After consideration … looking at the prices and weights of assorted 12V lead-acid batteries, thinking about what I’ve got, what I can do … I’ve scratched the so-called “mid-range” power supply from my plans. Yeah, the high-power supply is heavier, but … it’s here. And it multi-tasks. I just can’t see spending any more in that department.
So, I’ve fractionally come to my senses.
My launch systems basically revolve around three power supplies:
4 AA or 1 9V in the small, light-duty launch systems, suitable for light duty, single engine flights.
The Black & Decker Jumpstart 450, for extended flight days with many, many launches.
… and a third, lighter than the Jumpstart but stronger than the pocket batteries, suitable for medium flight days or multiple-engine launches.
My crazed scheme to turn two salvaged Power Wheels batteries into the third power supply has come to naught: once I finally got around to recharging them, they barely can push 3V each. The amperage might be good enough, but that’s just not enough voltage to give me good confidence.
And of course, I learned this AFTER I’d bought the supplies to adapt the Power Wheels external wiring for my nefarious purposes.
Plan B looks to be buying a 12V motorcycle battery. The fitting to adapt it to the mid/heavy-duty launch system is easily obtained (and much simpler than my planned Power Wheels system). And it would recharge from the Jumpstart.
The last piece of the launch system puzzle is a sturdier, more versatile launch pad. AKA the AeroTech Mantis, $80. (And yes, that means I did order my Pratt GO Box launcher yesterday.)
Hallmark Movie Channel is airing one of my favorites this weekend: A “Hallmark Hall of Fame” production of Agatha Christie’s “Witness for the Prosecution.” It stars Sir Ralph Richardson, Deborah Kerr, Beau Bridges, Donald Pleasance, Michael Gough, and Diana Rigg — all giving wonderful performances, though I think Sir Ralph steals the show. Recommended highly, 3 thumbs up, 6 stars of a possible 5, all that jazz.
Now if only they’d come up with the “Hall of Fame” presentation of “Harvey” with James Stewart and Helen Hayes…
The Mars Phoenix lander touched down in the north arctic plains as pretty as one could ever ask for. I watched it all live on NASA TV, as usual. Very interesting to compare/contrast this landing to that of the Spirit rover.
Spirit’s EDL was 12 minutes; Phoenix only 7. (EDL: Entry, Descent, Landing)
Spirit deployed its chute at a fairly high rate of speed, several thousand km/s. Phoenix not until it was going much slower, about 1100 km/s (and it had safeguards to make sure it didn’t deploy the chute if still going too fast.)
Spirit’s signal was often lost; Phoenix was in constant communication via a link to the Mars Odyssey orbiter. (And even if we hadn’t gotten all that data back in real-time, the Mars Reconnaissance Orbiter and the European Mars Express orbiter were “eavesdropping” and could have relayed it all on a time-delay. In fact, they probably have, just to give every scrap of signal retrievable.)
And of course the biggest difference: Spirit had an unpowered descent, relying on airbags to protect it for the final few hundred meters and the impact. Phoenix used 12 hydrazine thrusters of a new kind, allowing the lander to a) maneuver away from the parachute/aeroshell after they were detached; b) orient the lander so that the solar panels would be in an optimal position (aligned east-to-west and to the south compared to the rest of the lander); and c) decelerate the vehicle while doing the least possible disturbance of the soil at the landing site.
Phoenix has about 10 days of on-site testing and check-out ahead, and then about 80 days of scooping up the Martian tundra and seeing what it’s like. Don’t expect any mission extensions (though they might get one) — Phoenix is a “scout” mission, meant to be relatively inexpensive and narrow-focus. Plus it’s not like they can dig somewhere else. All the hydrazine left in the fuel tanks is now frozen solid. Phoenix is where it is for keeps.
80% chance of precipitation. Thunderstorms likely after 11am.
I think my flight day is rained out.
Apparently there’s an entire sector of educational rocketry retailers I hadn’t known about. Hmm.
Pitsco sells a very inexpensive rocket kit — instructions and intro to rocketry booklet plus parts for $4.25, much cheaper in large bulk. Casey assembled this in late February, but one of the fins got knocked off in the bus and I had to remake it. This was a good opportunity, actually, as Casey had glued the other fins on “backwards,” with a very Buck Rogers-y flair but also with the fin grain parallel to the body tube. When I cut out the replacement fin, I did so with the grain in a better orientation.
And then they used hot glue to bond the fins, which meant no real strength in the joint — which is why Casey’s fins kept getting knocked off. What is it with teachers and glue guns anyway? And then to align the fin, they used long strips of masking tape to try to tension them into position. Oy.
So, after a bit of painting and finally a break in the weather, they flew on Thursday. Outcome? Two words: Lawn Dart. In four words, Mostly Finless Lawn Dart, as the two original fins sheared along the grain. All the resources say “don’t have your grain like this,” but don’t really say why. I thought it would just make the glue bond weaker, but the glue held — the fins just snapped about 8-10 mm out from the body. Reconstructed fin? Just fine, thanks.
The recovery system failure had multiple causes, I think: one, not enough wadding; two, flight prep done five weeks before flight. Even if it had deployed, I had no confidence in the thin bread-wrapper chute or in the shroud lines.
But Casey was very happy to watch it fly, even if it came back in a sorry state. I’m proud of her for enjoying the experience as it was and not as she might have wished. We went over the rocket and discussed what went wrong, and we know what to do going on (and what happens if we don’t do). I count those all as big wins.
Onward to housecleaning and fishtank prep, since the weather is too drizzly to do yard work. And then, with luck, some more flying on Monday morning.
You will be pleased to hear that The Lady of the Manor saw the film “The Golden Compass.”
Okay, you probably won’t be pleased to hear that. You will, however, be pleased to learn that she wanted to learn how the story all turned out, so she bought the huge omnibus trade paperback of “His Dark Materials.”
She feels even better about this purchase since I explained that there probably WON’T be any more movies in that series.
Dakota County (MN) 4-H Federation placed 18th of the 100 invited finalist teams. Well done!
Hart County (KY) 4-H placed 78th. You guys did great to get there. Congratulations!
TARC Official Website has the story, scores, and pictures!
Trimming the perimeter of the front yard
Replacing the mowed sprinkler head.
Folding and hanging my clothes; washing some towels.
Assembling motor mounts/shock cord units.
Well… I did get the lawn mowed. I also got a sprinker head mowed. Somehow I don’t think it will grow back.
With gusty winds forecast for today, I decided I didn’t want to tempt fate by trying to re-erect the greenhouse last night. Probably Wednesday.
Also didn’t get to the cradles. I’m thinking I’ll take the foamboard, some glue, my cutting board and X-acto knife, and the pattern to work and hack on them there between tasks.
The note on the calendar says “Casey — delayed start”. I’m hanging around this morning just to make sure it really is.