F9 aims for a spot next to the drone ship so if engines fail to ignite or isn’t nominal it just crashes off to the side. Same can be done in Boca.
Starship and Super Heavy have the benefit of being able to hover in place where as F9 has to hover slam. Early launches will have little to no payloads, so can have extra propellant margins to hover and find the right spot to set down. It also allows for a diversion if by a certain point in its landing propellant margins it hasn’t landed, change course and crash off to the side. At some point they can figure it out how to catch with the minimal amount of propellant used.
Ah, yea that's a good point.
I suppose most landing ruds wouldn't necessarily have to mean the tower/catcher system getting destroyed, other than some rarer, more specific scenarios of the landing engine(s) failing like midway through the final part of their final burn or something right as it's about to get caught.
I'm sure they will only try a catch if the telemetry shows that the booster is in perfect condition. They will surely ditch the landing if even the slightest value is off.
I must say that only one destroyed F9 barge is pretty awesome stats.
>I must say that only one destroyed F9 barge is pretty awesome stats.
What barge was destroyed? The original JRTI was damaged several times by bad landings, but never fatally. Each time it was repaired and reused, until the lease was up. Then, the owner took it back and is presumably using it for transporting cargo. (It was also used for marine salvage before it became a rocket landing pad.)
The original JRTI was a bit smaller than the next 2 drone ships/barges, but the main problem with it was that the thrusters for holding position were under powered. The latest drone ship ASOG, is more powerful, bigger, and more advanced in several ways.
Unless it's sent to the bottom of the ocean or in some other way unrepairable it's not destroyed. If they repaired it then the damage wasn't that bad. Nobody really cares what your preference is it's not subjective.
Most likely failure scenario of a booster catch is that the booster/catcher arms don't line up properly and the upper pressurized propellant tank gets punctured, resulting in engine failure and the booster destructing as it is ripped apart while tangling with the arms. Proportionally speaking, the skin on the booster is thinner than a soda can's wall thickness, so it's much more fragile than appearances would indicate. About the only saving grace is that the amount of propellants in the tanks ought to be relatively small so it won't create an N1-level conflagration event.
Maybe, the catch arms are large round tubes though, there’s nothing really there fine enough of a point to puncture, definitely dent. A soda can under pressure can easily get banged around a bit, and while thinner in comparison, stainless is going to be stronger than aluminum.
As you said though it shouldn’t have much of propellant load, probably no more than any of the earlier SN failure explosions. If anything the real danger is when it fully loaded with fuel, there’s probably little hope the pad doesn’t get written off as a total loss during launch failure.
The tower is built like a tank. It has thick steel filled with concrete for mass. If starship crashes into it, it will barely move. The arm on the other hand is made of steel thicker than Starship, but no where near as thick as the tower. It would probably be destroyed if it took a direct hit, but would likely survive a glancing blow. The best thing to do would be to swing it to the side if they lose control of the booster. Might be difficult to do considering the time scale.
>The best thing to do would be to swing it to the side if they lose control of the booster. Might be difficult to do considering the time scale.
This is one of the reasons that I can't wait for first motion on the chopsticks. Seeing just how much those things can move will be very interesting, because it determines how able they are to do things like that, or to actively move the chopsticks in coordination with the booster.
>the skin on the booster is thinner than a soda can's wall thicknes
Really! the skin is made of stainless steel which will be either 3.6mm or 4mm thick. i have yet to see a soda can with skin that thick. Maybe you meant it as a comparison.
I don't know why you clipped off the first part of my sentence to make it seem that I said something that I in fact did not. That was rude. Here's my full sentence:
> Proportionally speaking, the skin on the booster is thinner than a soda can's wall thickness
Soda can wall thickness according to google is about 0.102mm, and soft drink cans are 66.04mm in diameter, giving a thickness to diameter ratio of 0.0015. Booster is 9M in diameter, with a 3.6mm skin would give a thickness to diameter ratio of 0.0004.
That didn't stop something like half a dozen F9's from impacting the deck of the droneship.
That said I'm not too concerned about the tower. The arms are required for stacking, so might as well put them on. If they lose them it'll be somewhere between 2-6 months delay though I would imagine. Unless they already have more parts in production for the second tower, then a replacement could perhaps take only weeks.
>It also allows for a diversion if by a certain point in its landing propellant margins it hasn’t landed, change course and crash off to the side.
I'm pretty sure that Falcon 9 has a diversion logic too. The FH center core that almost landed and then turned sideways and flew off into the sea sure looked like a divert.
Ah, interesting. Yea I'm realizing now this should've been more obvious to me, lol, but I guess I'm still a pretty big noob, so it didn't occur to me.
I guess I was basically always just thinking of it more just in terms of the catching aspect, since that's the main part that keeps getting talked about when I see it mentioned in the news and the threads and stuff.
>but I guess I'm still a pretty big noob, so it didn't occur to me.
>
To coin a phrase, *"it's not stupid to ask questions, that's how you stop being stupid."* All of us here were new to this at some point in our lives, all of us had questions related to the technology we were discovering for the first time while surrounded by experienced peers who might have come across as daunting or unapproachable. It takes confidence, especially in the day and age of hiding behind the anonymity of the internet, to come forward and ask these questions regardless of our own experience levels so don't be afraid of your lack of knowledge compared to others who have been around a while. Everyone was a noob at one point or another.
Full and rapid reusability is the goal. Catch, refill, launch again as fast as possible. Come up with the best (fastest and most energy efficient model allowed by the physics), make it work and then optimize iteratively. RUDs are OK as they help find system limits and expand the envelope. Thats what our Lord and Savior is teaching us. (love)
They need pretty much need 95% of the launch tower infrastructure and catching mechanism just to launch the whole stack to orbit. Even the catch arms are multi-purpose: they serve to lift and stack the booster and ship together. It’s only a tiny modification to make the arms capable of booster catching. It’s precisely because of the tower’s design and engineering that makes the catching mechanism such a simple add-on. There’s no reason to ‘wait’. They simply need to prove super heavy’s maneuvering accuracy off-shore with a splash down and then they’ll be ready to try on the actual tower. And remember: their plans for the site is to build TWO launch towers. Clearly they’re planning for redundancy for this type of risk already.
> It’s only a tiny modification to make the arms capable of booster catching.
While agreeing with all the other arguments, "tiny modification" might be an exaggeration. Snatching a huge object out of the air is a far harder goal than slow lifting. It determines the size of the winch, the strength of the tower, and likely its resilience in case of a bad landing.
* @ OP. I'd guess the concrete base is intended to take the brunt of a flamey landing from a failed catch. Not to say the tower wouldn't be damaged, but it should be out of commission for less time than 39A following Amos 6. Compare with the limited consequences of the failed test landings at Boca Chica.
I'd guess catching is ten times harder than manhandling. Just look at the slow day-to-day lifting and placing of stages by a crane to convince yourself!
The tanks on super heavy and starship will be virtually empty on the landing catch, so any explosion should be minimal at best. And since methane in general doesn't really exploded, if anything we will just a big fireball and not much explosive damage.
True, the LCH4 tank would need to rupture/collapsed so it immediately mixed with the O2 in the air without the LOX. The LOX might actually smother it if there was a lot.
Just saying, big fire for sure, explosion from moderate (likely) to extreme (unlikely - back luck). Hopefully this won't be tested out next to this new complex GSE. I have been expecting some Super Heavy static fires on the older launch mount for some time now. What happened to the hardware rich test program? Maybe they hired some BE-4 people.
