Rosetta's Philae probe makes historic landing on comet

If I fire my thrusters in the direction that I'm traveling, then the exhaust are accelerated away from me while I'm being decelerated.  How can I be engulfed in those exhaust gasses if those exhaust gasses are traveling faster than I am and being dissipated into the vacuum of space?

If I understand correctly, the exhaust gases are not accelerated away but ejected at constant velocity from the spacecraft that at the same time is slowing down, so in a way the exhaust appears to accelerate but it is the space craft that slows down. How the exhaust is dissipated into the vacuum space is another story. The exhaust gases just continue to fly away at constant speed in the space - like a big sausage shaped cloud. It means that the part of the exhaust cloud or sausage that was ejeceted first has a higher speed than the part of the cloud or sausage that was ejected last due to the fact that the spacecraft slows down in the meantime. The exhaust cloud sausage will thus elongate itself in space ... forever. Unless you are close to a planet or moon that will attract the exhaust cloud by gravity. If you brake very close to a planet or moon trying to land, I assume you will get engulfed in the gases that are bouncing off from the ground below.

 

Don't forget molecules in the gas phase like to bounce off each other as well. No trouble landing.

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Unless you are close to a planet or moon that will attract the exhaust cloud by gravity. If you brake very close to a planet or moon trying to land, I assume you will get engulfed in the gases that are bouncing off from the ground below.

  Why should this be a problem?  Being engulfed in gasses when landing doesn't seem to bother helicopters or Harrier jets at all.

If I understand correctly [...]

It's more than obvious by now that you don't understand anything "correctly".  One only has to look at your absurd web pages to realise that LOL.

A marine "engineer" with dubious aerospace and astronautical qualifications who seriously  believes he's an instant expert on Rosetta's Philae probe, and apparently, all other space technology.

Sad really.   

A marine engineer is a boat mechanic who plays with his rusty nuts in the bilge.

One only has to look at your absurd web pages to realise that LOL.

Thanks for visiting my popular web pages. I know you lack basic knowledge and education to fully understand them, but you tried. Maybe some day you will learn what I say?

Thanks for visiting my popular web pages. I know you lack basic knowledge and education to fully understand them, but you tried. Maybe some day you will learn what I say?

LOL..... a "boat mechanic".   

I certainly hope not Anders;  I don't want all my friends to think I've had a frontal lobotomy!

Quote from: Heiwa on December 15, 2014, 07:54:45 AM

Thanks for visiting my popular web pages. I know you lack basic knowledge and education to fully understand them, but you tried. Maybe some day you will learn what I say?

LOL..... a "boat mechanic".   

I certainly hope not Anders;  I don't want all my friends to think I've had a frontal lobotomy!

Do you have friends? LOL Lobotomy is not really required in your case with no brains at all. But ... thanks for visiting my popular web site.  I really try to adapt it to all kind of visitors, incl. you. It seems it works.

The Tsiolkovsky rocket equation is, as we all know (I mention it on my web site), used to see how a rocket or spacecraft accelerates, while getting lighter with a constant force (exhaust gasses escaping at 2400 m/s) applied to it. If it can be used for deceleration is another matter. The force is then applied in the opposite direction or the rocket/spacecraft flies backwards, i.e. has been flipped around 180° in the direction of flight. The force must be applied in the right direction. If not you accelerate/decelerate into empty space.  (...)

Let's sum up. When asked

what would be the final speed and energy of a rocket weighting 1000 kg , including  500 kg of fuel, burning it with an ejection speed of 4500 m/s ?

You answered

I suggest the final speed of the remaining 500 kg is 5362 m/s

then

There is only one result - 5362 m/s (or maybe 5256 m/s?). If you get other results (sic) you are mistaken

and finally gave your "formula"

A. Calculate the kinetic energy of the total mass 1000 kg spacecraft at 7000 m/s velocity relative Earth in space (mv²/2).
B. Calculate the kinetic energy of the fuel mass 500 kg after it has been ejected from the spacecraft as hot gas at velocity 4500 m/s relative the spacecraft polluting the space at 2500 m/s velocity relative Earth and having slowed down the space craft to unknown speed.
A-B is then the kinetic energy of the 500 kg spacecraft after braking (ejection of 500 kg fuel as hot gas), speed of which is easy to find (sqr((2(A-B)/500))).

I'm afraid, but you are dead wrong here. You simply cannot compute kinetic energies from different referentials and you cannot evaluate kinetic energy from a variable mass system this way.

