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The Orbital Index

Issue No. 278 | Jul 17, 2024


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Does Clipper have a MOSFET problem? NASA’s Europa Clipper mission recently came under scrutiny at the Agency due to reports of its MOSFETs failing under lower-than-expected radiation levels (at least according to a “non-NASA” customer using the same MOSFETs). The intense radiation in Jupiter’s radiation belts, especially from heavy ions expelled by Ionian volcanism and then trapped and accelerated by Jupiter’s magnetic field, 20,000x stronger than Earth’s, can cause Single Event Effects (SEEs), including Single Event Upsets (SEUs, aka bit flips) and Single Event Latch Ups (SELs) in MOSFETs. The total ionizing dose of radiation also builds up over time, causing transistors to accumulate charges at their silicon-oxide boundaries, increasing leakage current, and creating interface traps—these effects alter the voltage needed to turn the MOSFET on or off, disrupt the flow of electrons, and lead to increased energy use and overheating. Anticipating Jupiter’s environment, Clipper’s primary electronics are housed in a 9.2 mm aluminum-zinc alloy radiation vault, but some electronics must still operate outside the vault. In addition to the vault, common radiation mitigation techniques such as error-correcting codes (ECC) and triple modular redundancy (TMR) are also used by the mission to manage SEUs and hardware degradation. Testing by a NASA “tiger team” of the MOSFETs in question (from Infineon Technologies, who say they have “stringent processes in place to ensure compliance with all relevant quality and performance standards for our products.”) is happening in parallel with final preparations for launch in October—the outcome of this testing will likely determine whether the ~$5B craft is launched or delayed for some amount of rework. If needed, potential solutions include replacing Clipper’s faulty chips with more robust versions or adjusting the spacecraft’s trajectory to minimize radiation exposure (although the latter could reduce the amount of Europa that is covered by flybys). Perhaps oddly, the very same harsh Jovian radiation that threatens Clipper is thought to be a potential driver of life on Europa, oxidizing the upper layers of its subsurface ocean to produce energetic molecules, which may become the building blocks of microbial life deeper down.

A scanning electron microscope view of MOSFET damage after exposure to Ta ion irradiation.

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To detect dark matter, we just need to build a bird feeder that spins two squirrels around the rim in opposite directions at relativistic speeds and collides them together.XKCD #2186

Falcon finally has a mishap. With 364+ flights of Falcon-family boosters and just 4 failures, Falcon 9 has been the most reliable and active rocket ever built. Despite all this success however, this week, SpaceX had a Starlink launch fail during an upper-stage relight, deploying 20 Starlink satellites into a 135 km orbit, 150 km lower than planned. The Falcon upper stage developed a visible liquid oxygen leak which caused an engine anomaly when relit. The upper stage was not destroyed, however, and was able to perform Starlink deployment and passivation but was unable to circularize the mission’s orbit. Deployed Starlink satellites were losing ~5 km of altitude per orbit due to atmospheric drag. Despite firing their electric propulsion at maximum thrust, it is assumed they will not be able to raise their orbit quickly enough and will re-enter and burn up in the near future. With two crewed launches in the near future, in addition to the potential launch of Europa Clipper (see above) in October, all Falcon launches are currently grounded pending an FAA mishap investigation. Once a root cause has been identified, SpaceX can likely resume flight and rebuild its track record of reliability quickly due to its current cadence of launching every 2.7 days over the first half of the year—the company has requested an early return to flight while the investigation proceeds based on the results of a ‘public safety determination’ from the FAA, much like it has previously requested of Starship launches.

Liquid oxygen ice building up on the Falcon upper-stage MVac engine prior to the anomaly.

News in brief. Dawn Aerospace received approval from New Zealand to fly their rocket-powered suborbital spaceplane at hypersonic speeds, up to a 24,400 m altitude ceiling Chinese commercial launch provider iSpace suffered another launch failure with their Hyperbola-1 rocket due to an anomaly in the fourth stage SpaceX moved the next Super Heavy booster to the launchpad in preparation for Starship’s fifth flight Skyroot Aerospace successfully completed a proof pressure test of the first stage of their Vikram-1 rocket Virgin Galactic completed a new manufacturing facility in Arizona for final assembly of their suborbital Delta vehicles that will launch from New Mexico A four-person NASA volunteer crew exited a simulated Mars habitat after spending 378 days in isolation X-Bow Systems, a solid rocket motor startup from Albuquerque, secured a $70M Series B to expand production and build a new manufacturing facility in Texas Italian space logistics startup D-Orbit launched a US arm of the company which will seek to transform their orbital transfer vehicle into a satellite bus with help from Apollo Fusion founder Mike Casidy NASA astronaut Joe Engle, who piloted both the X-15 and space shuttle, passed away at 91 years old Poland’s Łukasiewicz Institute of Aviation launched their ILR-33 AMBER 2K rocket, powered by 98% hydrogen peroxide, to 101 km above Earth, the first Polish rocket to reach space.
 

Poland’s Łukasiewicz Institute of Aviation’s ILR-33 AMBER 2K rocket launching from Andøya Space Centre in Norway.

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The Goldstone Solar System Radar imaged the 150-meter-wide tumbling asteroid 2024 MK shortly after it approached within 295,000 km of Earth on June 29th. Goldstone used their 70-meter dish to transmit radio waves and a “smaller” 34-meter antenna to receive the reflected signal. This bistatic mode enabled imaging of details down to about 10 meters wide on the asteroid’s surface. Planetary radar still blows our minds. Credit: NASA/JPL-Caltech