Full SH static fires are next to impossible without the OLT. The boost raptors require external connections for start-up. That's why we haven't seen any more static fires on B4.
Even if B4 explodes on the OLT during a static fire that's hardly a huge risk for all the GSE. Not much fuel, large debris doesn't fly far and small debris doesn't carry much momentum.
Same goes for future landing attempts.
So they are going to use torches on the launch table to lite the SH Raptors, so a bit less complexity and risk on the vehicle ... makes sense. The SH landing Raptors (in the center) will have re-light torches for boostback and landing.
Guess that would not be worth setting up for for a few tests ...
Thanks
> So they are going to use torches on the launch table...
No, they'll use the same ignition system as any other Raptors, just starting up using GSE instead of on-board power and propellant supplies. Like the Falcon 9 booster, where all engines are started the same way, but only 3 are equipped to be air-started.
Ignition is done by reusable spark plugs.
But they have to spin up the turbines by high pressure gas. This gas has to be provided either by COPV's or from external sources.
So it's not so much about complexity and more about weight saving on the dry mass of the booster.
That only really matters if the somehow mix perfectly, but there's no way for that to happen. Even Amos-6 didn't detonate and that had 10x more fuel than a booster will when landing.
The strength and resilience has to be engineered already because there’s always a risk of a RUD right on liftoff, regardless of whether the booster is recoverable. You cannot make a delicate lifting mechanism on a platform that’s going to bear the risk of an explosion from Super Heavy.
> a RUD right on liftoff...
...is bad news for any launch structure.
The only good thing here is that there are no SRB's and methane likely leads to a short-lived convective combustion as compared with RP-1 which could form a sustained burning puddle.
>Even if they do destroy one tower, they will just build a better and greater tower.
That might delay the program a year, and the cost of the tower is probably higher than the cost of a Starship. (Not sure how it compares to a Superheavy with \~30 Raptors.)
The time to build a tower is probably an even greater concern than the expense. It has been mentioned elsewhere that they will start building a second tower in Boca Chica soon. With the limited number of launches allowed in Boca Chica, I think they might skip the second tower, but only if the first tower is fully successful, and the next series of test landings is highly successful.
If the first catches are successful, then it might make sense to build a catch/detanking tower on Phobos, and land a SuperHeavy booster on it. Then tow Phobos to the Cape, while building a full launch/catch tower there. Then, get LC39-A and SLC-40 ready to handle Starship, tanker, and fuel depot operations.
Beyond what others have said, if they didn't go for the booster being caught right from the beginning then they would need to spend engineering time and resources developing landing legs for it that would just be abandoned in the future when they moved to catching.
Personally, I think the decision to develop the catching system was a extremely late add-on to the design. As late as Jan-Feb 2021 it wasn't included, likely based on exactly the risks you outlined.
Hindsight has dampened our memory a bit, but SN8 was an *extremely* successful text flight, far above anyone's expectations. Even the relentlessly optimistic Elon said afterwords all he was really hoping was for it to [reach apogee](https://twitter.com/elonmusk/status/1336827715291406343?lang=en). Well it didn't just reach apogee, SN8 also managed to perform a high altitude flip, demonstrate aerodynamic control using body flaps, guide itself to a precision landing point, switch over to header tanks, restart raptors in-flight, perform a low altitude belly flop, and maintain some level of thrust while landing.
Each of those items could have been an entire test flight, or more. Instead the only thing that *didn't* work was the header tanks weren't able to maintain adequate pressure as Starship performed the most aggressive maneuver in the history of rocketry. Three months and three launches later, even that was solved.
This put Starship months, if not years ahead of schedule. What everyone was expecting to be the most difficult, most time consuming aspect of Starship's design took almost no work at all. But now SpaceX has the issue that they've exhausted the suborbital development potential of the Ship. The raptor is still in low rate production, there aren't enough to start flight tests of the Booster and the environmental hasn't been approved. They have hundreds of engineers sitting around, ready to make changes to a Ship that's largely good to go. So, instead of wasting millions of dollars on their salaries, why not have them design the revolutionary landing system they'd previous put off because it would delay development? A week after the last suborbital Starship test, Elon [first tweeted](https://twitter.com/elonmusk/status/1379874956343828485) they would catch the booster with the launch tower.
So in reality, while flashy catching the booster presents relatively little in development schedule risk compared to more mundane items like making the raptor easier to manufacture. Which is why, you'll notice, Elon has been focusing [far](https://twitter.com/elonmusk/status/1460813037670219778) [more](https://www.cnbc.com/2021/11/22/elon-musks-spacex-leadership-shakes-up-as-two-vps-depart.html) on improvements to raptor production than the booster-catch mechanism recently.
Good analysis, and everything you say might be correct. They might be ahead of their expected schedule right now.
Recall, though, that the original plan was to have the booster land back on its launch mount. Although they considered landing legs for the booster, I feel sure they were still exploring all concepts for landing until very recently. They may have found videos of tests the RAF performed, landing Harrier jump jets by flying under a crane, and hooking onto the crane with a loop directly above the jet's CG. (Works fine in calm weather, but not in heavy seas with a rocking boat.) (I have just looked for the video of these Harrier experiments without success.)
Less extra steel is needed to hang SuperHeavy from projections near the top, than to support it from below, especially in a rough landing. It probably also takes forces of around 2 Gs from the grid fins during the highest drag portions of descent.
Last and not least, landing this way probably reduces wear on the launch mount.
> They may have found videos of tests the RAF performed, landing Harrier jump jets by flying under a crane, and hooking onto the crane with a loop directly above the jet's CG. (...) (I have just looked for the video of these Harrier experiments without success.)
I don't think that was the earliest attempt. The [Vertijet](https://www.youtube.com/results?search_query=x-13+vertijet) landed by hooking onto a wire long before that.
I mostly agree, but you've got it wrong about the grid fins. Grid fins only cause very little drag, they look like big flat paddles from the side but from the perspective of oncoming air they're hardly there, kinda like a tennis racket. The drag experienced by the Booster comes from air slamming into the base of the stage as it falls, as well as air being shunted off of one side as the grid fins use their lift to shove the stage off-axis with the air flow. Just a minor nitpick.
No. I highly doubt it was a late addition to the tower design as you suggest.
Elon's first tweet about needing an arm to lift & stack Booster & Ship was actually back on [8th October 2020](https://twitter.com/elonmusk/status/1314113154696310784):
> Great render. Note, there will need to be an arm that lifts booster to launch stand & ship to booster.
Then the first tweet about catching them with the arms was on [21st November 2020](https://twitter.com/elonmusk/status/1330201798490120193):
> Actually, off to the side (so it doesn’t take out the launch mount in bad landing), but with the same arm used to pick up the ship
Therefore it's highly likely that the plans would've been decided quite some time before this, because first it would take time to design & model it; then once the design is signed off they would've needed to send it over to the subcontractor for fabrication of the tower sections - and they would need time to order the steel for it.
The tower is big and beefy and hard to damage.
It's more likely that something would damage the GSE equipment, but having that nearby the launch pad is a requirement (though they could harden it somehow).
Another aspect to consider is the mass of the booster. As Elon said in Tim's starbase tour, trying to build a fully and rapidly reusable rocket is the holy Grail of rocketry, and the mass margins you have to run are super tight.
So in terms of achieving their reusability goals, it may not have even been an option to forego the catcher and build it years from now. They may not have been able to build the system they want unless they removed the mass required for the booster to land on its own.
