Issue No. 205

The Orbital Index

Issue No. 205 | Feb 8, 2023

🚀 🌍 🛰

Another round of NIAC awards has landed. We’ve covered NASA’s fantastical, very-speculative NIAC awards in the past. Well, another round is upon us, this time all Phase I awards, so on the very speculative side of very speculative. Some favorites include: a 50-meter aperture space telescope using fluidic shaping (more here), photophoretically levitated microflyers to study the Earth’s upper atmosphere, a proposal for a “a beam of microscopic hypervelocity (>120 km/s) particles propelled by laser ablation” to push spacecraft on fast transit interstellar precursor missions, an interferometric array of thousands of smallsats at L5 to search for the magnetic fields of terrestrial exoplanets via their 100 kHz-15 MHz radio emissions, and a long-distance x-ray/gamma-ray “flashlight” for remote spectroscopy on planetary bodies. The other winners involve Lattice Confinement Fusion, radioisotope-based thermoradiative converters for CubeSats, diffraction-based exoplanet imaging, bend-formed in-space structures, a new class of high-Isp & high-thrust NTP propulsion, cyanobacteria and fungi as building agents, aerogel nuclear fission fragment rocket engines, a low-cost (that must be relative) flying boat mission for Titan, and a Lunar South Pole Oxygen Pipeline (probably also useful for burritos). 🤪🚀

TitanAir, the ekranoplan of liquid hydrocarbon seas.

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Stoke’s unique upper stage. Stoke Space, a Washington State-based medium lift startup aiming at the fully reusable launch market from day one, has continued to pull back the curtains around its design for a uniquely multipurpose upper stage (Dodd also just released an in-depth walkthrough video). While the first-stage has its own challenges—the plan is to use an in-house full-flow, staged-combustion engine, only the fourth engine of this type to be developed—the upper stage is where Stoke is swinging for the fences. This stage features an actively cooled heat shield. Liquid hydrogen flows through tiny channels in its surface, absorbing heat during re-entry, expanding, and then, as a hot gas, powering the turbo pumps to feed yet more fuel through the heat shield to the upper stage’s 30 combustion chambers. (Notably, this system self-regulates its cooling by using heat from re-entry to drive the feed pumps. It is also theoretically fault tolerant: micro cracks in cooling channels will lead to over cooling instead of a loss of cooling.) The combustion chambers, laid out around the circumference of the heatshield, technically form a single engine since they share turbopump machinery. They utilize the shield to produce high expansion ratios and an aerospike effect for increased efficiency from high altitude, to full vacuum, and, finally, back to sea level. Expansion gas from this actively-cooled, open-cycle engine is exhausted from the center of the heat shield as “base bleed” for the aerospike effect, taking the place of a traditional long tapered spike shape and allowing the rounded, “truncated spike” heat shield dome to achieve high thrust (paper). Re-entry will be shield (and engine) first, and employs its skewed dome geometry to allow precise trajectory control by rolling with RCS thrusters during the un-powered re-entry phase. Close to landing, the upper stage will re-ignite its 30 thrust chambers and use phased shut-off pintle injectors for deep throttling, thrust differential, and precise shutdown to propulsively land. Together, the fully-reusable, 30 m tall, two-stage rocket will deliver ~1.65 tons to LEO. The upper stage is where the majority of Stoke’s technical risk lies, and so the startup—well funded by Breakthrough Energy Ventures and Alexis Ohanian’s 776—is tackling this challenge first. With initial hot fires complete, it is now moving quickly towards upper stage hop tests later this year at its Moses Lake, WA testing facility; meanwhile, the booster is much earlier in development, with component design still in progress.

A render of Stoke’s upper stage using thrust differential from its 30-chamber engine to perform a precise propulsive landing.

News in brief. The French-German startup Exploration Company raised €40M to develop their reusable Nyx space capsule (interestingly, it will have an open source operating system) Voyager Space raised $80M to work on their commercial space station, Starlab A US Air Force F-22 fighter shot down a high-altitude Chinese surveillance balloon off the coast of Florida—it was at ~19,000 meters at the time and had traversed North America from the Aleutian Islands across Canada and south to Florida Orbital Sidekick raised $10M for energy pipeline hyperspectral monitoring satellites, two of which will launch on Transporter 7 SpaceX launched another 49 Starlink sats with their seventh launch in January, then promptly launched their 8th mission, which was also Falcon 9’s 200th… and then sent Spanish Hispasat to GEO Curiosity found another metallic meteorite on Mars NASA says that, given available launch and onboard resource capacity, the ISS is now at “full utilization A Japanese H2A rocket launched a military EO satellite LeoLabs (who recently commissioned their newest radar in Australia) pointed out a very near miss conjunction between an SL-8 rocket body and Cosmos 2361 which would have produced copious debris A few days later, Cosmos 2499 (a different Russian satellite, launched in 2014) broke up into at least 85 pieces at 1,169 km altitude.



A SAR image of Tycho Crater on the Moon taken from Earth by the NSF’s Green Bank Telescope and the Very Long Baseline Array. At 5-meter resolution, this is the highest-resolution terrestrial radar image of the Moon ever collected. A 500 kilowatt planetary radar system is under development which will be 1000x more powerful. We’re still amazed that humans managed to bounce radar signals off of Jupiter… in 1964.

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