How did we land Rosetta on the Philae comet?

How did we land Rosetta on the Philae comet?

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htrowsoc

Original Poster:

603 posts

201 months

Saturday 15th November 2014
quotequote all
I'm no scientist by any stretch of the imagination, but do show a keen interest.

What I find hard to believe is how did the European space agency manage to get the Rosetta module to go 40,000 mph (or near enough), AND achieve the same trajectory as the comet?

Unbelievable.

outnumbered

4,381 posts

241 months

Saturday 15th November 2014
quotequote all
Are you saying you find it unbelievable in a tinfoil-hat, "the moon landings were faked" way ?

Otherwise, it's just Newtonian physics, pretty much, but I guess they needed a decent amount of computing power to work out the trajectory needed to get the required accelerations from gravity slingshots, and end up in the right place after 10 years.

Mr E

22,128 posts

266 months

Saturday 15th November 2014
quotequote all
Very really, by slowing other orbital bodies down (infinitesimally)

htrowsoc

Original Poster:

603 posts

201 months

Saturday 15th November 2014
quotequote all
outnumbered said:
Are you saying you find it unbelievable in a tinfoil-hat, "the moon landings were faked" way ?

Otherwise, it's just Newtonian physics, pretty much, but I guess they needed a decent amount of computing power to work out the trajectory needed to get the required accelerations from gravity slingshots, and end up in the right place after 10 years.
I just find it hard to believe that we could safely approach an object moving at 40,000 mph when you consider an escape velocity of 25,000 mph, with these kind of speed differentials I can't see how this is even remotely possible as the margin for error would be enormous.

htrowsoc

Original Poster:

603 posts

201 months

Saturday 15th November 2014
quotequote all
Mr E said:
Very really, by slowing other orbital bodies down (infinitesimally)
How do you go about slowing down another orbital body? Not sure if serious..

Leithen

12,135 posts

274 months

Saturday 15th November 2014
quotequote all
htrowsoc said:
Mr E said:
Very really, by slowing other orbital bodies down (infinitesimally)
How do you go about slowing down another orbital body? Not sure if serious..
Gravity Assist.

htrowsoc

Original Poster:

603 posts

201 months

Saturday 15th November 2014
quotequote all
Using gravity assist wouldn't slow down another orbital body. Gravity assist is the process of using another orbital body's gravitational pull (such as Jupiter) to achieve a higher velocity in space.

So could the ESA achieve an exact speed based on the trajectory towards the orbital body which was used for gravitational assist?

HoHoHo

15,161 posts

257 months

Saturday 15th November 2014
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I think it's nothing more than a room full of very, very, very clever people who understand how objects move in space and how to speed up/slow down accordingly. They programe the go button when they need to and program the stop button when they need to - simple as that.

If we all understood it, we'd all be rocket scientists and would be earning a fortune yes

hidetheelephants

27,857 posts

200 months

Saturday 15th November 2014
quotequote all
htrowsoc said:
outnumbered said:
Are you saying you find it unbelievable in a tinfoil-hat, "the moon landings were faked" way ?

Otherwise, it's just Newtonian physics, pretty much, but I guess they needed a decent amount of computing power to work out the trajectory needed to get the required accelerations from gravity slingshots, and end up in the right place after 10 years.
I just find it hard to believe that we could safely approach an object moving at 40,000 mph when you consider an escape velocity of 25,000 mph, with these kind of speed differentials I can't see how this is even remotely possible as the margin for error would be enormous.
The escape velocity for 67P is <1m/s, which is 3.6km/h or ~2mph.

htrowsoc said:
Using gravity assist wouldn't slow down another orbital body. Gravity assist is the process of using another orbital body's gravitational pull (such as Jupiter) to achieve a higher velocity in space.

So could the ESA achieve an exact speed based on the trajectory towards the orbital body which was used for gravitational assist?
By definition gravity assist must affect the larger body in the same way as the smaller, it's just very small and no-one notices.

perdu

4,885 posts

206 months

Saturday 15th November 2014
quotequote all
Without getting technical, 'cos I couldn't even begin, they used gravity from other forces/sources in the solar system to speed up Rosetta enough that it eventually caught up with the place in space where it was calculated to be going to

Ten years later

simples

I think they have done an amazing job, hope little 'wotsit' gets a few volts charged up occasionally just so it can peep up, "hi folks I'm still sat 'ere".


Mr E

22,128 posts

266 months

Saturday 15th November 2014
quotequote all
htrowsoc said:
How do you go about slowing down another orbital body? Not sure if serious..
Completely and totally serious. The energy has to come from somewhere.

timbob

2,158 posts

259 months

Sunday 16th November 2014
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htrowsoc said:
I just find it hard to believe that we could safely approach an object moving at 40,000 mph when you consider an escape velocity of 25,000 mph, with these kind of speed differentials I can't see how this is even remotely possible as the margin for error would be enormous.
It's not as if we fired Rosetta at 25,000mph straight at a comet passing by at 40,000mph in some kind of deep space clay pigeon shoot!

In all seriousness, look up a game called Kerbal Space Program. Download it and play it, or just watch some YouTube videos - it'll teach you how we managed to do it.

Eric Mc

122,861 posts

272 months

Sunday 16th November 2014
quotequote all
Computers are helpful in working out the calculations as they speed up the process by a lot - but it can be done without the need of computers. There are lots of ways of doing complex calculations without a total reliability on computers.

As has been mentioned, gravity assist is a handy way of gaining more speed for a space probe and altering its direction so that it can rendezvous with another body. The technique has been used many, many times to allow probes to get to parts of the solar system that otherwise would have needed very, very powerful (and expensive) rockets.

There are couple of errors in the title as well -

Rosetta is the name of the main space probe, which is in orbit around the comet.

Philae is the name of the lander.

The comet is actually called comet 67P/Churyumov–Gerasimenko. The names are those of its two discoverers. Comets are always called after the names of the people who discover them.


Edited by Eric Mc on Sunday 16th November 09:11

MartG

21,252 posts

211 months

Sunday 16th November 2014
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anonymous said:
[redacted]
The really really hard bit is getting the funding frown

Eric Mc

122,861 posts

272 months

Sunday 16th November 2014
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Absolutely.

The maths and science bit is generally very well understood by now. The engineering is difficult and the funding is sometimes impossible.

"No bucks, no Buck Rogers".

anonymous-user

61 months

Sunday 16th November 2014
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All is revealed here:


rosetta_trajectory_animation


Pretty clever stuff!

Mr E

22,128 posts

266 months

Sunday 16th November 2014
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Max_Torque said:
All is revealed here:


rosetta_trajectory_animation


Pretty clever stuff!
That's really cool.

Shaolin

2,955 posts

196 months

Sunday 16th November 2014
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Rosetta didn't land anywhere, and the comet isn't called Philae - and breathe....

Eric Mc

122,861 posts

272 months

Sunday 16th November 2014
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As pointed out by me six posts before your's.

hornet

6,333 posts

257 months

Sunday 16th November 2014
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htrowsoc said:
I'm no scientist by any stretch of the imagination, but do show a keen interest.
Clearly not keen enough to get the name of the comet or the lander correct, or indeed simply go to the ESA Rosetta mission page and read about it there! Apologies if that sounds insulting, but come on, all the information you could ever want (including the answer to your question) is right there :-

http://www.esa.int/Our_Activities/Space_Science/Ro...