Let's show it  A given mass of fuel will give you a constant overall breaking force, whatever initial speed you consider. right ?
You should find the same delta v for a rocket travelling at 7000 m/s  and another one travelling at 4500 m/s for example.

Plug these numbers (7000 m/s and 4500 m/s starting speed) into your "equation". You will find different delta v values.
Done.
Your maths are wrong.

The only correct answer is found from the "well known Tsiolkovsky rocket equation". As you should be familiar with differential calculus,you should be able to read and understand the underlaying concepts. Here is the french Wikipedia article http://fr.wikipedia.org/wiki/%C3%89quation_de_Tsiolkovski for your reading ease.
You will see that it works as well for accelerating and braking bodies. Alpha2Omega gave you the correct answer. Plain and simple.

I know you cannot admit you are wrong because your entire "popular website" is based on these kinetic energy misconceptions, but you may one time have some intellectual honesty.

If you disagree with the Tsiolkovsky rocket equation, please feel free to demonstrate how it fails.

I'm afraid, but you are dead wrong here. You simply cannot compute kinetic energies from different referentials and you cannot evaluate kinetic energy from a variable mass system this way.

He has literally been reasserting his mistaken methodology for years depsite some very thorough and easy to understand rebuttals.  He either does not understand the rebuttals and is too proud  to accept them; understands the rebuttals and is too dishonest to address them; is playing ostrich like the worst parody of a talking head politician or is delusional and is clinging to his delusion.  I am not sure which it is.

But ... thanks for visiting my popular web site.

No need to thank me Anders.  Being a skeptic, I was initially led to it by THIS site:  "The Unique World of Anders Bjorkman (Heiwa)" which I can thoroughly recommend to both the flat earthers and round earthers here.  And I know you truly think your silly site is "popular", although it sounds to me more like you're repeatedly confirming it to yourself rather than any visitors.  But then that's just your arrogance and/or naivety showing through LOL.

I really try to adapt it to all kind of visitors, incl. you. It seems it works.

Have you ever thought [sic] of "adapting" your site for scientists?  You know; people like me who can actually think for themselves instead of being steamrollered by a total bullshit artist so far up his own fundamental orifice that he can't see the sun.  I really think you need to give up posting here Anders before you make an even bigger fool of yourself.

If that's at all possible?   

ausGeoff, not to try to derail this thread, but I notice that you use [sic] a lot.  You do realize that it is generally used to acknowledge that there is a misspelling, but you are leaving that misspelling because it is what the other person said?  Anyway, I don't think you have used it correctly yet. 

Oh deary me..... jroa's favourite whipping boy gets another slap.  What a surprise LOL.

BTW jroa, you really need to check your English language usage manual...  Occasionally a writer places [sic] after his or her own words, to indicate that the language has been chosen deliberately for special effect, especially where the writer's ironic meaning may otherwise be unclear.

You take everything far too literally.  Lighten up mate!

How is what I said wrong?

The notation's usual purpose is to inform the reader that any errors or apparent errors in quoted material do not arise from errors in the course of the transcription, but are intentionally reproduced, exactly as they appear in the source text.

Thanks for visiting my popular web pages.

We see this a lot, as well as, it seems, every time and everywhere I've seen Heiwa show up, he's plugging the damn thing. He seems obsessed by the number of visits it gets. The one time I decided to visit it (it's been a while) I was warned off by the AV software I was using. Last night, after mentioning that last point in a post here, something occurred to me.

Heiwa, are you being paid to spread malware? Is that why you're constantly flogging your website and trying to lure people to visit? Do you get paid by someone for each visit? If so, did you ever ask yourself why? If you're not intentionally doing this, have you done anything to disinfect it in the last couple of years, and are you taking measures to be reasonably sure it stays clean? Anyone who has been there, is he selling ads? Maybe that is a more innocent explanation for the ceaseless touting, but I take those warnings seriously - they are rare, and it's usually (always?) the sketchier places (which this seems to fit) where I see them, so giving them wide berth seems prudent.

I have no way of knowing if his site is free of malware or not, but have no intention on visiting unless some convincing evidence that it's clean is provided (I'm not even sure what that would be; I suppose I'll know it if I see it).

How is what I said wrong?

Quote from: http://en.wikipedia.org/wiki/Sic

The notation's usual purpose is to inform the reader that any errors or apparent errors in quoted material do not arise from errors in the course of the transcription, but are intentionally reproduced, exactly as they appear in the source text.