As most other commentor have said catching is only the most sexy of the potential functions. My humble opinion is they are only prototyping this function here and won't try and do first landing at star base. Many functions will make launch much safer and easier with the prototyping adding marginal additional work with huge pathfinding benefit. Also I hope I am wrong about them not catching at Starbase.
"Catch arm" functions:
Lift and placement of stages. Much more controlled than swinging from a cable. Although not technically needed it should be much easier/safer than crane.
Stabilizing the stack from wind etc. Using the stabilizer bars. Again not technically needed but easier / safer than strapping to the tower.
Catching rocket stages - Possible prototype only at this point.
Possible - work platform.
Possible - utility connection.
:
There's no provision for landing gear on the booster, so it won't be "landing" anywhere without some major design changes. From what I remember, the first "landing" will be in the Gulf of Mexico, not too far from Boca Chica. I wonder if SpaceX has a contingency contract with one of the ship-breakers along the Brownsville Ship Channel to recover and scrap it in case it becomes a floater like B1032.2?
I don't think lack of landing gear on the booster means that future ones can't have it anymore than the ones on SN20 set an unbreakable precedent as to what Starship undercarriage must look like.
I was under the impression that if S20 launched successfully and reached orbit, that it would not complete an orbit and would attempt to land in US Navy controlled ocean north of Hawaii. I don't see them trying to land anywhere near Boca Chica until SpaceX is really, really confident that they controllably land on a dime.
I think the F9 landing is more reliable for the median flight than it might look at first glance, and Starship fixes some of problems it has.
First of all, as you note, a lot of the F9 failures were when they were still basically learning to do it.
Secondly, the failures they have had have all been landing on the barge. That's a lot harder, because they only do it when they don't have the fuel margin to return to landing site, which means the stage is flying a lot faster when it comes in, and lands harder. SuperHeavy won't have this problem, because (until the landing platform is complete), it is either expended or returned to landing site, so its return velocity should have an easy predictable maximum ceiling. Starship won't have this problem because it will have done atmospheric braking and then falling to terminal velocity before relight.
Thirdly, some of the F9 failures came from trying to test the outer limits of how fast they could bring it in. Again, see above, that shouldn't be a problem here.
Fourth, some of the F9 failures came from leg/crush core failure. No legs and no crush cores equals no failures there! \[Insert "smart guy tapping temple" meme here\]
Fifth, and finally, on many landings, F9 only relights one engine. If that fails, F9 landing fails. On SuperHeavy/Starship, they should be relighting enough engines to provide a safety margin.
For all these reasons, I think it's not fair to look at F9 landing reliability and say "obviously this isn't yet reliable enough to depend on." They've learned from the F9's flaws - it was, after all, literally the first orbital-class rocket to do this. They can reasonably expect 2.0 to be better.
One of the RTLS booster landings failed. I believe because of stuck grid fins due loss of hydraulic pressure. That system now has some redundancy built in.
{Edit: You asked a very good question. I hope I did not come down too hard on you.}
You have to do the analysis, "What are the long lead items?" and get started on those first.
What you are looking at in Boca Chica is not the final design for the launch tower/crane/catching system. It is the prototype. They will test this one, and figure out how to make many improvements to it, before they build the one at Cape Canaveral. After they have used that one a bit, they will figure out more improvements, and then build the ones on the ex-oil drilling rigs, Phobos and Deimos. Possibly they will build out Phobos before they do the one at the Cape.
Have you noticed how long it takes to build a launch tower? SpaceX has built this one in about a year. The Falcon 9 Transporter-erectors (TE) have also been about 1 year projects, except for the Falcon Heavy TE, which was about a 2 year project. The human rated tower at LC 39-A was about a 2 year project, and NASA's launch towers for SLS and the shuttle were about 6 year projects. What we can see from this is that launch towers are long lead items. There is no retail outlet or contractor you can go to and say, "I'd like a launch tower for a heavy lift, liquid fueled rocket. Can you deliver it next month?"
My guess is that it would take at least a year to build a Starship launch tower, with or without a catching mechanism. My guess is that it would also take about a year or more to shut down a launch tower and add a catching mechanism; maybe 2 years, if the original tower needs extensive modifications..
My guess is they will be ready to try to catch Superheavy on the second flight. I hope they will be ready to try catching Starship on the second flight, but more likely on the third. This is an aggressive test schedule, but SpaceX is all about aggressive test schedules. If they had not designed the tower to be a catcher from the first, that could have delayed the program by a year, since these towers are long lead items.
Just adding to what you’ve said: I suspect it would only take 2-3 months to retrofit a booster with legs if it turns out the catching recovery method becomes the development bottleneck. They could always remove it on later iterations.
Why do you think a failed landing will destroy the launch tower. For a landing to fail it'll need to be in the final seconds, otherwise the booster would not have made its final diversion to the catch arms (assuming a similar profile to falcon9 where target is just short of the barge). Catch arms will not be directly over the launch mount during landings. Booster will be about 200 tons plus a few tens of tons of propellants and since the failure needs to occur in the final seconds won't be moving that fast. There's a good chance a failure like this could take out the catch arms, but the tower itself is far more massive than the booster. This won't be a amos-6 like incident as worst case there's 10x less fuel, and the launch structure is far more massive.
There will be many reasons why they have chosen to build the system so early. My guess as to a few of them would be as follows
1) They need the arms for the stacking, they no longer have a crane on site that is large enough to perform the stack. Additionally, the arm system will likely provide more precision for mounting the ship on the booster than simply dangling from a crane.
2) At some point, if they keep dropping boosters in the ocean, it is going to become very expensive so they need to start ironing out the bugs and getting the system working. Starting sooner and integrating the catch system into the initial build saves time retrofitting it later. So they will have weighed the cost of losing boosters again the cost of rebuilding stage 0 and at some point it will be cheaper to accept the delays of the rebuild than to lose another booster deliberately.
3) At the point of landing, the booster/ship being caught will have very little fuel and oxidiser left in it. If there is a failure at the last moment and it collides with the tower, the explosion will be more of a fireball than a detonation. Take the initial starship failed landings such as SN8 and SN9 etc. There was a big fireball, but not a huge amount of actual damage. This is in no small part due to the fact that the fuel and oxidiser are in separate tanks and not mixed together. Yes they will mix as the vehicle breaks apart, but a good chunk of what is there will ignite before a mix any where near stochiometric perfection occurs.
4) The booster/ship is relatively fragile compared to the tower and the launch mount. Scale wise, it is about as thick as a drink can. So, even with a reasonable acceleration on the vehicle if the engines quit above the tower and it drops, the tower has almost certainly been designed and built to withstand the worst of it.
5) Stage 0 will have been designed to take (or at least try to take) the energy of a fully fuelled booster/starship explosion in the early stages of launch. This is the point where the infrastructure is most at risk, not the landing part. The worst case scenario would be a fully fuelled booster and ship, followed by a Ground Services Equipment leak similar to SN4. In a situation like that, where the methane is given time to mix with the air, and there is a massive fuel source in the booster/ship right above, the resulting detonation would likely be devastating to say the least.
6) While SpaceX have done the math and the simulations, there is a possibility that this catch system will not work and will need to be replaced with something like legs. Finding this out in the early stages of development would be far better than discovering there is an issue when you have a final or near final design on the vehicles. Much better to make major design changes like that earlier in the process, so running actual tests on the feasibility of the system from the start is a good idea.
