Airlock

SpaceX: Current missions and future plans. (Renamed thread.)

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Edited by Vanamonde
Clarifiying subject of thread.
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There is a point where the term "diminishing returns" begins to apply to recovering booster stages. I think that attempting to recover F9H core stages would be well beyond that. If SpaceX wants to reduce cost of the F9H by recovering engines from the core stage, I think they should look towards the past--specifically, the Atlas booster, and the S-ID first stage for evolved Saturn Vs proposed in the late 60s. Both used a "stage and a half" design where the outboard engines were mounted on a "collar" that could be jettisoned once they were no longer needed. While the Atlas's booster engines were expendable, the S-ID design was intended to not only increase payload, but to also reduce cost by having the four outboard engines recovered and refurbished for reuse on a future launch. The inboard engine on the S-ID would be a sustainer, and would not be recovered, but by recovering four out of five first-stage engines, the bulk of the stage cost could be recovered, compared to the S-IC.

The new F9 design, with the circular ring of outboard engines as opposed to the square nine-pack design used on the early boosters, would be ideal for a similar "stage-and-a-half" setup; it could even be configured as a dual-collar design, such that only four engines are jettisoned at a time, allowing even earlier reductions in thrust (and making recovery of all the engines simpler due to having less weight to land safely)...

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There is a point where the term "diminishing returns" begins to apply to recovering booster stages. I think that attempting to recover F9H core stages would be well beyond that. If SpaceX wants to reduce cost of the F9H by recovering engines from the core stage, I think they should look towards the past--specifically, the Atlas booster, and the S-ID first stage for evolved Saturn Vs proposed in the late 60s. Both used a "stage and a half" design where the outboard engines were mounted on a "collar" that could be jettisoned once they were no longer needed. While the Atlas's booster engines were expendable, the S-ID design was intended to not only increase payload, but to also reduce cost by having the four outboard engines recovered and refurbished for reuse on a future launch. The inboard engine on the S-ID would be a sustainer, and would not be recovered, but by recovering four out of five first-stage engines, the bulk of the stage cost could be recovered, compared to the S-IC.

The new F9 design, with the circular ring of outboard engines as opposed to the square nine-pack design used on the early boosters, would be ideal for a similar "stage-and-a-half" setup; it could even be configured as a dual-collar design, such that only four engines are jettisoned at a time, allowing even earlier reductions in thrust (and making recovery of all the engines simpler due to having less weight to land safely)...

I don't see SpaceX redesigning their flight hardware any time soon. While they might consider it if their current designs underperform, Elon has made it pretty clear their expectations of reusing the Falcon Heavy core and upper stage are low. I'll give them the benefit of the doubt and expect it will all come down to achieving a repeated series of successful, accurate landings on sea-platforms.

The primary goal of the sea-platform is to provide a method from which precision reentry and landing can be proven. The reuse of the Falcon Heavy core is just speculation on my part.

Edited by Airlock

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what if you had the FH boosters fly back to the mainland, while the core landed on a barge?

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I have no idea how stable a barge at sea can be. It may be very possible they'll have some type of superstructure to insure it doesn't fall over once landing. Probably wouldn't be too hard to design something like this in KSP.

If SeaLaunch can do their thing from a converted oil platform, it must be possible. Maybe SpaceX could move to something more stable, like that. The barge could just be a proof of concept.

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There is a point where the term "diminishing returns" begins to apply to recovering booster stages. I think that attempting to recover F9H core stages would be well beyond that. If SpaceX wants to reduce cost of the F9H by recovering engines from the core stage, I think they should look towards the past--specifically, the Atlas booster, and the S-ID first stage for evolved Saturn Vs proposed in the late 60s. Both used a "stage and a half" design where the outboard engines were mounted on a "collar" that could be jettisoned once they were no longer needed. While the Atlas's booster engines were expendable, the S-ID design was intended to not only increase payload, but to also reduce cost by having the four outboard engines recovered and refurbished for reuse on a future launch. The inboard engine on the S-ID would be a sustainer, and would not be recovered, but by recovering four out of five first-stage engines, the bulk of the stage cost could be recovered, compared to the S-IC.

The new F9 design, with the circular ring of outboard engines as opposed to the square nine-pack design used on the early boosters, would be ideal for a similar "stage-and-a-half" setup; it could even be configured as a dual-collar design, such that only four engines are jettisoned at a time, allowing even earlier reductions in thrust (and making recovery of all the engines simpler due to having less weight to land safely)...

Problem with only returning the engines is that they would have to splashdown, adding control and fuel to do an accurate landing would be complicated, Another design where the engines was in a sort of miniature boosters who separated and landed might be possible but would be an totally different design.

Else I agree with you, one benefit is that the core and the boosters share most design so they might reconfigure aging boosters as core stages instead of doing major services.

An barge might be possible, not sure how stable it would be, thing it require some stabilization system it would also need an service ship.

