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First landing ever of spacecraft on a comet happend less than 12 hours ago!



 
 
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  #1  
Old November 13th 14, 02:17 AM posted to sci.astro
Bjørn Sørheim
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Posts: 24
Default First landing ever of spacecraft on a comet happend less than 12 hours ago!


Philae on Comet 67P/Churyumov–Gerasimenko.

And then no discussion about it on sci.astro??
What have this ng turned into? More or less a sesspool of destructive
people?

B.S.
  #2  
Old November 13th 14, 04:08 PM posted to sci.astro
Mike Dworetsky
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Posts: 715
Default First landing ever of spacecraft on a comet happend less than 12 hours ago!

Bjørn Sørheim wrote:
Philae on Comet 67P/Churyumov-Gerasimenko.

And then no discussion about it on sci.astro??
What have this ng turned into? More or less a sesspool of destructive
people?


Pretty much. It should perhaps be renamed sci.psych.abnormal.

Was there anything specific you wanted to know about Philae?

Apparently the lander bounced three times before coming to rest on the
surface of the comet, and I suspect the initial "silence" from ESA was due
to not being able to figure out why some of the readings were varying
unexpectedly such as IR and magnetometer right after touchdown. A few
images from the surface have now been received. The lander seems to be up
against some sort of vertical rock on one side which may be shading the
solar cells. They need to know more about the exact geometry before
attempting to move it, as doing something now might make matters worse.

--
Mike Dworetsky

(Remove pants sp*mbl*ck to reply)

  #3  
Old November 13th 14, 05:24 PM posted to sci.astro
Bjørn Sørheim
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Posts: 24
Default First landing ever of spacecraft on a comet happend less than 12 hours ago!

On Thu, 13 Nov 2014 15:08:50 -0000, "Mike Dworetsky"
wrote:

Bjørn Sørheim wrote:
Philae on Comet 67P/Churyumov-Gerasimenko.

And then no discussion about it on sci.astro??
What have this ng turned into? More or less a sesspool of destructive
people?

Pretty much. It should perhaps be renamed sci.psych.abnormal.


;-)

Was there anything specific you wanted to know about Philae?

Apparently the lander bounced three times before coming to rest on the
surface of the comet, and I suspect the initial "silence" from ESA was due
to not being able to figure out why some of the readings were varying
unexpectedly such as IR and magnetometer right after touchdown. A few
images from the surface have now been received. The lander seems to be up
against some sort of vertical rock on one side which may be shading the
solar cells. They need to know more about the exact geometry before
attempting to move it, as doing something now might make matters worse.


I watched the press confrence today (with some difficulty - NASA is
better than ESA in this respect, for shure).

So most questions were answered in that press briefing.
Philae is currently in a very dire situation on the surface, with one
leg sticking apperently into space up against a 'rock' face. Do this,
do that, as was the plan, and Philae will tip over or leave the comet
again.
This is close to catastrophe, on the other hand close to a success.
The life-giving solar panels (on the top) are receiving currently only
1.5 hours of expected 6-7 hours pr. rotation. Most experiments, at
least the mechanical ones, are not possible to do right now, because
of uncharted consequences. At least let's hope they will get some good
images before it could be over. As stated in the press conference, the
top main priority is being able to investigate and analyse the
material of the comet, which never have been done on a comet before.
Alas, this is almot impossible with the current tilt and position of
Philae, as it is placed right now.

It seems like landing on a comet with such very low gravity needs a
very sophisticated landing mechanism (which must work) and very
controled automatic operation. This didn't work this time around for
ESA. The causes must be studied carefully.

B.S.
  #4  
Old November 14th 14, 09:46 AM posted to sci.astro
Mike Dworetsky
external usenet poster
 
Posts: 715
Default First landing ever of spacecraft on a comet happend less than 12 hours ago!

Bjørn Sørheim wrote:
On Thu, 13 Nov 2014 15:08:50 -0000, "Mike Dworetsky"
wrote:

Bjørn Sørheim wrote:
Philae on Comet 67P/Churyumov-Gerasimenko.

And then no discussion about it on sci.astro??
What have this ng turned into? More or less a sesspool of
destructive people?

Pretty much. It should perhaps be renamed sci.psych.abnormal.


;-)

Was there anything specific you wanted to know about Philae?

Apparently the lander bounced three times before coming to rest on
the surface of the comet, and I suspect the initial "silence" from
ESA was due to not being able to figure out why some of the readings
were varying unexpectedly such as IR and magnetometer right after
touchdown. A few images from the surface have now been received.
The lander seems to be up against some sort of vertical rock on one
side which may be shading the solar cells. They need to know more
about the exact geometry before attempting to move it, as doing
something now might make matters worse.


I watched the press confrence today (with some difficulty - NASA is
better than ESA in this respect, for shure).

