Near Satellite Collision Last Night

https://www.space.com/satellite-near-collision-miss-over-pittsburgh.html

Is this the same story? Because this was back in January....What would be the total force of the impact, if it were to occur? It would be cool to see something like this happen, of course I wouldn't want to be anywhere near when it did happen, and it certainly isn't worth the risk of a chain reaction that continued until every satellite was wiped out....Yikes!

if they both did crash,... that would be the least of the problems,.. the junk it would create could take out a lot more satellites.

It just seems that very little would survive an impact that violent, I mean these satellites are not light weight, some upwards of 2,000lbs, it would be like a 32,000 mph car wreck...theoretically, if they both weighed the same, and had the same exact shape and the same orientation, and were approaching at opposite directions, then they would merge into a large flat sheet of mixed material....and it would be instantaneous ...seems like a great deal of heat would be the result, maybe it would just go 'poof' and disappear...?

Or else with the reduced net velocity simply fall to earth as debris.

Maybe some of the debris would spear off into space to fall as a meteorite onto another planet for them to discover that in the dim periods of their ancient history that there was (intelligent) life on the third rock from this sun.

Or else with the reduced net velocity simply fall to earth as debris.

What happens in a collision, except for smashing each into pieces of various sizes, is that each piece undergoes a change in velocity, delta v. (Delta v is larger for smaller pieces.)

An analysis from: https://www.spaceacademy.net.au/watch/debris/collision.htm

So, each piece is then in a new elliptical orbit, tangent to the old circular orbit. The tangent point is either the perigee or apogee of the new orbit, depending on whether the velocity is greater or less than before.

You can plot altitude versus orbital period in a Gabbard diagram:

"Debris Orbital Decay

Gabbard diagrams are also useful for indicating the orbital decay of debris fragments. We have already seen in one of the tables above that when a collision occurs at a sufficiently low altitude some of the fragments that are ejected in the opposite direction to the original motion will be forced into orbits with a perigee below the Earth's surface. These will undergo atmospheric entry in less than half the period of their orbit. Because most of these particles will be those of smaller mass, they will in general burn up during reentry. Heavier fragments that may have a chance of depositing at least some of their mass on the Earth's surface will generally be the last fragments to decay due to atmospheric drag.

It is not necessary for a fragment to have a negative perigee to survive less than one orbit. Any fragment with a perigee of less than about 100 km will encounter so much air resistance (drag) that it will never make it back to apogee, and will deorbit in less than one period.

Fragments above this height will lose energy, mostly at perigee, and this will reduce their apogee height. Interestingly enough, their perigee height changes a lot less, until the apogee is brought down close to the perigee. The lower the perigee height of a fragment the larger the reduction in apogee height. This is seen on a Gabbard diagram as a drooping of the apogee plot at the left of the diagram.

The following two diagrams illustrate this decay. The first diagram is a plot within one orbit of the collision, which this time has taken place at a height of 300 km.

The yellow points represent those fragments with perigees below 100 km, and which are thus not present after one orbit.

Note the progressive droop in apogee as the period gets smaller. This plot simulates the fragment population some days after the collision, in conditions of sunspot minimum (ie minimal solar X-ray and shortwave UV output, which implies low atmospheric densities in the upper atmosphere)."

https://www.spaceacademy.net.au/watch/debris/collision.htm

Thanks, Rocket science is not my background, so please humour my simplistic example.

Aren't those diagrams and calculations based on "inelastic" collisions, like a pair of rocks. The items described, while rigid to you or me would seem relatively elastic to each other during a collision at that velocity, sort of like two cars colliding where there is significant energy absorbed through deformation during the impact unless merely a glancing blow.

I was imagining potential for a significant portion to remain tangled together (Or significantly decelerated) with insignificant velocity while maybe less that 10% was flung away on those alternate orbital options you described.

A collision between satellites would definitely be "inelastic" in that part of the kinetic energy would be consumed damaging or destroying one or both participants. The result of a collision between satellites would vary widely, depending on whether it was a glancing blow or a direct collision. At these speeds, the kinetic energy per kilogram exceeds energy per kilogram of high explosive, so for each satellite, it is as if it had exploded in orbit, with each fragment given a delta-v in a random direction to its previous velocity.

The Gabbard diagram does not assume either an elastic or inelastic collision, only that there is a delta-v added to the previous orbital velocity of each fragment, resulting in an elliptical orbit tangent to the original circular orbit.

Definitely a train wreck, you can't look away. But every time this happens, we get closer to the tipping point where it goes critical.

"The combined mass of the two objects, which are expected to zip past each other at a whopping relative velocity of about 32,900 miles per hour, is an estimated 6,170 pounds. LeoLabs has since updated its models ... and things are looking grim.

