Lunar Moths and Hydrogen

Space, Space Programs, Manned and Unmanned Missions
Joined: 09 Aug 2013, 03:20

26 Jul 2016, 21:20 #1

Craig was an old school engineer. He was literally the kid with the chemistry set who blew up his parents garage. His search for knowledge was endless and constant. Accordingly, he never turned aside a serious question without a serious answer. I wanted to learn as much as possible about everything I could when I went to work for a contractor who worked for NASA. Craig was my first mentor and one that I never tired of talking to. 

Craig had so many personalilty quirks that he didn't really fit in with any group. He made up for this with an aptitude for work that was second to none. No job that Craig ever worked on was ever completed because he would endlessly improve every process. This necessarily drove his bosses to distraction as schedules meant absolutely nothing to him. He would tinker with things endlessly, always making improvements but at the same time always killing schedules. 

I saw him take some of the worst tongue lashings from our chief engineer imaginable. He would peel the paint off the wall with the scoldings he gave Craig about schedules. Craig would squint through his thick glasses and smile the whole time, no matter how personal or hot the scolding. This would only make those above him even madder and I saw several of them leave the room sputtering nonsense at the end of one of these sessions during my time working with Craig. He never seemed even mildly perturbed by such things. It was all about improving the end product in his mind and he knew he was the best at doing that. 

His knowledgebase was so wide and so well respected that they couldn't fire him. I never asked him a question about anything that I didn't get a detailed answer. Sometimes, he would tell me he needed to do some research before answering me but a day later, sometimes two days later; he would find me with five or six pages of handwritten notes. These notes would have diagrams and math formulas with his weird sense of humor embedded throughout. He liked to write things out in old english as in "Ye olde pythagorean theorem here meets with thou chart of the elements". 

He loved learning. It was his reason for existence. Every day was simply another exploration of something he didn't know but wanted to. He didn't have a family at home, but instead several cats that he had found as strays. He worked after hours at a local private school where he was kind of the janitor/maintenance man and all around free tutor on a variety of subjects. 

One of the first times I rode in his vehicle, a 1975 Toyota truck, he drove me nearly to distraction by talking the whole time while he looked at me. He also geared down for stop signs and traffic lights at least a mile ahead so that we coasted up to them. When we got to the building we were going to, he slowed to a crawl in the parking lot and finally coasted into the concrete curb hard enough to almost throw me against the dashboard. When I asked him what he was doing he explained that he was preserving his brakes. The truck was 11 years old at the time and still had to original brake pads on it. He told me that he had a 1970 Dodge Charger that still had the original brake pads on it as well. It was a challenge to Craig to never have to use the brakes. 

more later.....
Last edited by blackirishkarma on 27 Jul 2016, 00:55, edited 2 times in total.
The increase of misery in the present state of society is parallel and equal to the increase of wealth..... Unknown member of Parliament 1840's

Joined: 09 Aug 2013, 03:20

27 Jul 2016, 00:52 #2

Some years into my employment at NASA we were building some new capability in GH2 (gaseous hydrogen) testing. When I was hired we had a set of 10,000 PSIG pumps and a pipeline for sending the gas to the test area a mile down the road. Hydrogen is such a small particle that it is difficult to contain in it gaseous form so 10,000 PSIG of it is something to be deeply respected. It is also flammable in the extreme, the flammability range for Hydrogen is 4-76%. In other words, anywhere between those two ratios it is flammable. 

A good comparison would be to Natural Gas which is mostly Methane. Natural Gas has a flammability range of 4-15%. It won't burn in air below that ratio and it won't burn above it. As you can see, Hydrogen has a vastly wider range of flammability so it is very, very easy to get an ignitable mixture if you release some in the atmosphere through a leak on the system. 

We were in the process of upgrading our system to a 16,500 PSIG upper limit. This required new pumps, new pipelines, and new storage vessels. NASA had some new vehicle designs that would require testing at this higher limit so we were charged with installing a pumping system to accomplish this goal. As I was to learn over and over, a lot of commercial vendors will oversell their capabilities when it comes to dealing with a government agency such as NASA. Since no one was using hydrogen at these pressures they weren't really in the business of making pumps for these pressures but since NASA was willing to pay for someone that would we got bids from several vendors. 

As in a lot of bid processes the people who know the most about what they are bidding on are seldom the low bidder for the simple reason that they also know the most about the difficulties involved in new development projects. I won't name companies by name but the low bid we got was from a company that didn't have the best of reputations for liquid cryogen pumping systems. Craig suggested to NASA that we might want to do some feasibility studies before accepting bids but they were in a hurry to get going and the company won the bid even though we had a lot of reservations about their ability to produce a pump capable of reaching this pressure. 

As it turned out, Craig was right. When the pumps showed up we couldn't acheive 8,000 PSIG with the pumps. We had piston failures, seal failures, and bearing failures before we even got halfway to the specified pressure. To be fair, pumping liquid hydrogen is not an easy thing to do at any pressure. At -420 Degrees F it is very hard on materials that it comes into contact with. Add in the complexity of pumping something with such a small particle size and it gets even worse. We had quite of bit of experience at high pressure pumping of cryogens of several different types but Hydrogen always gave us the most trouble as well. 

The most efficient way to pump gaseous systems is to pump them in their liquid state and then convert them to a gas. That way, you get the advantage that is gained in volume during the phase change from liquid to gas. Hydrogen increases in volume 851-1 when you go through this phase change so a small liquid pump can create a huge amount of gas pressure with the proper heat exchanger equipment on the other end of it. In our system we used a steam heat exchanger which was essentially a tube bundle flowing liquid hydrogen through it at high pressure that was surrounded by a stainless steel jacket filled with steam. We controlled temperature on the outlet of the heat exchanger by oversizing the steam supply and using a small liquid hydrogen bypass. By adjusting the flow of liquid hydrogen bypassing the heat exchanger at -420 we could then mix it with the hot gas exposed to the steam to acheive 70-80 degrees F flowing into the pipeline. 

