# Issue No. 116

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# The Orbital Index

Issue No. 116 | May 12, 2021

🚀 🌍 🛰
 ¶Starship survives to hop another day. SN15 flew and landed and failed to explode for the first time (and on the 60th anniversary of the first American in space, no less). Starship SN15 ascended through low lying cloud cover, performed a nominal climb to 10 km, then belly-flopped, and finally completed a successful two-Raptor soft landing—SN10’s hard landing was due to low thrust during its single-engine touchdown. A small methane fire at the base of the vehicle was again visible after landing, possibly due to a thermal protection blanket coming loose and catching fire. But, unlike SN10, the fire did not appear to be caused by structural damage and there was no unplanned return to flight. SN15 boasted many advances over previous Starship testbeds, including improvements to flight structures, plumbing, avionics software, and its Raptor engines. SN15 will likely fly again, and SN16 is nearing completion, with the possibility of rolling out to the pad in the next week (the most optimistic tank watchers are suggesting it might also fly this month). We’ll see what comes next. When the belly flop landing was first proposed, some felt it was incredibly unlikely that SpaceX would successfully complete a landing. And so, this landing represents a significant step forward for SpaceX, opens the door for an aggressive timeline to reaching orbit with Starship, and is a major milestone in their quest to build a Mars-capable transportation system.
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 ¶Papers. The size of Venus’s planetary core and the exact length of its day have been measured for the first time (paper). The core appears to be 7,000 km in diameter, similar to Earth’s. Researchers used powerful planetary radar pulses emitted from Goldstone, reflected off the planet Venus, and received again at Goldstone and the Green Bank Telescope to measure very small changes to the planet’s 243 Earth-day long rotation. Over 15 years of observations they observed fluctuations in the length of Venus’s day by 21 minutes, as well as tiny axial wobbles, both of which can be explained by a core of the estimated size. We do not yet know if the Venusian core is solid or liquid. A bacterium discovered 2.3 km below the surface of the ocean uses chlorophyll to photosynthesize the near-infrared blackbody glow of 400° C deep-sea hydrothermal vents (paper). Let that sink in—it basically photosynthesizes heat. Everywhere we look on Earth we find life (ex. 3 km underground, in radioactive waste, in bubbling tar, or in the upper stratosphere), often living off of something that we’d never consider food (plastic, meteorites, the radiolysis of water, or heat itself). It’s hard to believe that we won’t eventually find life happily existing in extreme conditions elsewhere in the Universe too.Relatedly, if there are exotic microbes living in places like Enceladus or Europa and getting ejected into space, missions like Europa Clipper need to know what these critters would look like after having smashed into their proverbial windshields at several kilometers per second. To answer this question, researchers at Imperial College London pyrolyzed samples of bacteria and archaea to analyze the molecular fragments that are left (paper). They can now look for these same signatures during future missions as well as in archived data from Cassini.
 ¶That’s a 10! Falcon 9 booster B1051 performed yet another Starlink launch and achieved SpaceX’s long-promised goal of 10 launches and landings with a single booster. (Booster B1049 is right behind, hitting nine flights last week.) This is also the number of launches that ULA’s Tory Bruno suggested would be required to make booster reuse financially worthwhile (to be taken with a grain of NaCl from a company that has no plans for full reusability, though Vulcan might eventually be able to reuse its BE-4 engines). Falcon 9 boosters may be able to be reused 100+ times with significant equipment replacements as needed. SpaceX’s booster fleet currently consists of 7 flight-proven F9 boosters (responsible for 37 launches), with a new Falcon Heavy (B1064-1066) and Falcon 9 (B1067) planned to enter service later this summer.
 ¶News in brief. Brainchild of the late Paul Allen, Stratolaunch’s Roc aircraft, the largest plane in the world by wingspan, completed its second test flight—the new owners hope to use it as a launch platform for experimental hypersonic vehicles; Blue Origin confirmed July 20th as the launch date for their first crewed suborbital flight and would like you to pay a lot of money to join them (they still have yet to announce long term pricing); Unseenlabs raised €20M for RF geolocation of ships and Firefly Aerospace raised $75M to continue development of their Alpha smallsat launch vehicle and Blue Ghost lunar lander; the Parker Solar Probe broke its own record (again) as the fastest human-made object, moving at 147 km/s as it swung through perihelion 10.4 million km above the Sun—at this speed, about .05% the speed of light, it could circle the Earth in 4.5 minutes; fragments of China’s Long March 5B core stage landed in the ocean near the Maldives—China received much criticism and ultimately got lucky that its uncontrolled reentry didn’t occur over land, as in 2020 when a Long March 5B core stage scattered debris over Côte d’Ivoire; continuing Australia’s support of its nascent launch industry, Catherine Roberts will become the country’s first Space Commander; with the confirmation of NASA Administrator Senator Bill Nelson, Steve Jurzyk has announced his retirement and has been replaced as Associate Administrator by Robert Cabana, current director of KSC—meanwhile, Vice President Harris will chair the National Space Council; and, OSIRIS-REx fired its main engines for 7 minutes and started its 2.5-year voyage back to Earth with samples from Bennu.  Stratolaunch’s Roc, the largest plane in the world by wingspan, during its second test flight.  ¶Etc.An exploration of meandering rivers that never existed. (Really, all of the portfolio pieces on his site are beautifully explained.)Use your data science skills to help identify anomalous signals (one example could be aliens) in scans of Breakthrough Listen targets and win$15k with SETI Breakthrough Listen’s Kaggle data science competition.NASA’s upcoming Psyche mission to the rusting metallic asteroid of the same name will be the first to use Hall thrusters in deep space. Hall-effect thrusters are a type of ion engine that confine an ionized propellant with a magnetic field and then accelerate it with an electric one. Psyche’s Russian-made SPT-140 xenon Hall thrusters are integrated into a Maxar-built satellite bus based on the ones used in their commercial communications satellites. The SPT-140s use up to 5 kW of solar power to produce ~0.27 N of thrust, 3X the thrust of Dawn’s ion thrusters. Related: What could volcanoes look like on a metallic world like Psyche? Enter ferrovolcanism.There are also many other types of electromagnetic thrusters. An untested new type is a plasma thruster that uses magnetic recombination rather than electric fields (paper). These thrusters would produce higher exhaust velocities than conventional plasma thrusters and have the ability to use both heavy and light elements as fuel. The challenge, as with most electric propulsion techniques, will be to find a sufficiently large power source, which in this case would probably have to be fission- or fusion-based. Related: Scott Manley has a review of far future engine technologies (using KSP, natch). How Many Decimals of Pi Do We Really Need? JPL uses 15.
 Winner of this year’s Tournament Earth astronaut photography contest, this photo by Kate Rubins shows Lake Van in Turkey, the largest alkaline lake on the planet. It is endorheic—meaning it has no outlet—and has a pH of 10. The swirls are turbidity plumes of calcium carbonate, debris, and organic matter. The lake also has the largest known modern microbialite deposits, which were common on ancient Earth (and hopefully Mars).

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