Space and Science BS Thread

I know that the Planatary Defense group at JHU will be determining that in the next couple of years. They will have the initial images from the Italian cubesat, but they will know more once Hera makes the flyby in 2 years.

I believe the craft was moving at 13,500 mph at the time of impact.

 

Welcome! Glad to have you aboard

 

I watched the official stream until about 5-10 minutes after. Switch over to NSF and caught Das and Elyse (spelling?) from the Intrepid Museum. What a nice production and show.

It’s amazing what opportunities YT presents. For example, Das was conjecturing if DART hit a boulder. He and Elyse were toggling back and forth between the last full pic DART sent back and the partial, much closer pic with only a few bands of the pic coming through. They were attempting to pin point where it hit.

About 5 minutes later, Das gets a pic from his friend with the partial pic super imposed over the last full pic with the data matched from the partial to the full. Amazingly, the blank portion of the partial pic was made transparent and cross hairs were imposed to pinpoint where DART hit.

It’s an amazing time to be alive!

 

Aww, man! I missed that after wards! I only watched a couple minutes after the impact.

 

https://twitter.com/nasakennedy/status/1574757582975156224?s=46&t=oPhglfY81zDHhG_LtgQ9QQ

 

Wild…
https://twitter.com/astrosnapper/status/1574578176214196225?s=46&t=oPhglfY81zDHhG_LtgQ9QQ

Another view:
https://twitter.com/nasa_lsp/status/1574775690943205382?s=46&t=SdPDjTMOHCTfE0SkCQp29Q

 

The simple formula is conservation of momentum where the sum of masses times velocities before the collision equals the sum of masses times velocities after it, including that of ejected materials and any changes in spin rates. “Simple” because it ignores changes from kinetic energy to thermal energy and eliminates a boatload of calculations. Elastic collisions are easier(think billiard ball) because ideally the bodies don’t deform but even those have to account for induced spin(angular momentum) as well as the velocity(which has a vector as well as speed). Since in this case both bodies deformed and there was almost certainly ejected material, to get a precise calculation of velocity after the collision you would need to both account for the heat generated and the momentum of each particle ejected. You also need to know how far from the center of mass the path of the satellite was to account for a change in the spin of Dimorphos. It gets messy in a hurry adding up all of those vector quantities each of which has different components adding to either momentum or angular momentum minus the loss due to conversion to heat energy. I’m not sure but I think the cube sat only has cameras for visible light and not infrared so there’s no way to measure the thermal bloom, only a visual record of the ejected material and the crater afterwards. That means we can only estimate data on ejected material. I’m not even sure how well we can measure the spin of Dimorphos afterwards or whether all we can get is the period of the orbit. How far off center it was hit will determine what percentage of momentum went to spin and what went to orbital velocity.
The more smushing that goes on the less change to overall momentum.

 

Amazing:
https://twitter.com/elonmusk/status/1574773851523022850?s=46&t=oPhglfY81zDHhG_LtgQ9QQ

Full pic:

 

https://twitter.com/alexwitze/status/1574770713273442306?s=46&t=8sCPCD7wW3VyRzUMMEGwPA

https://twitter.com/liciacube/status/1574791158844346368?s=46&t=SdPDjTMOHCTfE0SkCQp29Q

 

This is what I was talking about: https://twitter.com/nasaspaceflight/status/1574547013328203776?s=46&t=SdPDjTMOHCTfE0SkCQp29Q

 

https://twitter.com/emrekelly/status/1574801019451674624?s=46&t=SdPDjTMOHCTfE0SkCQp29Q

 

Scott Manly just uploaded a copy of them along with his thoughts.
https://m.youtube.com/watch?v=hg4DiOmKlVM
it looked a lot more impressive than I expected given the disparity in mass.

 

Scott noted the lack of craters but it occurs to me that with the tidal forces and rubble nature craters might be flexed/shifted out of existence.

 

That's totally wicked!

 

I wonder if the impact combined with tidal stress is enough to break it up. A current theory is that tidal stress broke up a moon and created Saturns rings. Looking at the images it seems the larger boulders collected towards the extreme ends of the possibly tidally locked oblate moon. If it had nothing in the middle but lighter, loosely collated rocks it might have been more susceptible to the impact.

 

I wonder, if it did break up, if the gravitational pull from Didymos would/will be enough to pull Didymoon back together?

 

If it did break up I doubt it could pull itself together with Didymos right there but I probably overstated the case for it being broken up in the first case. It would be cool however to confirm my notion that any crater might be healed by shifting from tidal stresses. We still need to see the crater first though.

 

The Licia cube sat has two cameras; a high resolution b&w called Leia and a wider fov one with red, blue and green filters called Luke. According to NASA it will take weeks to transmit all of the images because it’s antenna and transmitter are so small. It’s supposed to remain active up to six months or more but has no further mission objectives.

 

History in the making:
https://twitter.com/iss_casis/status/1575189362102485004?s=46&t=OLfjn1NHIy5W5ytZ-UStVw