The Orbital Index

Virgin Orbit rings in 2021 with an orbital launch. Virgin Orbit’s second orbital attempt for LauncherOne went off without a hitch (their first attempt failed shortly after ignition due to a problem with the LOX lines to the engine). The 21-meter, two-stage vehicle (which can deliver 500 kg to orbit) was released from Cosmic Girl (a modified Boeing 747-400) at 10,700 m over the Pacific Ocean. The primary benefit of launching from an aircraft at this altitude isn't lower fuel requirements, but the clear skies and many inclinations that you can launch into due to a plane’s mobility. This launch carried 10 cubesats (via NASA’s Educational Launch of Nanosatellites program) and was dedicated ‘For Eve’ after Richard Brandon’s mother who passed away from COVID-19 earlier this month. Virgin Orbit joins SpaceX and Rocket Lab in the elite club of NewSpace startups that have successfully made it to orbit. Also in this club—albeit employing either hydrazine or solid fuels and likely significant Chinese military tech transfer—are iSpace and Galactic Energy. We’re thrilled for Virgin Orbit and look forward to seeing many more launches, including to deep space.

SLS finally finishes something ahead of schedule 🙄. NASA & Boeing’s SLS Green Run hot-fire test at the Stennis Space Center was automatically aborted 67 seconds into the intended 8-minute test due to engine gimbal hydraulics reporting over-limit readings on one of the four RS-25 engines. (each previously-reusable Space Shuttle Main Engine costs over $100 million, but is now destined only to burn up upon reentry). In an actual launch scenario the booster would have continued flight, and likely experienced no side-effects since testing limits are conservative, but this makes us glad they decided not to skip this test. NASA now has the unpleasant choice of foregoing a full hot-fire test (it required >250 seconds of data to be considered successful) or to re-test the engines and allow the uncrewed Artemis I launch to slip yet again, this time to 2022. The Orion capsule for the mission recently completed testing and is awaiting final integration and fueling.

Survivorship Earth. There are numerous ways that Earth could have become uninhabitable over the last 4 billion years. The Sun’s luminosity increased 30% over that time, requiring balancing forces to prevent the planet from overheating. Meanwhile, volcanoes, meteors, or both too much or too little CO₂ all also could have easily rendered life extinct. Conventionally, it is assumed that feedback loops tend to stabilize these forces, but a recent paper suggests that luck also plays an enormous role. In simulations of 100,000 initially-habitable planets, only ~9% remained habitable in at least one simulation over a 3 billion year window, and only 1 out of the 100,000 remained habitable through 100 simulations. Survivorship bias likely plays a large role in how we view the Universe.

Magnetospheres. Another thing that makes a planet less habitable is being bombarded by flares and coronal mass ejections from its host star—and, about 4 billion years ago, our Sun was treating Earth to these types of events. But, according to a recent NASA-led study, we were fortunately protected by our young Moon, whose still hot, convecting iron core generated its own protective magnetosphere that merged with Earth’s at the poles. Life on Earth should be grateful that “the high-energy solar wind particles could not completely penetrate the coupled magnetic field and strip away the atmosphere.” Evidence comes from residual magnetism and traces of nitrogen (likely from Earth’s atmosphere) found through modern studies of Apollo-era lunar surfaces. Related: a tour of the solar system’s best magnetospheres.

• After mentioning NASA’s Pioneers program last week, we thought of the Pioneer anomaly. The momentum of emitted infrared thermal radiation from a spacecraft can impart a tiny, but detectable, photon pressure. The Pioneer anomaly was an observed deviation from the projected trajectories of Pioneer 10 and Pioneer 11, determined to be due to this effect—the crafts’ RTGs generated heat concentrated in one area of the spacecraft, causing non-uniform photon pressure and changing the vehicles’ velocities by ~1 km/h over 10 years. This also occurs in the YORP effect, which tends to slowly spin up asteroids’ rotations.
• Relatedly, an interesting review of the statite concept, a spacecraft that effectively forgoes Keplerian orbit to hover stationary over the Sun by using photon pressure on a solar sail to exactly counteract gravity. The article discusses how the method could be used to wait for interstellar objects, such as ’Oumuamua, and then free-fall toward the Sun, slingshotting around it to catch up with the object (paper).
• While red dwarf stars are known to emit powerful flares, new research suggests that their planets might still remain habitable (paper).
• Curiosity rover: 3,000 days on Mars
• According to NASA, 2020 tied for the warmest year on record. (Also: the quantity of human-made ‘anthropogenic mass’ overtook the quantity of biomass on Earth this year. Go team us?)

• Associate Editor for The Planetary Society
• Senior Software Developer, Containers & Integration (Fully Remote) for Kubos