SpaceX Falcon 9 historic landing thread (1st landing attempt & most recent missions)

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timbucktoo said:
Is the cost of reusing this rocket booster any cheaper than just building another one?
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This particular one that fell over and exploded? No. A new one is cheaper. :wink:

But if one can be successfully landed and reused, it is expected to be much cheaper that building a new one for each launch.
 
Cory said:
Certainly way out of my depth here, but it does seem the variables imposed through the floating X are extreme. Not sure how deep the water is where they are, but I wonder if they could set up something similar to a shallow water offshore drilling rig. Actually have a solid unmoving platform for landing with the safety of open water. Probably a good reason why not, but seems possible to anchor a platform to a shallow sea floor for long enough for proof of concept to asses the risk and potentially move to dry land.
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Different missions have different flight profiles. For example the ISS missions require a high inclination (azimuth angle) launch to the North East. Other launches are to various inclinations to the East-South East, or South-East. Depending on where the satellite orbit will lend up, or whether it is going to do a "dogleg maneuver" when it gets to the equator to do an equatorial orbit (which is a key step towards geosynchronous orbits). And that's just the inclinations. Different payload masses means the optimal downrange position for the landing barge may be closer or farther. Although some very heavy payloads do not allow any extra fuel for the first stage to land. And some lighter payloads will allow so much extra fuel that it will lbe able ot fly back to the Cape for RTLS landings. And then there is Falcon-9-Heavy, which ultimately will lave two side boosters do RTLS, while the center core flies WAY farther downrange (guesstimate 1000 miles as opposed to about 200-ish).

So, that would be a LOT of fixed landing platforms. It's way easier to just have one that can be positioned in the right place. Some even speculate that eventually SpaceX will stop using the barge (it is rented), and do RTLS landings for everything that isn't expendable. But I'm not convinced of that.

Anyway, I think they'll work it out. The problem is not so much the barge as in this case the control system over-responding for some reason. They need to analyze why and what to do to resolve it. Although if it was an RTLS landing on land….. it would prioritize landing with minimum horizontal velocity rather than try to "hit X" like it needs to at sea (as long as it will not stray outside the landing area safe zone)

The Bi-Propellant valve thing…..if it means the engine was say a second late in igniting then it was coming in way faster than intended, without the throttle range to make up for a late start. Some have even said the video seems intentionally slowed down to perhaps a much as half-speed…. no confirmation on that. So a way faster than intended "landing" may have wreaked havoc with the control response.

It also looks like the wind may have been more than expected. Still, the control system should not have over-controlled that much so wind may be a contributing factor but probably not the main issue.

In case there was anyone who was still wondering why the platform is unmanned, the last two or three seconds is all you need to see to figure it out…
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Anyone "still wondering"? Man, anyone wondering such a thing at all may not be capable of typing on a keyboard to read TRF to begin with. That would be "light a match to see how much gas is left in the tank" stuff right there….

And, to end with the video goodie below. Someone made a magnified enhanced video of the landing attempt. You can even see the ASDS barge "Mister Bill" rolling a little bit (not a factor). Seems like it just hit too hard and was tilting too fast right to left as it hit, that it most likely snapped off the "left" leg, allowing it to fall over.
I almost chuckle every time I see the RCS thrusters try to save it, because i have done just that (as have thousands of others) in Kerbal Space Program to help "landers" stay upright after landing. So it is almost unreal to see it being done…. for real.

- George Gassaway

[video=youtube;t1aBgNYAWtM]https://www.youtube.com/watch?v=t1aBgNYAWtM[/video]
 
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OK, having seen the "Kaboom", I'm unofficially renaming the ASDS landing barge formerly known as "Just Read the Instructions".

It is now "Mister Bill".

Three at-sea landing missions in a row where it got beat-up.

See message #336 as to what the "Mister Bill" reference is about.
https://www.rocketryforum.com/showt...sday-Apr-14-4-10-PM-EDT&p=1426211#post1426211

- George Gassaway

7nXJmFG.jpg
 
rcktnut said:
I viewed it earlier, no good now, I don't know what the big deal is with them, they are trying to recover it, better than just letting it splash down and sink in the ocean. We should be able to see their progress, live even, we're paying for it.
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What we are paying for is all those NRO launches with their fancy classified national security payloads.
 
So they almost made it. My question is this, if they do land it safely on the barge what's next? Are they going to attempt to lay it down? Are they just going to dump the fuel and oxidizer and let the thing fall off the deck?
 