So most questions were answered in that press briefing.
Philae is currently in a very dire situation on the surface, with one
leg sticking apperently into space up against a 'rock' face. Do this,
do that, as was the plan, and Philae will tip over or leave the comet
again.
This is close to catastrophe, on the other hand close to a success.
The life-giving solar panels (on the top) are receiving currently only
1.5 hours of expected 6-7 hours pr. rotation. Most experiments, at
least the mechanical ones, are not possible to do right now, because
of uncharted consequences. At least let's hope they will get some good
images before it could be over. As stated in the press conference, the
top main priority is being able to investigate and analyse the
material of the comet, which never have been done on a comet before.
Alas, this is almot impossible with the current tilt and position of
Philae, as it is placed right now.

It seems like landing on a comet with such very low gravity needs a
very sophisticated landing mechanism (which must work) and very
controled automatic operation. This didn't work this time around for
ESA. The causes must be studied carefully.

B.S.


Hindsight is usually clearer than foresight. When the lander was designed
and built (around 15 years ago) it was not possible to use techniques that
might be possible now. The original plan was to launch in 2003 but a
previous failure of the Ariane 5 launch system delayed the launch by a year
and changed the choice of destination comet. And the design and
construction started several years before that.

The main requirement would seem to be an ability to slow the descent speed
to near zero just before surface contact. This requires radar and a rocket
engine that can be throttled. Both add mass to the lander, so one or more
scientific experiments would probably need to be removed to accommodate it.

--
Mike Dworetsky

(Remove pants sp*mbl*ck to reply)

  #5  
Old November 14th 14, 08:03 PM posted to sci.astro
Jens Schweikhardt
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Posts: 19
Default First landing ever of spacecraft on a comet happend less than 12 hours ago!

Mike Dworetsky wrote
in :
....
# The main requirement would seem to be an ability to slow the descent speed
# to near zero just before surface contact. This requires radar and a rocket
# engine that can be throttled.

I'd say a rocket engine to change a minuscule delta v of 1m/s of a 100kg
mass prior to touchdown is way overkill. A gas bottle of some sort
probably has enough oomph with much less engineering headaches. But I
doubt that just before landing on an unknown surface with unknown
properties and the desire to analyse it chemically you want to
contaminate it with rocket engine exhaust... I trust the scientist
and engineers of Rosetta/Philae much better understood the problem
as I do.

Regards,

Jens
--
Jens Schweikhardt http://www.schweikhardt.net/
SIGSIG -- signature too long (core dumped)
  #6  
Old November 14th 14, 08:13 PM posted to sci.astro
Rodney Pont[_5_]
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Posts: 31
Default First landing ever of spacecraft on a comet happend less than 12 hours ago!

On 14 Nov 2014 19:03:48 GMT, Jens Schweikhardt wrote:

# The main requirement would seem to be an ability to slow the descent speed
# to near zero just before surface contact. This requires radar and a rocket
# engine that can be throttled.

I'd say a rocket engine to change a minuscule delta v of 1m/s of a 100kg
mass prior to touchdown is way overkill. A gas bottle of some sort
probably has enough oomph with much less engineering headaches. But I
doubt that just before landing on an unknown surface with unknown
properties and the desire to analyse it chemically you want to
contaminate it with rocket engine exhaust... I trust the scientist
and engineers of Rosetta/Philae much better understood the problem
as I do.


Yes, the harpoons were supposed to do the job but for some reason they
didn't fire.

--
Faster, cheaper, quieter than HS2
and built in 5 years;
UKUltraspeed http://www.500kmh.com/


  #7  
Old November 14th 14, 11:21 PM posted to sci.astro
Mike Dworetsky
external usenet poster
 
Posts: 715
Default First landing ever of spacecraft on a comet happend less than 12 hours ago!

Jens Schweikhardt wrote:
Mike Dworetsky wrote
in :
...
# The main requirement would seem to be an ability to slow the
descent speed # to near zero just before surface contact. This
requires radar and a rocket # engine that can be throttled.

I'd say a rocket engine to change a minuscule delta v of 1m/s of a
100kg mass prior to touchdown is way overkill. A gas bottle of some
sort
probably has enough oomph with much less engineering headaches. But I


"Rocket" does not require ignition of hot gases. As you say, a bottle of
compressed gas could do the trick, or something similar to attitude jets
used on Apollo, Shuttle, etc.

I suspect the landing speed was more than 1m/sec, but even that could cause
a lot of bounce.

doubt that just before landing on an unknown surface with unknown
properties and the desire to analyse it chemically you want to
contaminate it with rocket engine exhaust... I trust the scientist
and engineers of Rosetta/Philae much better understood the problem
as I do.

Regards,

Jens


--
Mike Dworetsky

(Remove pants sp*mbl*ck to reply)

  #8  
Old November 15th 14, 10:39 AM posted to sci.astro
Mike Dworetsky
external usenet poster
 
Posts: 715
Default First landing ever of spacecraft on a comet happend less than 12 hours ago!

