Issue No. 73

The Orbital Index

Issue No. 73 | Jul 15, 2020

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DARPA wants a nuclear thermal propulsion system. DARPA is soliciting proposals from companies to develop a flyable nuclear thermal propulsion (NTP) system for demonstration in 2025 through their Demonstration Rocket for Agile Cislunar Operations (DRACO) program. NTP-based rockets vaporize liquid hydrogen using an onboard nuclear reactor and can produce a specific impulse (Isp) of 850-1,000 sec (liquid- and gas-core variations could produce up to 1,500s and 3,000s respectively). That is about twice the fuel efficiency of a traditional chemical rocket. Development by the US and Russia of NTP has so far been sporadic and incomplete. Modern technologies, like heat-resistant refractory metals and advanced simulation, may help NTP finally become a reality. NASA has been investigating NTP as well (pdf), which we talked about way back in Issue 6. Related: while appearing to be unchanged in design since 1995, this site provides incredible depth about all things nuclear rockets.

Waterfall vs Agile in Spacecraft development. After the high-profile failure of Boeing’s Starliner to reach the ISS in December due to software issues, and the subsequent news in February of a second software issue that almost caused the loss of the vehicle just prior to reentry, NASA has now completed two reviews and released 80 recommendations for Boeing’s software and hardware development process. NASA also released additional guidelines for all of its contractors. In the latest issue of Space Business, Tim Fernholz suggests that the aerospace industry may need to give less credence to “heritage” hardware and software and questions whether Boeing’s reliance on waterfall software development may have hampered their development in comparison to SpaceX’s agile approach. From a NASA pdf: “SpaceX and Boeing have very different philosophies in terms of how they develop hardware. SpaceX focuses on rapidly iterating through a build-test-learn approach that drives modifications toward design maturity. Boeing utilizes a well-established systems engineering methodology targeted at an initial investment in engineering studies and analysis to mature the system design prior to building and testing the hardware.” Starliner OPT-2 may launch again uncrewed later this year, with a first crewed mission in 2021.

NEOWISE shines bright at night. Comet NEOWISE, which has been producing gorgeous early morning viewing, can now be seen in the northern hemisphere in the evening. The comet was first spotted by the asteroid-hunting telescope of the same name. NEOWISE is the rebranded WISE infrared space telescope, which ran out of the liquid helium and frozen hydrogen coolant needed for its primary infrared astronomy mission in 2010, and was reactivated for less sensitive NEO observations briefly in late 2010 and continuously in 2013. NEOWISE, the comet, is the most visible since Hale-Bopp in 1997. We encourage you to get outside (and bring someone you’re quarantining with) to check it out as it approaches perigee on the 22nd—it will likely fade quickly thereafter. Bring a pair of binoculars to spot its split tail—a comet’s bluish ion tail points directly away from the sun due to solar wind, while the more visible white/yellow dust tail also points away from the sun, albeit less directly due to the interaction of gravity and radiation pressure on its very small dust particles. Related: Before heading out to take a look at NEOWISE, you might want to read a short intro to using binoculars for astronomy (and then also take a look at Jupiter this month!).

Comet NEOWISE as seen from the ISS. (Or, as viewed by the Parker Solar Probe.)

News in brief. The ISS had to dodge some space debris, burning the engines of the attached Progress MS-14 cargoship for 100 seconds to give the station a Δv of 0.5 m/s; a secret NRO payload is launching today on a solid-fueled Minotaur 4—the first launch for this vehicle in three years; Perseverance is now atop its Atlas V; the US House Appropriations Committee’s proposed 2021 NASA budget does not include money for a 2024 crewed Artemis Moon landing, but does hint that maybe Europa Clipper will launch on a commercial rocket (aka Falcon Heavy) instead of spending ~$1.5 billion more for a ride on SLS; unfortunately, InSight’s mole still isn’t working; the Chinese Apstar-6D communication satellite launched to geostationary transfer orbit on a Long March 3B, while the Chinese commercial solid-fueled Kuaizhou-11’s first launch failed with two satellites aboard; NASA reclassified the planetary protection status of the Moon with a directive to allow most activities without restrictions outside of the poles and historic landing sites (a directive relating to Mars calls for study on how to allow for human presence on the surface); ESA and ArianeSpace delayed the launch of the Ariane 6 to the second half of 2021; and, Orion’s heat shield passed an important milestone on its way to being part of the crewed Artemis-2 mission.

Kevin Gill recently added some more photos to his collection of lovingly-processed Jupiter photos.

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