Issue No. 36


The Orbital Index

Issue No. 36 | Oct 29, 2019

🚀 🌍 🛰

Highlights from the 70th International Astronautical Congress. A few items of note from last week’s IAC:

SABRE hits a cool Mach 5. The Synergistic Air-Breathing Rocket Engine (SABRE), which we covered way back in Issue #4, hit a major milestone last week. Its pre-cooler, called HTX, was successfully tested with inlet air at temperatures exceeding 1000° C. The pre-cooler diverts intake air through a heat exchanger made up of 50 km (yes, km) of tubing with just 30 μm thick walls. HTX can transfer 1 GW/m3 from the hot intake air to cryogenic hydrogen, dropping its temperature to -150° C in just 1/20th of a second. The cooled air is then compressed, combined with the hydrogen, and fed into SABRE’s combustion chamber. Testing was conducted in Colorado by feeding super hot exhaust from an F-4’s turbojet engine into HTX. When flying, SABRE will use atmospheric intake air at up to Mach 5.14 and 28.5 km in altitude, or ~20% of the altitude and speed required to reach orbit. Altogether, this allows for a peak Isp of ~3,600 seconds at sea level. Compare this to a max of ~450 s for traditional engines and 800 s for nuclear rockets, which we do not recommend using at sea level. Vacuum performance will be a fairly standard ~460 s. This allows for an SSTO spaceplane design—we’re curious to see what type of engine bell is chosen to perform both at sea-level and in vacuum (although we hear Aerospikes are great for SSTO). Up next for SABRE: wind tunnel testing of the compression chamber in Germany.

News in brief. NASA’s 2021 Lucy mission to study Jupiter’s Trojan asteroids completed Critical Design Review; a NASA report calls for modernization of Planetary Protection practices [full pdf] that haven’t changed significantly since the early days of space exploration; Virgin Galactic (SPCE) became the first publicly traded space tourism company—it’ll be interesting to see how many people are willing to pay $250,000 for a 90 min flight with 5 min of weightlessness and whether an eventual “low” cost of ~$60,000/seat will increase the size of the market significantly; so far so good for James Webb sun-shield tests; Japan is planning to join the Artemis program; the eROSITA X-ray telescope that launched in July has seen first light; and, the X-37B military space plane landed after a record 780 days in orbit (we still don’t really know what its been doing up there).

HTX, SABRE’s pre-cooler test system containing 50 km of tubing.

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