Gosh, I'm pretty sure they intend to come home with it, and try to put it through a re-certification for another flight. Certainly that's the long term goal, so why not start exercising the whole process right away?
 
I'm sure they would like to. I'm just wondering what the mechanics of that process would be. It's a very unwieldy payload. How do you SAFELY approach it, defuel, and lash it down to the deck on a moving barge?

IMHO the answer is that they just need to prove that they can safely land it. Once they accomplish that the FAA will let them move to land where they can actually try to recover the booster under more controlled conditions.
 
ChrisAttebery said:
I'm sure they would like to. I'm just wondering what the mechanics of that process would be. It's a very unwieldy payload. How do you SAFELY approach it, defuel, and lash it down to the deck on a moving barge?
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All good and valid questions. My only answer is I'd love to watch them figure all that out!

ChrisAttebery said:
IMHO the answer is that they just need to prove that they can safely land it. Once they accomplish that the FAA will let them move to land where they can actually try to recover the booster under more controlled conditions.
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Well, there's certainly a lot of talk about just that, but I bet one successful example out of several attempts will not be enough to get FAA permission to go for dry landings.

Also, assume for the moment that wet landings end up working well. How many flight/payload profiles would leave enough fuel left in the 1st stage to return to the barge but NOT return to Florida? I wonder what percentage of flights on their manifest are in that gray zone? If it's significant, I bet a business case might be made for retaining the ability for both kinds of recoveries long after the testing phase is done.
 
ChrisAttebery said:
I'm sure they would like to. I'm just wondering what the mechanics of that process would be. It's a very unwieldy payload. How do you SAFELY approach it, defuel, and lash it down to the deck on a moving barge?

IMHO the answer is that they just need to prove that they can safely land it. Once they accomplish that the FAA will let them move to land where they can actually try to recover the booster under more controlled conditions.
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There may be a post about this in an earlier part of the thread.

My understanding is that after it lands on the barge, a crew would come aboard to secure it, and the barge would be towed back to port. I have no idea what the details of that process would be. I think it stays in an upright position, which must be kind of awkward. I guess they would secure the legs to the deck and hope for calm weather! I have no idea how they would defuel it and how they would lay it down and remove it from the barge once it is in port.

My idea was to REFUEL, not defuel, and then fly it back! But apparently that's more expensive and risky than towing a barge...
 
As far as the defueling goes, maybe it's not that hard.

We're talking LOX and Kerosene, right? For the LOX: Just open a valve and wait. It'll boil off eventually. For the Kerosene, just leave it in the tank. It's not that different than the diesel fuel that runs the barge, and nobody seems too concerned about those tanks, so why not have a little more?
 
jmattingly13 said:
Well, when they scrub a launch, they have to defuel before they can bring the rocket back down. I'm guessing there are drain valves they can use to empty the tanks.
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True, but when a launch is scrubbed, the rocket is at a launch complex with a gantry and is hooked up to a lot of support equipment that we don't see on the barge. I'm sure they have a solution! and it's not that difficult. I was just saying I don't know the details of how it is done.
 
Wow, fantastic video from onboard the barge.

It seems to me that the landing was both too hard in vertical velocity and also pitching over to put way too much stress onto a leg which broke. Once the leg broke, the tip-over was inevitable. So, it ultimately fell over because the landing was "too rough", something was likely to break. The main cause….not really identified yet. The control system seemed to over-react but there may have been something that caused it to overreact (if the "sticky Bi-Prop valve" caused the engine to ignite too late to slow down properly enough).

ChrisAttebery said:
So they almost made it. My question is this, if they do land it safely on the barge what's next? Are they going to attempt to lay it down? Are they just going to dump the fuel and oxidizer and let the thing fall off the deck?
Click to expand...

This is not a stunt. The whole idea is to be able to reuse the booster.

When it lands, it only has a few gallons of Fuel (RP-1) and Oxidizer (LOX) left in it. They could simply leave the RP-1 in it (it is highly refined Kerosene, less flammable than a car's gas tank), while the Liquid Oxygen can be vented as a gas and likely purged by air or better yet something inert like nitrogen.