According to the company's latest calculations, the objects are expected to come within 80 feet of each other (±59 feet). The probability of a collision is greater than 10 percent. If the satellites collide, the impact could spread a network of debris throughout low-Earth Orbit."

This wasn't over Pittsburgh, but down by Antarctica.

6,000 lbs? what are they like marbles or somethin'?

<...This wasn't over Pittsburgh, but down by Antarctica....>

That suggests that it is alright.

That suggests that it is alright.

No, I don't have anything against Pittsburgh (nor Antarctica), just answering SE's question (in #1):

<"https://www.space.com/satellite-near-collision-miss-over-pittsburgh.html

Is this the same story? Because this was back in January....">

It wouldn't make much difference what part of the earth is under the collision point. The debris from each satellite pretty much stays in the original orbital plane. A portion of it is forced into a lower orbit and may reenter within one orbit or many orbits later after being slowed down by atmospheric friction.

Each satellite orbit has a maximum latitude north and south. Since most of the debris falls out underneath the satellite's orbit as the earth rotates, people living north or south of the latitude extremes of the orbit are safe. In the band between the maximum orbit latitude north and south, the maximum exposure is at the maximum northern and southern latitudes (because it spends more time there) and less at the equator.

Here is an example showing the relative probabilities for a satellite where the orbit maximum latitudes are north and south 50 degrees. This is based on the amount of orbit time the satellite spends at various degrees of latitude.

In order to answer this question, assuming do decay in NEO, you would have to know the construction of the Russian Satellite and the Chinese Rocket Motor (to determine how they would disintegrate), each units exact mass, and velocity.

The final velocity of the combined objects depends on the masses and velocities of the two objects that collided. The units for the initial and final velocities are m/s, and the unit for mass is kg.

mass of a first object (kg)

mass of a second object (kg)

initial velocity of the first object (m/s)

initial velocity of the second object (m/s)

final velocity of the combined objects (m/s)

The final velocity can be found for the combined paintball and can by rearranging the formula:

Compliments of SoftScholl.com (Inelastic Collision Formula)

This is a simplification for a purely inelastic collision, like two lumps of clay impacting each other. I don't see any vector mechanics or rotational mechanics in these equations. Had these objects actually collided those factors and how the objects fractured are why the Gabbard diagram predicts a spread of different velocities and trajectories.

What amazes me is the level of precision demonstrated in this prediction. Two objects in orbit with a relative velocity between each other of 32000 mph coming within 80 feet of each other and the chance of collision is only 10%. At that velocity 80 feet goes by in only 1.7 milliseconds.

With effectively no atmosphere for any wind effect, the only change in orbits could only come from a brief gravitational attraction. I wonder if any orbital change was detected and if that deviation could measure how close they did come?

Well, shape and albedo will have some effect, the solar thrust may be very low but it not worth ignoring.

The shape, albedo and solar thrust will have the same effect before, after and during the near collision. With the high resolution position and velocity measurements that can predict an 80 foot window in near earth orbit I am hoping for an observed change in orbit due to that brief proximity.

What are the chances of them hitting exactly straight on?

Pretty slim I would think;And being irregularly shaped objects, they are more than likely going to break up and go careening in all directions like a cue ball breaking a rack of billiard balls.

Some will fall out of orbit,some will change orbit,some large objects,some small.

The direction and speed of all the debris would be too complicated to predict individually.

I think it would create a large cloud of trash that could eventually take out many other satellites,far into the future, as this slow motion train wreck plays out.

Humans are the trashy-est animals that ever existed on this planet.

We have not only created massive garbage dumps on Earth,we have carried our bad habits into space.

You cannot throw anything away..there is no "away".

There are a lot of people that make their living from waste, there's no reason that cannot expand to include all waste, much can be incinerated for energy...When you look at waste you look at job opportunities of the future....It would be happening already if the waste industry wasn't so heavily regulated and controlled...Try going to a dump to get materials for recycling....

https://en.wikipedia.org/wiki/Waste_picker

https://www.nytimes.com/2019/04/07/us/trash-pickers-san-francisco-zuckerberg.html

Great, them I won't have to wait till November each year for the Leonids meteors, we could have them all year round.

I remember 2001 in country Victoria, Australia (Ned Kelly country) 2am, nice warm weather, sitting in a deck chair and the sky was full of shooting stars.

<...What are the chances of them hitting exactly straight on?...>

Zero, for they would have had to depart from each other from the same place at the opposite side of the earth at the same relative velocity as that of the collision. To have begun in the same place prior to departure their orbital velocity would have been zero, which means that they wouldn't have been able to stay in orbit before departure.

After impact a fair percentage of the cloud of material formed would have found itself on the path to de-orbit.

<...What are the chances of them hitting exactly straight on?...>

Very small, but not exactly zero. They could both be in different size elliptical orbits in the same plane, tangent at the collision point.