Issue No. 243

The Orbital Index

Issue No. 243 | Nov 8, 2023

🚀 🌍 🛰

Dragonfly update. NASA’s next extraterrestrial rotorcraft recently completed wind tunnel testing with a half-scale test article (and its aeroshell) in both a subsonic tunnel and NASA Langley’s Transonic Dynamics Tunnel—the latter can simulate Titan’s atmosphere when filled with a distinctly un-Earthly heavy gas environment. Titan’s low gravity (15% of Earth’s) and thick atmosphere (1.5 bar) make it a great place to fly the 3.7-meter-square, 420 kg rotorcraft, requiring just 2.5% of the hover power that it would need on Earth, a key enabler for its flights of up to 8-10 km which could reach a maximum altitude of ~4 km. To achieve these mission profiles (first covered by us all the way back in Issue No. 19) the craft features four coaxial rotors heavily informed by Ingenuity’s success—it can even lose one rotor and continue functioning. Once the mission completes its difficult >1.5-hour entry, descent, and landing (EDL presentation), one of its largest challenges will be thermal management in Titan’s -180° C atmosphere. Dragonfly’s thermal control system uses the moon’s nitrogen-rich atmosphere, pulling heat off the craft’s nuclear MMRTG with fans and pushing it through a duct and into the body of the craft. The complex system keeps internal science systems at operational temps and, importantly, the flight system’s 100+ kg, 11.5 kWh battery, at ~10° C throughout the mission despite both Titan’s frigid outside environment and Dragonfly’s high internal heat dissipation needs during powered flight periods—the latter is managed using a phase change material (PCM) to limit the temperature of the battery to the melting point of the PCM. (If you find the task of keeping a small, car-sized robot’s internals at Iceland-in-the-summer temperatures while it flies around on a moon in the outer solar system, then this paper is for you.) As of 2020, launch is now scheduled for 2027 with an arrival at Saturn’s largest moon in 2034 to conduct a nominal 3-year science mission. The mission also completed its preliminary design review (PDR), an important mission milestone, earlier this year. In other Titan developments, in 2020 the moon was found to host cyclopropenylidene (C3H2), a molecule previously only detected in pockets of the interstellar medium (paper). Cyclopropenylidene is thought to be a precursor to more complex building blocks of life.

Titan’s half-scale rotor test article, mounted for wind tunnel testing.

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  • Based on simulations (paper), two mysterious masses, deep in the Earth’s mantle below Africa and the Pacific Ocean—known as large low-shear-velocity provinces (LLVPs)—may be remnants of the hypothesized protoplanet Theia, thought to have formed the Moon when it impacted a young Earth. These regions of denser material show up on seismic data of our planet’s interior (check out that slick animated gif). The paper proposes that their increased density is from high iron content like we see on the Moon, and that the material was delivered by Theia, settling and accumulating atop the Earth’s core after the titanic impact. Related: A cool simulation of the Theia impact.
  • Binary neutron star mergers produce gamma-ray bursts (GRBs) and kilonovas. We know that GRBs can be dangerous to life on planets when the planets are in line with the burst’s directed gamma-ray beam. A new paper looks at the risk to life on planets that happen to be off-axis (and traditionally assumed safe) from GRBs, or which receive energy from kilonovas. They found that “X-ray emission from the [kilonova] afterglow may be lethal out to 5 pc [16 light years] and the off-axis gamma-ray emission may threaten a range out to 4 pc, whereas the greatest threat comes years after the explosion, from the cosmic rays accelerated by the kilonova blast, which can be lethal out to distances up to 11 pc.” Fortunately, while these events have a “similar kill distance to supernovae”, they’re far less common. Related: there are six known future supernova candidates within 300 pc.
  • 14,300 years ago a truly massive solar storm may have struck the Earth, one an order of magnitude larger than the infamous 1859 Carrington Event which started fires in telegraph stations and created visible aurorae around the world. Evidence for this event comes from spikes in radiocarbon (C-14) levels in ancient tree rings preserved in trunks along the Drouzet River in the French Alps (paper). C-14 is an isotope generated during upper atmosphere particle collisions and, along with beryllium in polar ice cores, is one of the best ways of dating historic solar activity. Nine super solar storms, known as Miyake Events, have now been identified over the last 15,000 years, the last ones in 993 and 774, with the newly found 14,300-year event being the largest, twice the size of the most recent pair. Interestingly, once dated, Miyake Events can be used as clocks on ancient wood—for example, Viking houses in Newfoundland were dated by identifying the 993 event in their lumber and then counting tree rings from there (paper).