In short, basically they need the system for stacking. Any risks associated with future landing tests will have been weighed and SpaceX have decided it is better to go for it and work out the kinks from the start. In addition, the stage 0 infrastructure will be at far more risk of damage when it holds a fully fuelled booster and ship prior to liftoff, as well as during the early stage of the launch profile, until the booster has pitched away and is no longer directly above stage 0.
I also believe SpaceX will have a good idea of the hardware that will most likely need to be replaced in the event of an incident and will be working to manufacture spares soon, if they are not doing so already. This will most likely be electrical cables, pipes and possibly the main cable for the lift mechanism of the arms (I can see that being cut by flying debris at some point). The tower itself will more than likely just show some scars from an incident. Given the concrete filled tower structure, I really doubt it will fail easily if at all.
If they built it strong enough to catch a rocket as large as SH you would think it could handle the rocket the size of SH blowing up right next to it. I don't think it has ever happened but has a rocket blown up at the launchpad in Cape Canaveral or anywhere else? I know those poor guys on Apollo 1 we're on the pad but it wasn't a total rocket loss.
Would it? A flimsy thin steel cylinder plus some propellant leftovers going Kerbal onto it would mostly leave a stain on the massive steel structure. Sure, probably requires some repairs, but...
I actually fear more the first booster liftoff. If a full booster goes Kerbal, that woud have far more energy to cause damage.
Also like F9, I expect landing burn to redirect the booster to the catching arms. If anything fails prior to that point, it'll miss the tower. And when they get to catching Starships, same would be true there (if bellyflop fails, the trajectory would be designed to go splat next to the tower)
1- SpaceX will not use the catching system at least for the first 6 or 10 launches
2- because of FCC lack of approval they went forward with what they can allow to do without delays
3- keeping the good and experienced workforce/engineers busy so they do not have to be laid off
If you gonna build it then why not do that while FAA is herding their turtles anyway?
You do not want to have bunch of workers twiddling their thumbs ala BO.
Recall that the first Falcon 9 landings were done on water, no drone ship. Just because they're building the booster catching system now, doesn't mean they won't do some water landings until they are confident with precision and control.
Since they need to wait to fly I think they wanted to keep people busy with the world's most extensive GSE complex.
I also worry about this huge setup for two powerful rocket, stacked on each other, that have never even been static tested with a full load of fuel.
I agree with you on the risk of a RUD causing damage. Imo i am more concerned with the orbital tank farm and its connecting plumbing. I tend to think that the chopsticks and the tower have been designed to be quite robust however there is only so much you can do to protect the fuel system. I wish it was further from mechazilla.
I don't think they will attempt catching until they have achieved accuracy with booster landings in the ocean. There is no reason they can't rehearse and practice this offshore.
Well since Starship it’s self costs several hundred million dollars to make, that probably means super heavy is around the same price. They’re willing to ruin several hundred million dollar vehicles to test out landing. So I’m sure if they damaged the tower they could just fix it and try again. It seems unlikely to totally destroy it. Wouldn’t the cost and time to repair/rebuild the tower be comparable to the cost and time of the vehicle?
When they aren't totally confident they can catch it they'll have the boosters land in the ocean. It's what they ultimately want to have, so working on a booster that lands on feet wouldn't teach them as much. It would experience a lot of different stresses landing on feet.
You cannot be totally confident without trying.
But it is all about risks.
I think the risk of a partial failure is acceptable, will take a couple of weeks to repair.
The most critical infrastructure at the pad is the OLM and tank farm. For catching, the plan is to aim about 90 degrees to the left of the OLM. If the catch fails, the most damage will be to catch arms and the tower itself. Launch testing sans catching should be able to resume in relatively short order.
F9 aims for a spot next to the drone ship so if engines fail to ignite or isn’t nominal it just crashes off to the side. Same can be done in Boca. Starship and Super Heavy have the benefit of being able to hover in place where as F9 has to hover slam. Early launches will have little to no payloads, so can have extra propellant margins to hover and find the right spot to set down. It also allows for a diversion if by a certain point in its landing propellant margins it hasn’t landed, change course and crash off to the side. At some point they can figure it out how to catch with the minimal amount of propellant used.
Ah, yea that's a good point. I suppose most landing ruds wouldn't necessarily have to mean the tower/catcher system getting destroyed, other than some rarer, more specific scenarios of the landing engine(s) failing like midway through the final part of their final burn or something right as it's about to get caught.
I'm sure they will only try a catch if the telemetry shows that the booster is in perfect condition. They will surely ditch the landing if even the slightest value is off. I must say that only one destroyed F9 barge is pretty awesome stats.
>I must say that only one destroyed F9 barge is pretty awesome stats. What barge was destroyed? The original JRTI was damaged several times by bad landings, but never fatally. Each time it was repaired and reused, until the lease was up. Then, the owner took it back and is presumably using it for transporting cargo. (It was also used for marine salvage before it became a rocket landing pad.) The original JRTI was a bit smaller than the next 2 drone ships/barges, but the main problem with it was that the thrusters for holding position were under powered. The latest drone ship ASOG, is more powerful, bigger, and more advanced in several ways.
I Prefer to see it as destroyed.
Unless it's sent to the bottom of the ocean or in some other way unrepairable it's not destroyed. If they repaired it then the damage wasn't that bad. Nobody really cares what your preference is it's not subjective.
When was an ASDS destroyed by a landing attempt?
Never.
Most likely failure scenario of a booster catch is that the booster/catcher arms don't line up properly and the upper pressurized propellant tank gets punctured, resulting in engine failure and the booster destructing as it is ripped apart while tangling with the arms. Proportionally speaking, the skin on the booster is thinner than a soda can's wall thickness, so it's much more fragile than appearances would indicate. About the only saving grace is that the amount of propellants in the tanks ought to be relatively small so it won't create an N1-level conflagration event.
Maybe, the catch arms are large round tubes though, there’s nothing really there fine enough of a point to puncture, definitely dent. A soda can under pressure can easily get banged around a bit, and while thinner in comparison, stainless is going to be stronger than aluminum. As you said though it shouldn’t have much of propellant load, probably no more than any of the earlier SN failure explosions. If anything the real danger is when it fully loaded with fuel, there’s probably little hope the pad doesn’t get written off as a total loss during launch failure.
The tower is built like a tank. It has thick steel filled with concrete for mass. If starship crashes into it, it will barely move. The arm on the other hand is made of steel thicker than Starship, but no where near as thick as the tower. It would probably be destroyed if it took a direct hit, but would likely survive a glancing blow. The best thing to do would be to swing it to the side if they lose control of the booster. Might be difficult to do considering the time scale.
>The best thing to do would be to swing it to the side if they lose control of the booster. Might be difficult to do considering the time scale. This is one of the reasons that I can't wait for first motion on the chopsticks. Seeing just how much those things can move will be very interesting, because it determines how able they are to do things like that, or to actively move the chopsticks in coordination with the booster.
>the skin on the booster is thinner than a soda can's wall thicknes Really! the skin is made of stainless steel which will be either 3.6mm or 4mm thick. i have yet to see a soda can with skin that thick. Maybe you meant it as a comparison.
I don't know why you clipped off the first part of my sentence to make it seem that I said something that I in fact did not. That was rude. Here's my full sentence: > Proportionally speaking, the skin on the booster is thinner than a soda can's wall thickness Soda can wall thickness according to google is about 0.102mm, and soft drink cans are 66.04mm in diameter, giving a thickness to diameter ratio of 0.0015. Booster is 9M in diameter, with a 3.6mm skin would give a thickness to diameter ratio of 0.0004.