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Maybe SpaceX could move to something more stable, like that. The barge could just be a proof of concept.

Spacex are only landing it on a barge temporarily while they have to. They just need to prove it works before being allowed to land on land.

Also despite how it looks I think the rocket is surprisingly stable. Most of the weight is low down with the engines and the rest is just empty fuel tanks.

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Else I agree with you, one benefit is that the core and the boosters share most design so they might reconfigure aging boosters as core stages instead of doing major services.

this is actually a very good idea

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Launch date: Dec 16. Elon shared some pics with us. Grid fins confirmed.

Sorry for being brief - I'm stuck using a tablet.

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Edited by Airlock
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I can't wait. It'll be something historical if he pulls it off. The procedure once it's down would be interesting.

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Are they actually putting a payload into orbit or is his solely just a demonstration? Because I can't imagine SpaceX waiting on good sea conditions. Because they practicality never are... The sea is rough 90% of the time so are they really going to wait for calm seas before the launch? If so that Dec16 date has a good chance of being delayed...

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Granted the barge is unmanned or at least minimally manned, so more than likely there will be a boat close by that will have a crew on that will board the barge and tie down the rocket in some fashion for transport to shore.

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Are they actually putting a payload into orbit or is his solely just a demonstration? Because I can't imagine SpaceX waiting on good sea conditions. Because they practicality never are... The sea is rough 90% of the time so are they really going to wait for calm seas before the launch? If so that Dec16 date has a good chance of being delayed...

The barge is equipped with stabilizing thrusters to keep it in place with an error of only 3 meters. It's designed from the same technology drilling barges and oil platforms use to keep in place. It'll be rough, but it's a pretty big barge and it will definitely keep stay where it needs to be. How flat it will be depends on just how bad the weather is on the launch day. They are launching CRS-5 if I remember correctly which is the 5th resupply mission to the ISS.

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Also the barge has been confirmed to have some sort of wave damping system on it, which i bet can decrease the apparent wave height by ~2m

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Also the barge has been confirmed to have some sort of wave damping system on it, which i bet can decrease the apparent wave height by ~2m

I didn't think about it but that seems about right.

Oil rig transfer boats(I think it was these) and other yachts have pretty cool systems that dampen waves. I forget exactly how it works, it's been awhile since I've read about it, but they can make 5foot swells seem like perfectly calm. It's pretty amazing. It works by moving ballast around I think, I could be completely wrong though.

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2m? Wow.. I suppose the hope then is for no excessively rough seas. I hope we get good footage. It'll be quite the sight.

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Now THIS should be interesting. I hope they will have an aircraft around or a boat that can take HD video of the descent.

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From Elon: https://twitter.com/elonmusk/status/536263260056850432

"Base is 300 ft by 100 ft, with wings that extend width to 170 ft. Will allow refuel & rocket flyback in future."

They want to launch from the barge???

Not the WHOLE rocket... just the flyback stage. They land it, put 5 bucks in the tank, and it flys back to the launchpad

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Also the barge has been confirmed to have some sort of wave damping system on it, which i bet can decrease the apparent wave height by ~2m

I can't think of a way to "reduce the apparent wave height" without pumping water ballast back and forth in floating pontoons to increase/decrease their buoyancy as the waves pass. SpaceX's barge appears to have only one hull so this wouldnt be an option. At best, they could stabilize how much the barge rolls and pitches due to the waves while floating up and down in them and holding position to within 3 metres.The amount of up/down motion would then depend on the wave length (i.e. short wavelength waves that are freshly being churned up or are running against a current vs. long rollers left over from a distant storm.)

As for conditions at sea, you can view them online on NOAA's marine forecast web page. The forecasts and current conditions are updated a couple of times a day. I've posted an example below. Florida is in the lower left, the UK is in the upper right. Contours are the mean significant wave height in metres. Mean significant wave height is the average of the largest third of waves. That means that ~83% of waves are smaller than the given height while ~17% are bigger.

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Not the WHOLE rocket... just the flyback stage. They land it, put 5 bucks in the tank, and it flys back to the launchpad

Still though that's incredible. Is that really cheaper then just tugging the barge back to shore? Itd be quicker that's for sure... And time is money I suppose.

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PakledHostage you can dampen out the motion by using vertical motors, hydraulically lifting and lowering the deck, having extendable fins like on cruise ships, partially submerging the hull to reduce the freeboard, etc. There are a bunch of differernt ways all with their own drawbacks

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Still though that's incredible. Is that really cheaper then just tugging the barge back to shore? Itd be quicker that's for sure... And time is money I suppose.

Main problem with an relaunch is reliability and chance of fail during the return flight, it would not cost much outside that.

Problem with towing the barge is that you expose the rocket of sea spray.

I thought that flyback would be interesting for Russia as they fly over land, you can have an small base for the rocket to land, here you could do an better inspection than on the barge, rocket would also be to large to transport cheaply on roads.

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