These anomalies are known as Miyake events, named for the pioneering scientist who discovered them and was tragically devoured by a carnivorous tree.” XKCD #2847. (Also, how is there an XKCD for literally anything we want to write about?)

Dink doesn’t disappoint. Last week, Lucy’s first fly-by of a main belt asteroid resulted in an unexpected discovery during a test of the spacecraft’s new terminal tracking system, which keeps a target in frame as it zips past (in this case at 4.5 km/s). As the craft came within 430 km of the smallest main belt asteroid ever observed from close range, it snapped images that captured not one, but two asteroids forming a binary system. Dinkinesh, the larger of the two at 790 m in diameter is now known to be orbited by a smaller, as of yet unnamed 220-meter object. This discovery means Lucy's mission trajectory will now take the spacecraft by at least 11 objects—its original seven Trojans, plus Dinkinesh, two Trojan moons, and this new find. Dinkinesh translates to ‘you are marvelous’ in Amharic and is the Ethiopian name for the mission’s eponymous fossil.

The diminutive Dinkinesh and its positively minuscule, as-of-yet-unnamed, natural satellite from ~430 km.

News in brief. Indian commercial launch provider Skyroot raised $27.5M to accelerate and increase their launch cadence (their second commercial rocket Vikram-I is set to launch next year) The Netherlands and Iceland signed the Artemis Accords Northrop Grumman and York Space won $732M and $617M SDA contracts for 38 and 62 satellites respectively to build out the “Tranche 2 Transport Layer,” as part of the Proliferated Warfighter military communications constellation Starlink achieved breakeven cash flow ULA and SpaceX won massive contracts from the US Space Force (11 launches for $1.3B and 10 launches for $1.2B, respectively, which is a win for SpaceX) German startup POLARIS Spaceplanes conducted the first test flight of their subscale MIRA vehicle Apollo 16 astronaut Ken Mattingly died at 87 Space Pioneer, the first Chinese commercial space company to reach orbit with a liquid propellant rocket, raised an unknown amount (several hundred million yuan) to finish development of Tianlong-3, comparable to the Falcon 9 Finnish hyperspectral EO startup Kuva Space raised a €16.6M Series A In a possible world first, a ballistic missile was intercepted outside of the Earth’s atmosphere during war ● China’s Shenzou-16 safely returned three astronauts to Earth (despite having a torn single parachute) Virgin Galactic completed its 6th and final suborbital flight of the year with the planetary scientist for New Horizons, Alan Stern, aboard The second Starship test flight could happen in mid-November House GOP members introduced a commercial space bill to simplify government regulation of commercial space missions (this is a good thing, mission authorization for novel space activities under the Outer Space Treaty has been ambiguous and could use a formal home within the US government) A Falcon 9 flew for a record 18th time Andøoya Spaceport opened in Norway and will serve as the future launch site for Isar Aerospace.

Europe’s first operational spaceport in the Arctic Circle, located in Andøya, Norway.

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During a 51-second flight, Beijing’s Interstellar Glory Space Technology Ltd., aka iSpace, launched and soft-landed their methalox Hyperbola-2Y hopper vehicle. The test vehicle is 3.4 m in diameter and 17 m tall. The company is developing a reusable rocket targeting 2025.

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