I've tried to find a discussion of this using the search utility but haven't found it.Has anyone tried to estimate the effectiveness of the grid fins at various speeds? I'm curious to what extent they could change the angle of attack of a re-entering stage and therefore cause lift and possibly significantly reduce the need for such a fuel intensive boost back.Presumably this is dependent on whether they can be deployed whilst the stage is hypersonic?
Quote from: executor314 on 08/09/2014 04:05 am1000m F9R flight, new actuators, new software according to Reisman. ~25:40 in the video.http://new.livestream.com/AIAAvideo/space2014/videos/58462185What are actuators? I know it has something to do with stability.
1000m F9R flight, new actuators, new software according to Reisman. ~25:40 in the video.http://new.livestream.com/AIAAvideo/space2014/videos/58462185
Quote from: alang on 08/09/2014 11:17 pmI've tried to find a discussion of this using the search utility but haven't found it.Has anyone tried to estimate the effectiveness of the grid fins at various speeds? I'm curious to what extent they could change the angle of attack of a re-entering stage and therefore cause lift and possibly significantly reduce the need for such a fuel intensive boost back.Presumably this is dependent on whether they can be deployed whilst the stage is hypersonic?I remember when they were first seen, someone posted this link, which I thought did a great job of explaining a bit about grid fin utility.
It's not a dogleg, it's flying at an angle of attack during that phase. Vehicle is angled slightly more toward vertical than its velocity vector through the atmosphere. It can be seen in the Thaicom 6 launch (as well as a pre-MECO maneuver to get back to zero AoA), probably would also have been visible in SES-8 if the lighting angle was better.
According to the FAA the F9R-Dev1 made a flight on the first of August.
Thanks for the link deruch:Quote from: deruch on 08/10/2014 01:21 amQuote from: alang on 08/09/2014 11:17 pmI've tried to find a discussion of this using the search utility but haven't found it.Has anyone tried to estimate the effectiveness of the grid fins at various speeds? I'm curious to what extent they could change the angle of attack of a re-entering stage and therefore cause lift and possibly significantly reduce the need for such a fuel intensive boost back.Presumably this is dependent on whether they can be deployed whilst the stage is hypersonic?I remember when they were first seen, someone posted this link, which I thought did a great job of explaining a bit about grid fin utility.I eventually started to wonder about this after ugordon's comment about angle of attack change (by thrust vectoring I guess) during the ASIASAT-8 launch :Quote from: ugordan on 08/05/2014 01:58 pmIt's not a dogleg, it's flying at an angle of attack during that phase. Vehicle is angled slightly more toward vertical than its velocity vector through the atmosphere. It can be seen in the Thaicom 6 launch (as well as a pre-MECO maneuver to get back to zero AoA), probably would also have been visible in SES-8 if the lighting angle was better.
Quote from: Zond on 08/02/2014 05:35 pmAccording to the FAA the F9R-Dev1 made a flight on the first of August.Any confirmation that the flight took place? If so, was it successful? Why hasn't a video been released as usual?
IIRC it was Steve Jurvetson at SmallSat who confirmed the hop and said a video was forthcoming.
This may also have been discussed at length( can't find it), has anyone here looked at the implications of the lift effects of a rotating cylinder, if the returning stage can be modelled as such:http://www.grc.nasa.gov/WWW/k-12/airplane/cyl.htmlClearly, by the time the legs open there is no such effect, but is it clear yet whether spin is an important feature at an earlier point? That link suggests that any such lift would both perpendicular to the direction of travel and perpendicular to the length of the tube. On the face of it that effect doesn't seem very useful and possibly problematic, but it does help make me appreciate that trying to understand the aerodynamics of that returning stage is way beyond a high school education...
A cylinder will produce lift if the grid fins will place it at a slight angle to the airflow.
Quote from: guckyfan on 08/18/2014 07:02 pmA cylinder will produce lift if the grid fins will place it at a slight angle to the airflow.This is the key point. The stage will not be rotating, so lift produced by a rotating cylinder is irrelevant.But as guckyfan says, the grid fins will induce a small angle if attack, and dynamic pressure acting on the exposed side of the (non-rotating!) cylinder will induce a small sideways lift force that will cause the stage to move sideways. The key will be to see how much of a "glide slope" they can induce this way, and therefore how much cross-range distance they can achieve. I expect that to be one of the test objectives at Spaceport America.
Quote from: Kabloona on 08/19/2014 04:46 pmQuote from: guckyfan on 08/18/2014 07:02 pmA cylinder will produce lift if the grid fins will place it at a slight angle to the airflow.This is the key point. The stage will not be rotating, so lift produced by a rotating cylinder is irrelevant.But as guckyfan says, the grid fins will induce a small angle if attack, and dynamic pressure acting on the exposed side of the (non-rotating!) cylinder will induce a small sideways lift force that will cause the stage to move sideways. The key will be to see how much of a "glide slope" they can induce this way, and therefore how much cross-range distance they can achieve. I expect that to be one of the test objectives at Spaceport America.Yes, maybe it won't be much, but should allow the stage to at least compensate for drift caused by wind. Perhaps it can do more.