It has been dark, cold and rainy up here on fake Mars for nearly two weeks now. Saturday night we hit energy crisis mode. In general we run off solar power, but with so little sun we have been relying on our back-up systems quite a bit. Our back-up systems are hydrogen fuel cells (which were nearly out of hydrogen, our last shipment had been in January), and a gasoline generator (which we had two jerry cans of gas for at the start of the week, but were down to our last half-can by Saturday).
Our PI’s truck was in the shop all last week, and she couldn’t come to bring us more gas until Monday. Doing some careful calculations, and banking on the weather report being correct for Saturday we expected that we would be able to make it through to Monday morning. We got a bit of solar charging of the batteries on Saturday, but needed a top-up with the generator if we were going to get the base loads through the night. Neil turned on the generator, and it was fine for about an hour. After dinner I checked the charging curve, and the battery SOC was going down and not up. “That is a crazy charging curve. We’re not charging”. I got Zak to look at it too, we went to check the batteries, and sure enough they were discharging instead of charging. We shut down the generator since we were just burning fuel for no reason.
Team meeting – something is wrong with the energy systems, it could be the generator connection, someone would have to go out and check. Neil and Sophie suited up, Zak and I supported from in the Hab and continued trouble-shooting and brainstorming. We contacted STS (second-tier support), to get them involved. Sophie and Neil came back in, not having found anything obviously wrong with the generator.
We had to keep power to our critical systems. Our list of critical systems:
#1 – The Toilets. If we lose power to the toilets, the entire Hab would end up smelling rank.
#2 – The Lab Freezer. If we let the samples in the lab freezer thaw we lose over 4 months of human data (saliva, urine, feces) that have been collected for NASA, Joce, and Neil’s research.
#3 – Communications. We don’t want to lose power to the internet, and therefore FTS (first-tier support).
We had 20% charge left on the batteries, and a generator that seemed to be working fine but not charging the batteries. And the gas that was in the generator plus another 3 gallons.
The generator has a plug on it for a 110 V extension cord, so Sophie and Neil went out on EVA to plug in some extension cords to the generator and run them back to the Hab so that we could bypass the batteries for the critical loads. The toilets themselves use about 500 W of power for the fans and heaters inside them. To get them through the night would have required more energy than we had in the batteries. The lab freezer was also hooked up directly to the generator. The telemetry and communications were left on the batteries, as they only use about 100 W, and the battery charge would be enough. Joce and Allen went around unplugging everything else in the Hab, and then we shut down complete electrical circuits at the breaker, just to make sure there was no more draw on the batteries.
In the meantime, first Zak and I, then Neil and I were trouble shooting the batteries and inverters with our STS contacts. We checked to see if we were getting AC power from the generator – we were, and the voltage was in spec. Next we tried rebooting the inverters, rebooting the batteries, rebooting the controls – nothing worked. After a couple hours, our support knew they would have to come up and continue trouble-shooting the generator in the morning. In the meantime, we were to run down the last of our hydrogen to try keeping the batteries charged, and continue as we were with the essential systems connected to the generator.
We didn’t think we had enough fuel left in the generator to make it through the night, so Sophie and Neil went on one last EVA just after midnight to top up the generator with the very last of our fuel.
Zak, Neil and I woke up early, and the cavalry arrived just after 7am. We switched the critical loads back to the batteries so that if Aleks (our super STS) had to turn off the generator to trouble-shoot or fix anything, we’d retain power to the toilets and freezer. Aleks found an issue with the generator – a fuel line pressing up against a lever that regulates the generator’s frequency and voltage – that was causing the frequency of the generated electricity to be unstable. The inverters would not connect to an unstable energy source, and as a result would not accept the energy to charge the batteries. It was good enough for some fans and heaters and freezers, but not for the batteries. Aleks secured the fuel line out of the way, the batteries started to charge again, and we were back in business. He topped up the generator for us, and another member of STS, Paul, brought us a couple new bottles of H2 for the fuel cells later in the morning (Paul and Aleks built the Hab, and just finished off an electrolyzer so we have a solar-powered source of H2 now).
So Aleks and Paul saved us from imminent smelliness, and I was super proud of the crews resourcefulness in coming up with solutions to keep everything going until help could arrive.
It was cold and dark, but it was also kind of fun to have a real challenge to step up to. In parting, here’s a screen shot of one of the EVA videos from that night. Gives you a sense of the cold dark energy-poor mode we were running in, and also everyone’s sense of humour and good nature through it all.