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curious why don't they deploy parachutes or floatables and then slowly do a controlled descent using the rockets? I mean is this most efficient way of landing t

curious why don't they deploy parachutes or floatables and then slowly do a controlled descent using the rockets? I mean is this most efficient way of landing the rocket, essentially going backwards on re-entry? What if the rocket catches a gust of wind and flips on its side? Bad weather?

thomas11 12y ago
One reason, according to Elon Musk, is that parachutes or floatables won't work in the thin atmosphere of Mars. So if Mars is the vision, they must develop something that works there.
danielweber 12y ago
Parachutes are hard and have their own failure modes. IIRC even emergency parachutes have taken out some test rockets when they weren't supposed to have been deployed at all.
simonh 12y ago
SpaceX did try parachutes at first, but there were too many down sides. Parachutes impart heavy stresses on the rocket so aside form the weight of the 'chutes you have to strengthen the rocket, adding even more weight. They also don't allow for landings that are either precise or vertical. In theory you could use 'chutes to slow the rocket for part of the descent, but to land vertically at a precise point you'd still have to add legs and use fuel for a propulsive landing. At which point the 'chutes are adding very little value. Landing in the sea with floatables means you get a very wet rocket contaminated with saltwater and potentialy flotsam. Seawater plays havock with the hot precision metal parts of the rocket engine. Also again you have to strengthen the rocket to survive the tumble into the sea and wave action. So using parachutes adds significantly more weight without giving you what you want, and ditching into the sea also means more structural weight and mucks up your engines.
InclinedPlane 12y ago
For exactly the same reason that doesn't happen when landing an airplane, it's not efficient, it's complex, it's error prone. Parachutes means you have a recovery zone not a precision landing. Efficiency is all about operational efficiency, and fuel is the cheapest thing in the whole system. Burning a little fuel so that you can have a fully powered, highly controlled, high precision landing means that you are able to recover tens of millions of dollars of spacecraft reliably, and that's far more important than saving a few dollars in fuel. Precisely the same reason why airplanes do powered landings even though they have wings and it would be far, far easier for them to coast to a landing without using parachutes or whatnot. As for wind, the rocket isn't going to be launched if there's a risk of high wind gusts regardless, and most anything else the vehicle is capable of compensating for with its thrust and fins.
- outworlder 12y ago
  They might use drag chutes after touchdown however.
jccooper 12y ago
WRT wind tipping the stage: while in flight, it has several control mechanisms to counteract wind, and may have some inherent stability as well. After landing, it's extremely bottom heavy. Got a bunch of engines and legs down there, and up top a big empty tube. I imagine it's still possible in bad weather, but they'll probably try to avoid that. I imagine it will also be tied down or put on a recovery ship some time after landing.

thomas11 12y ago

One reason, according to Elon Musk, is that parachutes or floatables won't work in the thin atmosphere of Mars. So if Mars is the vision, they must develop something that works there.

danielweber 12y ago

Parachutes are hard and have their own failure modes. IIRC even emergency parachutes have taken out some test rockets when they weren't supposed to have been deployed at all.

simonh 12y ago

SpaceX did try parachutes at first, but there were too many down sides. Parachutes impart heavy stresses on the rocket so aside form the weight of the 'chutes you have to strengthen the rocket, adding even more weight. They also don't allow for landings that are either precise or vertical. In theory you could use 'chutes to slow the rocket for part of the descent, but to land vertically at a precise point you'd still have to add legs and use fuel for a propulsive landing. At which point the 'chutes are adding very little value. Landing in the sea with floatables means you get a very wet rocket contaminated with saltwater and potentialy flotsam. Seawater plays havock with the hot precision metal parts of the rocket engine. Also again you have to strengthen the rocket to survive the tumble into the sea and wave action. So using parachutes adds significantly more weight without giving you what you want, and ditching into the sea also means more structural weight and mucks up your engines.

InclinedPlane 12y ago

For exactly the same reason that doesn't happen when landing an airplane, it's not efficient, it's complex, it's error prone. Parachutes means you have a recovery zone not a precision landing. Efficiency is all about operational efficiency, and fuel is the cheapest thing in the whole system. Burning a little fuel so that you can have a fully powered, highly controlled, high precision landing means that you are able to recover tens of millions of dollars of spacecraft reliably, and that's far more important than saving a few dollars in fuel. Precisely the same reason why airplanes do powered landings even though they have wings and it would be far, far easier for them to coast to a landing without using parachutes or whatnot. As for wind, the rocket isn't going to be launched if there's a risk of high wind gusts regardless, and most anything else the vehicle is capable of compensating for with its thrust and fins.

outworlder 12y ago
They might use drag chutes after touchdown however.

jccooper 12y ago

WRT wind tipping the stage: while in flight, it has several control mechanisms to counteract wind, and may have some inherent stability as well. After landing, it's extremely bottom heavy. Got a bunch of engines and legs down there, and up top a big empty tube. I imagine it's still possible in bad weather, but they'll probably try to avoid that. I imagine it will also be tied down or put on a recovery ship some time after landing.