John wrote:
On Fri, 14 Nov 2014 19:13:26 +0000 (GMT), "Rodney Pont"
wrote:

On 14 Nov 2014 19:03:48 GMT, Jens Schweikhardt wrote:

# The main requirement would seem to be an ability to slow the
descent speed # to near zero just before surface contact. This
requires radar and a rocket # engine that can be throttled.

I'd say a rocket engine to change a minuscule delta v of 1m/s of a
100kg mass prior to touchdown is way overkill. A gas bottle of some
sort
probably has enough oomph with much less engineering headaches. But
I
doubt that just before landing on an unknown surface with unknown
properties and the desire to analyse it chemically you want to
contaminate it with rocket engine exhaust... I trust the scientist
and engineers of Rosetta/Philae much better understood the problem
as I do.


Yes, the harpoons were supposed to do the job but for some reason
they didn't fire.


Surface too cold and the poor things wanted to stay near the nice,
warm battery packs?
Or, more realistically, ten years in deep, dark, cool vacuum without
WD-40. It's an astonishment *anything* worked.


Um, no, in space most lubricants are a very bad idea, as they solidify or
turn into a hard jelly. Lubricants are best avoided.

Indeed, I'm quite saddened by how little everyone is amazed,
astonished, enthused and impressed by this feat. Humans have landed -
however crookedly - a robot onto a *comet*. That's a marvelous and
magical achievement.
It's also temporary. Little Philae will eventually be kicked into the
wider dark as the comet evaporates, to become a tiny, man-made planet
all on its own. Philae may well last longer than the worldlet it is
exploring.
J.


--
Mike Dworetsky

(Remove pants sp*mbl*ck to reply)

  #9  
Old November 15th 14, 09:56 PM posted to sci.astro
Dr J R Stockton[_194_]
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Posts: 35
Default First landing ever of spacecraft on a comet happend less than 12 hours ago!

In sci.astro message , Fri, 14
Nov 2014 08:46:54, Mike Dworetsky
posted:


The main requirement would seem to be an ability to slow the descent
speed to near zero just before surface contact. This requires radar
and a rocket engine that can be throttled. Both add mass to the
lander, so one or more scientific experiments would probably need to be
removed to accommodate it.


Radar may not be needed.

A few phone-cameras around or near the equator of the lander, used
during descent to put the mean horizon in the right place, and
subsequently for pretty pictures.

A phone-camera on each foot, facing downwards, and an algorithm which
makes, using thrusters, the mean rate of ground movement in each camera
the same and radially outwards at a constant suitable rate; when focus
or brightness is lost, landing has occurred.

A centre-line recoilless gentle shotgun, used first, to spray suitable
ammo at the ground to ensure that it is not featureless.


And, on general grounds, phone cameras looking in the 20 icosahedral-
face (= dodecahedral-vertex) directions, in case the scenery is not
where it was intended to be.

--
(c) John Stockton, near London. Mail
Web http://www.merlyn.demon.co.uk/ - FAQish topics, acronyms, and links.
  #10  
Old November 16th 14, 10:32 AM posted to sci.astro
Mike Dworetsky
external usenet poster
 
Posts: 715
Default First landing ever of spacecraft on a comet happend less than 12 hours ago!

Dr J R Stockton wrote:
In sci.astro message , Fri,
14 Nov 2014 08:46:54, Mike Dworetsky
posted:


The main requirement would seem to be an ability to slow the descent
speed to near zero just before surface contact. This requires radar
and a rocket engine that can be throttled. Both add mass to the
lander, so one or more scientific experiments would probably need to
be removed to accommodate it.


Radar may not be needed.

A few phone-cameras around or near the equator of the lander, used
during descent to put the mean horizon in the right place, and
subsequently for pretty pictures.

A phone-camera on each foot, facing downwards, and an algorithm which
makes, using thrusters, the mean rate of ground movement in each
camera the same and radially outwards at a constant suitable rate;
when focus or brightness is lost, landing has occurred.

A centre-line recoilless gentle shotgun, used first, to spray suitable
ammo at the ground to ensure that it is not featureless.


And, on general grounds, phone cameras looking in the 20 icosahedral-
face (= dodecahedral-vertex) directions, in case the scenery is not
where it was intended to be.


The requisite phone cameras were still in early development when the lander
was designed and constructed. It's an obvious idea 15-20 years later. And
some serious processing power (using up some mass budget) would be needed to
do the job. But the descent was initially fairly level, relative to local
terrain. The real problem was failure of the anchors to fire and the
subsequent bounces. Even that would not have been a problem if the lander
had not had the bad luck to come down close to a vertical surface that
blocked light to the solar panels.

--
Mike Dworetsky

(Remove pants sp*mbl*ck to reply)

 




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