F9R 1000m Fin Flight | Onboard Cam and Wide Shot
Why Space Exploration Stack Exchange recommends it
Space Exploration Stack Exchange users link it as primary visual evidence of how SpaceX tested aerodynamic control surfaces and landing hardware on the Falcon 9 first stage.
Recommended by 1 people across 1 different months, 2014 to 2016.
What it is
SpaceX's official footage of an F9R test flight to 1000 m at its McGregor, Texas development site, shown with both an onboard camera and a wide shot. It was the first flight to test steerable fins that control the rocket during the fly-back phase, and it follows the earlier Grasshopper program.
Cited in 3 Wikipedia articles, including Falcon 9 v1.1, Falcon 9 prototypes, Grid fin.
What people said
Recommends TildalWave · 2015-05 · Space Exploration Stack Exchange · on “Does SpaceX performed low subsonic speed wind-tunnel runs of Falcon 9 booster in landing configuration and with legs eventually opened?”
Yes, see the quote below. And to complement those wind tunnel tests, SpaceX also uses F9R Dev [LINK] (formerly known as Grasshopper) test vehicles to test their VTVL (vertical takeoff, vertical landing) technology in the subsonic regime. Here's one video [LINK] (out of many) how that looks like: This test ( F9R 1000m Fin Flight [this video] ) included all aerodynamic control surfaces that a Falcon 9 first stage would use. But, for deceleration to subsonic regime, which these F9R Dev test flights don't yet include, SpaceX is being helped by NASA and there have indeed been wind tunnel tests (176 runs) done in NASA's Marshall Space Flight Center. According to this article on Physics.org [LINK] from
Cites Daniel F · 2014-12 · Space Exploration Stack Exchange · on “What is the function of the hypersonic grid fins on SpaceX's booster?”
In this video [this video] , are they being used for landing? I can't imagine how they should prove to be useful at that low speed.
Cites hshib · 2016-04 · Space Exploration Stack Exchange · on “Why doesn't the Falcon 9 booster use rigid air brakes during landing attempts?”
It seems that they initially planned to use the landing legs as air brakes. Elon Musk stated [LINK] that: If you then do some interesting things, like look at our landing gear, they're essentially like giant body flaps, so the drag - when we deploy the landing gear, the drag massively increases, so we have dual use of the landing gear as giant body flaps and as landing gear. That actually cuts the terminal velocity in half and therefore the fuel - the propellant we need to stop the vehicle in half, and actually it's quite an efficient method of landing precisely. This maybe just an earlier idea which didn't materialized. Looking at the earlier reusability video [LINK] , you see that legs are
Cites user12102 · 2016-06 · Space Exploration Stack Exchange · on “How effective are Falcon 9 1st stage grid fins in the last few seconds before landing?”
This answer [LINK] discusses the three methods that the Falcon 9 1st stage uses for attitude control during re-entry and landing. They are: cold nitrogen jets, "hypersonic" grid fins, and thrust vectoring of the engines. It is pointed out there that the grid fins are moving even in the last seconds of landing. I suggested [LINK] that like the front arms of the Tyrannosaurus Rex - they may move when it moves, but that doesn't mean that they are necessarily doing anything useful. The following questions and their answers are relevant: What is the function of the hypersonic grid fins on SpaceX's booster? [LINK] How long does the F9 first stage remain hypersonic under control of its grid fins? [