4 ms·
a) because they launch out over the ocean b) because you can't turn a solid rocket off once you've landed c) and because of the rocket equation any added mass
by Taniwha 7y ago
a) because they launch out over the ocean
b) because you can't turn a solid rocket off once you've landed
c) and because of the rocket equation any added mass costs so much more, if they could afford the mass for solids for landing they could just add more liquid fuel and do the spacex thing, that would likely use less mass
- baybal2 7y agoa) rocket should have huge positive buoyancy b) you just have to size them right for the rocket mass and terminal velocity with a parachute c) definitely, but propulsive landing also does not come with fuel as the only mass penalty. You also have to add mass of heavy hydraulics and sensors into consideration.
- pjc50 7y agoThe SpaceX reason for doing barge landings rather than just fishing the rockets out of the sea is that salt water is very damaging to the rocket. Landing on the barge requires active directional control. Most of the Soyuz deceleration is done with parachutes, I'm not sure how that scales to a whole first stage.
- Taniwha 7y agoyes, exactly, salt water is VERY VERY bad Your main engines are gimballed for guidance, that mass cost is already paid
- baybal2 7y agoI hardly can imagine why. Their rockets are carbon fibre, aluminum-lithium, and steel alloys with such overkill corrosion rating that they should stand strong acids, not simple seawater. And mass cost of hydraulics for propulsive landing != hydraulics for regular gimbal steering. Those should be very different in their power and mass. Not only they have to steer the gimbal much faster and harder, but also aerodynamic elements on the rocket, fuel throttle, and those legs they land on.
- pjc50 7y agoThe expensive bit is all the electronics and turbomachinery in the engines.
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