Jan 07 2019

Ascension Postpones Orbit for Capsule Technology Testing

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.

While unfortunate, this isn’t a complete surprise given the Mk1 is a lifter designed to push a second stage out of the atmosphere. We had just hoped it would have enough juice to reach a highly-elliptical orbit on its own from within the atmosphere, since it couldn’t re-orient or re-ignite itself for a more efficient burn in space. Even though the first two flights failed to achieve this goal, they still provided us with lots of valuable data on the rocket’s performance, allowed us to further develop our AFCS software and also proved it can indeed lift 1t into space as it was designed to. So we certainly did not waste our time! The Ascension program still plans to make orbit this year, but it will now have to wait for the second stage engine (oh, we were so sure of ourselves back then!) to complete its initial testing phase before being delivered to us no earlier than March.

So what is happening for this upcoming launch? The team will instead be preparing the rocket to perform a sub-orbital flight of the Mk1 capsule that arrived late last year, however it is not the capsule that will fly on this next flight but another test weight. The test weight will be roughly the same size and mass as the capsule, will carry a heat shield and cold gas thrusters. The shield and thrusters will both be technology demonstrations on this flight to see how they perform in actual conditions. The test weight will be attached to the lifter with a decoupler and it will be separated from the lifter stage once in space. The test weight will undergo various maneuvers while in space using the thrusters before orienting heat shield down for re-entry, followed by parachute deployment and recovery downrange in the Kerblantic. The mission will also be flown using a planned ascent trajectory from LVD to see how well it matches an actual launch.

If the mission goes well, the next lifter should be ready by the time the Mk1 capsule is done with its space certification. Assuming the capsule is deemed fit for flight, it will be on the next rocket with a test dummy inside – still not an actual astronaut, although all 4 of them have already made it clear they would do it. Okay, Bob was a little hesitant. Whether or not we put a kerbal aboard the following flight depends entirely on the results of the mission, so we still can’t say when a kerbal will be sent into space but it could be as soon as the second quarter of this year!

ArrowstarTech is used to represent the creator of KSPTOT and does not represent a true corporate entity