Pentagon to Shoot down Spy Sat

Pat Flannery wrote:

Al G wrote:

Note the Kinetic Kill Vehicle. With no explosives, this shouldn't scatter
parts to far.


Assuming the hit it head on, impact velocity will be a minimum of around
17,000 mph as the satellite runs into the ascending KKV. That is going
to scatter stuff far and wide, although most of it will descend out of
orbit in fairly short order as the net effect will be to decelerate the
debris.

Probably greater than 95% of it coming down in the first rev. Shoot down is
probably the right term. As orbits decay, drag is greatest at perigee, this
circularizes the orbit. At such a low altitude, the best possible or lowest
drag orbit for it's orbital energy is circular. When the satellite
explodes, the perigees of every single piece will be equal to or lower than
it's current circular orbital altitude. There is no way to increase the
perigee altitude in the collision. So the explosion will decrease the
perigee of the vast majority of the satellite. Sure, some of it may have an
increase apogee, but also have an almost equal decrease in it's perigee (of
the same magnitude). The pieces that have the highest apogee will reenter
on there first perigee.

The very small percentage that have a longer orbital lifetime would have to
have been blown in the direction of the velocity vector without lowering
perigee. And even these small pieces will quickly circularize and decay as
they have a higher ballistic coefficient.

There is no way to increase perigee in the collision, only decrease it, so
Shoot down is a good term.
--
Craig Fink
Courtesy E-Mail Welcome @

John wrote:
This is from another group . . . but I got to admit . . . this is just
not passing the sniff test yet.


http://www.latimes.com/news/nationwo...,7685340.story

"The plan calls for firing a tactical missile at the satellite when it
reaches a low orbit of about 130 nautical miles. Officials said Navy
ships would attempt to shoot down the satellite from the northern
Pacific Ocean.
Marine Gen. James E. Cartwright, vice chairman of the Joint Chiefs of
Staff, said the action was not intended to ensure that classified
components on the craft were destroyed before hitting the ground, saying
any sensitive instruments would be destroyed when the satellite
reentered Earth's atmosphere.
"There's some question about the classified side of this," Cartwright
said at a Pentagon news conference announcing the decision. "Once you go
through the atmosphere and the heating and the burning, that would not
be an issue in this case. It would not justify using a missile to take
it and break it up further."
Military commanders conferred with NASA officials to ensure the
operation didn't interfere with the orbiting International Space Station
or space shuttle Atlantis. NASA Administrator Michael Griffin said the
risk posed to either one by the destruction of the satellite was
negligible."

By blowing it apart in low orbit weeks before it would have naturally
decayed, good sized chunks of it will be scattered all over its orbital
path before reentry, so in other words you are actually increasing the
odds of something falling on someone's house by doing this.
Hydrazine is a monopropellant that detonates if heated (as we found out
the hard way on the Contour spacecraft), so if the satellite had fallen
naturally, it almost certainly have exploded at high altitude and dispersed.
The remark about the tank being "well insulated" is interesting... if it
needs to be well insulated, it's on the exterior of the satellite and
exposed to sunlight. That in turn means it would not be sheltered by the
satellite's structure during reentry.
This is almost certainly about the proposed Russo-Chinese space weapons
treaty we rejected two days ago:
http://afp.google.com/article/ALeqM5..._E6fDr_NfYJdCQ

Pat

On Feb 14, 5:58 pm, Pat Flannery wrote:

By blowing it apart in low orbit weeks before it would have naturally
decayed, good sized chunks of it will be scattered all over its orbital
path before reentry, so in other words you are actually increasing the
odds of something falling on someone's house by doing this.


incorrect, the pieces would smaller
Hydrazine is a monopropellant that detonates if heated (as we found out
the hard way on the Contour spacecraft),

Wrong. That was known since the early days of the space program and
it was Contour'a SRM that came apart

so if the satellite had fallen
naturally, it almost certainly have exploded at high altitude and dispersed.
The remark about the tank being "well insulated" is interesting... if it
needs to be well insulated, it's on the exterior of the satellite and
exposed to sunlight. That in turn means it would not be sheltered by the
satellite's structure during reentry.

Totally incorrect. You state the exact opposite of what needed.
Exposed to the sun would heat it. Burying it in the structure is the
best place to help insulate it

On Feb 14, 5:58 pm, Pat Flannery wrote:

Hydrazine is a monopropellant that detonates if heated (as we found out
the hard way on the Contour spacecraft), so if the satellite had fallen
naturally, it almost certainly have exploded at high altitude and dispersed.

Propellant tanks (and hydrazine tanks in particular) survive reentry
remarkably well. They have a large ballistic coefficient, esp. when
nearly empty. This means that, as essentially big, empty balloons,
they can decelerate high up in the atmosphere, early during reentry,
and are thus spared the most intense aerodynamic heating.

