James Webb Space Telescope is a boondoggle

Andrew why don't you just admit you were wrong?

Always remember, the inability of admitting to making a mistake is also a
clear sign of a kook or con-artist.

Earl Colby Pottinger


--
I make public email sent to me! Hydrogen Peroxide Rockets, OpenBeos,
SerialTransfer 3.0, RAMDISK, BoatBuilding, DIY TabletPC. What happened to
the time? http://webhome.idirect.com/~earlcp

Andrew Nowicki wrote:

Thanks for correcting me, but I am not yet convinced
that LEO is too hot for infrared telescopes. JWST's
mirror will be kept at the temperature of 50 K or less.

but since JWST will not be in LEO, then you are spouting gibberish.


That looks like a more plausible explanation of
the L2 orbit. If JWST is launched far beyond the
LEO, it should have ion thrusters and enough fuel
to return to LEO for repair or upgrade. It seems
possible to run the ion thrusters and take pictures
at the same time -- the ion thrusters would produce
acceleration of less than 0.001 m/s^2.

snip

There is not much public discussion about telerobotic
servicing despite the fact that both terrestrial
and space telerobots perform rather well. The telerobot
may be slow and it may need special tools, but I can
hardly imagine any task that a sophisticated telerobot
like Dextre cannot perform. It would be really interesting
to launch Dextre and let it practice its skills on crippled
satellites. From my point of view the technical challenges
of telerobotic servicing are much more interesting than
all the other space programs combined. Telerobotic
servicing is fun! Its partly cerebral (can it be done?)
partly physical (like video games), and safe (humans running
around in uncomfortable space suits and risking their lives
are not needed). Robot competitions are popular among young
people, especially Japanese and MIT students, but space
cadets hate telerobots.

IOW you think Garage Wars is way cool, and you are at a level of
maturity where you think that anything that gets done should be done
becuase it's cool, not for parctical or operational reasons (which tend
to be very dull and tedious).

One day when you grow up you will understand

The Lanzerotti panel had 21 members, but only 3 of them
were robotic experts: Rodney A. Brooks, Vijay Kumar,
and Stephen M. Rock. Their final report was propaganda,
rather than science. Goddard Director Edward Weiler and
his engineers still believe that Dextre can repair Hubble.

Sometimes a satellite is crippled because one of its
mechanical parts is stuck. A little knock from a primitive
telemanipulator could fix this problem.

it's usually a lot more cost-effective to just replace teh satellite
instead of developing the infrastructure to go fix the one that breaks.

That will be the case as long as launch costs are what they are, and
nothing you have suggested remotely addresses that tiny little point.

Cool new technology is fun to daydream about, but if there's one thing
that we all should have learned from teh dotcom meltdown, it's that cool
new technology often serves no useful purpose, or is so expensive to
develop and maintain that you'd be much better off sticking with
existing technology.

--
Terrell Miller


"Every gardener knows nature's random cruelty"
-Paul Simon George Harrison

In sci.space.policy Andrew Nowicki wrote:
The Planck spacecraft is going to be launched into the Earth-Sun
L2 orbit where it will be cooled by refrigerators to 0.1 K!
source: http://www.rssd.esa.int/SA/PLANCK/in...ayl/node8.html

This idea looks like madness to me because these extreme
refrigerators are not reliable. They have mechanical parts
that may be glued by contaminants.

Sure, but imagine the returns if it works? Part of science exploration
is taking risks. There are many other things that could cause the mission
to fail.


SPICA is almost as ambitious. Its refrigerators are going to
cool it to 1.7 K.

So many vulnerable satellites... so few telerobots to repair them...

And nobody with money to pay for the telerobots anyways.

--
Sander

+++ Out of cheese error +++

Andrew Nowicki wrote:

The Planck spacecraft is going to be launched into the Earth-Sun
L2 orbit where it will be cooled by refrigerators to 0.1 K!
source: http://www.rssd.esa.int/SA/PLANCK/in...ayl/node8.html

This idea looks like madness to me because these extreme
refrigerators are not reliable. They have mechanical parts
that may be glued by contaminants.

