On Wed, 2 Oct 2013 16:30:58 -0400 (EDT) JMKrell@xxxxxxx wrote:
In a message dated 10/2/2013 11:51:17 A.M. Pacific Daylight Time, rsteinke@xxxxxxxxxxx writes:On Wed, 02 Oct 2013 10:57:11 -0700 David Masten <dmasten@xxxxxxxxxxx> wrote:On 10/2/2013 10:32 AM, Henry Spencer wrote:On Wed, 2 Oct 2013, Aplin Alexander T wrote:If you interpret "retro-propulsion" in the specific sense of firingMusk pointed out during the post-flight Q&A that "I believe the first time that any rocket stage has attempted to do a supersonic retro-propulsion." Apparently it was successful (this was the 1st stage's initial 3-engine re-entry burn).mainMy understanding is that the concern is over the dynamics of the engine startup in the presence of strong shocks. From what I've seen and heard, SpaceX lit the engines well above any appreciable atmosphere.engines forward while still in detectable atmosphere, yeah, I think that's true. Kistler was going to do it, but they never flew. Nor did the shuttle ever do an RTLS abort.DaveI think they are also worried about aerodynamic instability when flying through the turbulent remnants of the exhaust plume. Instability from the exhaust plume is not an issue during the three engine retro burn. The aerodynamic forces during the single engine burn are greater than any exhaust plume turbulence. John Krell
I meant that JPL was worried about that for Mars landers. And it may not be "we know it will be a problem." It may be more like "We can't prove it won't be a problem."
