SpaceX News

[GIThruster]

I cant imagine them successfully landing a rocket on a barge sitting on 18 foot waves.

Ah, I get what you mean now but you've placed the cart before the horse... the landing test would not drive the launch decision. If the weather is otherwise go for launch then impassable seas shouldn't affect the launch at all.

And should such high seas cause SpaceX to abort the experimental landing attempt then all that would be lost is a launcher that's already been bought and paid for... as an expendable

It may be bought and paid for but it is still worth about $15M and I would certainly not launch if I knew it meant I had to throw away $15M in my pocket. And note, it is worth whatever it is worth (a launch is $60M so $15M for the first stage seems a fair guess) it saves $15M on EACH launch its reused. It could be reused 20X or thrown out on the first use. If they can be reused 15XEach, that stage is really worth $200M. Are you so sure you'd throw it away?

[mvanwink5]

The issue is time as launches are infrequent, and no one will give permission to launch on land (unless it is an island) until it can be shown to be able to land without going boom. To land on a barge is far more difficult than landing on a bulls eye on a patch of dirt in the middle of some disinterested cows.

[Skipjack]

The issue is time as launches are infrequent, and no one will give permission to launch on land (unless it is an island) until it can be shown to be able to land without going boom. To land on a barge is far more difficult than landing on a bulls eye on a patch of dirt in the middle of some disinterested cows.

you mean land on land. And the permission thing is rather stupid and typical of government idiots. If they can hit the bullseye over the ocean, they can do it over land. The F9R has demonstrated the rest more than sufficiently well. The rest is just counting two and two together. Plus, if it hits the landing pad hard, it is still not a huge disaster. After all they are more than willing to risk the same in Texas.

[GIThruster]

Well, if it hits the pad hard it could explode, which would be bad. Fact is, they need to plan for that to happen and have a sufficient area around the rocket cleared so that when it happens, no one is hurt. And it might never happen, but odds are Murphy will not be lax and eventually, there will be a way kewl fireball and lots of roasted bits. And this should in no way stop the program. The only thing that should stop the program is if a rocket on return, falls out of the sky into some unplanned, populated area. That would be worse than bad. It would be very, very bad.

[Skipjack]

It may be bought and paid for but it is still worth about $15M and I would certainly not launch if I knew it meant I had to throw away $15M in my pocket. And note, it is worth whatever it is worth (a launch is $60M so $15M for the first stage seems a fair guess) it saves $15M on EACH launch its reused. It could be reused 20X or thrown out on the first use. If they can be reused 15XEach, that stage is really worth $200M. Are you so sure you'd throw it away?

A few launch delays can easily cost them more then 15 million...

Well, if it hits the pad hard it could explode, which would be bad..

By that time it will be mostly empty. You don't worry about cars or even gasoline tankers crashing and driving through populated areas and I see airplanes fly over residential areas all the time. The biggest danger is from the fact that it is so big.

Fact is, they need to plan for that to happen and have a sufficient area around the rocket cleared so that when it happens, no one is hurt.

They will land near the launch site. So that area will most likely be cleared anyway. The vehicle will be a lot less dangerous on the way back, than it is on the way up.

The only thing that should stop the program is if a rocket on return, falls out of the sky into some unplanned, populated area. That would be worse than bad. It would be very, very bad.

Very unlikely to happen. They will probably do the return trajectory in such a way that if the engines fail to do the braking burn, the stage will land in the ocean. Only if the braking burn slows down the decent (thus giving it more time to translate the last stretch to the landing site) it will make it all the way to the landing platform. Since in all cases, SpaceX will launch their rockets into open Ocean, there should never be a case, where it would traverse populated areas on its way to the launch site. And again, the "fireball" would be rather small since the rocket stage will be pretty much dry.

[hanelyp]

Well, they did have pretty tall waves when they launched CRS3, if I remember correctly (18 foot, or so). They were high enough that the recovery ship could not make it there. I cant imagine them successfully landing a rocket on a barge sitting on 18 foot waves.

Certainly not on a conventional barge. A small water area ship designed for high seas might work. But building a custom ship for just a couple uses is a big expense.

[GIThruster]

And again, the "fireball" would be rather small since the rocket stage will be pretty much dry.

