Issue No. 98

The Orbital Index

Issue No. 98 | Jan 6, 2021

🚀 🌍 🛰

How even do cosmic rays? There was a good Astrobites post early last year about cosmic rays: very high energy extragalactic charged particles, some of which slam into the Earth’s atmosphere, generating showers of secondary particle radiation. Some cosmic rays have mind-boggling levels of energy, such as the Oh-My-God Particle detected in 1991, a single subatomic particle that carried 51 J, around “the same amount of energy as a professional tennis serve” — 100 quintillion times the energy of a visible light photon. Since they are charged particles, tracing cosmic rays back to their sources of acceleration is hard due to their paths being bent by extragalactic magnetic fields. It is likely that many cosmic rays are accelerated by bouncing back and forth inside of gigantic shockwaves, such as those inside relativistic jets or supernova remnants (this is known as Fermi acceleration). The paper covered by Astrobites postulates another mechanism of acceleration for the highest energy particles: linear acceleration inside of relativistic jets from active galactic nuclei, perhaps like the ones imaged by the Event Horizon Telescope. Whatever their source, cosmic rays are both a radiation challenge for space exploration and a useful tool for probing high energy physics, with protons sometimes having energies tens of millions of times that which we can produce in our puny little particle accelerators.

ISRO planning for the decade. After a year of few launches, heavily impacted by the country’s poor management of the pandemic, ISRO released India's space plans for the next decade (translated press release), hot on the heels of Chairman Sivan’s one-year extension to his term as Secretary of Space. Plans include several projects that will see completion in the short term: a first and second launch of the Small Satellite Launch Vehicle (SSLV) vehicle, the upgraded Chandrayaan-3 lunar lander mission, and Gaganyaan, India's first orbital crewed mission (currently scheduled for December with two uncrewed missions leading up to it). More expansive goals include semi-cryogenic propulsion (the SCE-200), green fuels, electric propulsion, and MethaLox engines (all the cool kids are into MethaLox these days). These propulsion programs would deliver a new heavy-lift vehicle, a fully electric satellite platform, improved GTO mass (5.5 tons), as well as at least partial (and maybe full) reusability. Additional goals include more Earth observation capabilities and a broadband internet satellite constellation of their very own.

Catching Super Heavy (!?). In traditional Musk fashion, last week Elon mentioned on Twitter that the Starship team is now planning (considering?) catching Starship’s Super Heavy booster with the launch tower instead of having it land on legs like Falcon 9. This would rely on the booster’s massive grid fins to bear the weight (~280 metric tons without fuel), and on its ability to hover (unlike Falcon 9) to increase precision. The tower would then place the booster back on the launch stand. This follows Musk’s mantra of “the best part is no part. The best process is no process” by eliminating both parts (landing legs, crush cores, hydraulics) and processes (moving Super Heavy back to the launch pad, resetting landing legs). Meanwhile, Starship SN9 could fly as soon as this weekend. Meanwhile, meanwhile, SN10 is now fully stacked and might end up at the launch site simultaneously with SN9 later this month.

News in brief. A US bill protecting Apollo lunar sites and artifacts was signed into law—however, it doesn’t seem to explicitly protect lunar artifacts of other nations; a French military surveillance satellite was successfully launched by a Soyuz rocket (capping off a failure-free year for Roscosmos); the upgraded Cargo Dragon will depart the ISS on Monday, completing its first formal commercial resupply mission; and, Virgin Orbit will attempt another air launch of LauncherOne on Sunday (1/10).


A carbon-composite structural model of Sierra Nevada Corp’s currently-abandoned crewed Dream Chaser in its natural habitat. The crewed version failed to gain further funding as part of the Commercial Crew Program, but the cargo-only version has been funded as part of CRS-2.

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