With only a few gallons left, the vehicle is incredibly tail-heavy since the engines are relatively heavy but the empty fuel tankage is relatively light. So, after landing, it sits where it lands for the trip back. It will be secured by crew members welding "steel boots" over the landing leg "feet", welding the boots onto the steel deck (no joke). Also, aircraft jack stands will be put in place under the Falcon's "hard points" (what it sits on the launch pad with). So that will help hold it secure for the ride back.

BTW - the above has been described before in this thread. I know it's a long thread, but there's a lot of neat stuff in many of the posts

It needs to go under a bridge to make it back to the dock… it is so tall that IIRC they have to do it at low tide, it is that close to being too tall to fit under the bridge.

When they finally do get one to land successfully, supposedly the booster will be shipped (by truck) to New Mexico's SpacePort America and make several suborbital test flights. Once they can be confident enough that the reusable boosters will be able to launch orbital missions, then they'll offer missions with re-used boosters, at a greatly reduced price.

The point where the whole thing will be successful will be not simply when customers buy flights on the reused boosters, but when several of those re-used boosters successfully and reliably launch those payloads. Even if things go well, that's going to be a span of years (hopefully only a few) to get to that point, not months.

So, several key steps along the way, but the biggest and most historic one for awhile will be the first successful landing (with the rocket undamaged).

- George Gassaway
 
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Here in the port they have massive high lift cranes to capture the rocket to remove from the barge. We have a submarine base here that has lifts that they could use as well.
 
I'm wondering if they were trying something close to a 'suicide burn'. From what I understand (I'm no expert), but the idea is max thrust at practically the last second. In theory its the most efficient in terms of fuel usage, but the timing has to be spot on. Again, I also understand that the F9R's engines aren't very throttleable...unlike a car where you can easily modulate the power, that's not possible with their engines.

Again, I have no idea if this is true or not, but it would explain why they look like they're falling like a safe until just before touchdown.

FC
 
FastCargo said:
I'm wondering if they were trying something close to a 'suicide burn'. From what I understand (I'm no expert), but the idea is max thrust at practically the last second. In theory its the most efficient in terms of fuel usage, but the timing has to be spot on. Again, I also understand that the F9R's engines aren't very throttleable...unlike a car where you can easily modulate the power, that's not possible with their engines.

Again, I have no idea if this is true or not, but it would explain why they look like they're falling like a safe until just before touchdown.

FC
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I used to try this with Lunar Lander, and it never worked very well for me.
 
I get that George. I'm interested in the actual logistics once it's on the barge. It seems dangerous to me to have people on the barge while if the booster isn't secured. The footprint is fairly small compared to its height. What if it's not centered on the barge? Is the CG low enough that they can winch it around a rolling deck? Once its secured I can imagine that the rest is fairly standard logistics for large bulky items.

georgegassaway said:
This is not a stunt. The whole idea is to be able to reuse the booster.
Click to expand...
 
ChrisAttebery said:
I get that George. I'm interested in the actual logistics once it's on the barge. It seems dangerous to me to have people on the barge while if the booster isn't secured. The footprint is fairly small compared to its height. What if it's not centered on the barge? Is the CG low enough that they can winch it around a rolling deck? Once its secured I can imagine that the rest is fairly standard logistics for large bulky items.
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Again a lot of that has already been mentioned in this thread.

Dangerous? Lots of dangerous jobs in the world, this would not make the top 100, maybe not even the top 100 most dangerous jobs at sea. But sure, even considering the precautions and procedures, some risk, which presumably the crew are aware of and paid well for the risk (like hazardous duty pay). Or some of the pros (Sea Tug crew) might call it just another day at sea…..with an unusual piece of cargo on a barge.

However, if the weather is bad, they probably are not going to try to put crew aboard to secure it, till the conditions get within acceptable limits.

I already said in a recent message the CG is VERY low due to the engine mass at bottom and fuel/Lox tanks being empty, which was also repeating info already in the thread.

space-ship-d92e11ef.jpeg


The barge can handle cargo mass of about 24 million pounds. Or about 200 times heavier than the Falcon first stage. So it if lands with all 4 feet on deck, but not dead center, the barge can handle the off-center mass without undue risk (yes, it may list 1/2 degree, maybe 1 degree worst-case).