This is a fairly critical step because the pipeline itself was rated for pressure at this temperature. If the temperature got too high the pipline would rupture and if it got too cold the pipeline would rupture. Rupturing pipelines with 16,500 PSIG of pressure on them was not something to be encouraged, more especially when you would then release pure hydrogen at a rate guaranteed to autoignite from the friction. 

The manufacturer sent their representative to watch the test process but they really didn't have a clue as to how to fix the pumps since they were failing so low on the pressure range. They were late in their original delivery of the pumps which put the test program we needed the pumps for in jeopardy. NASA decided to accept the pumps as is and to use their own expertise (our group) to fix the problem. I was to see this type of solution in several problems we encountered during my employment with this group. NASA's budgets are renewable every year so failures in programs often lead to cancellation of programs. They are notoriously sensitive to failure accordingly. 

We soon had the pumps taken apart and were studying material property conditions as well as machining tolerances and clearances. It turned out that all three had issues. The materials used were wrong, the tolerances were wrong, and the seal materials were not the right kind. We started making new parts in our machine shop and generally redesigning the pumps on the fly. Craig was in charge of the process and he was being his usual meticulous self. This meant the progress was slow but steady as we often got sidetracked into issues that might improve efficiency 1% while running up costs 25%. Craig never really paid any attention to this type of ratio. 

My boss at the time, had put me on the project to sort of keep Craig going in the right direction and minimize these sidetrack issues. It wasn't really that hard to do as Craig and I had a good working relationship by then and he wasn't interested in schedules or budgets to start with. Whenever we ran into one of these issues I would just casually remind him that schedule mattered and we were high profile at the moment. 

We made steady improvement and soon had the pumps up to the specified pressure after we redesigned and rebuilt them. We were having some trouble with wear and longevity however as they had a short life cycle before the seals wore enough to start leaking. The leaks were internal and would simply make the pressure quit climbing as a cylinder effectively leaked back into the supply side every stroke. 

Over a period of about three months we worked a lot of sixteen and seventeen hour days on this project. We were past the initial pucker factor when everyone was on pins and needles that something would rupture under the higher pressure and had a good system of testing changes that was showing steady improvement results but it did make for some long nights.

The hydrogen pumping facility was some distance removed from every other building or facility for the simple reason that if something went catostrophically wrong it would level a good size area. It was back in a pine thicket at the edge of where Marshall Space Flight center joined the Wheeler Wildlife Refuge. If was fenced in with an 8 foot chain link fence with barbed wire on top to keep people and large animals out. We routinely saw raccoon, oppossum, skunks, and groundhogs on the pad itself and occasionally a deer would somehow get inside the fence as well. 

On this particular night we had already had a whole family of skunks come through while we were testing. They just wandered up and ransacked a garbage can on the edge of the pump pad while we watched, never paying any attention to all the noise from the pump running. It was getting very late, probably around 2 in the morning and we had been at it since 7 the previous morning so everybody was a little loopy and tired. 

We had made an adjustment to the seat pressure just before 11 and were in the process of running at full pressure when I noticed Craig off to the side of the pad jumping up and down and waving his arms. Normally, this would have been a reason to panic but he was facing away from the pad while he did it so I couldn't really figure out what he was doing. I pointed to Craig and the head mechanic just shook his head and laughed like it was just another Craig thing and he didn't have a clue what it meant. 

more later....
The increase of misery in the present state of society is parallel and equal to the increase of wealth..... Unknown member of Parliament 1840's

Joined: 09 Aug 2013, 03:20

27 Jul 2016, 14:48 #3

I walked over to Craig to see what was going on. 

"Help me," he said, "if it gets in here it will die."

I looked to see what it was. It took my eyes a second to adjust to the darkness after the lights of the pad but I soon saw what "it" was. It was a large lunar moth, the brilliant green colored type and "it" was what Craig was gesturing wildly to chase away. I started waving my arms and helping him chase it away from the pad as it seemed terribly important to him at the time to get the moth away from our the pad where we were doing our testing. 

After a few minutes we succeeded in chasing it completely out of the fenced in area where it calmly sailed away off into the pine thicket behind the pad. As we watched it flutter harmlessly off into the night, Craig let out a sigh of relief. 

"That was close," he said, as if I had a clue what he was talking about. 

"What was that all about?" I asked, curious to know why we were making fools out of ourselves chasing a moth off into the trees. 

"Oh.... well... they navigate by starlight" Craig started explaining. "That's how a lunar moth finds its way back home. If they get too close to artificial light it overrides their ability to navigate and they will literally kill themselves fluttering around and into the light because they no longer have any sense of direction."

I had seen moths flying around and around lights at night for my whole life. It had never occurred to me to question why they did it. I just assumed they somehow liked the light. When I started thinking about it, I remembered how frantic they always looked while it was going on and I realized it made perfect sense. I have since read that there is a lot of disagreement as to how this works exactly but most scientists agree that artificial light throws off their ability to navigate. 

After thinking about it for a while I realized I had experienced that phenomena on a couple of different levels at different periods of my life. Not necessarily losing my sense of direction but having one object so bright come into view that a more constant and less overwhelming source of direction became completely overwhelmed. It's a nice metaphor for that feeling of wearing yourself out while going in circles when it occurs. It isn't necessarily because we like the light. Sometimes it simply overwhelms our ability to find our way. 
The increase of misery in the present state of society is parallel and equal to the increase of wealth..... Unknown member of Parliament 1840's