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back to article Voyeurs invited to watch space truck dock

Fans of live video matings can catch the docking of the Johannes Kepler space truck and the International Space Station's Zvezda module later this afternoon. The happy event is expected at 16:45 CET (15:45 GMT), and the European Space Agency will be streaming live footage from 15:15 GMT, right here. ATV docking with the ISS. …

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Joke

"redundant hardware"

see, now THAT is how you destroy data on unused SSDs!

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Go Johannes Kepler

That's all.

Oh, about destroying data on SSDs...

At a previous firm, we had to recover the data stored on chips from a flight control computer that had been crashed and burned. The pcb was a pile of copper traces and glass-fibre dust. The ceramic tops and bottoms of the ICs had come off because the glass seal that runs through the middle of the ICs had melted. The die from inside the chips were probed, and the data was recovered. (The data said that the plane did exactly what the pilot said).

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I didn't realise they were quite that durable

Have a thumbs up!

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WTF?

abc and/or 123

Can someone who knows about these things tell us why the ISS is low enough to encounter atmospheric drag?

Why not just boost it once, so the subsequent drag is negligible?

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Anonymous Coward

Cost, mostly

"The chosen orbital altitude is a trade-off between the delta-v needed to reboost the station and the delta-v needed to send payloads and people to the station. The upper limitation of orbit altitude is due to the constraints imposed by the Soyuz spacecraft."

- http://en.wikipedia.org/wiki/Orbital_station-keeping#Station-keeping_in_low-earth_orbit

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Econmics I'd assume..

It's easier and more cost effective to have the ISS under a wee bit of drag in the super duper thinnest dregs of the atmosphere, than it is to run a heap of rockets and all that, up a few hundred KM* higher.

(*Not exact distances - just an educated guess)

It's better to give the ISS a little bit of an orbital boost - with a little bit of rocket fuel now and then, than it is to strap all of that up into EVERY ONE of the bigger, heavier and further ranging rockets, needed to run higher into a virtually drag free low earth orbit with the drag free ISS.

It's not right or wrong, it's the most cost and resource effective compromise.

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Boffin

There is still trace atmosphere quite a long way out...

http://www.windows2universe.org/spaceweather/sat_drag.html

That'll explain.

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Boffin

atmosphere...

Goes up a very long way and it varies a lot its thinner when its dark and cold and thicker during the day, and it has tides like the sea too.. the problem is it is exponential ie the further you go the thinner it is but it actually goes a very long way, now if you move the space station a lot further away it starts to get radiation problems..

see wiki for more: http://en.wikipedia.org/wiki/Van_Allen_radiation_belt#Inner_belt

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Re: Cost, mostly

"constraints imposed by the Soyuz spacecraft."

That's strange. I thought that the ISS is at a low at the moment, and will be boosted by ATV2 later, but it needs to be low for the shuttle to bring it all the extra goodies they'll be getting in a few days.

However it is true that the orbital inclination is to allow for rockets launched from Kazakstan to reach it easily. (Although IMHO the orbital inclination means that it passes over more of the Earth, which may have benefits)

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Perhaps More Importantly...

...at this low orbit the ISS is inside earth's magnetic field, protecting it from solar particles.

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Boffin

@IIsRT

"Atmosphere" goes up a *lot* further than you might think. The relevant NASA item are the "space vehicle design criteria" otherwise called the SP8000 series. SP8028 (radiation torques) states that solar radiation is the biggest force above an orbit of 1000km, which is roughly the bottom of the inner Van Allan radiation belt so about the highest you'd want to put a long term crewed station.

Disturbance forces at 100 statue miles (c160Km) in E Ring (Rocket Propellants & Pressurization Systems) scaled on a scale where the aerodynamic forces (drag) is 1 give a gravitational potential force (aligning heaviest part closest to Earth) as 0.061, solar light pressure forces at 0.000443 and geomagentic at 0.0000013

1 unit on this scale is 1x10^-6g of acceleration.

Bottom line. ISS is *big*. The atmosphere extends a *lot* further out than you might think (but not in any way breathable) and if you *did* put it far enough out that *air* drag forces became even smaller you'd start to see the rise of solar wind forces while being cooked by the high energy particles trapped in the radiation belts.

There is also the little matter that Shuttle is at the *limit* of its altitude to deliver modules to the ISS orbit. Tripling it's altitude would be a *major* task and would *massively* complicate re-supply.

NASA has looked at alternate boost methods for *decades*. Obvious ones are Ion rockets (it's not like you don't have a big enough array to power them) or the "resistojet," which was designed to use waste (water, human etc) and expand the result through a nozzle. Low thrust but near continuous operation.

BTW NASA does not *have* a rocket to deorbit the ISS. An uncontrolled deorbit would be quite dangerous. of course they *could* declare it a national laboratory or donate to the UN (like CERN) *if* they were told to.

Hope that helps.

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g e
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But...

will we be able to buy the illustrated book from Waterstones ?

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Commentary

I hope David Attenborough is on stand-by

'Now, the space station raises its docking aperture signifying that it is receptive to Kepler's advances...'

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music

With An der schönen blauen Donau as the background music?

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Happy

Or perhaps...

... take a lesson from another Stanley Kubrick film and play "Try a Little Tenderness"

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Bah!

So, not so much a truck as a skip, then?

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Happy

Docking! Docking!

All you ever think about is docking!

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