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To the Sun

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To the Sun

Old 12th Aug 2018, 12:26
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To the Sun

I can't find any mention of this through PPRuNe so here's the launch video.


Whether or not it survives long enough to be useful remains to be seen.
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Old 12th Aug 2018, 12:37
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At what stage does the gravitational attraction become 'irresistible'?
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Old 12th Aug 2018, 12:41
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I don't think it ever can be resisted to be honest..
What I mean is, the Voyager probes took 30 years to get away from the suns gravitational influence.
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Old 12th Aug 2018, 12:48
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Originally Posted by TURIN View Post
I can't find any mention of this through PPRuNe so here's the launch video.

https://www.youtube.com/watch?v=L8ABCfetZdo

Whether or not it survives long enough to be useful remains to be seen.
It will be OK as long as they only use it during the night.
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Old 12th Aug 2018, 15:00
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I watched Atlantis being launched at night several years ago.

Very Impressive! The only thing I have seen that can burn through money faster then my wife.
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Old 12th Aug 2018, 15:20
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Not so much a problem of escaping gravity as slowing down to allow it to be captured more closely.

All the rocket power was to slow the probe down, just the way a shuttle fired retro rockets to slow down to lower its orbit on recently. Even using Venus to slow down during the first pass the downhill slope it accelerates to over 100 miles per second at perihelion before climbing out again - a very short quick pass. Over the next 7 years it then does 6 more slingshots retrograde around Venus to lose more energy each time and slow the speed to extend the time near perihelion.

https://en.wikipedia.org/wiki/Parker_Solar_Probe
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Old 12th Aug 2018, 15:22
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A trip to the sun....clearly well thought out, going by night ‘n all.....
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Old 12th Aug 2018, 19:59
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"Oh, my goodness! The sun!!!"
"What is it?"
"It's a big fiery ball up in the sky, but that's not important right now..."
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Old 12th Aug 2018, 20:22
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Love that hydrogen fire just before lift off. Forgot this was on today, after sitting at the computer yesterday, only for it to be cancelled.
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Old 12th Aug 2018, 20:32
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I presume that 'human' flights are limiter WRT acceleration, but do unmanned flights have limitations, or can they pile-on the lift to higher levels?

I realise that extra boost requires extra fuel which has to be lifted, so maybe it makes sense to do the acceleration when some of the dead-weight has been burned off?

Edited to add:- I see Patrick Moore was the commentator . . .

Last edited by G-CPTN; 12th Aug 2018 at 20:48.
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Old 12th Aug 2018, 20:49
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Originally Posted by G-CPTN View Post
I realise that extra boost requires extra fuel which has to be lifted, so maybe it makes sense to do the acceleration when some of the dead-weight has been burned off?
This probably is exactly what's meant by "rocket science", and you can probably find the equations on Wikipedia.

A non-human payload is also going to be built to certain acceleration limits, as are bits of the rocket itself.
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Old 12th Aug 2018, 21:05
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Think of the fuel as potential thrust and as weight. The optimum is to convert all the fuel to thrust at launch so the only thing accelerated is the payload. Which is what, effectively, a cannon does. Downside, an acceleration of about 50,000G.

Survivable for electronics - some artillery shells now have GPS and camera circuitry in the nose - but not for solar panels etc.

You accelerate as rapidly as possible through the atmosphere (throttle down/up at maximum Q), then convert weight to thrust as fast as possible, then accelerate as fast as possible.

Which leads to the strange but true point that rockets aren’t very efficient. An ion thruster which can keep up a thrust of any a fraction of a pound but for weeks will give a far higher velocity in space than a rocket which expends more than 90% of its fuel accelerating it’s fuel......
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Old 12th Aug 2018, 23:25
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And they still haven't got a logo to stick on it!
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Old 13th Aug 2018, 07:46
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Oh.
Rockets.
I was expecting a thread about white van man and the toffs who write the headlines...
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Old 13th Aug 2018, 08:41
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Originally Posted by G-CPTN View Post
At what stage does the gravitational attraction become 'irresistible'?
I think I understand your question - you are asking when the Sun's gravity takes over. The answer is that it's always in control, but once the first slingshot around Venus happens later this year, the probe is pretty much committed. At the point when the Parker enters a Venus orbit thrusters could be used to end the mission but that's unlikely to happen and after that it's on a ride driven by the Sun and Venus' gravity. There will be many orbits of the probe around the sun and it won't get to closest approach until 2024, but it's only really around Venus when its trajectory can be altered (or on its way there) significantly.

Essentially, it's always going to be influenced by the sun's gravity other than the times it's close to Venus.
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Old 13th Aug 2018, 09:02
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Originally Posted by ORAC View Post
Which leads to the strange but true point that rockets arenít very efficient. An ion thruster which can keep up a thrust of any a fraction of a pound but for weeks will give a far higher velocity in space than a rocket which expends more than 90% of its fuel accelerating its fuel......
ORAC - not sure if you saw this, but it's to do with the Fermi Paradox, i.e., why hasn't the Galaxy been colonized by aliens? One reason might be that chemical propulsion might not even get a civilisation into space if all they use is chemical propulsion just like us. As you point out, rockets are inefficient and severely restrict what we can do but we're lucky enough living on Earth that chemical energy can still provide enough energy to go to the moon or Mars. More here:

https://www.space.com/40375-super-ea...ns-launch.html
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Old 13th Aug 2018, 10:18
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Is this a response to me or someone else and what is its relevance?
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Old 13th Aug 2018, 11:02
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Survivable for electronics - some artillery shells now have GPS and camera circuitry in the nose
The VT Proximity shells of WW2 had valves in them and were fired from anti-aircraft guns, so it's nothing basically new.
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Old 13th Aug 2018, 11:08
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Response to you - just because chemical energy alone wouldn’t get them out of the gravity well doesn’t mean they’d be trapped. [email protected]/microwave pulsed systems would be able to do it - especially those initially using systems to detonate atmosphere in a bowl cavity on the bottom of a vehicle before shifting to injecting fuel.
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