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(but flight too) A question about Falcon 9 security


goldenpeach

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Hi!

the question is simple: let's imagine that the second stage of falcon 9 stage is in the good trajectory for landing on earth.

During the landing, before the engine ignite to slow down, we discover that the said engine won't ignite.

What security measure does Spacex have for that? Do they somehow destroy the stage or have they other small engine to place it on a trajectory that will make the stage "land" somewhere else?

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If they are clever (and they usually are), they put the first stage into a flyback trajectory that ends in a crash zone (ocean, marshes, etc...). If the engine restarts properly, then it diverts to the landing zone. This is for the first stage.

Flying back the second stage is impractical. The only time it was mentioned was in that "Muse" inspirational video from several years back, but everyone including SpaceX knows that it's not worth the propellant penalty and extra weight. The second stage has to reach orbital speed to return to the landing site, so it would need a pretty heavy heat shield to survive reentry, which would severely reduce the payload fraction.

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If they make it reliable enough then there might not be much of a need for contingency plans. Huge jets with probably more fuel fly over our heads all the time, and sometimes they do fall on our heads. However, it happens so rarely that little is done about it.

Unfortunately, I imagine that a rocket will never be made as reliable as a passenger jet, or at least not in the near future.

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Unfortunately, I imagine that a rocket will never be made as reliable as a passenger jet, or at least not in the near future.

I wouldn't be too sure, depending on your definition of "near future" of course. The wright brothers did their first powered flight in 1904 if I'm not mistaken. The boeing 707 started production in 1958, only half a century later.

If the falcon 9 test tomorrow is successful and re-usable rockets become a thing, then cost will go down immensely. And if cost goes down, it will attract more investors, more development, etc.

I think the next couple decades will be very interesting in terms of spaceflight and energy/fuel production methods.

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I wouldn't be too sure, depending on your definition of "near future" of course. The wright brothers did their first powered flight in 1904 if I'm not mistaken. The boeing 707 started production in 1958, only half a century later.

Not comparable. When powered flight developed, there was a huge demand for mass transportation. People needed to reach destinations where they would be able to conduct business, meet with relatives, find a job, build a new life, or just visit. None of that demand exists for spaceflight. There is nothing for normal people like you and me to do up there, except float around and look out of a window. There is no business, no new life, no cheap resources.

If the falcon 9 test tomorrow is successful and re-usable rockets become a thing, then cost will go down immensely. And if cost goes down, it will attract more investors, more development, etc.

No. Reusing the first stage does not cut cost "immensely". The cost of the hardware is a small fraction of the total cost of launching a payload into space. The biggest cost is infrastructure and manpower, which are not really impacted by reusability.

I think the next couple decades will be very interesting in terms of spaceflight and energy/fuel production methods.

It will be interesting, but accelerating payloads to orbital speed will always require large amounts of power. That kind of power will always cost a lot to produce, handle, and transform into kinetic energy in a safe and secure manner.

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Why would it have to return? I'm sure there would be plenty of places downrange suitable for landing. Then recovered stage could be transported back for repairs and refurbishing by heavy cargo plane or a ship.

You need to return it to the launch site somehow. The second stage practically gets to orbit, which means that you might as well do a full orbit and land at the launch site. If you land it downrange, it doesn't change much in terms of deorbit and reentry, but you also add the cost and delay of bringing back the stage on a plane or a ship. Those options are not cheap and go against your goal of "fast turnaround". The second stage is pretty small, with only one engine. It's much cheaper than the first stage to produce, so it really doesn't make sense to spend more money to recover it.

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Not comparable. When powered flight developed, there was a huge demand for mass transportation. People needed to reach destinations where they would be able to conduct business, meet with relatives, find a job, build a new life, or just visit. None of that demand exists for spaceflight. There is nothing for normal people like you and me to do up there, except float around and look out of a window. There is no business, no new life, no cheap resources.

