Photos taken by several local people from a public road in the vicinity of the test site – some of which were provided to L2, while others were posted openly on the internet – provide a glimpse of the landing leg structures that appear to be closely based on the hardware that SpaceX is expected to employ when they actually fly with legs on a Falcon 9.
…limitations at the Texas site result in an AGL (Altitude above Ground Level) ceiling for Grasshopper of 2,500 feet.
Once GH2 arrives in New Mexico, it will be able to fly to much greater altitudes.
Gywnne said at ISPCS in October that they hoped to be flying out of New Mexico by the end of the year, so it looks like they’ve slipped that schedule. I was going to ask her at a meeting I had with her a couple weeks ago, but we were interrupted before I had a chance.
The Grasshopper legs are deployed for launch. Is there any provision for retraction? Or is the the plan to change to retracting for actual Falcon 9R launches?
By ‘retracting’ I’m meaning ‘angular rotation of the legs to make them parallel (or -more- parallel) to the centerline’, not just ‘get shorter individually’, which they can obviously do.
From the look of them, I’m guessing they swing vertically downward during ascent to minimize drag, and the C section shape protects the pistons from the exhaust plume.
This would of course mean that they lower the gear after liftoff and retract it for landing, which sounds backwards. ^_^
And it looks like the turnaround crew will also have to wipe the soot off the bottom of the rocket in between flights.
They will probably be stowed for liftoff, since it doesn’t make sense to stress the legs for full tanks. They have to be as light as possible, so they will be stressed for landing weight only (nearly empty tanks). Extension is probably irreversible, with the legs serviced and retracted manually.
I’m not sure that’s how they’ll work. Take a close look at the pictures. The bottom section is hinged at the base of the rocket and it’s outer end is connected to a cylinder that attaches higher up on the stage, forming the same basic shape as the grasshopper one’s legs. But in the photos, with the leg in the deployed position the cylinder is almost fully retracted, so the leg can swing upwards to lay flush with the rocket, it can only swing further downward as the cylinder extends.
My guess is that the legs will be in the landing position for ignition, keeping them out of the way of a lot of the back blast, and then swing down during liftoff to align with the rocket (acting a bit like long tail feathers). They’ll probably remain in that position until shortly before touchdown. Given the C-shape of the lower leg, it would have enormous drag if extended in forward flight.
But that’s just my guess from looking at the geometry in the photos. You could make a nice compact and streamlined mounting if the legs swung all the way upward to nestle against the side of the tank, which is what I would have guessed if not for the cylinder’s extension in the photos.
And you would be guessing WRONG. How could you miss the answer, right in front of you? See images from SpaceX’s F9 page:
http://www.spacex.com/falcon9
Your engineering analysis leaves from for improvement.
Another image to look at:
http://www.spacex.com/news/2013/03/26/landing-leg
Zowie, that’s a very thin cylinder because the diameter of the sections increases almost imperceptibly, which is why I didn’t even pay attention to the sectioning.
But why would they use a conventional steel section at the very end if they were going to so much trouble, or is that a special shock absorbing section?
Yes, that is the assumption by most observers – that leg extension will lock all sections in place, except for the final steel section to absorb landing shock.
When the location for Spaceport America was first selected it was with the intention of allowing orbital launches using RLV, including reusable boosters. They could in practice use the Grasshopper to actually put a payload in orbit using one of the corridors over WSMR that was mapped out as being safe. The Grasshopper could either return to the launch site or land at WSMR and then be refueled to hop back over the mountains to the launch site.