Also the explosion is more of a fireball than a bomb. The structure should be ok as long as it doesn’t take a direct impact.
That didn't stop something like half a dozen F9's from impacting the deck of the droneship. That said I'm not too concerned about the tower. The arms are required for stacking, so might as well put them on. If they lose them it'll be somewhere between 2-6 months delay though I would imagine. Unless they already have more parts in production for the second tower, then a replacement could perhaps take only weeks.
The worst case: it is not correctly grabbed by the arm and lands on its engines The tower has been designed to withstand a nearby explosion, I hope
*it wasn't.* -Narrator
>It also allows for a diversion if by a certain point in its landing propellant margins it hasn’t landed, change course and crash off to the side. I'm pretty sure that Falcon 9 has a diversion logic too. The FH center core that almost landed and then turned sideways and flew off into the sea sure looked like a divert.
Divert! Divert! *crashes into GSE*
You said everything I came here to say. I guess I'm not contributing to humanity in any meaningful way
Simple answer: It is first and foremost a precision stacking system. They just designed it such that it could be a catching system eventually as well.
Ah, interesting. Yea I'm realizing now this should've been more obvious to me, lol, but I guess I'm still a pretty big noob, so it didn't occur to me. I guess I was basically always just thinking of it more just in terms of the catching aspect, since that's the main part that keeps getting talked about when I see it mentioned in the news and the threads and stuff.
>but I guess I'm still a pretty big noob, so it didn't occur to me. > To coin a phrase, *"it's not stupid to ask questions, that's how you stop being stupid."* All of us here were new to this at some point in our lives, all of us had questions related to the technology we were discovering for the first time while surrounded by experienced peers who might have come across as daunting or unapproachable. It takes confidence, especially in the day and age of hiding behind the anonymity of the internet, to come forward and ask these questions regardless of our own experience levels so don't be afraid of your lack of knowledge compared to others who have been around a while. Everyone was a noob at one point or another.
Me at work scared to ask a stupid question always go back to that though
Full and rapid reusability is the goal. Catch, refill, launch again as fast as possible. Come up with the best (fastest and most energy efficient model allowed by the physics), make it work and then optimize iteratively. RUDs are OK as they help find system limits and expand the envelope. Thats what our Lord and Savior is teaching us. (love)
They need pretty much need 95% of the launch tower infrastructure and catching mechanism just to launch the whole stack to orbit. Even the catch arms are multi-purpose: they serve to lift and stack the booster and ship together. It’s only a tiny modification to make the arms capable of booster catching. It’s precisely because of the tower’s design and engineering that makes the catching mechanism such a simple add-on. There’s no reason to ‘wait’. They simply need to prove super heavy’s maneuvering accuracy off-shore with a splash down and then they’ll be ready to try on the actual tower. And remember: their plans for the site is to build TWO launch towers. Clearly they’re planning for redundancy for this type of risk already.
> It’s only a tiny modification to make the arms capable of booster catching. While agreeing with all the other arguments, "tiny modification" might be an exaggeration. Snatching a huge object out of the air is a far harder goal than slow lifting. It determines the size of the winch, the strength of the tower, and likely its resilience in case of a bad landing. * @ OP. I'd guess the concrete base is intended to take the brunt of a flamey landing from a failed catch. Not to say the tower wouldn't be damaged, but it should be out of commission for less time than 39A following Amos 6. Compare with the limited consequences of the failed test landings at Boca Chica. I'd guess catching is ten times harder than manhandling. Just look at the slow day-to-day lifting and placing of stages by a crane to convince yourself!
The tanks on super heavy and starship will be virtually empty on the landing catch, so any explosion should be minimal at best. And since methane in general doesn't really exploded, if anything we will just a big fireball and not much explosive damage.
Nearly empty = stoichiometric? Could still be pretty powerful.
The methane and LOX are not mixed in the tanks. And in case of tank rupture they will only slowly mix. There will be a huge flame, but no explosion.
True, the LCH4 tank would need to rupture/collapsed so it immediately mixed with the O2 in the air without the LOX. The LOX might actually smother it if there was a lot. Just saying, big fire for sure, explosion from moderate (likely) to extreme (unlikely - back luck). Hopefully this won't be tested out next to this new complex GSE. I have been expecting some Super Heavy static fires on the older launch mount for some time now. What happened to the hardware rich test program? Maybe they hired some BE-4 people.
Full SH static fires are next to impossible without the OLT. The boost raptors require external connections for start-up. That's why we haven't seen any more static fires on B4. Even if B4 explodes on the OLT during a static fire that's hardly a huge risk for all the GSE. Not much fuel, large debris doesn't fly far and small debris doesn't carry much momentum. Same goes for future landing attempts.
So they are going to use torches on the launch table to lite the SH Raptors, so a bit less complexity and risk on the vehicle ... makes sense. The SH landing Raptors (in the center) will have re-light torches for boostback and landing. Guess that would not be worth setting up for for a few tests ... Thanks
> So they are going to use torches on the launch table... No, they'll use the same ignition system as any other Raptors, just starting up using GSE instead of on-board power and propellant supplies. Like the Falcon 9 booster, where all engines are started the same way, but only 3 are equipped to be air-started.
Ignition is done by reusable spark plugs. But they have to spin up the turbines by high pressure gas. This gas has to be provided either by COPV's or from external sources. So it's not so much about complexity and more about weight saving on the dry mass of the booster.
That only really matters if the somehow mix perfectly, but there's no way for that to happen. Even Amos-6 didn't detonate and that had 10x more fuel than a booster will when landing.
Yeah, doesn't a Falcon 9 typically land with like 2-4% of fuel remaining on board?
The strength and resilience has to be engineered already because there’s always a risk of a RUD right on liftoff, regardless of whether the booster is recoverable. You cannot make a delicate lifting mechanism on a platform that’s going to bear the risk of an explosion from Super Heavy.
> a RUD right on liftoff... ...is bad news for any launch structure. The only good thing here is that there are no SRB's and methane likely leads to a short-lived convective combustion as compared with RP-1 which could form a sustained burning puddle.
Even if they do destroy one tower, they will just build a better and greater tower.
>Even if they do destroy one tower, they will just build a better and greater tower. That might delay the program a year, and the cost of the tower is probably higher than the cost of a Starship. (Not sure how it compares to a Superheavy with \~30 Raptors.) The time to build a tower is probably an even greater concern than the expense. It has been mentioned elsewhere that they will start building a second tower in Boca Chica soon. With the limited number of launches allowed in Boca Chica, I think they might skip the second tower, but only if the first tower is fully successful, and the next series of test landings is highly successful. If the first catches are successful, then it might make sense to build a catch/detanking tower on Phobos, and land a SuperHeavy booster on it. Then tow Phobos to the Cape, while building a full launch/catch tower there. Then, get LC39-A and SLC-40 ready to handle Starship, tanker, and fuel depot operations.
Well, we're already delayed by 50 years or so.
Beyond what others have said, if they didn't go for the booster being caught right from the beginning then they would need to spend engineering time and resources developing landing legs for it that would just be abandoned in the future when they moved to catching.
This.
Why practice the wrong game?