I wasn't actually trying to make a real comparison, just show that technological advancement can go much quicker then you'd expect, and that it's a self-strengthening effect. The more advanced technology becomes, the faster we can innovate, which leads to better technology, etc. As for incentives: scientific knowledge is obviously the biggest one. For example: one of the more recent resupply missions to the ISS included a scientific experiment to study the processes in which alzheimer's disease works in microgravity. With the absence of gravity, certain processes which are impossible to observe on earth can be studied which could lead to a breakthrough in Alzheimer treatment. That's a nice incentive for pharmaceutical companies right there.

No. Reusing the first stage does not cut cost "immensely". The cost of the hardware is a small fraction of the total cost of launching a payload into space. The biggest cost is infrastructure and manpower, which are not really impacted by reusability.

infrastructure and manpower to produce the hardware. With fully disposable rockets, you're throwing all that manpower and money down the drain every single launch. If you can cut down from "fully build a rocket from scratch during the course of several months" to "fill it with fuel and put it back on the pad within a week", costs can be brought down a lot. (obviously this is an exageration for illustration purposes, but you get the gist of it). I believe SpaceX is currently aiming at re-launching the falcon 9 at a third of the cost it would normally be, and if re-usability becomes standard, prices could drop down to 10% of the current ones. Possibly even lower if new technologies surface.

It will be interesting, but accelerating payloads to orbital speed will always require large amounts of power. That kind of power will always cost a lot to produce, handle, and transform into kinetic energy in a safe and secure manner.

Define "a lot". Of course it will always cost millions of dollars to construct a rocket, and obviously spaceflight will always be more expensive than regular atmospheric flight because it simply takes more energy, but it can certainly be done a lot cheaper than it is now. Right now it costs about 4000 to 20 000 dollars to put 1kg in low earth orbit. If that can be brought down to 500, you can theoretically have a ticket for a single person for roughly 40 000 dollars. And that's not including any cost cutting you can expect if dedicated passenger carriers will be developed. Or you can go on a sub-orbital spaceflight for a shorter, but cheaper spaceflight. That's teh route companies like virgin galactic are pursueing

I'm not expecting to be able to go to space for a hundred bucks, but commercial spaceflight is becoming a thing. The question I believe is not *if* space will ever be accessible to the general population, but when. And I hope that will still be in my lifetime.

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For example: one of the more recent resupply missions to the ISS included a scientific experiment to study the processes in which alzheimer's disease works in microgravity. With the absence of gravity, certain processes which are impossible to observe on earth can be studied which could lead to a breakthrough in Alzheimer treatment. That's a nice incentive for pharmaceutical companies right there.

That is one example. However, microgravity research hasn't really piqued the interest of pharmaceutical companies to the point of making them invest in orbital science. Although the idea of using microgravity for developing new drugs has been bandied about for yours, the truth is that not a single pharmaceutical company has even launched a cubesat or flown an experiment to the ISS. They simply are not that interested.

infrastructure and manpower to produce the hardware. With fully disposable rockets, you're throwing all that manpower and money down the drain every single launch. If you can cut down from "fully build a rocket from scratch during the course of several months" to "fill it with fuel and put it back on the pad within a week", costs can be brought down a lot. (obviously this is an exageration for illustration purposes, but you get the gist of it). I believe SpaceX is currently aiming at re-launching the falcon 9 at a third of the cost it would normally be, and if re-usability becomes standard, prices could drop down to 10% of the current ones. Possibly even lower if new technologies surface.

No. Infrastructure and manpower to develop the vehicles, handle them, maintain them, integrate payloads,fuel the rocket and payload, monitor launch and pre-launch activities... And there is also the administrative and sales overhead. There are thousands of people that work at SpaceX and the various NASA space centers that have nothing to do with manufacturing. In fact, the manufacturing facilities are only a small part of the whole thing, and don't typically employ the most expensive employees.

On the other hand, reusing hardware means that you build less of them, which in turn means that the unit cost of each item is much higher because you don't benefit from economies of scale. If you build 10 rockets a year instead of 100, then the cost of each rocket is much higher. You don't divide your costs by 10.

