Today was a day of setbacks and progress.
Early in the morning the drive train components (belts and pulleys and chains and sprockets) arrived. We decided to go with the chain drive first, just to be on the safe side. Unfortunately, we ended up bending the roller shaft right at the point where it necked down to the 1/4″ portion where the sprocket was attached. When we tried to bend the shaft back, that 1/4″ section snapped clean off. That was a kind of crappy way to start the day off, to be sure. We realized after the fact, that our attempt to keep the boom away from the chain and sprocket had ended-up binding it against one side of the deployer in a way that actually bound up the feed system.
We took a while trying to troubleshoot that and figure out how to proceed. In the end, we realized that if we centered the boom correctly using the front guides, we could probably make the existing design work, if it weren’t broken. So we decided to take two parallel approaches. We realized that we could modify the damaged roller in a way that a long enough 1/4″ hardened steel shoulder bolt could replace the snapped-off 1/4″ aluminum shaft. I headed out at 4pm to see if the local Fastenal had long enough 1/4″ shoulder bolts (they did), and then I took the parts over to S&S Concepts (the guys who cranked out the bracket that supports the nose end of the gear motor so it isn’t cantilevered), and Dennis made all the mods while I watched. It was pretty impressive, he ended up holding a ridiculously tight tolerance. AJ then gave the shoulder bolt some of his Dremel virtuosity, and after another little bit of work, Mike and AJ are out there installing the new “composite roller” into the boom deployer right now. With luck by the time I’m done with this blog post, we’ll have the boom deployer working again.
While we’re waiting here’s some pictures:
We didn’t make any progress on the HMI sheet metal today. Unfortunately there seems to be a dearth of sheet metal supply houses around here. We’re likely going to ping the guys at Kenray tomorrow to see if we can buy some scraps off of them for the HMI sheet metal. Anyone in the Denver area know where a guy can buy some 1/16″ thick sheets of aluminum in some bendable alloy?
Controls and Electronics
So Forrest was still here in the morning when we got in. Overnight, he got enough of the electronics worked out in proto-board form that we were able to control the boom deployer again off of the Wii Nunchuck. Except this time, it was using the electronics on the protoboard instead of a the breadboard and mix of wires and power supplies.
Forrest also got the EA pad electronics prototyped, and did some testing using our own copy of the high voltage electronics. We got the 2nd rev EA pads in today, and Ron Pelrine gave us some pointers on much smaller high voltage resistors which will allow Forrest to package the boom-end electronics a lot more tightly.
Also the new flex cable came in. While the Cicoil stuff was pretty sweet (including the ability to have effectively pneumatic and fluid lines built into the same “ribbon cable” as electrical and digital signal lines), the Parlex ribbon cables we got in today were thinner than the Cordura cloth protective overwrap that came on the BattleMast boom, so we can bond it directly to the exposed strip of composite boom on the inside center of the boom. That way when the boom rolls between the rollers, the compression loads won’t be directly seen by the ribbon cable. We also went out this evening and found some spray adhesive that should work for both polypropylene (the BattleMast’s composite matrix material) and the polyester insulation on the ribbon cable. We’ll probably bond that up tomorrow morning.
While the pads and some of the Gripper hardware is in, windstorms out in Mojave created enough blackouts yesterday that the gripper parts weren’t able to ship till today. We’ll have those all in tomorrow morning, but Ron will be out of town through the end of the week, so we’re going to end up having to do this round of integration on our own. Fortunately he was able to work with Forrest a bit on things, and AJ was here for the last mechanical interface setup…but it’s going to be extra crazy.
While AJ was giving the composite roller hardware some Dremel TLC, Mike, Kirk, and I started doing some practicing for the actual flight experiment. We temporarily took over the vault, and measured out the rough dimensions of our wedge of the Zero-G flight, and practiced standing up without moving our heads very much, getting the experiment setup and run, and getting ready to get back down on the ground all within the timeframe we had available for the flight. These practices will be a lot better once we have the HMI hardware finished, because this boom deployer isn’t light, and is going to be strapped to Mike’s right arm. But we made a lot of headway, and hopefully by the time the flight rolls around, we’ll be ready.
The end result of all of this is that other than the sheet metal pieces we need for the HMI system and the electronics mounting at the end of the boom, we have all the hardware either in-house or coming in to put the boom the rest of the way together. We are getting close to having a drive system working well enough for the boom deployment experiment, and the electronics are coming along. We’ve also started prepping for the flight experiment. We don’t have a ton of time left, but we’re making headway.
Practicing on the ground will definitely help you prepare for the flight. As Richard Carpenter blogged, the main issue will be a lack of familiarity with the new environment and the shift your brain and body go through to get there.
You’ll be down on the mat during the 1.8 G pulls with the boom next to you, not on top of you – remember everything will weigh almost twice as much – so shifting gravities and setting the equipment in the first seconds of microgravity will be critical. The more practice you get with the equipment on the ground, the less you have to think about it in the air.
Once you have the equipment ready to go, I’d strongly suggest repeating the flight simulation with a third person timing your activity. Use conservative times such as 17 – 20 seconds of micro-g and about 43 – 40 seconds of high g.
Can’t wait to see the video!!
Director, Research and Education
The daily posts show an interresting progression…I am hooked and want to see what happens on day 0. Are you going to be able to post a video of the test?
We’ll definitely be posting some flight video when we can.
Getting a little bit nervous reading parts of these last updates ^_^; but you seem to be in pretty good shape for the flight already.
And what Trevian said,
Very cool stuff. It’s a shame however that you won’t be flying out of NASA Ames Research Center. Would have been cool to check out some of your technology!
San Jose International is only about 30min away. We could easily arrange a meetup while we’re in town.