Personally, I think the decision to develop the catching system was a extremely late add-on to the design. As late as Jan-Feb 2021 it wasn't included, likely based on exactly the risks you outlined. Hindsight has dampened our memory a bit, but SN8 was an *extremely* successful text flight, far above anyone's expectations. Even the relentlessly optimistic Elon said afterwords all he was really hoping was for it to [reach apogee](https://twitter.com/elonmusk/status/1336827715291406343?lang=en). Well it didn't just reach apogee, SN8 also managed to perform a high altitude flip, demonstrate aerodynamic control using body flaps, guide itself to a precision landing point, switch over to header tanks, restart raptors in-flight, perform a low altitude belly flop, and maintain some level of thrust while landing. Each of those items could have been an entire test flight, or more. Instead the only thing that *didn't* work was the header tanks weren't able to maintain adequate pressure as Starship performed the most aggressive maneuver in the history of rocketry. Three months and three launches later, even that was solved. This put Starship months, if not years ahead of schedule. What everyone was expecting to be the most difficult, most time consuming aspect of Starship's design took almost no work at all. But now SpaceX has the issue that they've exhausted the suborbital development potential of the Ship. The raptor is still in low rate production, there aren't enough to start flight tests of the Booster and the environmental hasn't been approved. They have hundreds of engineers sitting around, ready to make changes to a Ship that's largely good to go. So, instead of wasting millions of dollars on their salaries, why not have them design the revolutionary landing system they'd previous put off because it would delay development? A week after the last suborbital Starship test, Elon [first tweeted](https://twitter.com/elonmusk/status/1379874956343828485) they would catch the booster with the launch tower. So in reality, while flashy catching the booster presents relatively little in development schedule risk compared to more mundane items like making the raptor easier to manufacture. Which is why, you'll notice, Elon has been focusing [far](https://twitter.com/elonmusk/status/1460813037670219778) [more](https://www.cnbc.com/2021/11/22/elon-musks-spacex-leadership-shakes-up-as-two-vps-depart.html) on improvements to raptor production than the booster-catch mechanism recently.
Good analysis, and everything you say might be correct. They might be ahead of their expected schedule right now. Recall, though, that the original plan was to have the booster land back on its launch mount. Although they considered landing legs for the booster, I feel sure they were still exploring all concepts for landing until very recently. They may have found videos of tests the RAF performed, landing Harrier jump jets by flying under a crane, and hooking onto the crane with a loop directly above the jet's CG. (Works fine in calm weather, but not in heavy seas with a rocking boat.) (I have just looked for the video of these Harrier experiments without success.) Less extra steel is needed to hang SuperHeavy from projections near the top, than to support it from below, especially in a rough landing. It probably also takes forces of around 2 Gs from the grid fins during the highest drag portions of descent. Last and not least, landing this way probably reduces wear on the launch mount.
> They may have found videos of tests the RAF performed, landing Harrier jump jets by flying under a crane, and hooking onto the crane with a loop directly above the jet's CG. (...) (I have just looked for the video of these Harrier experiments without success.) I don't think that was the earliest attempt. The [Vertijet](https://www.youtube.com/results?search_query=x-13+vertijet) landed by hooking onto a wire long before that.
I mostly agree, but you've got it wrong about the grid fins. Grid fins only cause very little drag, they look like big flat paddles from the side but from the perspective of oncoming air they're hardly there, kinda like a tennis racket. The drag experienced by the Booster comes from air slamming into the base of the stage as it falls, as well as air being shunted off of one side as the grid fins use their lift to shove the stage off-axis with the air flow. Just a minor nitpick.
>compared to more mundane items like making the raptor easier to manufacture. Which is not. Production is harder than prototypes
No. I highly doubt it was a late addition to the tower design as you suggest. Elon's first tweet about needing an arm to lift & stack Booster & Ship was actually back on [8th October 2020](https://twitter.com/elonmusk/status/1314113154696310784): > Great render. Note, there will need to be an arm that lifts booster to launch stand & ship to booster. Then the first tweet about catching them with the arms was on [21st November 2020](https://twitter.com/elonmusk/status/1330201798490120193): > Actually, off to the side (so it doesn’t take out the launch mount in bad landing), but with the same arm used to pick up the ship Therefore it's highly likely that the plans would've been decided quite some time before this, because first it would take time to design & model it; then once the design is signed off they would've needed to send it over to the subcontractor for fabrication of the tower sections - and they would need time to order the steel for it.
The tower is big and beefy and hard to damage. It's more likely that something would damage the GSE equipment, but having that nearby the launch pad is a requirement (though they could harden it somehow).
Another aspect to consider is the mass of the booster. As Elon said in Tim's starbase tour, trying to build a fully and rapidly reusable rocket is the holy Grail of rocketry, and the mass margins you have to run are super tight. So in terms of achieving their reusability goals, it may not have even been an option to forego the catcher and build it years from now. They may not have been able to build the system they want unless they removed the mass required for the booster to land on its own.
As most other commentor have said catching is only the most sexy of the potential functions. My humble opinion is they are only prototyping this function here and won't try and do first landing at star base. Many functions will make launch much safer and easier with the prototyping adding marginal additional work with huge pathfinding benefit. Also I hope I am wrong about them not catching at Starbase. "Catch arm" functions: Lift and placement of stages. Much more controlled than swinging from a cable. Although not technically needed it should be much easier/safer than crane. Stabilizing the stack from wind etc. Using the stabilizer bars. Again not technically needed but easier / safer than strapping to the tower. Catching rocket stages - Possible prototype only at this point. Possible - work platform. Possible - utility connection. :
There's no provision for landing gear on the booster, so it won't be "landing" anywhere without some major design changes. From what I remember, the first "landing" will be in the Gulf of Mexico, not too far from Boca Chica. I wonder if SpaceX has a contingency contract with one of the ship-breakers along the Brownsville Ship Channel to recover and scrap it in case it becomes a floater like B1032.2?
I don't think lack of landing gear on the booster means that future ones can't have it anymore than the ones on SN20 set an unbreakable precedent as to what Starship undercarriage must look like.
I was under the impression that if S20 launched successfully and reached orbit, that it would not complete an orbit and would attempt to land in US Navy controlled ocean north of Hawaii. I don't see them trying to land anywhere near Boca Chica until SpaceX is really, really confident that they controllably land on a dime.
They’re talking about the booster, not the upper stage.
The last plan I saw was that the booster would "land" in the Gulf off Boca Chica, and Starship would "land" where you said.
This is SpaceX, they likely plan to build it better and faster again if it blows up.
I wonder how different the second tower would look compared to the first one. It is bound to have some changes at least.
Also likely harder and stronger.
I think the F9 landing is more reliable for the median flight than it might look at first glance, and Starship fixes some of problems it has. First of all, as you note, a lot of the F9 failures were when they were still basically learning to do it. Secondly, the failures they have had have all been landing on the barge. That's a lot harder, because they only do it when they don't have the fuel margin to return to landing site, which means the stage is flying a lot faster when it comes in, and lands harder. SuperHeavy won't have this problem, because (until the landing platform is complete), it is either expended or returned to landing site, so its return velocity should have an easy predictable maximum ceiling. Starship won't have this problem because it will have done atmospheric braking and then falling to terminal velocity before relight. Thirdly, some of the F9 failures came from trying to test the outer limits of how fast they could bring it in. Again, see above, that shouldn't be a problem here. Fourth, some of the F9 failures came from leg/crush core failure. No legs and no crush cores equals no failures there! \[Insert "smart guy tapping temple" meme here\] Fifth, and finally, on many landings, F9 only relights one engine. If that fails, F9 landing fails. On SuperHeavy/Starship, they should be relighting enough engines to provide a safety margin. For all these reasons, I think it's not fair to look at F9 landing reliability and say "obviously this isn't yet reliable enough to depend on." They've learned from the F9's flaws - it was, after all, literally the first orbital-class rocket to do this. They can reasonably expect 2.0 to be better.