Since SpaceX is so tight-lipped about details, nobody publicly knows, if SpaceX did think that a small bit of listing might be an issue, if there might be a plan to account for off-center mass by pumping water into some compartments in the other side…. the barge has 32 ballast compartments that can be flooded/ballasted. So, again while they have not gone into such details, either their engineering analysis has told them that an off-center center landing will not cause an issue for the barge being towed back, or otherwise they may have a plan for pumping water to ballast the opposing side. Now if water ballast was required, yes, that would be a risk until crew members completed the pumping, but again some of the Sea Tug crews may consider that just another day at sea…(of course if SpaceX was really really worried about ballasting and possibly rougher seas than safe to put a crew aboard to do the pumping….. it does not take Rocket Science to have pumps set up to be remotely activated to do ballast pumping unmanned. THey do describe it as "autonomous", albeit it can't do the boot welding to secure the feet and add the jack stands.....well..... observers assume humans will do that anyway.....).

Now I will absolutely admit that when I first heard of the landing barge I had a lot of concerns myself. And for a long time SpaceX didn't indicate at how they would solve them (and it turns out most are not big enough problems. Then there can be problems so big such as how to handle a severe storm the answer is it's too expensive to try to make it handle a landing and post-landing in a severe storm, so the answer to that is abort the landing attempt. Same way the US Navy does not try to land aircraft on carriers during violent storms).

The welded on "boots" and aircraft jack stands seem reasonable. They just need to get one to land safely. Once it's landed it ought to be safe to bring back to port…. unless they have the misfortune of getting caught in a bad-enough storm at sea.

And, to end with an interesting and sad pic. The ASDS barge "Mister Bill" made it back to port Thursday. The old text on the deck now says something like "Just .... ... .....uctions" . In the photo below, someone added a yellow line to indicate the apparent horizontal motion of the exhaust as it tried to land.

- George Gassaway

index.php
 
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FastCargo said:
I'm wondering if they were trying something close to a 'suicide burn'. From what I understand (I'm no expert), but the idea is max thrust at practically the last second. In theory its the most efficient in terms of fuel usage, but the timing has to be spot on. Again, I also understand that the F9R's engines aren't very throttleable...unlike a car where you can easily modulate the power, that's not possible with their engines.

Again, I have no idea if this is true or not, but it would explain why they look like they're falling like a safe until just before touchdown.

FC
Click to expand...

It makes sense that it is true. The Merlin engines run on a gas generator cycle, which uses a turbopump to move propellant into the main combustion chamber. To modulate the fuel flow rate into the combustor, you have to decrease the flow through the turbine to decrease the power of the pump, and thus also the flow rate through the pump. The turbomachinery in a rocket engine is just like the turbomachinery in a jet engine. It takes time to spool up and spool down, so the response time to a change in throttle command is longer than instantaneous.

georgegassaway said:
index.php
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I'm just impressed that non on the equipment on the barge shows much of a sign of damage. They've detonated a couple rockets on the deck now and all we saw was a scorched deck and a dented sea van (at least on attempt #1)
 
ChrisAttebery said:
I get that George. I'm interested in the actual logistics once it's on the barge. It seems dangerous to me to have people on the barge while if the booster isn't secured. The footprint is fairly small compared to its height. What if it's not centered on the barge? Is the CG low enough that they can winch it around a rolling deck? Once its secured I can imagine that the rest is fairly standard logistics for large bulky items.
Click to expand...
The barge is massive so in a sea state where they would use it to recover the booster, I'm sure they had it designed to minimize heaving.

The barge is unmanned during the landing attempt, and I'd be surprise if they don't have a LOX dump system so the explosion hazard is eliminated if the rocket fell over after it landed vertically. I doubt they would attempt to relocate the rocket at sea, but would simply secure it to the barge before they tow it back to port.

A final point is that the barge is really just an intermediate step in their recovery process. Space-X's ultimate plan is to fly the booster back to a landing pad near the launch site which is significantly cheaper then the cost of operating a large tug and barge at sea which I'll estimate could be as high as $10,000 per hour depending on ship size, crew size, fuel consumption and fixed cost amortization. For example, the Shuttle program has (3) 170' crewed ships and a number of barges to transport the boosters from Louisiana to the Cape, to recover the boosters after the launch and bring them back to the Cape, and then to return barge them back to Louisiana. Both NASA and CNES advised Space-X on the real costs of recovering boosters. https://aviationweek.com/blog/nasa-cnes-warn-spacex-challenges-flying-reusable-falcon-9-rocket which is what I have been posting for quite a while. This article is a must read for those who believe that booster recovery saves money.........

Bob
 
I would suggest that the detailed rebuttal in the comments below that article are even more of a must read....
 

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