Overall, the cost of the first stage hardware is only a fraction of the total launch price. Reusing that hardware only saves you a fraction of the cost of that hardware. And remember that the launch is only a fraction of the cost that a customer pays to build and operate a satellite. In the end, you are looking at a reduction of the price of a launch of 20% max, if you're lucky, which means that customers might save $10 million out of the current $60 million they pay to launch their $300 million satellite. It's an appreciable reduction, but it's not going to revolutionize access to space.

Define "a lot". Of course it will always cost millions of dollars to construct a rocket, and obviously spaceflight will always be more expensive than regular atmospheric flight because it simply takes more energy, but it can certainly be done a lot cheaper than it is now.

I don't think it can be done much cheaper than what SpaceX does today. They are cheaper because they are run with lean processes, subsidized technology, and a young and overworked workforce. But they are about as lean and mean as it can get without taking uncontrolled risks. There are no miracles.

Right now it costs about 4000 to 20 000 dollars to put 1kg in low earth orbit. If that can be brought down to 500, you can theoretically have a ticket for a single person for roughly 40 000 dollars. And that's not including any cost cutting you can expect if dedicated passenger carriers will be developed.

You're talking about a 95% reduction in launch costs. That is simply isn't realistically possible with any current technology. And Virgin is a technological dead end with an elitist business model. Jetsetters are interested in going to space because it's rare. Once half of the jetset has flown on Virgin, it loses its novelty appeal.

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On the other hand, reusing hardware means that you build less of them, which in turn means that the unit cost of each item is much higher because you don't benefit from economies of scale. If you build 10 rockets a year instead of 100, then the cost of each rocket is much higher. You don't divide your costs by 10.

Which is why SpaceX is big into low-thrust High-TWR engine clusters- By building one or two merlin engine per month, they can launch only a few rockets a year and still benifit from a degree of mass production.

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Which is why SpaceX is big into low-thrust High-TWR engine clusters- By building one or two merlin engine per month, they can launch only a few rockets a year and still benifit from a degree of mass production.

Yep, but their facility is sized for a production rate of 400 Merlins per year, which means that they are wasting money on an oversized factory. Only SpaceX management can do the proper cost/benefit calculation for reusability, and they can only do that after they have some experience in actually recovering, refurbishing, and relaunching. For all we know, the stress of reentry might cause buckling or unrepairable stress marks on the tankage, which might make the whole enterprise unviable. Nobody knows at this point.

My point is that it is not as clear-cut as some people seem to think. Reusability only makes sense if you dramatically increase the launch rate and the refurbishing costs are minimal. The launch rate can only increase if there is an increase in demand. A 20% cut in launch costs is not going to suddenly create a massive demand for orbital launches.

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Currently SpaceX is not going to spend the time, money and payload to try to recover the second stage. But Per FAA and other US regulatory agencies, all US launch vehicles have to have some sort of self destruct. Normally there is a guy (when launching from Vandenburg/Cape Canaveral AFS he is a military guy) that literraly has a nice button before him to blow the rocket to bits. Also some of the computers have it programmed in if the rocket goes off course.

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If the stage is on a free fall trajectory that ends at a landing pad and you blow it to pieces because the engine doesn't start, then you only have a whole lot of rocket bits that are still going to end at the landing pad.

You'd really want to divert the rocket, which you can't do if the engine doesn't start or you've lost control.

The best solution is to aim for a crash area, and divert the rocket to the landing pad when you are sure that everything works.

Edited by Nibb31
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Reusability only makes sense if you dramatically increase the launch rate and the refurbishing costs are minimal. The launch rate can only increase if there is an increase in demand. A 20% cut in launch costs is not going to suddenly create a massive demand for orbital launches.

I disagree with the condition that the launch rate must be increased for reusability to make sense. It's all about the marginal costs. If refurbishing a stage costs $10 million and a new stage costs $15 million, you're better off refurbishing. Production space that used to be used for building Falcon 9 stages can be put to other uses, such as Dragon2 construction, construction of the Raptors or the next lifter design. At the very worst, production space can be sold/subleased to another company, assuming SpaceX isn't able to use the space themselves for something else. The Hawthorn facility is 1,000,000 sqft or so, and the cost of the space, is probably no more than $40/sqft/year.

