SpaceX Falcon 9 Successful Drone Ship Landing

bigddybn said:
I did. Perhaps you should do it as well. You'd see that you explained the advantage of landing downrange from the launch location which I don't dispute for a second. What you didn't explain was the advantage of an ocean landing vs picking a remote spot on land. If your craft is in orbit already then you could simply hold the orbit a bit longer to reach your target re-entry point. I'd be surprised if they aren't already doing this now since a slow moving barge isn't going to be able to reposition itself much to catch up to a rocket moving at many time the speed of sound to account for some uncontrolled variable. You'd make the correction with the rocket in flight.

The advantages of a land target:

Doesn't move
Doesn't rock
Doesn't need to be (re)positioned
Doesn't need to have all facilities packed into a self contained barge
Doesn't rely on relatively calm seas
Doesn't need to be able to transport an inherently unstable vertically positioned rocket
Doesn't require retrieval from the bottom of the ocean should something go wrong.

The advantages of a water target:

Cool youtube videos?

I'm asking a legitimate question about the mechanics of the launch, not questioning the amazing technical achievement that has been accomplished. There is no need to interpret it as an attack on someone's personal savior or fanboy favorite.
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Then go read up on Delta-V budget:

Delta-v budget - Wikipedia, the free encyclopedia

The delta-v requirements for sub-orbital spaceflight are much lower than for orbital spaceflight. For the Ansari X Prize altitude of 100 km, Space Ship One required a delta-v of roughly 1.4 km/s. To reach low Earth orbit of the space station of 300 km, the delta-v is over six times higher about 9.4 km/s. Because of the exponential nature of the rocket equation the orbital rocket needs to be considerably bigger.
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The higher the orbit, or the LARGER the satellite, the higher the delta-V budget is.

Delta v = fuel consumption. END OF STORY.

KEY TO NOTE HERE: THE PAYLOAD SIZE AND ORBIT DETERMINE HOW MUCH FUEL YOU HAVE REMAINING DURING LANDING. Space X can't just ask the guys nicely if they'd like to reduce the orbit altitude, or if they could maybe please cut the weight of the satellite in half; they have to work with whatever they have remaining in the tank.

This means sometimes they won't be able to land at all due to having too little thrust left (they don't have parachutes, so you have to use fuel to halt the falling rocket from terminal velocity down to ZERO).

SpaceX landing attempt failed, as expected | EarthSky.org

But most of the time they should have enough fuel left to land over water, and on the more rare occasion they have enough fuel left to return to land THEY WILL DO SO.
 
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defaultluser said:
Then go read up on Delta-V budget:

Delta-v budget - Wikipedia, the free encyclopedia



The higher the orbit, or the LARGER the satellite, the higher the delta-V budget is.

Delta v = fuel consumption. END OF STORY.

KEY TO NOTE HERE: THE PAYLOAD SIZE AND ORBIT DETERMINE HOW MUCH FUEL YOU HAVE REMAINING DURING LANDING. Space X can't just ask the guys nicely if they'd like to reduce the orbit altitude, or if they could maybe please cut the weight of the satellite in half; they have to work with whatever they have remaining in the tank.

This means sometimes they won't be able to land at all due to having too little thrust left.

SpaceX landing attempt failed, as expected | EarthSky.org

But most of the time they should have enough fuel left to land over water, and on the more rare occasion they have enough fuel left to return to land THEY WILL DO SO.
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Thank you for a meaningful post.

So basically the answer for THIS particular mission is "given the rocket we have, the payload we wish to deliver and the fuel we can carry, the water landing is the only option?" If land were an option they would have used it.
 
bigddybn said:
Thank you for a meaningful post.

So basically the answer for THIS particular mission is "given the rocket we have, the payload we wish to deliver and the fuel we can carry, the water landing is the only option?" If land were an option they would have used it.
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One addition to that: they possibly could have gotten this one back to land, but they wanted to try water because they were pretty confident about the improvements made since the last attempt, and the calm seas.

REMEMBER: they already landed on land earlier. To be economically viable to research how to refurbish and relaunch rockets en-mass, they needed the water landings to work too. So they concentrated on water after they got they easy landing on hard earth done :D.

Once they have the system in place to quick refurb and relaunch rockets, then they'll only do water landings when there's no other option. Landing on land will be so much faster turnaround time versus waiting for a barge to ship it to port.
 
I just finished Caliban's war (second book of the of the expanse saga) and this stuff almost got a tear out of me.
 
defaultluser said:
One addition to that: they possibly could have gotten this one back to land, but they wanted to try water because they were pretty confident about the improvements made since the last attempt, and the calm seas.

