Issue No. 35

The Orbital Index

Issue No. 35 | Oct 22, 2019

🚀 🌍 🛰

Finding fresh meteorites. Last week, I (Andrew) spent a few hours walking around dry lake beds with a very powerful magnet on a pole looking for meteorites. Shockingly, I didn’t find any. Problems included: seasonal lakes are wet too often, cracks hide small rocks, volcanic rocks look a lot like chondrites, and Andrew is impatient. But, there’s a better way: using cameras and weather radar to track meteors, modeling their “dark flight” wind-dependent free-fall trajectories for the last ~20 km before impact, and then searching the predicted strewn fields. Mike Hankey, who works with the American Meteor Society (AMS), kindly spoke with me about his work with Vishnu Reddy and Marc Fries on the RADARMET meteor tracking project. NOAA’s NEXRAD national network of 10 cm weather radar has been used to track bird migrations, volcanic eruptions, and the tragic breakup of Space Shuttle Columbia, and Fries suggested using it to detect meteor trails [Fries’ paper with details]. He leveraged data available online from the US National Climatic Data Center, and his team has since successfully recovered a number of meteorite falls. Unfortunately, Nexrad seems to have been re-tuned and is now less sensitive to meteor debris—in 2012 at least 4 falls showed up, but since then they’ve been lucky to see one annually. Mike’s latest effort is setting up a next-generation camera network, joining those run by NASA, IMO, EFN, DFN, and others. You can help by reporting fireball observations to the AMS/IMO (or the DFN in Australia), and/or by setting up your own sky camera and joining their volunteer network. Related: Jon Larsen’s gorgeous electron microscopy of micrometeorites found on rooftops... so you could also just look on your roof.

ESA has a new parachute plan. ExoMars 2020, the joint ESA and Roscosmos martian rover mission, has struggled to complete high-altitude parachute testing. The landing craft relies on a two-stage system: a 15 m chute for supersonic entry speeds, with a 35 m chute deployed once speeds decrease below Mach 0.8. While low-altitude testing of the subsonic chute (the largest ever used on a Mars mission) was successful [video], two high-altitude tests this year have both resulted in damage to the parachutes during deployment (in one case causing radial tearing to the chutes). ESA is now down to the wire on qualifying these critical components, and if they aren't successfully tested by late April, this mission will probably become ExoMars 2022. (Due to the ExoMars Schiaparelli landing anomaly, we doubt they’ll use chutes with a known high possibility of failure.) To address this timeline, ESA plans to work with NASA to ground test the chutes using specialized equipment at JPL. Related, this isn't the only mission currently struggling with parachutes: the SpaceX mk3 design, a first 4-chute system, failed a test in April (although the most recent results look promising [video]), and Boeing, who has generally had fewer difficulties with their system for Starliner, also had some anomalous tests reported (and disputed).

A helical engine that wasn’t. David Burns at NASA’s Marshall Space Flight Center recently proposed a "helical engine" (paper) that would use relativistic effects to produce acceleration without reaction mass. It suggested that if particles bouncing back and forth inside a chamber could have more mass when going in one direction than in the other, there would be a net acceleration. Burns’ proposal is to accelerate ions to relativistic velocities, causing their masses to increase when moving in one direction, but not in the other. With most “breakthroughs” of this sort (the EmDrive most notably), it is unlikely that this has any meaningful scientific basis. However, we believe it is important to push the bounds of physics with the goal of a breakthrough in propulsion. The Tau Zero Foundation pursues this sort of work and is a spinoff of NASA’s now-shuttered breakthrough propulsion physics program. On the other hand, if someone says they can turn a 52 card deck into a 53 card deck, you might want to be skeptical.

News in brief. The fuselage of Sierra Nevada Corporation’s Dream Chaser, which will carry cargo to the ISS, has been completed; SLS’s initial launch date will likely slip again to 2021, even as NASA awards Boeing a cost-plus contract for 10 rockets, arguably incentivizing them to take even more time; Chang'e 4 has survived for 10 lunar days on the far side of the Moon, and is now heading into another frigid 14-day lunar night (NASA is considering a rover that can operate through the night); a couple of weeks ago, a balloon with 1 million cubic meters of helium hoisted a 680 kg exoplanet telescope to the edge of space; NASA revealed the Exploration Extravehicular Mobility Unit (xEMU) spacesuits to be worn on the Moon by Artemis astronauts (compare to previous spacesuits in this gallery, and see Scott’s video about it); InSight stepped on its Mole and made 2 cm of progress (so far) through the Martian duricrust 🥳; NASA astronauts Jessica Meir and Christina Koch performed the first all-woman spacewalk; Firefly did an aboutface, annoucing they’ll be (perhaps disappointingly) partnering with Aerojet Rocketdyne to use their AR1 engines for Beta; and, Rocket Lab launched a tech demonstration satellite for Astro Digital into a 1,000 km orbit, their highest yet [launch video featuring New Zealand’s stunning Mahia Peninsula].

Comet 2I/Borisov as seen by the HST on its hyperbolic path through our solar system. (Meanwhile, if we want to visit an interstellar object closer to home, 2015 BZ509, in its retrograde orbit around Jupiter, is a likely candidate.)

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