Chapter 24

“So how long have you been working on spacecraft?” Chuck asked.

Jose, ‘Call me Joe’, was showing Chuck around the craft he and Morty had been working on. “Seems like all my life,” he said. I started out working on Apollo 13, switched to the Shuttle program after Apollo ended, and after that I started a consulting company. I was working on reusable civilian orbital vehicles and thinking about retirement when Lina’s father contacted me, but when he mentioned you folks were developing an all-electric drive I got interested. A lot of people have been working on that concept, but they’re not getting much thrust. When Frenchy told me you had a craft that was already flying, that hooked me.” Joe pointed to the ship and continued. “What we’re doing here, as far as the frame and exterior hull is concerned, is basically what we did when we built the first shuttle, but we don’t have to deal with rocket engines, fuel tanks, or the plumbing and pumps that go with them. This bird looks like the shuttle to some extent, but it’s not nearly as complicated.

“The big challenge was figuring out where we’d store the hydrogen and extra oxygen. The fuel cells use both, so taking this ship beyond the atmosphere means we have to carry separate fuel and oxidizer systems for the cells. You don’t want to run into a situation where you have to choose whether to breathe or use the oxy to power the fuel cells! That’s where the solar panels come in.” Joe pointed to the fuselage. “Those are high-efficiency thin-film multiple-wavelength photovoltaic units, mounted over a metal substrate that makes it easy to install them, and protected on top by thin glass panels. They cover most of the body and the wings, top and bottom, so whichever way we’re oriented or the source of the EMR, some of the PV cells will be working. They can’t provide enough takeoff power for the impellers to overcome the Earth’s gravity, but they’ll work fine in space.

“Based on the efficiency figures Morty gave me, they’ll generate enough power to provide constant acceleration at a tenth of a gee. That will drop off after we get farther out, close to Mars for example, so this ship may never go beyond the Moon. We may decide after we get into space to run the fuel cells at reduced output anyway, just to keep the ship warm. Come on inside and let me show you what we’ve got.”

“So you’ve designed a hybrid,” Chuck asked, “a ship that uses fuel cells to keep the batteries charged during takeoff, PV cells after that for sustained power?”

“Well, it was Morty and me that designed it,” Joe admitted, “but you’ve got the idea. Lina also did a lot of the work, mostly on the interior layout but also when we were designing the fuel tanks for the wings. As you know, Morty wanted to use nuclear reactors but we couldn’t get them. Using fuel cells is an interim step, enough to get us to space and as far as Mars, because we also can’t carry enough fuel and oxy for extended trips. We need the fuel cells for landing and takeoff power, but also in case there’s a need for emergency maneuvering. I got to be an old pilot by not being a bold one! A tenth of a gee max on PV cells is better than nothing, and at constant acceleration the ship’s velocity builds to something respectable, but I’ll sleep better knowing that I can call on ten gees if necessary.

“There’s still a lot of work to be done before we try to build a real interplanetary ship, but we’ve got to take this one into space and make a few mistakes to see what we’re doing wrong. The suits that Frenchy got us will work for extra-vehicular activity, but we want the interior to be a shirt-sleeve environment. People can’t be expected to live in spacesuits for a week. The crew will also need room to move around, and more privacy than they get in the space station. If you’re going to take ordinary people into space, you need to engineer the space around them so it’s as much like their home environment as possible. That’s where the big interplanetary ship comes in, and that’s when we’ll need the nuke reactors. With that much power available, you can accelerate continuously at one gee, only going weightless during turnover. We may never need o turn the ship, at least I don’t think we will; we’ll just reverse the impellers, so that instead of pushing forward to accelerate have them push backwards to slow the ship down. I’m still thinking about that. It might be cheaper to flip the ship and switch the cameras so they point backwards in the direction the ship is going. If you feed that view to the screens over the pilot’s seat, it will look like that’s the direction you’re going.”

“Seems strange!”

“You’ll get used to it, controlling a spacecraft using display screens, and you’ll have to. I did, you can too, because the old Mark One Eyeball is the next thing to useless in space! Anyway, we finished installing the hatch that Morty was working on while you were gone. The hull exterior is complete, and I finished the twenty-four hour pressure test half an hour before you got back from the ranch. The ship’s holding pressure, although we detected a slight drop in the central section during the test. That may have to do with the seals, not quite in their final position, or maybe it was because I used three atmospheres of interior pressure for the test. That gave me a differential between the ship and the outside of two atmospheres. In space, it will be only seventy percent of one atmosphere inside the ship, zero outside, so the seals may hold. Meaning that in space, we might not have any leaks at all, but we’ll be taking extra oxygen anyway just in case. There are scrubbers in the crew section up front to remove carbon dioxide before it can build up to dangerous levels, so all in all, I don’t expect any problems with the ship’s internal atmosphere. If I’m wrong, we’ll just have to wear the suits and hook up to the ship’s oxy and electrical systems until we’re back on the ground.

“The front compartment didn’t show any leaks, neither did the aft power section, but the cargo section amidships has that big loading hatch. If there really are seal problems, that’s where they’ll be. Easy solution, depressurize the cargo bay unless we’re stowing and securing cargo or removing the straps before we offload a shipment to space. Depending on the cargo, we may need to work in that section and it’s a lot easier if you don’t have to wear the suits. The aft section is where the fuel cells are. The hydrogen is in tanks in the starboard wing, dissolved in ammonia. We extract the H2 and pipe it to the fuel cells. They pull their oxy out of the aft section’s internal atmosphere, so we’ll need to keep that section fully pressurized. I won’t be using pure oxy back there because of the danger, probably a mix of 50% nitrogen and oxy.”

“Sounds good. Let’s take a look at that aft section.”

“This way. It’s not quite finished yet, the cells are in and connected but the radiator piping isn’t. We went with molten carbonate fuel cells, MCFC, expensive in a sense because we’ve got to install the plumbing to dump the waste heat the cells generate. I hate that idea, wasting heat, so I intend to eventually pump it through a Stirling cycle engine/generator. It increases the efficiency of the MCFC units.”

“So the cells generate too much heat? Is that why you put them in the aft section?”

“It’s easier to deal with the heat problem that way, yes. The ship’s frame is titanium and so is the skin in the engine section, so heat isn’t a serious problem. There’s a divider with separate fans in the heat exchange system. One channel of the ‘Y’ fitting leads to the cabin radiators, the other goes to a system of external radiators. They’re the things that look like fins, running the length of the fuselage on both sides. I’ll test the complete system on the ground, first inside the building, then during local flights that don’t go past the stratosphere. We might have to tweak the handling characteristics, and the local trips will tell us how much we still have to do.”

“Sounds good. Grandpa was always concerned with safety, so taking it one step at a time makes sense to me. How close are we to flying this bird?”

“A week, ten days at most before first lift off the cradle. The pilot and copilot stations are in and checked, but we still have to install cabinets for storage of crew equipment and we haven’t built them yet. Passenger seats, too; based on Morty’s figures, this ship is overpowered, so we need good seats for the rest of the crew. I doubt I’ll accelerate this one past four gees, but unless people are trained to deal with it, four gees can cause blackouts. I’d really prefer to never go beyond two gees, four in an emergency, ten as never-exceed.”

“How much power will the fuel cells put out?”

“They’re designed for a sustained maximum of a megawatt. You could draw more than that, maybe an additional quarter megawatt for a short time, but that consumes more hydrogen and generates a lot more heat that has to be dumped somehow. I won’t go past the design maximum unless there’s an emergency.”