You are right, AusGeoff is wrong. This is not unusual.

Heiwa, are you being paid to spread malware?

Not at all. Somebody linked to my web pages at this forum, somebody else suggested that info there was not correct ... and there we are ... off topic most of the time. I evidently maintain that the whole Rosetta (topic) spacecraft is a European Space Agency, ESA, hoax since 20 years and show it quite convincing at my web page about it (and I am happy that it is linked to). Reason seem to be to maintain the NASA Apollo show since 1969 that space travel and similar is possible (which it isn't) and to keep useless astrophysicists ockupied. Imagine having studied astrophysics for many years, then not finding any job apart from ESA and there being asked to spread psuedoscientific garbage in space and on Earth. I just feel sorry for those people. It is scientific fraud. But politically correct, which I am not.

How is what I said wrong?

Quote from: http://en.wikipedia.org/wiki/Sic

The notation's usual purpose is to inform the reader that any errors or apparent errors in quoted material do not arise from errors in the course of the transcription, but are intentionally reproduced, exactly as they appear in the source text.

You are wrong because you didn't keep reading:

Sic may also be used derisively, to call attention to the original writer's spelling mistakes or erroneous logic

Emphasis mine.

Quote from: Alpha2Omega on December 15, 2014, 11:50:20 AM

Heiwa, are you being paid to spread malware?

Not at all. Somebody linked to my web pages at this forum, somebody else suggested that info there was not correct ... and there we are ... off topic most of the time. I evidently maintain that the whole Rosetta (topic) spacecraft is a European Space Agency, ESA, hoax since 20 years and show it quite convincing at my web page about it (and I am happy that it is linked to). Reason seem to be to maintain the NASA Apollo show since 1969 that space travel and similar is possible (which it isn't) and to keep useless astrophysicists ockupied. Imagine having studied astrophysics for many years, then not finding any job apart from ESA and there being asked to spread psuedoscientific garbage in space and on Earth. I just feel sorry for those people. It is scientific fraud. But politically correct, which I am not.

It's funny that when you are confronted by people with expertise in the fields you critique (I.e. Aeronautics) it is your ideas that appear fraudulent. Why is it that you never address the flaws in your energy balancing modelling or acknowledge that much of the information you claim NASA has never published in fact is extremely accessible?

FYI there was no good reason to change the thread title in your post.

Heiwa, do you admit that your answer to my initial question is incorrect ?

It's funny that when you are confronted by people with expertise in the fields you critique (I.e. Aeronautics) it is your ideas that appear fraudulent. Why is it that you never address the flaws in your energy balancing modelling or acknowledge that much of the information you claim NASA has never published in fact is extremely accessible?

Hm, I haven't met any experts of aeronautics in this forum, only anonymous neurotics. The simplest way to prove me wrong is to copy/paste the relevant part from my web page, point out the error, etc. here or in a mail to me. the latter has been done by friendly people, so my web page today is perfect without faults. I publish all findings openly, etc. I don't hide behind ridiculous pseudonyms.
Re NASA and the Apollo trip, NASA has not been able to explain how e.g. braking simultaneous course change takes place flying backwards in the strong Moon gravity field. If you are 1° out of course you either crash or end up in deep space and you have no margins with the fuel. Anywhere. Buzz and company just watching! Buzz is today an alcoholic wreck that you can meet at various TV shows. Pathetic. NASA and the Stardust trip is another joke; a spacecraft flying by planet Earth dropping off a capsule of stardust. LOL. And the ESA Rosetta trip is pure fantasy - small Rosetta being kicked around by Earth and Mars so it arrives exactly parallell with P67 after 10+ years. LOL And all re-entries to Earth from space! Impossible all of them.

It is all a magic show using stupid illusionists' tricks. Only children believe the nonsense.

Heiwa, do you admit that your answer to my initial question is incorrect ?

No - the speed after braking is 5362 m/s, i.e. Delta-v is 1638 m/s, but, it seems, I used an exhaust velocity of 2363 m/s = more realistic. Any problems? Not bad without paper/pen - only head!
Note that answer is only valid, if the brake force is applied exactly in the direction of travel. If not, you wear off and the speed in direction of travel is much less.   

Yet you still pedal your wrong maths even after it has been shown to you as wrong on countless occasions on god knows how many websites. Why?

Quote from: Antonio on December 15, 2014, 10:04:24 PM

Heiwa, do you admit that your answer to my initial question is incorrect ?

