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back to article Heavenly SPEARS gives LOHAN a hot satisfying BANG

The Low Orbit Helium Assisted Navigator (LOHAN) team has been sifting the data from last weekend's successful test of the Special Project Electronic Altitude Release System (SPEARS) control board, and is delighted to report that it worked as advertised. Click here for a bigger version of the LOHAN graphic SPEARS is designed to …

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Silver badge

Battery Shorting?

Why the decision to short the batteries? It seems like a good way to start an accidental fire and lose the entire assembly. Just curious.

Also, the 'Arm' safety switch should really be activated when moved UP. As a good practice safeties should utilize gravity as an added protection against falling components and/or hands moving away from the device :)

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Re: Battery Shorting?

The text mentions a fuse being blown by the timer at the end. I guess the fuse is between the battery and the rest of the circuitry.

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Alert

Re: Battery Shorting?

Popping a visible fuse sounds a lot safer than shorting batteries. That's never really a safe thing to do.

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Boffin

Re: Battery Shorting?

As above - the battery circuit is shorted upstream of the fuse, which blows.

Thus preventing little Johnny getting his hands on a live rocket motor...

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Happy

Re: Battery Shorting?

Ah. Thanks for the clarification.

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Thumb Up

An the award...

for best neologism goes to stratodangle.

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Stratodangle

David Blaine is on the phone, he wants in....

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Joke

Re: Stratodangle

No, no, no - that's a twatdangle.

Do pay attention.

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Facepalm

Re: Stratodangle

He did the twatdangle in 2003.

(all due respects to Mr Brigstocke)

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PIC

Could the blast from the match have blown it out?

Maybe something a little less like a banger?

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Flame

Re: PIC

I did wonder about that. It might be the case, but its not designed to cause too much blast. We're after a slow hot burn rather than a big bang, so there isn't actually very much blackmatch in there. Also there is some wadding separating it from the PIC.

I think the next thing to do is a bit more testing. We need to get some PIC down to the frosty -60°C found up at that height. I think we'll get a mini rig set up in a dry ice bath and see if we can dig into the root cause of its refusal to burn.

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Coat

Thought you Brits had already solved this design problem

Just need to include a live chicken.

And clearly I'm not from the civil service.

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DJO
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Joke

Re: Thought you Brits had already solved this design problem

But that solution only works for spherical chickens in a vacuum.

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Re: Thought you Brits had already solved this design problem

I'm pretty sure all chickens are spherical in a vacuum - if only briefly.

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Happy

Re: Thought you Brits had already solved this design problem

Sorry, old chap; those are our neighbours, and they experimented with pigeons...

http://en.wikipedia.org/wiki/Project_Pigeon

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Have I missed the explanation?

That of, who is the frogman hitching a ride.

When I first saw him, when you earlier posted the video, I suspected that he must be a 'safety engineer' should another water landing occur.

Anyway, congrats again.

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Re: Have I missed the explanation?

Is it significant we haven't been treated to an exclusive interview with the intrepid frogonaut?

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(Written by Reg staff) Bronze badge

Re: Re: Have I missed the explanation?

Well, he didn't have much to do this time around.

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Trollface

Title...

I wonder how much money I would need to make the title mean what I hoped it would mean, the next argument is do we need a time machine to go back a few years before both participants went nuts and were less scary looking, or would we be happy with the crazy scary looking up-to-date versions as they may be more willing to do it for less money?

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Facepalm

Must be more carefull naming things

This was a no brainer and doomed to fail

So goddamn ill-chosen clumsy to christen the aircraft to CHAV and believe it to work flawlessly.

Have never seen a CHAV work. Even less work flawlessly.

Just my 50p

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Switch Labelling

3 switches should be labelled:

1. "Atomic Batteries to Power"

2. "Turbines to speed"

3. "Let's Go!"

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Re: Switch Labelling

Agree completely with the need to dramatise things up a bit. Especially after attending this a couple of weeks ago:

http://www.livefromjodrellbank.com/news/transmission_004-the-australian-pink-floyd-show-info/

The show was MC'd by one of the top Jodrell Bank boffins, and just before he introduced the headline act (which involved projecting films onto the Lovell telescope dish), he used the site walkie-talkie to issue the immortal instruction "Telescope to Show Position". Whereupon the dish stopped looking upwards and was trundled round to give optimum audience experience:

http://www.ctmd.co.uk/JodrellBank.jpg

If they'd had a charity auction for the opportunity to issue that instruction, I would have bid muchly.

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Anonymous Coward

Error: PIC undefined in this context

Could we get a definition of the acronym "PIC" used in this article? At first I was thinking you were burning out a microcontroller....

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Re: Error: PIC undefined in this context

"Error: PIC undefined in this context " Plastic Igniter cord

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Re: Error: PIC undefined in this context

Although, having said that as it's grey it's Mantitor from Brazil. PIC was an ICI product not produced any longer.

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MrT
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Nice PCB work...

...custom screen-printing and neat SMD soldering.

Almost as if Special Projects Bureau is planning to release a hobby kit version. You know, for a reasonable price, just in time for Christmas. Please... :-)

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(Written by Reg staff) Bronze badge

Re: Nice PCB work...

Hmm...

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With relatively cleared areas all around, has anyone done a study on why these payloads almost always seem to find TREES to land in? Or ponds, or swamps, or lakes, or ....

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(Written by Reg staff) Bronze badge

...the English Channel?

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Anonymous Coward

Re. motors

Shorting out the battery via a fuse is all very well but the current pulse is going to be 5-6* the rated current.

I'd have used something like a solid state normally open relay driven by a second smaller battery, when that runs out the power shuts down under controlled conditions.

Also worth mentioning, there are reasons aerospace stuff has quadruple redundancy such as four independently wired igniter circuits.

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Silver badge

Re: Re. motors

There are a number of things going on here, many of which have been discussed previously, but for the sake of completeness:

A processor on its own supply which is

- talking to the GPS unit

- talking to the comms transmitter

- talking to a logging MD card

- and of course triggering the pyro stuff

But what we really really want to avoid is the chance of the rocket going off accidentally, and most of all when someone is close to it... so we don't want to start the thing, for example, and then connect the wires with volts on them. To avoid this, the multi-stage arming requirement where the operator is looking to ensure there are no warning lights at any stage: no power to the relay *before* the relay is connected; no power *from* the relay before the wires are attached. For obvious reasons we don't want to attach and then just turn stuff on...

Equally, we don't want the risk of the thing coming down for whatever reason with a live rocket motor *and* live power. In such a condition - with the risk of mechanical shock or damage when it hits the ground - we can't rely on either the processor or the relay to be working properly; there's a risk of just touching the thing and it going off. So the idea of the fuse is a second-line defence to to ensure that there is no power in the igniter circuit as soon as practicable after we expect the launch to occur.

Managing that by using a normally-open relay held shut is complicated by the expected life of the batteries at very low temperatures.

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