Ok guys, it’s been a little while since my last update on the blog, so I figured I’d let you all in on how things have been going lately. We’ve had a fairly busy month, and things are likely only going to get more intense, especially since it looks like we’ll be competing in the Lunar Lander Analog Challenge this October, and it looks like we have our work cut out for us.
It took a little while longer than we had hoped to arrive, but we finally got the pieces in to finish up most of the rest of the XA-0.1 structure this last week. We got the pieces to finish the footpads for our landing gear, and after welding them ourselves, we decided to also paint the gear ourselves. The aluminum extrusions for our propellant bay arrived last week, but our supplier had botched part of the order. The cool thing was that they were decent enough to not only send us the correctly cut pieces at no charge, but they even overnighted it at their own expense. Once we got the pieces in, we were able to fit up the propellant bay structure, as well as the avionics bay support structure. During fitup we caught a few minor assembly issues that we were able to find good solutions to, and now the thing looks great (and is sturdy as a rock too).
After getting the propellant tanks hydrotested then LOX cleaned, we insulated the LOX tank, and then fiberglassed over it to make it a little more damage resistant, and put a coat of paint on the glassed tank. Removing the protective covering we put on the tank to keep foam, fiberglass, resin, and paint out is going to be a bit ticklish, but we should have everything in soon to start getting both tanks plumbed out.
Talking About Plumbing…
Especially with a multi-engine vehicle, you quickly learn that most of rocketry is plumbing. We even have some pictures to prove it! One of the big unknowns we had for the XA-0.1 design was how much pressurant this thing was going to take to push the propellant out of the tanks. We did some analysis, but weren’t entirely sure how good our model was, so we decided to do a quick experiment, so we grabbed some spare hoses and valves, and pieced together a blowdown test rig to see how thirsty our tankage really is for pressurant.
The interesting thing was how close Pierce’s model was to the actual figure we got after munging the data. It’s nice being able to do experiments like that along the way to check your assumptions. We’ll probably want to repeat the experiment once our real regulators get in. They’re a bit more manly than the wimpy, so-called “high-flow” ones we were using for the test.
In the next week or two, we should have the majority of our plumbing in-house, and then installed, including the valves and regulators and pressurant tanks. It’ll definitely be interesting to see what our vehicle looks like once all the valves, regulators, pressurant tanks, and plumbing runs are installed. I wouldn’t be surprised if the thing ends up looking something like a flying Praxair truck with legs.
In contrast to our experience with how well our structures supplier did with making things right when they screwed up, we’ve been having a bit of a headache with getting reliable machine shops for our engines. Down the road, we’re likely going to insource a lot of this work, particularly once we have some better machining equipment, but for now, we’re mostly stuck farming the complicated stuff out. The good news is it looks like by the next update I should have some pictures of our first fully regen cooled engine attempt for the blog.
While we’ve been waiting for that to come in, we’ve taken advantage of the opportunity to do more testing on the 2nd generation engine. We’re only up to something like 70 firings on this generation of the engine (we’ve had 72 firings counting the two firings we had on the first generation of the engine). We’re getting more experience and intution with using the throttle valves that we recently installed. We think we’ve figured out which part of our system it was that was giving us goofy performance data, and we should have that fixed and ready to test again by early next week.
We’ve been doing some of the design work on the vernier engine modules for the actual vehicle, and will probably be having a sample of them made in the near future to verify that the fit-up actually works. The engine work is probably going to be our gating item for flying XA-0.1, but we’re getting closer. I’ll see if I can post some pictures of our engine setups once we have them mounted.
Pierce and Ian are getting really close to wrapping up their TVC system designs, and we’ll likely be having the battle of the gimbals early next month. Both are amazingly fast, it’ll just be a question of which can work more precisely and reliably. I’ll have to see if I can post a movie or something if we can get the two going back to back.
Lunar Lander Analog Challenge
Now that we have access to the rules from the Centennial Challenges office and the X-Prize Foundation, we’re starting to try and figure out how we want to approach this prize. Dave told me tonight that he was putting together a few thoughts about it, so I’ll let him blog about it when he gets the chance. I may also write a few of my own feelings about the incentives this prize creates over on my own blog.
With that said, I think that’s all we have at the moment regarding the XA-0.1 vehicle project, but hopefully we’ll have some more interesting developments to talk about soon.