¶Apophis. Scientists will be watching the 370 meter-wide asteroid 99942 Apophis fly by the Earth this Friday, albeit from a safe 0.11 AU away. On Friday the 13th, April 2029, however, Apophis will pass within 31,000 km of the Earth’s surface, inside the orbit of geostationary satellites. Fortunately, while originally estimated at a 1-in-37 chance of a collision in 2029, that possibility has since been ruled out. At the recent “Apophis T-9 Years” workshop there were proposals for CubeSats, small landers, and larger SLS-launched sample return missions targeting the 2029 flyby. It’s also possible that OSIRIS-REx, after dropping samples off at Earth, could head to Apophis as a mission extension with multiple flybys and finally a rendezvous. On average, an asteroid of Apophis’s size impacts the Earth every 80,000 years, and while Apophis won’t impact the Earth in 2029 or 2036, there is still a small possibility of an impact in 2068 (but this too will likely be ruled out by upcoming planetary radar measurements). Until we are confident of a miss, however, we should be very careful because even “[a] tiny change in Apophis’ velocity before the April 2029 flyby, caused by the collision of a small satellite with the asteroid, could shift the asteroid’s trajectory by several Earth radii in 2068.” Jeff Foust has a good discussion. |
|
¶Heavy Delays. This past week we learned of schedule changes for three in-development heavy lift rockets with very different development histories. NASA, after SLS failed its full-duration hot fire test in January, has now postponed the re-test for at least three more weeks due to LOX pre-valves on the Core Stage that won’t open fully (the LH2 pre-valves were repaired in the fall). Platforms have to be installed so that technicians can use specially-fabricated tools to access and repair the valves. This continues the litany of delays, overruns, and failures for the incredibly expensive and under-powered giant. In a recent scathing critique, Casey Handmer calls for SLS’ outright cancellation, claiming that its Shuttle heritage has hurt its safety, development speed, and ultimate usefulness, and that it is only propped up by lobbying, political maneuvering, and NASA’s unwillingness to acknowledge a failure. He quips, “even if SLS wasn’t architecturally unsafe, poorly managed, incredibly expensive, a technological dead end, obsolete, and cursed by a low production rate, it would still have nowhere to go.” SLS’s Block 1 design doesn’t have the power to send humans to the lunar surface (thus the need for the separately-launched Human Landing System) or Mars, or to send large spacecraft to deep space exploration targets. While the allure of returning to the Moon permanently is strong, SLS feels more and more like an unrealistic way to accomplish that goal. Meanwhile, Blue Origin updated New Glenn’s first launch date to NET 2022Q4, roughly what CEO Bob Smith suggested it should be upon taking the helm in 2017. New Glenn has struggled through development, in part due to its massive scale up from New Shepard—building a heavy lift rocket before ever reaching orbit is a monumental undertaking. Blue Origin cast shade toward Space Force for not selecting them in their recent contracting process—but blaming them can yield nothing positive for the company. It’s also probably not the real cause of the delay, with the company’s priorities being focused on leading the National Team’s bid to build the HLS and delivering flight-qualified BE-4 engines to ULA for this summer’s maiden Vulcan Centaur launch—the staged-combustion methalox engine suffered late-stage development hiccups with its turbo pump. (Blue Origin recently released videos of their Cape Canaveral rocket factory, tank cleaning and testing facility, and work at Launch Complex 36.) In stark comparison, last week Starship SN10 performed a static fire (video), a Raptor engine was swapped out (video), and a second static fire was performed in less than 48 hours (video)—the engine was removed due to suspect data produced during the initial test. SN10 is now cleared for a flight and triple-engine landing attempt NET today, pushed back from last Friday. While SLS is further along, it’s been under development in some form since the late ‘90s. The difference in development velocity (we’ll call it ∆v) between these three vehicles is striking. (Related: following close on the heels of the Inspiration4 entry deadline closing, the #dearMoon project announced pre-registration for 8 seats on its commercial circumlunar flight scheduled on Starship in 2023.) |
|
¶The future of Rocket Lab is Neutron. Rocket Lab announced development of Neutron, an 8-ton, medium-lift launch vehicle with a focus on mega-constellation construction and an eventual goal of being human-rated (here’s a good Twitter thread on how it might fit into the market). Neutron is targeting 2024 and will require Rocket Lab to pursue different techniques from Electron’s all-composite body and 3D printed engines. The next generation, reusable rocket will be built at an undecided location near NASA’s Wallops Flight Facility in Virginia. Electron’s electric pump-fed 3D-printed Rutherford engines are only 26 KN, so something larger will be required (for comparison, the original Merlin 1 engine was 340 KN). At the same time, news arrived of Rocket Lab going public via a (very trendy) SPAC transaction valuing the company at $4.1 billion. Last, but certainly not least, in a superbly cut video, CEO Peter Beck made good on his promise to eat his own hat if the company ever pursued reusability (highly recommended). |
|
¶Papers. - A new model of Jupiter’s gravitational effect on comets (paper) suggests that as many as 20% of long-period comets falling in from the Oort cloud can be thrown by Jupiter’s gravity into an orbit very close to the Sun, where they eventually fragment. The Chicxulub impact that killed the dinosaurs may have been shrapnel from one such ‘sungrazing’ long-period comet, not a main belt asteroid, which helps explain both its carbonaceous chondrite composition (paper) and its probability of occuring—this model increases the odds of long-period comets impacting Earth by a factor of about 10. Given comets’ exceptionally high velocities (an average of 51 km/s vs. 17 km/s for asteroids), this new model isn’t something we’re thrilled about. ☄️
- ESA’s Cheops orbital telescope found a planetary system with six exoplanets locked into a pattern of orbital resonance. It’s similar to the 4:2:1 resonance of Io, Ganymede, and Europa, in which Io completes four orbits of Jupiter in the time it takes Ganymede to complete two and Europa, one… but with the six planets forming a 18:9:6:4:3 orbital pattern. “The orbits in this system are very well ordered, which tells us that this system has evolved quite gently since its birth,” making it surprising that their densities are in a seemingly-random order with a “dense, terrestrial planet right next to a similar-sized but very fluffy planet – like a mini-Jupiter, and next to [one that is] very similar to Neptune.”
- Speaking of resonance, Titan and its other moons are moving away from Saturn faster than previously estimated, at about 11 cm per year. New research suggests that this migration also affects Saturn’s tilt—as the moons move away, the giant tilts more and more. This appears to have been a fairly recent phenomenon (paper). “It was only roughly a billion years ago that the gradual motion of its satellites triggered a resonance phenomenon that continues today: Saturn's axis interacted with the path of the planet Neptune and gradually tilted until it reached the inclination of 27° observed today.”
|
|
¶News in brief. China is officially moving forward with the development of their super heavy Long March 9—if this behemoth with a 10-meter core and 5-meter side boosters launches in 2030 as planned, it will be able to launch 140 metric tons into LEO or 50 metric tons to translunar injection, even more than the upgraded Block 2 SLS, and will pave the way for crewed Chinese missions to the Moon and Mars; a Russian Soyuz launched Arktika-M 1, the first spacecraft in an Arctic weather monitoring and communications program, into an elliptic Molniya orbit; an Indian PSLV launched Amazonia 1, a Brazillian deforestation monitoring satellite, and 18 smallsats; China launched three Yaogan-31 military ocean reconnaissance satellites—the trio will probably be used for triangulating radio transmissions, similar to the US Navy’s NOSS satellites; and, Spire Global is going public via (yet another) SPAC at a $1.6 billion valuation. |
|
|