Well no, it won't be dry. It will have enough propellant left to land. That's a fair amount of fuel. If it ever goes boom on landing, it will be a big boom. And again, they should plan for this. Even if only the 1st stage tips over and thunks to the ground, the tanks could rupture which one expects would cause loss of the entire stage, in an unplanned fireworks show.

[Skipjack]

And again, the "fireball" would be rather small since the rocket stage will be pretty much dry.

Well no, it won't be dry. It will have enough propellant left to land. That's a fair amount of fuel. If it ever goes boom on landing, it will be a big boom. And again, they should plan for this. Even if only the 1st stage tips over and thunks to the ground, the tanks could rupture which one expects would cause loss of the entire stage, in an unplanned fireworks show.

I said "pretty much dry". The final landing burn does not need that much fuel (assuming a 20 second landing burn it is about 500 kg by my back of the envelope calculation, probably less than that). By the time it has reached the pad, the risk is already quite low that something will go wrong since SpaceX has plenty of experience with the conditions during the final landing burn from their two Grasshopper experiments, which actually contains a lot more fuel than a returning stage would.
If the stage falls over after landing, it will most definitely rupture and there will be a boom. I would not consider it a big boom though. It wont be anywhere near as dangerous as a fully tanked rocket. Biggest concern would probably be the liquid oxygen. I am not sure what they could "plan for this", other than by locking the area down, which is already the case for the launch anyway.
I see more danger in damage to a barge in high seas, which could cause the stage to topple even after a successful landing. I would not want to be among those sent in to secure the stage in high seas, when the barge is rolling in 20 foot waves.

[ladajo]

Big waves at sea are not as common as you all seem to make them out to be.

Waves are a function of fetch and bottom topography.
Fetch is rarely predictable, and is very weather dependant, with some hat tip to any surrounding surface geograpahy for the area in question.

In any event, barges are cheap. He has a number of means to address booster stability and/or recovery. Maybe the first barge go around, he will just splash the thing over the side once it demonstrates touch down.

My 1.5 cents worth.

[Betruger]

If the stage is almost empty, isn't the CoG pretty low? How much angle would the barge have to reach before it and an F9R tied down would fail? There's got to be some feasible attachment schemes that don't interfere at all with landing.

[Skipjack]

If the stage is almost empty, isn't the CoG pretty low? How much angle would the barge have to reach before it and an F9R tied down would fail? There's got to be some feasible attachment schemes that don't interfere at all with landing.

I think the problem is more landing the stage on a target that bounces around in high waves and then once (if) it has landed safely, you need to bring someone in and set them over (in high seas) that would be crazy enough to handle the rocket stage in these conditions. I just don't see it happening. Too much of a safety issue. But maybe I am just too pessimistic (based on the CRS-3 weather) and things will be perfectly calm and everything will work out fine and bad weather is not all that common, or maybe the seas are just so much calmer 30 miles off the shore.

[ladajo]

There are a number of methods to gain platform stability. And it is easier in deeper water.
Probably the most simple is a platform mounted on submerged pontoons sized/spaced for the areas prevelant ground swell average peroids/peak to peaks.

20 ft waves are big, and not that common. They require a decent fetch.

I also don't think it would be all that big a problem to get some harnesses to secure the assembly after touch down. They could even be remotely fired.
We have done crazier stuff to catch airframes on ships.

Done right, the fuel mass is pretty much burned up at touchdown. All that is left is the assembly.

[Skipjack]

There are a number of methods to gain platform stability. And it is easier in deeper water.
Probably the most simple is a platform mounted on submerged pontoons sized/spaced for the areas prevelant ground swell average peroids/peak to peaks.

20 ft waves are big, and not that common. They require a decent fetch.

I also don't think it would be all that big a problem to get some harnesses to secure the assembly after touch down. They could even be remotely fired.
We have done crazier stuff to catch airframes on ships.

Done right, the fuel mass is pretty much burned up at touchdown. All that is left is the assembly.

And all that would cost a lot of money for not really all that much in gain. Well, I am sure they know what they are doing.

[ladajo]

The pontoon idea has been around a while.





Cost is relevant to scope and scale desired.
I think Space-X could keep it relatively cheap.

[ladajo]

And here is another interesting approach:

http://www.build.new-atlantis.org/pneumatic.htm

using:

http://www.amioceanpower.com/systemconfigurations.html