Issue No. 19

The Orbital Index

Issue No. 19 | Jul 2, 2019

🚀 🌍 🛰️

Awesome Space! We’re excited to announce Awesome Space, a community effort to collect the best free and open space-related tools, code, hardware, and data. (Awesome X is a metapattern of open indices for best-in-class resources.) We’d love if you shared it, and even more if you submitted contributions! Some current favorites: 

The dragon will fly. NASA selected Dragonfly to be its fourth New Frontiers mission, following New Horizons, Juno, and OSIRIS-REx. Dragonfly will launch in 2026 to begin a 7-year journey to explore Saturn’s moon Titan. Here’s a cheeky but informative Titan 101 video explaining how Titan is similar to Earth (...if you squint really hard) and an attractive place to search for extreme life. Last contact with Titan was in 2005 when ESA’s Huygens probe was released from the Cassini orbiter and survived on the surface for 90 min [descent video], becoming the first and only outer Solar System landing. The spacecraft will enter Titan’s predominantly N2 atmosphere and use parachutes to slow to 2.8 m/s before releasing the lander 1.2 km above the surface of Selk crater. The 420 kg rotorcraft lander (similar in weight to an Arabian horse 🐎) will cruise at 10m/s at a normal altitude of 500 m but may fly as high as 4 km (to study Titan’s planetary boundary line) during its 2.7-year primary mission. It will be powered by a 110W plutonium-fueled radioisotope thermoelectric generator (RTG, or more specifically the MMRTG) and carry onboard spectrometers, meteorology sensors, a gamma ray detector, a seismometer, and drills (for collecting surface samples). Waste heat from the RTG will maintain operational temperatures for batteries and electronics (except the gamma ray detector, which is mounted outside to be super-cooled by Titan’s -180° C atmosphere). During Titan’s days, Dragonfly will be able to take one flight per day for up to an hour (20+ total flights for the mission), surveying the surface, and then returning to a new, previously scouted landing site. Each night (~8 Earth days), the RTG will recharge its batteries. Flying will consume ~40% of battery capacity on flight days, but the overall energy budget is dominated by science activities and direct-to-Earth (DTE) data uplink. From the mission concept document: “Missions with high-gain antennas (HGAs) empirically require about 5 mJ per bit per astronomical unit to acquire and send science data to Earth.” The MMRTG will output ~70W (2.21 GJ/year) on arrival due to fuel decay & thermocouple degradation, and with ~40% used on flight, a back-of-the-envelope max of 3.9 GB per year (0.987 kbps!) of data could be transmitted over its primary mission, far surpassing the ~100 MB that was transmitted by Huygens. While Dragonfly is under development, NASA will be pointing the James Webb Space Telescope (JWST) at Titan once it launches in 2021.
Dragonfly's typical flight profile.

News in brief. The methane plume detected last week by Curiosity has sharply decreased back to baseline levels—data analysis is continuing; Rocket Lab completed their third successful Electron launch of the year; Boeing’s Starliner demonstrated successful recovery while missing 2 out of 5 parachutes when dropped from a balloon at 12,000 m; SpaceX’s STP-2 (cf. Issue 17) launched beautifully, delivering all payloads, demonstrating reused side cores on a Falcon Heavy, recovering a fairing for the first time after 18mo of chasing them in a fast boat with a big net, and recovering the boosters (but unfortunately not the center core, which made a dramatic last-minute automated abort decision due to a breached engine bay); and, China’s Yutu-2 rover and Chang’e-4 lander have both successfully woken up after hibernating through the 14.5-day lunar night while radioisotope heaters kept them warm (the moon is tidally locked, so it rotates once per Earth month).


The Yutu-2 lander’s solar panel and tracks on the far side of the moon.

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