The sensitivity and detonability of hydrazine is not as severe as
widely believed or reported. In fact, I am not aware of pure
hydrazine ever truly detonating (chemical explosion, perhaps, but
*not* high-order detonation), despite some very deliberate attempts to
do so.

The fact that hydrazine tanks can reenter intact has been a concern
for some time. In fact, NASA is now increasingly putting requirements
into their spacecraft specs that hydrazine tanks should "demise" upon
reentry, even in the case of a dead spacecraft (i.e., the propellant
tanks should disintegrate on its own, without the help of some type of
active device). Note that, for example, the specs for the upcoming
Global Precipitation Measurement mission and the next generation Gamma-
Ray Space Telescope specifically require that the hydrazine tanks must
passively demise upon reentry.
--
Andrew J. Higgins Mechanical Engineering Dept.
Associate Professor McGill University
Shock Wave Physics Group Montreal, Quebec CANADA
http://people.mcgill.ca/andrew.higgins/

On Feb 14, 9:31 pm, "
wrote:
On Feb 14, 5:58 pm, Pat Flannery wrote:

Hydrazine is a monopropellant that detonates if heated (as we found out
the hard way on the Contour spacecraft), so if the satellite had fallen
naturally, it almost certainly have exploded at high altitude and dispersed.

Propellant tanks (and hydrazine tanks in particular) survive reentry
remarkably well. They have a large ballistic coefficient, esp. when
nearly empty. This means that, as essentially big, empty balloons,
they can decelerate high up in the atmosphere, early during reentry,
and are thus spared the most intense aerodynamic heating.

The sensitivity and detonability of hydrazine is not as severe as
widely believed or reported. In fact, I am not aware of pure
hydrazine ever truly detonating (chemical explosion, perhaps, but
*not* high-order detonation), despite some very deliberate attempts to
do so.

The fact that hydrazine tanks can reenter intact has been a concern
for some time. In fact, NASA is now increasingly putting requirements
into their spacecraft specs that hydrazine tanks should "demise" upon
reentry, even in the case of a dead spacecraft (i.e., the propellant
tanks should disintegrate on its own, without the help of some type of
active device). Note that, for example, the specs for the upcoming
Global Precipitation Measurement mission and the next generation Gamma-
Ray Space Telescope specifically require that the hydrazine tanks must
passively demise upon reentry.
--
Andrew J. Higgins Mechanical Engineering Dept.
Associate Professor McGill University
Shock Wave Physics Group Montreal, Quebec CANADA
http://people.mcgill.ca/andrew.higgins/

Perhaps hydrazine is just a good sounding cover story for the load of
Pu238.
.. - Brad Guth

wrote:
On Feb 14, 5:58 pm, Pat Flannery wrote:


Hydrazine is a monopropellant that detonates if heated (as we found out
the hard way on the Contour spacecraft), so if the satellite had fallen
naturally, it almost certainly have exploded at high altitude and dispersed.


Propellant tanks (and hydrazine tanks in particular) survive reentry
remarkably well. They have a large ballistic coefficient, esp. when
nearly empty.

But this one is full. It has over 1,000 pounds of Hydrazine in it. So
it's going to come down like a Vostok reentry sphere and get damn hot.
The sphere is around forty inches in diameter. Considering its 1,000
pound plus weight that a fairly dense object, and one massive enough
that it will probably rip free of the rest of the satellite due to it
tearing itself out of its structural mounting as G forces build during
reentry.
Here's a transcript of the news conference BTW:
http://www.globalsecurity.org/space/...0214-dod02.htm

This means that, as essentially big, empty balloons,
they can decelerate high up in the atmosphere, early during reentry,
and are thus spared the most intense aerodynamic heating.

The sensitivity and detonability of hydrazine is not as severe as
widely believed or reported. In fact, I am not aware of pure
hydrazine ever truly detonating (chemical explosion, perhaps, but
*not* high-order detonation), despite some very deliberate attempts to
do so.

The fact that hydrazine tanks can reenter intact has been a concern
for some time. In fact, NASA is now increasingly putting requirements
into their spacecraft specs that hydrazine tanks should "demise" upon
reentry, even in the case of a dead spacecraft (i.e., the propellant
tanks should disintegrate on its own, without the help of some type of
active device). Note that, for example, the specs for the upcoming
Global Precipitation Measurement mission and the next generation Gamma-
Ray Space Telescope specifically require that the hydrazine tanks must
passively demise upon reentry.

Note this part of the news conference:

"GEN. CARTWRIGHT: Thank you.
Just to re-baseline, this is a National Reconnaissance Office satellite.
It was launched on 14 December, 2006. It's about roughly 5,000 pounds in
its weight. Historically, a satellite of this size and that weight,
roughly half of it would survive reentry.
We're saying in the modeling somewhere around 2,800 pounds would survive
reentry.
What is different here is the hydrazine. In this case, we do have some
historical background that we can work against for the tank that
contains the hydrazine. And we had a similar tank on Columbia that
survived reentry. So we have a pretty reasonable understanding that if
the tank is left intact, it would survive the reentry."

