Wednesday, October 07, 2009


I've been working on the Vertical issue, so I have not really gotten to work on the position hold and overall horizontal stability. In viewing the Masten Video Several things are clear,

1)Their motor movement is a lot smaller than mine, I think I probably have the gross actuator gain turned up too far.

2)Its real clear that they switch modes on the descent, IE the vehicle it goes into tight position hold mode, the engine then starts moving a lot more.

In any case its cool to watch the videos.


heroineworshipper said...

It seems to encounter ground effect & accoustic pressure waves coming back from the landing pad. Wish they showed more of the mechanisms working.

David said...

Two modes makes sense. The gross movement in any one direction would appear far less than your recent silver ball footage by a reasonable margin (no pun intended). Corrective oscillations are far greater when in hold position mode though the degree of off centre position appears still to be relatively small. Very good observations.

Masten have actually got their control code together very quickly. Given the few four engine test flights were almost uncontrolled and did not look close to working well (though this maybe a little harsh). They have stepped it up. It will be interesting when they go to multiple engines using differential throttling in the near future to see the flight control progress.

Anonymous said...

Paul, re (1) yes, I try to move the gimbal as little as possible because of: (2) The increased engine movement is due to a control problem that kicks in as the vehicle gets lighter, definitely not on purpose. I don't switch modes on descent (I thought of it but decided it wasn't worth it).

David, I started in MSS some time after those flights you mention and rewrote the entire control software from scratch.

Ian, (MSS GNC)