Issue No. 47

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The Orbital Index

Issue No. 47 | Jan 14, 2020

🚀 🌍 🛰

Popping the top off at Max-Q. Every time you watch a live stream of a launch you'll likely hear something like “vehicle is experiencing Max-Q”. This is the moment during ascent when the rocket experiences the most aerodynamic pressure. Simply put, Q is the pressure created by the rocket running into the atmosphere really, really fast, and Max-Q is the maximum of this pressure, occurring as the rocket accelerates while in the dense parts of the low atmosphere. (Mathematically, it’s the maximal value of q = ½ρv^2, where ρ is the local air density and v is the rocket’s velocity.) SpaceX’s upcoming In-Flight Abort (IFA) Test recently completed its static fire ahead of a launch scheduled for NET 1/18 at 8:00 am EST and will demonstrate Max-Q in a potentially dramatic fashion (unlisted SpaceX animation of the upcoming mission events). During the launch, the abort sequence for the Crew Dragon capsule will be triggered by a loss of thrust event when the booster’s 9 Merlin 1D engines are shut down just as the rocket hits Max-Q. Crew Dragon will then propel itself away using its eight (redesigned and less likely to explode 🤞🏼) SuperDraco thrusters. Meanwhile, the Falcon 9 booster and second stage, now sans-Crew Dragon, will be traveling at ~250 m/s with a suddenly much less aerodynamic profile. A similar test was conducted by Blue Origin on New Shepard back in 2016. However, Falcon 9's Max-Q is 50%-100% greater than that of New Shepard (21-28 kN/m^2 vs 14 kN/m^2) and both Falcon 9 stages are expected to be fully fueled, with only ~30% of the first stage’s 400,000+ kg of LOX and RP-1 expended. If Max-Q triggers breakup and ignition occurs, the result could be a seriously rapid and fiery disassembly. (Numbers for this item come from the awesome New Shepard flight 4 data & SpaceX DM-1 data.)

Venus may have active volcanoes. A new study suggests Venus may have active volcanoes. Informed by a model of how volcanic olivine should react with the Venusian atmosphere to become coated with magnetite and hematite, the authors looked for and found those iron minerals in data from the ESA’s Venus Express spacecraft (whose mission ended in 2014 after lasting about 5 times longer than planned). The presence of these minerals suggests fresh lava flows on the planet’s surface. The only current spacecraft at Venus is JAXA’s Akatsuki orbiter. However, several missions are under development including India’s Shukrayaan-1 (possibly launching in 2023) and Russia’s Venera-D (2026 or 2031), with additional proposed missions from NASA (pdf) and others.

A splotch of gamma rays. A huge gamma-ray “halo” has been discovered by NASA’s Fermi Gamma-ray Space Telescope surrounding the nearby (800 light year away) pulsar Geminga (paper). If it were visible to the naked eye, the gamma-ray glow would appear about 40 times the size of the full Moon—about the size of the Big Dipper. This glow is likely caused by starlight interacting with high energy electrons and positrons (anti-electrons) that have been accelerated by the spinning neutron star’s magnetic field. Photons bounce off the fast high energy particles and gain enough energy to become gamma rays through a process called Compton Scattering. Our proximity to this pulsar also helps explain an excess of high energy positrons that have been observed reaching the Earth.

A space-based view of recent Iranian events. Last week’s Iranian conflict, unfortunately, highlighted the impact of space-based systems on geopolitical developments: the US’s satellite-guided drone strike killed Iranian general Qassem Soleimani, imagery from Planet showed the precision of Iran’s guided missiles used in retaliation (which were detected on launch by US monitoring satellites), and the tragic destruction of the Ukraine International Airlines 747 was also detected by US infrared monitoring satellites.

News in brief. NASA’s SLS first stage has been loaded onto a barge for delivery to the Stennis Space Center where it and its four Space Shuttle RS-25 engines will undergo extensive testing (before being thrown away); the Dragon Capsule from CRS-19 has returned to Earth after spending about a month at the ISS (c.f. Issue 42 and Andrew’s visit to KSC for the launch); and, the Large Synoptic Survey Telescope (LSST) has been renamed the Vera C. Rubin Observatory after Vera Rubin, whose pioneering work on galaxy rotation is a basis for the prediction of dark matter—this is, shockingly, the first national US observatory to be named after a woman.

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