Tag Archive: Jebediah

Over the past week since returning from holiday break program teams have been working on how they want to approach operations in 2019. For the most part everyone stuck to what they had going when 2018 drew to a close, but the Ascension team is continuing to move forward with a big change they began to plan late last year which is to forego further attempts at making orbit with just the Mk1 lifter and instead focus on preparing for sub-orbital capsule flights.

The main reason behind this decision was due to successive failures at modeling an ascent profile that would reach a decaying orbit using the new Launch Vehicle Designer that comes with the Trajectory Optimization Tool from ArrowstarTech*, one of our external partners. Even when the test payload mass was reduced as much as possible, 278kg down from 1t, the rocket was still unable to reach a final state at MECO that would carry it around the planet at least once. The main problem is that the rocket uses control surfaces for guidance, which means it can only control its pitch for about half of the ascent – past 37km the air grows too thin for the control surfaces to have effect on the rocket’s orientation. Although the natural force of gravity can continue to lower the nose past that point, it will do so only based on how fast the rocket was pitching before then. In the modeling, if it pitches over fast enough to end the burn with a positive perikee, it stays within the atmosphere. If it pitches over less aggressively to prevent this, past the point of aerodynamic control its nose doesn’t drop fast enough to push the orbit perikee out from under the surface while still making it to space before MECO.

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