back to article LOHAN bloodhound unleashes solar-powered minitracker

Fans of our Low Orbit Helium Assisted Navigator (LOHAN) project with a particular interest in the radio electronics side of spaceplane missions will doubtless enjoy a first look at a new miniature tracker from team member Anthony Stirk - the sleek black PAVA 9. Anthony's PAVA 9 tracker Anthony's PAVA programme was inspired by …

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Lovely

And now make a little money out of it :=-)

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just a thought

I would have thought you chaps would have contacted the soon to be launched UK astronaut Major Tim to lob a paper plane toward earth (perhaps containing one of these trackers and Reg logo wing chevrons) from the ISS and perhaps write a column for the Reg on his antics and wether or not a paper aircrafts low mass/high drag would slow it enough on re-entry not to burn up.

Seems like a perfect fit to me, just sayin...

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(Written by Reg staff) Silver badge

Re: just a thought

Not a bad idea.

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Go

Re: just a thought

That is a bloody brilliant idea.

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Re: just a thought

Predicting the landing point for that would be fun! Getting approval from NASA to pitch it out a service lock would probably be costly though. Maybe get an EVA astronaut to carry it in a spacesuit pocket and oops it earthward?

It's an interesting question - would an object lobbed by an astronaut hit the earth in a reasonable time? Depending on which way you threw it, it could even go into a higher orbit.

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Re: just a thought

It would need a retro rocket motor to cancel enough of the ISS delta-V - essentially changing the orbit so that it intersects the atmosphere at some point. It would be an interesting targeting problem to hit the atmosphere high enough to give it a gentle enough deceleration. However I suspect that friction would still do for it as it got lower.

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Re: just a thought

Make it big and light (eg 1m x 1m tissue paper) and it will de-orbit itself reasonably quickly... I'd guess weeks/months rather than years. There is a tiny bit of atmospheric drag at ISS altitude, enough to do the job. I doubt it would burn up when it reaches the main bit of atmosphere because it has so little inertia: it would be just drifting in the wind before it has time to heat up.

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Re: just a thought

Too big and it would be a tad awkward for a suited astronaut to faff around with.

Time to de-orbit shouldn't be an issue, with an astronaut simply throwing it directly towards earth, gravity would do the rest causing it to constantly accelerate until the atmosphere became thick enough for friction to overcome its effects and start slowing it down or maybe burning it up, but that's ok too because the point would be that it's an interesting and fun science experiment, NASA gets to perform a simple and super low cost experiment that kids can appreciate (including big kids) which they seem to like, the Reg gets so much "WIN" that Charlie Sheen would spontaniously combust and Major Tim would get even more coverage and kudos especially if he were to participate in a column for the Reg (or better yet 2, one preflight and one post, explaining what he thinks would happen and then explaining the results). It's great PR all round.

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Re: just a thought

Perusing related links on here i came across this http://www.theregister.co.uk/2013/12/31/paper_plane_flight/

Size and shape would be perfect and its capable of holding the tracker.

On that note in the comments on that page, the suggestion for lobbing a paper aircraft from the ISS and wether or not friction would cause it to burn up were stated previous to my posting here.

I apologise to both Joe Gurman and Blitheringeejit as it must seem like i tried to plagiarize - I had no intention of stealing your ideas and did not in fact know you had made them till just now.

I guess great minds think alike.

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Anonymous Coward

but Anthony (pictured above at far left with fellow LOHAN team members (from L-R) Dave Akerman, Rob Eastwood, John Oates, Rob Eastwood, Paul Shackleton and Neil Barnes)

Is Rob becoming his own shadow clone?

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Shades of the Cambridge guided busway. When it started there were five bus companies going to use it, but by the time it opened that had reduced to two via mergers and takeovers. Some of the documents had apparently been updated by search and replace as it was eventually announced that "Whippet, Stagecoach and Whippet" would be running services from day one...

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(Written by Reg staff) Silver badge

Shadow clone

We seem to have gained an extra Rob there. Should read: Dave Akerman, Rob Eastwood, John Oates, Paul Shackleton and Neil Barnes.

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Get your money back!

LiPo+solar charger board, Looks like a ruler to me.

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Trollface

So, can this transponder be switched off by the Playmonaut?

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Comment removed, I think it falls into the "too soon" category. Still found the trollface comment funny though.

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there are much lighter 1.5 volt batteries than AAAs...try a Duracell D377 Watch Battery

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volts aren't everything - the amperage pulled by the device and the total maH needed for the trip is likely more than a watch battery can provide. That said, I've soldered ultrabright LEDs to disc batteries (CAREFULLY), and they can last for months!

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following myself up - the detailed article talks about the service time. A single AAA battery keeps the board running for 30 hours, 70 hours for a AA. Since they've had some "challenging" retrievals on past tests, they would not want to skimp on power capacity for the tracker. Given the mountainside landing on one of the tests, it would probably be worth going with an AA.

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Alert

The watch batteries don't have the capacity to power all the electronics. The GPS pulls about 25ma under acquire dropping to about 5ma once it gets into power saving mode. The only battery we recommend people use for this are the Energizer Ultimate Lithium's which are 1200mAH for the AAA and 3000mAH for the AA's and are known to work below -40'C. The watch battery is 24mAH so you can see the issue :)

For the record the tracker uses about 40-45mAH which is low, there are some inefficiencies in the step up convertor. The hardware in theory can squeeze more out of the battery as I can switch the GPS off entirely from the microcontroller but I've not coded this yet.

