Issue No. 9

The Orbital Index

Issue No. 9 | Apr 23, 2019

🚀 🌍 🛰️

More about the upcoming DART and Hera missions to Didymos and its Didymoon. Last week, when mentioning that NASA just bought a Falcon 9 ride for DART scheduled for June 2021 from Vandenberg, we promised we’d cover DART in a future issue. Well, this week we deliver! DART is NASA’s upcoming mission to the sub-kilometer near-Earth asteroid Didymos (Greek for “twin”) and its small ~0.2km tidally locked moon, nicknamed Didymoon, which orbits the asteroid every 12 hours. DART will be the first test of using a kinetic impact to change the motion of an asteroid for planetary defense. The Didymos system was selected due to proximity to the Earth, similarity to other realistic NEO threats, and low rendezvous delta-v requirement (only 5.1 km/s, while the Moon is ~6.0 km/s). Using onboard autonomous guidance and next-generation solar-electric propulsion, DART will strike Didymoon at 6 km/s, which is expected to change the orbital velocity of the moon by less than 1%, but which should still be measurable from Earth using telescopes and planetary radar imaging of Didymos (from Arecibo in Puerto Rico at ~1 megawatt). DART’s sibling mission is Hera, ESA’s proposed 2023 follow up to perform a post-impact survey. If funded, Hera will test autonomous navigation using diverse sensors, coming within 200m of the surface of Didymoon and taking pictures with resolution down to 2 cm per pixel. We plan to keep tracking this ambitious pair of missions and will include updates as they progress. Related: upcoming asteroid close encounters with the Earth from the International Asteroid Warning Network.

Northrop Grumman launched an Antares rocket loaded with a Cygnus cargo craft on its way to the ISS. The rocket also included over 60 cubesats and thinsats, the latter being designed and built by K-12 schools across the US. The Cygnus module will stay in LEO after undocking from the ISS in June for up to seven months to test the craft’s long term mission capabilities. Northrop Grumman launched the rocket from the Mid-Atlantic Regional Spaceport. (We’re not sure what ‘regional’ means in the case of Spaceports, but the facility on Wallops Island, Va. has several benefits including its central location and flexibility for smaller launch vehicles.)

The SpaceX Crew Dragon capsule from DM-1 suffered a catastrophic anomaly during testing. The anomaly, which occurred during a ninth and final test of the capsule, reportedly blew the capsule open, destroyed the test stand, and produced a large cloud of orange smoke due to the rapid release of hypergolic fuel (specifically Dinitrogen Tetroxide which turns orange as it’s temperature increases) from the SuperDraco thrusters. A video of the explosion leaked online, and the event is likely to negatively impact the timeline for Crew Dragon certification, although SpaceX has stated it may still be able to reuse the capsule. The company is also considering moving the upcoming booster return of the unmanned CRS-17 mission to their drone ship just off the coast instead of the planned Landing Zone 1 due to hypergolic fuel contamination at the site.

Papers. An interstellar meteor may have hit the Earth (at 216,000 km/h) in 2014 (arXiv); fairly evenly around the moon, and about 8 cm below the surface, the lunar soil is moderately wet (Nature Geoscience); and helium hydride (HeH+), predicted to be the first molecule formed after the Big Bang, has finally been detected in space (Nature).


“Space without the space”

Bonus picture: Going to space on pillars of fire.

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