In the case of Columbia, the hydrazine tank would not be full, as a good
deal of the fuel would have been used when the Shuttle was in orbit. So
your statement about the survivability of a near empty tank would apply
in the case of Columbia....except for the fact that the Columbia tank
was first exposed to the atmosphere after the Shuttle broke up over
Texas, so it was at far lower speed and heating than earlier in the
reentry sequence. Unlike Columbia, the tank on the decaying satellite
will not be shielded by a thermal protection system during reentry, so
the tank should be exposed considerably earlier in the reentry process
and at a lot higher speed and heating.

Pat

wrote:

The sensitivity and detonability of hydrazine is not as severe as
widely believed or reported. *In fact, I am not aware of pure
hydrazine ever truly detonating (chemical explosion, perhaps, but
not high-order detonation), despite some very deliberate attempts to
do so.

I would think that might be debatable in an orbital collision. If the
intercepter mass delivers a lot of it's energy into the hydrazine, I would
think the shockwaves in the liquid would tremendous, something that might
still be considered low order. But, there may be multiple shockwaves
crossing each other. So, the distinction between just a chemical burning
and the term high order detonation might become blurred or meaningless, as
a partially vaporized cloud of intercepter parts deliver their energy into
a large volume of hydrazine at a velocity that is way above the velocity
that is considered higher-order.

Kind of like saying it never achieved higher-order detonation, but it all
burn chemically in less time than it would have if it had detonated
higher-order.
--
Craig Fink
Courtesy E-Mail Welcome @

On Feb 15, 12:31*am, "
wrote:
On Feb 14, 5:58 pm, Pat Flannery wrote:

Hydrazine is a monopropellant that detonates if heated (as we found out
the hard way on the Contour spacecraft), so if the satellite had fallen
naturally, it almost certainly have exploded at high altitude and dispersed.

Propellant tanks (and hydrazine tanks in particular) survive reentry
remarkably well. *They have a large ballistic coefficient, esp. when
nearly empty. *This means that, as essentially big, empty balloons,
they can decelerate high up in the atmosphere, early during reentry,
and are thus spared the most intense aerodynamic heating.

The sensitivity and detonability of hydrazine is not as severe as
widely believed or reported. *In fact, I am not aware of pure
hydrazine ever truly detonating (chemical explosion, perhaps, but
*not* high-order detonation), despite some very deliberate attempts to
do so.

The fact that hydrazine tanks can reenter intact has been a concern
for some time. *In fact, NASA is now increasingly putting requirements
into their spacecraft specs that hydrazine tanks should "demise" upon
reentry, even in the case of a dead spacecraft (i.e., the propellant
tanks should disintegrate on its own, without the help of some type of
active device). *Note that, for example, the specs for the upcoming
Global Precipitation Measurement mission and the next generation Gamma-
Ray Space Telescope specifically require that the hydrazine tanks must
passively demise upon reentry.
--
* * *Andrew J. Higgins * * * * * *Mechanical Engineering Dept.
* * *Associate Professor * * * * *McGill University
* * *Shock Wave Physics Group * * Montreal, Quebec CANADA
* * *http://people.mcgill.ca/andrew.higgins/

" . . . demise . . ." Did they really use that word as a verb?

The use of our ABLs could minimize the extent of physical debris
that'll reach the surface.
.. - Brad Guth


Rand Simberg wrote:
On Thu, 14 Feb 2008 09:14:07 -0800 (PST), in a place far, far away,
made the phosphor on my monitor glow in such
a way as to indicate that:

Hear on the afternoon news, not much detail.
Thought I heard them say will use a missle to knock it down to retain
more control. Jeez now we'll have quite a mess up there. I'm sure
there will be more info shortly......................Doc

You can't "knock down" or "shoot down" a satellite with an
interceptor. They're just going to break it up into smaller pieces,
all of which will enter within a few weeks (faster than the satellite
itself was expected to).

They know exactly where it's coming down (within +/- a few km), and if
that's within China or Russia is why we're going in for the kill
before it's too late.
.. - Brad Guth


On Feb 14, 10:01 am, (Rand Simberg)
wrote:
On Thu, 14 Feb 2008 09:14:07 -0800 (PST), in a place far, far away,
made the phosphor on my monitor glow in such
a way as to indicate that:

Hear on the afternoon news, not much detail.
Thought I heard them say will use a missle to knock it down to retain
more control. Jeez now we'll have quite a mess up there. I'm sure
there will be more info shortly......................Doc

You can't "knock down" or "shoot down" a satellite with an
interceptor. They're just going to break it up into smaller pieces,
all of which will enter within a few weeks (faster than the satellite
itself was expected to).