No - the speed after braking is 5362 m/s, i.e. Delta-v is 1638 m/s, but, it seems, I used an exhaust velocity of 2363 m/s = more realistic. Any problems?

Yes a big one. I gave you some data, you said :

Paper and pen? Calculator?? Inaccurate numbers??? What's wrong with a fresh brain and using it for simple calculations? Anyway, plenty of people above think they know the answer and are therefore invited to present the calculations to reach it. It is simple astrophysics:
A. Calculate the kinetic energy of the total mass 1000 kg spacecraft at 7000 m/s velocity relative Earth in space (mv²/2).
B. Calculate the kinetic energy of the fuel mass 500 kg after it has been ejected from the spacecraft as hot gas at velocity 4500 m/s relative the spacecraft polluting the space at 2500 m/s velocity relative Earth and having slowed down the space craft to unknown speed.
A-B is then the kinetic energy of the 500 kg spacecraft after braking (ejection of 500 kg fuel as hot gas), speed of which is easy to find (sqr((2(A-B)/500))).

At this time you acknowledged that the speed used was 4500 m/s, didn't you ? In addition, you were very self-confident about it:

Quote from: Antonio on December 12, 2014, 02:18:21 AM

I'm finding very different results, that's why I'm kindly requesting your math, as I suspect some mistakes from it

There is only one result - 5362 m/s (or maybe 5256 m/s?). If you get other results (sic) you are mistaken. Try again!

And you are expecting me to believe that you inadvertedly swapped 4500 m/s by 2363 m/s "using only head " because it sounded more realistic??  really ?

Is your initial formula valid with your new numbers ?

 Ve=sqr(2*((1000*7000*7000/2)-(500*2363*2363/2))/500)

And you are expecting me to believe that you inadvertedly swapped 4500 m/s by 2363 m/s "using only head " because it sounded more realistic??  really ?

Yes! Most rocket engines I deal with (see my webpage) seem to have an exhaust velocity ~2400 m/s, so it appears that number entered my head when doing the calculation to make you happy. Anyway - rocket engines are mainly used to increase the speed of the spacecraft, e.g. to shoot up satellites into orbit around Earth through the atmosphere. Then the exhaust exists backwards at the bottom end of the rocket and aided by gyros and wing flaps (if atmosphere is still there) the spacecraft may be stabilized. Any crew are facing forward.

Rocket engines are rarely used to reduce the speed of a space craft, as then the space craft is flipped around 180° - the bottom becomes the forward end - and the exhaust is directed forwards in the direction of travel - hopefully. A small instability of the spacecraft will change its heading and the spacecraft will go off course - like a car running off the road. And the crew is facing backwards.

The first, full scale, serious reduction of speed in space of a spacecraft was, as far as I understand, the Apollo in the 1960's, when slowing down and turning to get into orbit of the Moon that in turn orbits the Earth at substantial speed. In that case the spacecraft (Apollo) was also subject to Moon gravity pulling the spacecraft down towards the center of the Moon, while the rocket engine pushed in some other direction.

IMHO opinion NASA lacked in the 1960's both the theoretical and practical knowledges and the actual equipment, means and people to carry out such reduction of speed of a spacecraft, so therefore I have my doubts about NASA & Co. And the technology to brake in space has hardly developed since, i.e. it remains impossible.

But as NASA got away with the Apollo swindle, they and ESA, Russians and Chineses just carry on to copy/paste the shit.

In the 1960's I (and many others) fell in love with Valentina Tereshkova, the first woman in space and a beautiful one too. When in the 1990's when I worked a lot in Russia and Ukraine, I happened to meet Valentina, still very pretty and funny, and asked her how she/her spacecraft had managed to slow down for landing. She told me:

"Anders, I never went into space as it was and is impossible. It was just a big propaganda trick to impress the Americans".

Quote from: Antonio on December 16, 2014, 07:06:18 AM

And you are expecting me to believe that you inadvertedly swapped 4500 m/s by 2363 m/s "using only head " because it sounded more realistic??  really ?

Yes! Most rocket engines I deal with (see my webpage) seem to have an exhaust velocity ~2400 m/s, so it appears that number entered my head when doing the calculation to make you happy. (...)

Lol, you didn't plug about 2400 m/s but 2363m/s ...you have lost all credibility there...