REMEMBER: they already landed on land earlier. To be economically viable to research how to refurbish and relaunch rockets en-mass, they needed the water landings to work too. So they concentrated on water after they got they easy landing on hard earth done :D.

Once they have the system in place to quick refurb and relaunch rockets, then they'll only do water landings when there's no other option. Landing on land will be so much faster turnaround time versus waiting for a barge to ship it to port.
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Just as one would suspect. Thanks.
 
grin so the nasa of today may drop rockets in the sea... but moon landing uses the same method... retro-rockets burning as it comes in for a landing... though if they just sink the barge if breaks and float a new one, likely they will have a dry landing pad in a couple decades... and if you don't care about a landing you can walk away from... then people are going to ask you want us to bail out when the speed is still too fast? The hardest part of landing is that safe landing in a airframe is that you have to go slow enough to drop out of the air and fast enough not to drop too fast. If you are accelerating from weightless you still have mass the whole time just not weight. As soon as you get closer to the ground the more that mass becomes weight. You can't accelerate faster than another 9.8 meters per second squared but you don't slow down naturally until you hit something... a retro-rocket has you hit a cloud of heated air over cooler air. basically you are pushing against a column of air under you as the hot air tries to explain into cooler air... if you bail out guess what that air is not heated...
what is funnier is that you hit ground well that is room temperature and has a much higher resistance to a change in temperature than water just look at the steam... by the way what is that couple frames of some other camera you see after the landing?

Clearly we need a better way to get support up to the space stations and fix the satellites... but clearly there is still work for both companies to do before the risk is less than the reward. Until then every flight will be playing the lottery some people win but when was the last time you won the lottery.
 
Just when one starts to loose faith in the human spirit, we go and do something like this!

Our species is pretty awesome!
 
bigddybn said:
If anyone is actually interested in a mature conversation about the very same topic that doesn't include juvenile keyboard warriors tossing out personal insults and cursing here the the exact same question with some informed answers including quotes from Musk himself. It would seem the reasons are a mixture of both all and none of the above.

Why did SpaceX attempt to land the booster on a barge instead of somewhere on land?
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Which gives you the same answer we have given you 5 times, but you just didn't like. You prefer to believe it is some kind of publicity stunt ("Cool youtube videos?").
 
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Isn't the whole 'land on the barge thing' really just to get around the problem of not being able to launch into the correct inclinations over unpopulated land in the United States? The US isn't like Russia where they have bountiful tracts of emptiness. Therefore they have to launch over the ocean typically.

I believe that's the answer that the guy who was asking on page 1.
 
AntiSocialMunky said:
Isn't the whole 'land on the barge thing' really just to get around the problem of not being able to launch into the correct inclinations over unpopulated land in the United States? The US isn't like Russia where they have bountiful tracts of emptiness. Therefore they have to launch over the ocean typically.

I believe that's the answer that the guy who was asking on page 1.
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Yes, back in the early days when they were developing rockets was risky business, they put rocket testing in the middle of nowhere, preferably launching over water.

They still launch over water to avoid killing people. Returning to the launchpad takes the same flight path, which shroud make people less scared about this.
 
As an engineer, I salute the engineers who pulled this off. On what level is this not badass. Also, I <3 the blond in the video. I want to touch her boobies. thank you.
 
AntiSocialMunky said:
Isn't the whole 'land on the barge thing' really just to get around the problem of not being able to launch into the correct inclinations over unpopulated land in the United States? The US isn't like Russia where they have bountiful tracts of emptiness. Therefore they have to launch over the ocean typically.

I believe that's the answer that the guy who was asking on page 1.
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That, and when launching equatorially, the US runs out of land without water to the East pretty quickly as latitude goes to zero. Plane changes are expensive!
 
bigddybn said:
It's a neat trick but I'm not sure what advantage the ocean landing has over putting it back on the ground like Blue Origin has done. Repeatedly and on the first try.

I understand all of that and I'm not pretending that Blue Origin has accomplished the same thing. I am asking a specific question. What advantage is there to trying to hit an unstable, mobile and constantly moving target vs a completely stable ground target?
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I think what you're trying to ask is what advantage does landing on the barge give over moving the launch site so that you can come down over land. E.g.: launching from Vandenberg Air Force Base in California and coming down in Texas (hypothetical, I didn't do the math).

Advantage is: KSC launch site is well equipped to handle this size rocket. Landing over ocean has a high safety factor.

There's a reason NASA chose the location for their launchpads and it wasn't because of weather (hurricane alley), it was because it's close to the equator, surrounded by water and low-populace, and is East coast so the trajectory takes them over the ocean and not land.
 
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