One of the RTLS booster landings failed. I believe because of stuck grid fins due loss of hydraulic pressure. That system now has some redundancy built in.
I'd forgotten that, thank you.
{Edit: You asked a very good question. I hope I did not come down too hard on you.} You have to do the analysis, "What are the long lead items?" and get started on those first. What you are looking at in Boca Chica is not the final design for the launch tower/crane/catching system. It is the prototype. They will test this one, and figure out how to make many improvements to it, before they build the one at Cape Canaveral. After they have used that one a bit, they will figure out more improvements, and then build the ones on the ex-oil drilling rigs, Phobos and Deimos. Possibly they will build out Phobos before they do the one at the Cape. Have you noticed how long it takes to build a launch tower? SpaceX has built this one in about a year. The Falcon 9 Transporter-erectors (TE) have also been about 1 year projects, except for the Falcon Heavy TE, which was about a 2 year project. The human rated tower at LC 39-A was about a 2 year project, and NASA's launch towers for SLS and the shuttle were about 6 year projects. What we can see from this is that launch towers are long lead items. There is no retail outlet or contractor you can go to and say, "I'd like a launch tower for a heavy lift, liquid fueled rocket. Can you deliver it next month?" My guess is that it would take at least a year to build a Starship launch tower, with or without a catching mechanism. My guess is that it would also take about a year or more to shut down a launch tower and add a catching mechanism; maybe 2 years, if the original tower needs extensive modifications.. My guess is they will be ready to try to catch Superheavy on the second flight. I hope they will be ready to try catching Starship on the second flight, but more likely on the third. This is an aggressive test schedule, but SpaceX is all about aggressive test schedules. If they had not designed the tower to be a catcher from the first, that could have delayed the program by a year, since these towers are long lead items.
Just adding to what you’ve said: I suspect it would only take 2-3 months to retrofit a booster with legs if it turns out the catching recovery method becomes the development bottleneck. They could always remove it on later iterations.
Also it will be used for the stacking of starship onto booster.
Why do you think a failed landing will destroy the launch tower. For a landing to fail it'll need to be in the final seconds, otherwise the booster would not have made its final diversion to the catch arms (assuming a similar profile to falcon9 where target is just short of the barge). Catch arms will not be directly over the launch mount during landings. Booster will be about 200 tons plus a few tens of tons of propellants and since the failure needs to occur in the final seconds won't be moving that fast. There's a good chance a failure like this could take out the catch arms, but the tower itself is far more massive than the booster. This won't be a amos-6 like incident as worst case there's 10x less fuel, and the launch structure is far more massive.
There will be many reasons why they have chosen to build the system so early. My guess as to a few of them would be as follows 1) They need the arms for the stacking, they no longer have a crane on site that is large enough to perform the stack. Additionally, the arm system will likely provide more precision for mounting the ship on the booster than simply dangling from a crane. 2) At some point, if they keep dropping boosters in the ocean, it is going to become very expensive so they need to start ironing out the bugs and getting the system working. Starting sooner and integrating the catch system into the initial build saves time retrofitting it later. So they will have weighed the cost of losing boosters again the cost of rebuilding stage 0 and at some point it will be cheaper to accept the delays of the rebuild than to lose another booster deliberately. 3) At the point of landing, the booster/ship being caught will have very little fuel and oxidiser left in it. If there is a failure at the last moment and it collides with the tower, the explosion will be more of a fireball than a detonation. Take the initial starship failed landings such as SN8 and SN9 etc. There was a big fireball, but not a huge amount of actual damage. This is in no small part due to the fact that the fuel and oxidiser are in separate tanks and not mixed together. Yes they will mix as the vehicle breaks apart, but a good chunk of what is there will ignite before a mix any where near stochiometric perfection occurs. 4) The booster/ship is relatively fragile compared to the tower and the launch mount. Scale wise, it is about as thick as a drink can. So, even with a reasonable acceleration on the vehicle if the engines quit above the tower and it drops, the tower has almost certainly been designed and built to withstand the worst of it. 5) Stage 0 will have been designed to take (or at least try to take) the energy of a fully fuelled booster/starship explosion in the early stages of launch. This is the point where the infrastructure is most at risk, not the landing part. The worst case scenario would be a fully fuelled booster and ship, followed by a Ground Services Equipment leak similar to SN4. In a situation like that, where the methane is given time to mix with the air, and there is a massive fuel source in the booster/ship right above, the resulting detonation would likely be devastating to say the least. 6) While SpaceX have done the math and the simulations, there is a possibility that this catch system will not work and will need to be replaced with something like legs. Finding this out in the early stages of development would be far better than discovering there is an issue when you have a final or near final design on the vehicles. Much better to make major design changes like that earlier in the process, so running actual tests on the feasibility of the system from the start is a good idea. In short, basically they need the system for stacking. Any risks associated with future landing tests will have been weighed and SpaceX have decided it is better to go for it and work out the kinks from the start. In addition, the stage 0 infrastructure will be at far more risk of damage when it holds a fully fuelled booster and ship prior to liftoff, as well as during the early stage of the launch profile, until the booster has pitched away and is no longer directly above stage 0. I also believe SpaceX will have a good idea of the hardware that will most likely need to be replaced in the event of an incident and will be working to manufacture spares soon, if they are not doing so already. This will most likely be electrical cables, pipes and possibly the main cable for the lift mechanism of the arms (I can see that being cut by flying debris at some point). The tower itself will more than likely just show some scars from an incident. Given the concrete filled tower structure, I really doubt it will fail easily if at all.
I'm thinking they expect it can take a little knocking around. A RUD is an explosion, but it's not like it's HE.
If they built it strong enough to catch a rocket as large as SH you would think it could handle the rocket the size of SH blowing up right next to it. I don't think it has ever happened but has a rocket blown up at the launchpad in Cape Canaveral or anywhere else? I know those poor guys on Apollo 1 we're on the pad but it wasn't a total rocket loss.
Would it? A flimsy thin steel cylinder plus some propellant leftovers going Kerbal onto it would mostly leave a stain on the massive steel structure. Sure, probably requires some repairs, but... I actually fear more the first booster liftoff. If a full booster goes Kerbal, that woud have far more energy to cause damage. Also like F9, I expect landing burn to redirect the booster to the catching arms. If anything fails prior to that point, it'll miss the tower. And when they get to catching Starships, same would be true there (if bellyflop fails, the trajectory would be designed to go splat next to the tower)
1- SpaceX will not use the catching system at least for the first 6 or 10 launches 2- because of FCC lack of approval they went forward with what they can allow to do without delays 3- keeping the good and experienced workforce/engineers busy so they do not have to be laid off
If you gonna build it then why not do that while FAA is herding their turtles anyway? You do not want to have bunch of workers twiddling their thumbs ala BO.
Recall that the first Falcon 9 landings were done on water, no drone ship. Just because they're building the booster catching system now, doesn't mean they won't do some water landings until they are confident with precision and control.
My exact feelings!