Please focus on the maths, answer to my question :

Is your initial formula valid with your new numbers ?
 Ve=sqr(2*((1000*7000*7000/2)-(500*2363*2363/2))/500)

Please focus on the maths, answer to my question :

Quote

Is your initial formula valid with your new numbers ?
 Ve=sqr(2*((1000*7000*7000/2)-(500*2363*2363/2))/500)

9613 is in my head. But what should it be? Increased speed? When braking? Sounds like NASA. Better forget it!

In the 1960's I (and many others) fell in love with Valentina Tereshkova, the first woman in space and a beautiful one too. When in the 1990's when I worked a lot in Russia and Ukraine, I happened to meet Valentina, still very pretty and funny, and asked her how she/her spacecraft had managed to slow down for landing. She told me:

"Anders, I never went into space as it was and is impossible. It was just a big propaganda trick to impress the Americans".

Heiwa, can you give some more details on this?

Quote from: Antonio on December 16, 2014, 09:15:09 AM

Please focus on the maths, answer to my question :

Quote

Is your initial formula valid with your new numbers ?
 Ve=sqr(2*((1000*7000*7000/2)-(500*2363*2363/2))/500)

9613 is in my head. But what should it be? Increased speed? When braking? Sounds like NASA. Better forget it!

I dunno, I'm applying YOUR formula with YOUR numbers, care to explain this result ?

Quote from: Antonio on December 16, 2014, 07:06:18 AM

And you are expecting me to believe that you inadvertedly swapped 4500 m/s by 2363 m/s "using only head " because it sounded more realistic??  really ?

Yes! Most rocket engines I deal with (see my webpage) seem to have an exhaust velocity ~2400 m/s,

Citation needed. From a source other than your own stuff.

You started this conversation erroneously arriving at 2500 m/s for the braking Ve by subtracting 4500 m/s Ve from 7,000 m/s vehicle velocity (relative to what?). This is completely wrong. Now it's 2400 or 2363 m/s. Where did these numbers come from? Please do not, yet again, refer us to your website; for the reasons given above, I will not go there.

so it appears that number entered my head when doing the calculation to make you happy. Anyway - rocket engines are mainly used to increase the speed of the spacecraft,

Citation needed. From a source other than your own stuff.

Even if this is true, it's irrelevant because "mainly used" does not mean "always used".

e.g. to shoot up satellites into orbit around Earth through the atmosphere. Then the exhaust exists backwards at the bottom end of the rocket and aided by gyros and wing flaps (if atmosphere is still there) the spacecraft may be stabilized. Any crew are facing forward.

So?

Rocket engines are rarely used to reduce the speed of a space craft,

Citation needed. From a source other than your own stuff.

Even if this is true, it's irrelevant because "rarely" does not mean "never".

as then the space craft is flipped around 180° - the bottom becomes the forward end - and the exhaust is directed forwards in the direction of travel - hopefully. A small instability of the spacecraft will change its heading and the spacecraft will go off course - like a car running off the road.

Any time you use a rocket to change the velocity of a vehicle, it will not go in the desired course if it's pointed in the wrong direction.

And the crew is facing backwards.

So?

The first, full scale, serious reduction of speed in space of a spacecraft was, as far as I understand, the Apollo in the 1960's,

Citation needed. From a source other than your own stuff.

when slowing down and turning to get into orbit of the Moon that in turn orbits the Earth at substantial speed. In that case the spacecraft (Apollo) was also subject to Moon gravity pulling the spacecraft down towards the center of the Moon, while the rocket engine pushed in some other direction.

OK. So? Figuring out how much and which "other direction" is how NASA's Astrodymanics guys earned their pay. It's an engineering problem with a solution that can be calculated by someone who knows what he is doing.

IMHO opinion NASA lacked in the 1960's both the theoretical and practical knowledges and the actual equipment, means and people to carry out such reduction of speed of a spacecraft, so therefore I have my doubts about NASA & Co. And the technology to brake in space has hardly developed since, i.e. it remains impossible.

But as NASA got away with the Apollo swindle, they and ESA, Russians and Chineses just carry on to copy/paste the shit.

"In my opinion..." OK. So?

Do you have any facts to back it up?

In the 1960's I (and many others) fell in love with Valentina Tereshkova, the first woman in space and a beautiful one too. When in the 1990's when I worked a lot in Russia and Ukraine, I happened to meet Valentina, still very pretty and funny, and asked her how she/her spacecraft had managed to slow down for landing. She told me:

"Anders, I never went into space as it was and is impossible. It was just a big propaganda trick to impress the Americans".

Can this be independently verified?