For this flight the 7.6g AAA will be fine gives over 26 hours. For the record nothing touches the L91 and L92 Energizer Lithiums for the weight vs capacity.

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Windows

Oh, we Geriatrics looove microelctronics..

Couldn't find my glasses Monday (they were hanging on my Zimmer frame, natch!)

Put Sleepy Pi* onto Raspberry Pi, and misaligned by a whole row. Result? 5V onto 3v3.

Dammit! Foresdt Pi (the one that was addicted to Saunalahti's 3G network) dead in a nanosecond.

I'm on the smegging dole. FFS, thinking of buying a new Pi is kinda like dreaming of waking up with George Formby. (Each to his own..)

Beercans and begging, here we go again....

*http://spellfoundry.com/products/sleepy-pi/

I'l get there..I will!. 'kinell...

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Headmaster

It's pAVA, not PAVA.

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(Written by Reg staff) Silver badge

Yes I know, but I'm waging war on UPPER/lower mixed acronyms.

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Holmes

The pre-launch checklist...

...must be growing to War and Peace proportions.

Would you re-design the internals to better accommodate all this kit should you, for some reason (ahem), need a version 2?

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(Written by Reg staff) Silver badge

Re: The pre-launch checklist...

We could certainly get some internal mounts moulded as part of the 3D printing process, for the Pi, for example, and certainly for the Pixhawk autopilot and GPS. In the end, though, the amount of time to do that in CAD is greater than simply putting everything in as it is now.

Regarding the checklist, it's actually an "operational manual", and it's growing by the day.

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Thor?

Yeth.

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Vulture 2 Suggestions

Fascinating project!

Don't want to step on any toes, but thought some of my experiences may help.

I thought that I may be able to help with suggestions, from an engineer and pilot with high-power rocket experience. I have successfully flown a two stage "L" powered rocket with radio second stage ignition and radio chute ejection.

Years ago, motor ignition was a constant problem. The solution was to use a reliable electric match (or two) and epoxy it into a plug (chunk) of actual propellant. The propellant will not ignite while cutting with a sharp knife. Cut a piece about 1" long and trim the sides to fit into the motor nozzle. Use a drill bit, in your hand, (no drill needed) to make a hole for the electric match. Use some quick set epoxy to glue the match inside the hole. When ready, epoxy the whole assembly inside the top end of the rocket motor. When that electric match is fired, that motor WILL burn. Never had a failure that way.

Igniters that pop, like a firecracker, will usually not light a motor.

If you are worried about the cold, you can test fire it after being wrapped in dry ice for an hour.

(disregard. it seems you have an altitude chamber)

Worries:

1 - These motor casings are quite hot after a burn. Even though it is cold up high, can the motor soften or melt the fuselage?

2 - As mentioned in a previous post, stability in the thin air may be a problem. Basic rocketry tells us that the aerodynamic center of pressure (CP) must be behind the center of gravity (CG). The more the better. You have a unique situation. There isn't much aerodynamic anything at 100,000', so, until you build a lot of speed, you will rely on the center of thrust being aligned with the center of gravity. If it isn't, you end up with a corkscrew flight pattern. This stability is easy to achieve, if the vehicle is symmetrical and all is aligned with the central axis. If not, you really need to make sure that the thrust is aligned with the CG. Hang the flight ready spaceplane from a string. The CG will be on the extension line of that string. If done from multiple points, you can get the exact CG from the intersections. I would guess the plane is symmetrical left and right, so the only unknown for the CG would be top to bottom, which effects the "pitch" axis. That's probably the most difficult one to get the motor aligned to, on this model.

Here's an afterthought. Just hang it from the center of the motor, if the string is perfectly aligned with the motor, you're good!

3 - In the thin air, this may not be an issue, but I have had 1/4" plywood fins completely break off an "L" powered rocket. It was due to turbulence/instability from a mirror shroud for a camera. It would be very difficult to break those by hand, but the aerodynamic forces snapped them clean off.

The wings on Vulture 2 look much more fragile. It might not survive a J motor flight at sea level, but maybe ok at 100,000'. Since there is little drag up high, your acceleration will be based on weight and motor impulse. If Vulture 2 weight is 4 pounds, final speed in thin air might be about 400mph on a "I" motor and 600mph on a "J" motor. Maybe the aerodynamic forces would be equivalent to less than 100mph at sea level. In that case you should be ok.

Wish you the best for a great flight!

Richard

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(Written by Reg staff) Silver badge

Re: Vulture 2 Suggestions

Suggestions always welcome, thanks. On your specific points:

We're working on an improved igniter for initial testing in our REHAB hypobaric chamber at low temperatures. Your input is appreciated.

1 - The motor's wrapped in space blanket and heat shrink, so the external temp won't reach a level to pose a threat to the nylon motor enclosure part of the fuselage, even on the ground (we've checked). As you say, it's cold up there, so no problem.

2 - We haven't yet mounted all the kit and tested the C of G, but that's imminent. Watch this space. The designers have an ideal C of G plotted, so it'll be interesting so see if the actual matches that.

3 - We've been fretting about the canards a bit. They're mounted using 8mm threaded steel rod expoxied (space grade expoxy) into the canard body. Should be ok, but it's a case of suck it and see.

The wings aren't as fragile as they look. There's an awful lot of complex internal bracing structure in there - the benefit of 3D printing.

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