That walkie-talkie death ray ... a different perspective

snip

Did you hear the Ch. 4 news fella who said that the Jag had its METAL bits melted? Duh.

Alternatively, just drop a huge tarpaulin over it.

Brian

I think its the aluminium bits that were distorted. And of course some plastic melted. Simon.

yerrs. injection moulding and indeed pressed metal will try to de-stress itself under high temperatures.

the photos I saw either show that aluminium was involved, or that there is alot more plastic in today's jags than you might suspect.

Davey :

I read today in the paper that the lens effect is difficult to predict at the design stage. That seems highly unlikely to me.

it is total complete bollocks in fact.

Imagine if the hubble telescope had gone into space and they hadn't been 'able to predict the lens effect'.

They didn't. IIRC they had to send someone up to fix it.

?Oh well. I suppose psychotic buildings firing lethal beams of pure energy is another thing we?ll have to get used to, like the congestion charge and parking permits.?

In article , Mike Barnes writes

I'd hesitate to call it a trivial calculation but I can see it being done quite accurately at spreadsheet level, albeit a rather large one.

Do what? There have been ray tracing programs about for decades. I remember half playing with them in the '80's but back then render times where measured in days and I hadn't the patience.

These days you'd probably get an almost instant result from one of the large CGI movie making server farms on something so simple. You could do a movie showing the daily movements of the "hotspot". You could teak the window alignments and model those effects as well. What might be harder would be to use that model to given an estimated temperature rise at any given point at/near the focus but TBH you don't really need that information you just need to defocus the spot.

hadn't

They prdiected precisely what the lens design was going to do. What they failed to do was make the lens to the design. They then successfully predicted the prescription to correct the manufacturing defect and correctly made and fitted that prescription.

On Wednesday 04 September 2013 09:15 Mike Barnes wrote in uk.d-i-y:

Bollocks. It's a simple ray tracing O-Level physics job.

They just didn't think about it.

I'd love to be a fly on the wall at the architechs' pass the blame meeting!

If that were true, how would they design such things as large telescopes? It's all done by the same rules, most of which were known hundreds or thousands of years ago. So the Hubble Space Telescope just happened by accident?

The actual problem was that they failed to correctly predict the effect of lack of gravity on the lens shape, so it had a slightly different focal point once it was up in space. The calculated fix did the job.

No, according to NASA it was a manufacturing error by Perkin-Elmer in building the instrument (the Reflective Null Corrector) used in measuring the mirror during manufacture.

ISTR that yes, it was manufactured wrongly but that NASA skipped a $10m final test to save money. Something that came back to haunt them.

Fair enough. The explanation I quoted was one given out at the time, maybe before they had analysed it properly.

They did, but they made it wrong.

A quick drawing would show the effect without any software needed.

They did get it wrong, maybe an architect did it?