneous simultaneous indications, then I can see that.

But still, wow!

Thanks for the great updates on this! I've been following it all morning.

robertross · « **Reply #73 on:** 01/14/2015 04:04 pm »

I wouldn't think there would be a sensor chip on an MDM board, but I could be wrong. It could be integrated together as a functionality card (sensor + MDM) for rack mounting.

MDM is Multiplexer/Demultiplexer, which in essence means it allows a bunch of individual wires (signals) to be combined together to be transmitted in serial format to a computer (usually a certain distance away), to be analyzed. The signal (or other control signals) can then be sent back to the MDM card from the computer to do things like turn off, isolate, go to channel B, ETC.

Jim · « **Reply #74 on:** 01/14/2015 04:22 pm »

Quote from: ThereIWas3 on 01/14/2015 02:02 pm

An "instrumentation failure" is still a failure. It isn't supposed to give false alarms.
It will be interesting to see what this turns out to be, so they can prevent it happening again.

That can't be prevented. instrumentation failure are always going to happen. False positives happen. The evacuation is erring on the safe side.

corgius · « **Reply #75 on:** 01/14/2015 05:25 pm »

NASA International Space Station Program Manager Mike Suffredini explains what happened today inside the ISS

erioladastra · « **Reply #76 on:** 01/14/2015 05:31 pm »

Quote from: SkipMorrow on 01/14/2015 03:34 pm

How do they detect an increase in the US side cabin pressure? Would the cabin pressure be the same throughout the ISS, including the Russian side?

There is a Pressure Control Assmebly that reads the pressure. Sensors also measure the quanity of fluid in the accumlator (reserve tank you can think of) to see if the level is changing. All of these sensors go through analog cards on the MDM

asmi · « **Reply #77 on:** 01/14/2015 05:32 pm »

Quote from: corgius on 01/14/2015 05:25 pm

NASA International Space Station Program Manager Mike Suffredini explains what happened today inside the ISS

Can somebody please provide an executive summary of what he said to those of us at work with youtube banned off?

erioladastra · « **Reply #78 on:** 01/14/2015 05:35 pm »

Quote from: SoulWager on 01/14/2015 12:13 pm

So the suspicion is that ammonia was leaking from the external cooling loop into the internal cooling loop, but there's no evidence of either loop venting into the station's interior? Is the water loop designed to contain the same pressure as the ammonia loop?

No - once ammonia is in the water it starts leaking into the cabin.

Targeteer · « **Reply #79 on:** 01/14/2015 06:09 pm »

Additional alarms have been heard on the loop and CAPCOM explained during the DPC that issues are now occurring with a Node 1 MDM. That issue is being evaluated. The plan and hope is to re-enter the USOS tonight but remaining there overnight is still being assessed. Recovery of loop B cooling will occur tomorrow because a bubble was likely introduced into the system by the shutdown actions today.