Drawn on a paper napkin (Stone Age MS Paint) during my lunch break. Pure Speculation. The Cradle Ring and 8 hydro-shafts would need to be massive and blast proof.
Imagine that there are guide slideways, and the final cone of acceptance has a half angle of about 15 degrees.Assume the slam is set for 1g.If the rocket was able to land within 1 m of ground zero, it would only engage the slides about 4 m above ground, at a vertical speed of 9 m/s, and this will move it at a horizontal speed of about 2 m/s.Not so crazy.
And this is the "shocks on the ground" version.The difference in angles is the same, to guarantee that first contact is made at the height of the C.G., and then the flippers center the stage and cushion the sideways forces.The choice is not clear, and depends on the ability to control the clocking of the stage, even after the first "flipper" makes contact. If clocking is guaranteed, then both sides of the mechanism can be only 3 planar members.If clocking is not guaranteed, then the "cone" needs to really be a cone. In that case, maybe it's easier to put the flippers on the rocket and the cone on the ground, like in the first picture.In the picture below, the "hole" is larger, since it has to fit rocket+fins. In the picture above, it had only to fit rocket plus retracted (flush to the body) flippers.
it is obvious that moving the cradle is easier then moving the rocket. in final moments any wind gust can ruin everything. and cradle is only need to hold 300 tons. for example some bridge cranes could move 750 ton things. after catching the booster it could be positioned/transported (if you have enough long rails you could catch it 300-400m off the pad) to launch hold downs.
Quote from: drzerg on 01/26/2017 06:38 amit is obvious that moving the cradle is easier then moving the rocket. in final moments any wind gust can ruin everything. and cradle is only need to hold 300 tons. for example some bridge cranes could move 750 ton things. after catching the booster it could be positioned/transported (if you have enough long rails you could catch it 300-400m off the pad) to launch hold downs.Been pondering how much of an effect the wind can have. The ITS weighs quite a lot (cannot find figures, but 100t?), so therefor has a lot of momentum. It will take quite a gust to cause excessive movement.
Quote from: JamesH65 on 01/26/2017 11:06 amQuote from: drzerg on 01/26/2017 06:38 amit is obvious that moving the cradle is easier then moving the rocket. in final moments any wind gust can ruin everything. and cradle is only need to hold 300 tons. for example some bridge cranes could move 750 ton things. after catching the booster it could be positioned/transported (if you have enough long rails you could catch it 300-400m off the pad) to launch hold downs.Been pondering how much of an effect the wind can have. The ITS weighs quite a lot (cannot find figures, but 100t?), so therefor has a lot of momentum. It will take quite a gust to cause excessive movement.Booster mass is 275 tonnes per the IAC presentation.A calculation assuming a Cd of 1.0 and a wind speed of 10 m/s gives a wind force of 58 kN on the 12m x 80m booster. Handy (but simplistic) calculator here: http://www.engineeringtoolbox.com/wind-load-d_1775.htmlIf the terminal control thrusters produce 100 kN and have an adequately responsive control scheme they should have little trouble countering wind gusts in moderate weather.
That's no cold gas thruster... that's a superdraco...
Quote from: meekGee on 01/26/2017 01:56 pmThat's no cold gas thruster... that's a superdraco...AIUI Musk stated at IAC that the ITS booster will use 10 tonne gaseous methalox thrusters for terminal landing guidance. Grid fins are useless for terminal guidance and cold gas thrusters are far too small.
You can build cold gas thrusters as big as you want. They're not "too small." They're too heavy for the total impulse needed.
Quote from: envy887 on 01/26/2017 02:11 pmQuote from: meekGee on 01/26/2017 01:56 pmThat's no cold gas thruster... that's a superdraco...AIUI Musk stated at IAC that the ITS booster will use 10 tonne gaseous methalox thrusters for terminal landing guidance. Grid fins are useless for terminal guidance and cold gas thrusters are far too small.I meant "SD-sized" - for a sense of scale...Yes, if it's designed for rapid turn around, working with methane makes more sense of course.By gasous I take it that it takes gas into the combustion chamber. A big blow torch. Does anyone know if the that's correct?