SPICA is almost as ambitious. Its refrigerators are going to
cool it to 1.7 K.

So many vulnerable satellites... so few telerobots to repair them...


Sad that you don't see that sometimes we *have* to send our toys
farther away than we can hope to reach them for repair...

(What's that? One of the Mars rovers has a flat?)

--

You know what to remove, to reply....

Andrew Nowicki wrote:
The Planck spacecraft is going to be launched into the Earth-Sun
L2 orbit where it will be cooled by refrigerators to 0.1 K!
source: http://www.rssd.esa.int/SA/PLANCK/in...ayl/node8.html

This idea looks like madness to me because these extreme
refrigerators are not reliable. They have mechanical parts
that may be glued by contaminants.

What part of the following do you not understand?

"The cooling scheme that allows to cool at 0.1K ... is based
on technical solutions that have been successfully tested in
flight or have been demonstrated on ground applications and
are being qualified for space."

It seems like they've done their homework, extensively. Have
you? Considering that their solutions have been "demonstrated
on ground applications and are being qualified for space"
whereas your theoretical telerobotic repair craft has, well,
not been so qualified or demonstrated, I'd say that would
count as a "no".

re SE L2, that is also the staging area of choice
in the recent IAA (Huntress) study for stepping
stones to Mars. Hence, there are more than just
dynamics reasons to want to go to SE L2 rather than,
say, lunar orbit, or ANY of the Earth-moon L points--
now we can plan on human vehicle access there in
the next decade.




"Christopher M. Jones" wrote in message
...
Henry Spencer wrote:
[ker-snip]
Note that when ESA built an infrared observatory, they went to the extra
trouble of putting ISO into a highly elliptical orbit, so it was well
away
from Earth most of the time.

Note also the more recent infrared and longer wavelength
observatories and their designated operating locations:

Launched missions:
WMAP: Earth-Sun L2 Lissajous orbit
Spitzer: Earth-trailing heliocentric orbit

Planned missions:
Herschel: Earth-Sun L2 Lissajous orbit
Planck: Earth-Sun L2 Lissajous orbit
SIM: Earth-trailing heliocentric orbit
SPICA: Earth-Sun L2
JWST: Earth-Sun L2
Darwin: Earth-Sun L2


There are pretty strong trends here.

Andrew Nowicki wrote:

The Planck spacecraft is going to be launched into the Earth-Sun
L2 orbit where it will be cooled by refrigerators to 0.1 K!
source: http://www.rssd.esa.int/SA/PLANCK/in...ayl/node8.html

This idea looks like madness to me because these extreme
refrigerators are not reliable. They have mechanical parts
that may be glued by contaminants.

Sander Vesik wrote:

Sure, but imagine the returns if it works? Part of science exploration
is taking risks. There are many other things that could cause the mission
to fail.

This is good comment. The makers of those mechanical
refrigerators know that they are not reliable, so they
run them for years here on Earth hoping to get all the
bugs out. The problem is that when they launch them on
top of violently shaking rocket launchers, some air may
leak inside the refrigerators through their seals. There
is a way to prevent this problem: fill the refrigerator's
interior or exterior with hydrogen or helium during launch.

Peltier (thermoelectric) refrigerators are much less
efficient than mechanical refrigerators but they have
no moving parts, so they are reliable, and, in my opinion,
more suitable for outer space than the mechanical
refrigerators. Mechanical refrigerators may shake and
contaminate the sensitive optics of a space telescope.

I agree with your comment that new technology should
be tested in outer space, but if there is high
risk of catastrophic failure (certainly the case
of mechanical refrigerators) the designers should
post on the Internet complete, meticulously commented
CAD model with a following plea:
"Please take a look at our design and contact us
immediately if you find errors."

JPL makes two (4K and 20K) hydrogen sorption refrigerators
(cryocoolers) for the Planck spacecraft. NASA launched
several simple (single-stage Stirling and pulse tube)
mechanical refrigerators and it claims that they are
reliable.

