Yep, and here's the relevant section about the roll issue:QuoteAs you can see in the video, the rocket wobbled at around cloud level, which was a combination of atmospheric turbulence combined with the rocket going through the transonic regime. The roll control vanes high on the rocket had good authority on the roll rate, but experienced a control inversion from 460-480m/s. That control inversion, likely from a shockwave reflecting off the cable fairing, meant that as the vanes moved to reduce the roll they actually increased it.Given unexpectedly increased roll control in the wrong direction the rocket did a snap roll, which increased the roll rate beyond the software's preset roll rate limit. Upon exceeding that limit, the rocket went into a preprogrammed mode to maximize the burn by locking the roll vanes and engine gimbal to center. The roll rate dropped and Stiga continued on unguided, watching the GPS to ensure that it was not exceeding the preset maximum range.
As you can see in the video, the rocket wobbled at around cloud level, which was a combination of atmospheric turbulence combined with the rocket going through the transonic regime. The roll control vanes high on the rocket had good authority on the roll rate, but experienced a control inversion from 460-480m/s. That control inversion, likely from a shockwave reflecting off the cable fairing, meant that as the vanes moved to reduce the roll they actually increased it.Given unexpectedly increased roll control in the wrong direction the rocket did a snap roll, which increased the roll rate beyond the software's preset roll rate limit. Upon exceeding that limit, the rocket went into a preprogrammed mode to maximize the burn by locking the roll vanes and engine gimbal to center. The roll rate dropped and Stiga continued on unguided, watching the GPS to ensure that it was not exceeding the preset maximum range.
Jan 14, 2012ID_AA_CarmackJohn CarmackNozzle extension for better high altitude performance on next flight pic.twitter.com/IX3EUXjB
https://twitter.com/#!/ID_AA_Carmack/status/158385393862066177/photo/1QuoteJan 14, 2012ID_AA_CarmackJohn CarmackNozzle extension for better high altitude performance on next flight pic.twitter.com/IX3EUXjB
The optimal nozzle is closer to a hyperboloid, but since in that case the part that would be non-conical is the part of the nozzle that's already there, they can't really change it. So, working with what they had, the conical extension makes by far the most amount of sense. If they were to machine a new altitude engine from scratch, then a hyperboloid nozzle would make sense (and have slightly higher thrust and Isp than the cone).
"Parachutes sucks" - John Carmack, before changing his mind
Maybe early-Carmack was right?
(personally, I just think that recovery mechanisms are hard... think of how long it took Armadillo to get to this point of flying to over 100,000 feet successfully twice... getting the recovery system to work reliably may take a while).
Quote from: Robotbeat on 01/29/2012 07:02 amMaybe early-Carmack was right?Quote(personally, I just think that recovery mechanisms are hard... think of how long it took Armadillo to get to this point of flying to over 100,000 feet successfully twice... getting the recovery system to work reliably may take a while).Yeah, they had a great recovery system.. legs and fuel.. but they decided they needed to go with parachutes and set that aside. Last I heard, the suborbital space tourism vehicle they're working on for Space Adventures is going to use parachutes too. (!)
Yeah, it's like someone switched the brains of Musk and Carmack about a year or two ago. (Carmack abandoned vertical landing and is taking up parachutes... Musk abandoned parachutes and is taking up vertical landing.)
Quote from: Robotbeat on 01/30/2012 07:02 amYeah, it's like someone switched the brains of Musk and Carmack about a year or two ago. (Carmack abandoned vertical landing and is taking up parachutes... Musk abandoned parachutes and is taking up vertical landing.)Parachutes apparently don't work from orbit or near-orbit, while VTVL seems complicated, expensive to engineer, and overkill for suborbital trips. Sounds to me like Carmack woke up to economic realities, and Musk woke up to physical ones. =)