Assuming refurbishing saves SpaceX $5 million per F9 launch and only refurbishes two boosters per year...

1) the reusing customers probably get some discount, let's say $2 million/launch. (40% of the gains from reusability)

2) let's say the "wasted" part of the facility is worth no more than $2 million / year (5% of total space, assume 50% of sqft is F9 S1 production and SpaceX goes from 20 S1 -> 18 S1 built per year. Probably bad estimates, but on the conservative side)

3) PROFIT! of ~$4 million/ year for SpaceX

Any discussion of per vehicle development cost is a succumbing to the sunk cost fallacy; we should only consider the ongoing costs of developing the reusability aspect (not trivial, the Grasshopper and Grasshopper 2 and the pad in TX and engineering the grid fins and landing legs etc aren't free, and are unnecessary for a disposable rocket.

None of this is to suggest that reusability (in the manner of SpaceX) is a magic bullet for lower cost access to space. In the fictional example above, the customer is only better of by some figure, maybe $1.5 million (insurers will almost certainly demand a higher premium for using reused rockets). I have no idea the cost of a F9 launch, the CRS missions from a quick search are ~$200 million. So a customer of a reused F9 might see a savings of ~1% of the launch cost. Not exactly a revolution, but still a good start (any cost savings are a good start, even if it's free snacks for employees in lieu of $1,000 more in their paychecks :P )

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Making an orbital depot would increase demand, NASA would need orbital services and they could contract out certain launches.

And the economies of scale would work for a reusable system, you would treat the service as the product. Of course you need a lot more launches...

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Yep, but their facility is sized for a production rate of 400 Merlins per year, which means that they are wasting money on an oversized factory. Only SpaceX management can do the proper cost/benefit calculation for reusability, and they can only do that after they have some experience in actually recovering, refurbishing, and relaunching. For all we know, the stress of reentry might cause buckling or unrepairable stress marks on the tankage, which might make the whole enterprise unviable. Nobody knows at this point.

My point is that it is not as clear-cut as some people seem to think. Reusability only makes sense if you dramatically increase the launch rate and the refurbishing costs are minimal. The launch rate can only increase if there is an increase in demand. A 20% cut in launch costs is not going to suddenly create a massive demand for orbital launches.

I agree with everything you said, I believe that the industry is being held down by the lack of access to cheap foreign labour and exchange of ideas. Imagine how low development, construction and refurbishment costs could go down if the US launch market had access to foreign engineering (say indian, we re talking about their salaries being almost one tenth of their american counterparts while still keeping the technical expertise).

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That would hurt engineering jobs in the American aerospace industry.

But would actually help the aerospace industry as a whole by reducing the costs and allowing for a more competitive environment with lower barriers of entry. Two things would happen overtime, american engineering would reduce its cost because companies would only hire those that werent that expensive, and second, the price of foreign engineernig would go up due to an increase in demand. After some time you´d reach an equilibrium point where the previously inflated engineering costs in the US would go down to their actual market levels and foreign engineering costs would go up due to an increase in demand.

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But would actually help the aerospace industry as a whole by reducing the costs and allowing for a more competitive environment with lower barriers of entry. Two things would happen overtime, american engineering would reduce its cost because companies would only hire those that werent that expensive, and second, the price of foreign engineernig would go up due to an increase in demand. After some time you´d reach an equilibrium point where the previously inflated engineering costs in the US would go down to their actual market levels and foreign engineering costs would go up due to an increase in demand.

I'm not sure how applicable this is to the aerospace industry...I'd imagine a lot of that tech has export controls (so you can't export the engineering). And why do you think engineering costs are inflated in the US (compared to their value)?

I was thinking about this some today, that the big improvements for lowering cost to space (for sat operators at least) is the relatively large improvements in sat life. A sat that lasts 15 years instead of 10 has 33% lower launch costs all by itself.

To get back to the OP, I think the F9 S1 has some form of thruster at the top for orientation, they may be able to angle the rocket enough to provide body lift away from some particular target, though I don't think that'd be the simplest engineering solution.

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