“SpaceX is proud to continue our successful partnership with NASA in support of this important interplanetary mission,” SpaceX President Gwynne Shotwell said in a company statement. “This award underscores NASA’s confidence in Falcon 9’s capability to perform critical science missions while providing the best launch value in the industry.”
DART remains on schedule for launch in July 2021 on a Falcon 9 despite the pandemic, said Elena Adams, mission systems engineer for DART at the Johns Hopkins University Applied Physics Lab, which is managing the mission, during the webinar. The spacecraft bus, with its electric propulsion systems installed, recently arrived at the lab for integration and testing.
Dr. Bonnie Buratti of the Jet Propulsion Laboratory will use Earth-based telescopic observations of Didymos and Dimorphos to better characterize the surface reflectivity and roughness of both objects before DART’s arrival, and later will use observations from DART itself to further refine this knowledge, in order to aid in mapping the geological features of the asteroids.Dr. Ludmilla Kolokolova of the University of Maryland, College Park will use sophisticated radiative-transfer models to analyze and interpret images of the ejecta plume taken by LICIACube’s cameras, in order to better understand the distribution of ejecta momentum enhancing the effect of DART’s kinetic impact.Dr. Jay McMahon of the University of Colorado, Boulder will apply the dynamical theory of interacting non-spherical bodies and radiative forces to better understand the changes in Dimorphos’s orbit caused by physical effects other than DART’s kinetic impact, in order to help interpret the post-impact Earth-based observations.Dr. Stephen Schwartz of the University of Arizona will develop a new computational approach to link fluid-based simulations of impacts to particle-based simulations of the resulting ejecta, in order to better connect the observed properties of the ejecta plume to the physical properties of Dimorphos’s surface
BTW, the reason we need to experimentally slam a spaceship into an asteroid rather than simply *calculate* how much it will deflect the asteroid, is because regolith physics is UNSOLVED and too hard to calculate! The splash of regolith on impact determines the deflection. 1/22/2 Because the splash flies *back* the opposite direction that the asteroid is being nudged, so it actually increases the change of momentum of the asteroid. But how much? Nobody can calculate a splash of sand. Sand physics is unsolved and super hard. https://nytimes.com/2020/11/09/science/what-makes-sand-soft.amp.htmlThe factor of the momentum change due to regolith splash is known as the “beta” of the impact. It is super important to measure so we can deflect an asteroid enough to miss the Earth, considering that spacecraft kinetics are not infinite.Sample the math in this seminal paper. This is sand (in a simplified case). https://eweb.unex.es/eweb/fisteor/vicente/publicaciones/preb07.pdf
Seems to me this test will need to be repeated on each type of near Earth asteroid. Surely you will get quite different ejecta depending on whether the spacecraft slams into a solid rock, a pile of rubble, a sandy surface, and so on.Also, for a real mission, I'd imagine you would want to leave the spacecraft attached to the second stage. It requires more maneuvering oomph, but increases your impact mass (or gravity tractor mass) for free. This is a quite different engineering problem (especially if you want to support a wide variety of launch providers, as you would in a real emergency). Maybe the next planetary defense mission can try this.
Quote from: LouScheffer on 11/26/2021 01:16 pmSeems to me this test will need to be repeated on each type of near Earth asteroid. Surely you will get quite different ejecta depending on whether the spacecraft slams into a solid rock, a pile of rubble, a sandy surface, and so on.Also, for a real mission, I'd imagine you would want to leave the spacecraft attached to the second stage. It requires more maneuvering oomph, but increases your impact mass (or gravity tractor mass) for free. This is a quite different engineering problem (especially if you want to support a wide variety of launch providers, as you would in a real emergency). Maybe the next planetary defense mission can try this.Heh. Will really like to see a real impactor like "Rods from God" for asteroid composition survey. All that is needed is attaching some ion thrusters for the cruise phase plus some hypergolic thrusters for the terminal phase to a 10 tonne metal rod. Along with some parasite post impact observation SmallSats that doubles up as vehicle flight control systems.
....the coupling coefficient is anticipated to be between 1.5 and 2.0 for the Didymos impact. Getting a good value from thus experiment will go a long way to refining a future prediction for a different asteroid. And in the end, in the unlikely case that such a deflection was needed, it would be over-designed for the worst case amplification factor and the worst case targeting. So another test is not needed, which is good because another mission is unlikely.
DART was an earmarked mission inserted into NASA's budget by a member of Congress. There have been numerous expert studies done over a number of years on dealing with the hazard posed by NEOs (I was study director on two of them). You won't find this mission recommended in those studies.
Quote from: Blackstar on 11/26/2021 11:24 pmDART was an earmarked mission inserted into NASA's budget by a member of Congress. There have been numerous expert studies done over a number of years on dealing with the hazard posed by NEOs (I was study director on two of them). You won't find this mission recommended in those studies.That's quite the leading comment. Care to share WHO the Congress member was? A Google search was fruitless. Link to the studies? Any opinion on WHY the earmark was inserted?
“asteroid composition survey” sounds like scienceDART is out of NASA’s Space Technology Mission Directorate