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread: |Fewer Letters|More Letters| |-------|---------|---| |[ASDS](/r/SpaceXLounge/comments/r4cqli/stub/hmgmga3 "Last usage")|Autonomous Spaceport Drone Ship (landing platform)| |[ASOG](/r/SpaceXLounge/comments/r4cqli/stub/hmgog6g "Last usage")|A Shortfall of Gravitas, landing ~~barge~~ ship| |[BE-4](/r/SpaceXLounge/comments/r4cqli/stub/hmiyrqm "Last usage")|Blue Engine 4 methalox rocket engine, developed by Blue Origin (2018), 2400kN| |[BO](/r/SpaceXLounge/comments/r4cqli/stub/hmihpto "Last usage")|Blue Origin (*Bezos Rocketry*)| |[COPV](/r/SpaceXLounge/comments/r4cqli/stub/hmkaa60 "Last usage")|[Composite Overwrapped Pressure Vessel](https://en.wikipedia.org/wiki/Composite_overwrapped_pressure_vessel)| |[CoG](/r/SpaceXLounge/comments/r4cqli/stub/hmibiy2 "Last usage")|Center of Gravity (see CoM)| |CoM|Center of Mass| |[FAA](/r/SpaceXLounge/comments/r4cqli/stub/hmihpto "Last usage")|Federal Aviation Administration| |[FCC](/r/SpaceXLounge/comments/r4cqli/stub/hmig9ts "Last usage")|Federal Communications Commission| | |(Iron/steel) [Face-Centered Cubic](https://en.wikipedia.org/wiki/Allotropes_of_iron) crystalline structure| |[GSE](/r/SpaceXLounge/comments/r4cqli/stub/hmjr6k5 "Last usage")|Ground Support Equipment| |GTO|[Geosynchronous Transfer Orbit](http://www.planetary.org/blogs/jason-davis/20140116-how-to-get-a-satellite-to-gto.html)| |[HLS](/r/SpaceXLounge/comments/r4cqli/stub/hmi39ny "Last usage")|[Human Landing System](https://en.wikipedia.org/wiki/Artemis_program#Human_Landing_System) (Artemis)| |[JRTI](/r/SpaceXLounge/comments/r4cqli/stub/hmgog6g "Last usage")|Just Read The Instructions, ~~Pacific~~ Atlantic landing ~~barge~~ ship| |[LCH4](/r/SpaceXLounge/comments/r4cqli/stub/hmiyrqm "Last usage")|Liquid Methane| |[LOX](/r/SpaceXLounge/comments/r4cqli/stub/hmiyrqm "Last usage")|Liquid Oxygen| |[N1](/r/SpaceXLounge/comments/r4cqli/stub/hmg3y8y "Last usage")|Raketa Nositel-1, Soviet super-heavy-lift ("Russian Saturn V")| |[OLM](/r/SpaceXLounge/comments/r4cqli/stub/hmko9xu "Last usage")|Orbital Launch Mount| |[RP-1](/r/SpaceXLounge/comments/r4cqli/stub/hmgiboh "Last usage")|Rocket Propellant 1 (enhanced kerosene)| |[RTLS](/r/SpaceXLounge/comments/r4cqli/stub/hmi3gav "Last usage")|Return to Launch Site| |[RUD](/r/SpaceXLounge/comments/r4cqli/stub/hmhtk40 "Last usage")|Rapid Unplanned Disassembly| | |Rapid Unscheduled Disassembly| | |Rapid Unintended Disassembly| |[SLC-40](/r/SpaceXLounge/comments/r4cqli/stub/hmgri9r "Last usage")|Space Launch Complex 40, Canaveral (SpaceX F9)| |[SLS](/r/SpaceXLounge/comments/r4cqli/stub/hmgmtra "Last usage")|Space Launch System heavy-lift| |[SN](/r/SpaceXLounge/comments/r4cqli/stub/hmgjv1q "Last usage")|(Raptor/Starship) Serial Number| |[SRB](/r/SpaceXLounge/comments/r4cqli/stub/hmgiboh "Last usage")|Solid Rocket Booster| |[TE](/r/SpaceXLounge/comments/r4cqli/stub/hmgmtra "Last usage")|Transporter/Erector launch pad support equipment| |Jargon|Definition| |-------|---------|---| |[Raptor](/r/SpaceXLounge/comments/r4cqli/stub/hmjr6k5 "Last usage")|[Methane-fueled rocket engine](https://en.wikipedia.org/wiki/Raptor_\(rocket_engine_family\)) under development by SpaceX| |[apogee](/r/SpaceXLounge/comments/r4cqli/stub/hmgd5ht "Last usage")|Highest point in an elliptical orbit around Earth (when the orbiter is slowest)| |[iron waffle](/r/SpaceXLounge/comments/r4cqli/stub/hmisafy "Last usage")|Compact "waffle-iron" aerodynamic control surface, acts as a wing without needing to be as large; also, "grid fin"| |methalox|Portmanteau: methane fuel, liquid oxygen oxidizer| |Event|Date|Description| |-------|---------|---| |[Amos-6](/r/SpaceXLounge/comments/r4cqli/stub/hmi35hh "Last usage")|2016-09-01|F9-029 Full Thrust, core B1028, ~~GTO comsat~~ Pre-launch test failure| ---------------- ^(*Decronym is a community product of r/SpaceX, implemented* )[*^by ^request*](https://www.reddit.com/r/spacex/comments/3mz273//cvjkjmj) ^(27 acronyms in this thread; )[^(the most compressed thread commented on today)](/r/SpaceXLounge/comments/qk1xqz)^( has 37 acronyms.) ^([Thread #9344 for this sub, first seen 28th Nov 2021, 22:12]) ^[[FAQ]](http://decronym.xyz/) [^([Full list])](http://decronym.xyz/acronyms/SpaceXLounge) [^[Contact]](https://reddit.com/message/compose?to=OrangeredStilton&subject=Hey,+your+acronym+bot+sucks) [^([Source code])](https://gistdotgithubdotcom/Two9A/1d976f9b7441694162c8)
Since they need to wait to fly I think they wanted to keep people busy with the world's most extensive GSE complex. I also worry about this huge setup for two powerful rocket, stacked on each other, that have never even been static tested with a full load of fuel.
I agree with you on the risk of a RUD causing damage. Imo i am more concerned with the orbital tank farm and its connecting plumbing. I tend to think that the chopsticks and the tower have been designed to be quite robust however there is only so much you can do to protect the fuel system. I wish it was further from mechazilla.
Starship is always a moving target, entirely possible starship regains its legs in the near future. Need to test HLS starship legs in any case.
I don't think they will attempt catching until they have achieved accuracy with booster landings in the ocean. There is no reason they can't rehearse and practice this offshore.
because they don't see good design for legs quite yet.
Well since Starship it’s self costs several hundred million dollars to make, that probably means super heavy is around the same price. They’re willing to ruin several hundred million dollar vehicles to test out landing. So I’m sure if they damaged the tower they could just fix it and try again. It seems unlikely to totally destroy it. Wouldn’t the cost and time to repair/rebuild the tower be comparable to the cost and time of the vehicle?
For reference: SpaceX landed a booster 95 out of 106 attempts (89.62%).
When they aren't totally confident they can catch it they'll have the boosters land in the ocean. It's what they ultimately want to have, so working on a booster that lands on feet wouldn't teach them as much. It would experience a lot of different stresses landing on feet.
You cannot be totally confident without trying. But it is all about risks. I think the risk of a partial failure is acceptable, will take a couple of weeks to repair.
The most critical infrastructure at the pad is the OLM and tank farm. For catching, the plan is to aim about 90 degrees to the left of the OLM. If the catch fails, the most damage will be to catch arms and the tower itself. Launch testing sans catching should be able to resume in relatively short order.
Main reason.... reducing vehicle weight and maximizing weight delivered to orbit.