Andrew Nowicki wrote:

So many vulnerable satellites... so few telerobots to repair them...

Sander Vesik wrote:

And nobody with money to pay for the telerobots anyways.

They are penny wise but pound foolish.

Dextre costs about $154 million (US$). Its mass is about 1662kg.
At 10000$/kg, launching Dextre into low Earth orbit will cost
about $17 million. The total cost of Hubble repair mission, not
counting the spare parts (which have already been made) and
additional tools (which are being made) is about $200 million.
Dextre needs additional tools that will be made in 31 months
(with penalties for late delivery).

ACCORDING TO ANTI-CANADIAN PROPAGANDA DEXTRE WILL COST MORE THAN
TWO BILLION DOLLARS AND ITS ADDITIONAL TOOLS CANNOT BE MADE SOONER
IN THAN 66 MONTHS. PLEASE CHECK THE FACTS. THIS IS THE FIRST BEST
PLACE TO START:
http://www.house.gov/science/hearing...PaulCooper.pdf

Can we change the name of this group to
sci.space.buffoonery?

--Damon

Dude, you're a crazy raving, plonk-worthy, crack smoking, fool.

MK

Andrew Nowicki wrote:

The Planck spacecraft is going to be launched into the Earth-Sun
L2 orbit where it will be cooled by refrigerators to 0.1 K!
source: http://www.rssd.esa.int/SA/PLANCK/in...ayl/node8.html

This idea looks like madness to me because these extreme
refrigerators are not reliable. They have mechanical parts
that may be glued by contaminants.

Sander Vesik wrote:

Sure, but imagine the returns if it works? Part of science exploration
is taking risks. There are many other things that could cause the mission
to fail.

This is good comment. The makers of those mechanical
refrigerators know that they are not reliable, so they
run them for years here on Earth hoping to get all the
bugs out. The problem is that when they launch them on
top of violently shaking rocket launchers, some air may
leak inside the refrigerators through their seals. There
is a way to prevent this problem: fill the refrigerator's
interior or exterior with hydrogen or helium during launch.

Peltier (thermoelectric) refrigerators are much less
efficient than mechanical refrigerators but they have
no moving parts, so they are reliable, and, in my opinion,
more suitable for outer space than the mechanical
refrigerators. Mechanical refrigerators may shake and
contaminate the sensitive optics of a space telescope.

I agree with your comment that new technology should
be tested in outer space, but if there is high
risk of catastrophic failure (certainly the case
of mechanical refrigerators) the designers should
post on the Internet complete, meticulously commented
CAD model with a following plea:
"Please take a look at our design and contact us
immediately if you find errors."

JPL makes two (4K and 20K) hydrogen sorption refrigerators
(cryocoolers) for the Planck spacecraft. NASA launched
several simple (single-stage Stirling and pulse tube)
mechanical refrigerators and it claims that they are
reliable.

Andrew Nowicki wrote:

So many vulnerable satellites... so few telerobots to repair them...

Sander Vesik wrote:

And nobody with money to pay for the telerobots anyways.

They are penny wise but pound foolish.

Dextre costs $154 million (US$). Its mass is about 1662kg. At
10000$/kg, launching Dextre into low Earth orbit will cost about
$17 million. The total cost of the robotic Hubble repair mission,
not counting the cost of spare parts (which have already been made)
is about $200 million. The total cost includes additional tools
that will be made in 31 months (with penalties for late delivery).

ACCORDING TO ANTI-CANADIAN PROPAGANDA DEXTRE WILL COST MORE THAN
TWO BILLION DOLLARS AND ITS ADDITIONAL TOOLS CANNOT BE MADE SOONER
THAN IN 66 MONTHS. PLEASE CHECK THE FACTS. THIS IS THE BEST PLACE
TO START:
http://www.house.gov/science/hearing...PaulCooper.pdf

The actual cost of the robotic Hubble repair mission is probably
MINUS billions of dollars because Dextre can repair many other
satellites and it can remove space debris. In other words NASA
can make lots of money on Dextre.