Issue No. 10

The Orbital Index

Issue No. 10 | Apr 30, 2019

🚀 🌍 🛰️

Some detailed CubeSat launch statistics. The statistics pair nicely with updates from last week’s CubeSat Developers Workshop. Some predictors of a CubeSat mission’s likelihood of success are: bulletproof safe-mode, ability to do on-orbit software and file updates, ability to perform hard resets from the ground, being built by a team with prior experience, and a lack of time-critical operational events. Related: NASA's Small Spacecraft Systems Virtual Institute (S3VI) has some great resources, including their Small Satellite Parts Search, their State of the Art of Small Spacecraft Technology publication, and their upcoming webinars about building small satellites.

The Universe is expanding faster than predicted. By observing Cepheid variable stars in the Large Magellanic Cloud, scientists using the Hubble Space Telescope announced the most accurate measurement of the Hubble Constant to date [pdf]. This measurement continues to show a discrepancy of approximately 10% between the predicted and observed values for the constant. 10% may seem small, but it’s unexplained, and the new measurement’s accuracy puts the possibility of this being a statistical fluke at 1 in 100,000. The Hubble Constant, typically written in km/s per megaparsec (1 megaparsec ≈ 3 million light-years), measures how quickly objects are currently moving away from us based on their distance—the further away the object, the faster it will be moving away from us, due to space itself expanding as the Universe grows in size. Using measurements of the Cosmic Microwave Background (CMB), the cold 2.72° K radiation permeating the Universe from when Hydrogen formed 379,000 years after the Big Bang, scientists can make predictions of the Hubble Constant we could expect to observe today. But the rate of expansion has been repeatedly observed to be higher than this prediction. Proposals for why this discrepancy exists include an unknown type of particle, dark matter interacting more with normal matter than is assumed, or unexpected “early dark energy.” Last week marked 29 years in orbit for Hubble, which continues to push science forward.

The Roc, Stratolaunch’s behemoth plane, flew for the first time [video] two weeks ago, becoming the world’s longest wingspan plane (longer than an American football field). Stratolaunch was funded by the late Paul Allen with the goal of launching rockets from the air from flexible locations. (But since the cancelation of their own rocket development program, it’s unclear which rocket it may eventually carry.) The Roc was built by Scaled Composites, Burt Rutan’s company which won the Ansari X Prize with SpaceShipOne in 2004. (If you haven’t read How to Make a Spaceship about SpaceShipOne and the X Prize, we recommend it.)

Beresheet succeeded in delivering the first commercial payload to the moon despite crashing into the surface, likely due to human error. Based on the lander’s impact velocity, the Arch Lunar Library it was carrying—a 30 million page “archive of human history and civilization” designed to survive for a billion years on 25 40-micron nickel discs—is likely intact on the moon’s surface. Now they just have to find it. NASA’s retroreflector probably survived the impact as well.

Rocket Launches: Japanese MOMO-F3 will attempt a launch for the third time. The launch is scheduled for a May 2nd liftoff (launch window opens at 11:15 am JST) after being pushed back due to bad weather and a valve that required replacement [live stream]. SpaceX will launch its seventeenth Commercial Resupply Services (CRS-17) mission to the ISS at 3:59 am EST on May 1st.[live stream]. And finally, the Electron STP-27RD mission from RocketLab will launch three U.S. Airforce payloads from New Zealand on May the 4th (window opens at 18:00 NZST) [live stream].

Saturn in Infrared from Cassini showing the hexagonal cloud pattern around its North Pole

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