[grinich]

Rockets are built to be pretty durable machines (obviously). The environment they operate in outside of the atmosphere is harsher in many ways.

Two big issues with sea landing: transport (tug, crane, huge truck, etc.), and corrosion/contamination from saltwater.

They'll still need to verify all systems and components before a second launch, but that's way easier to do when the vehicle is sitting empty on the pad next to all your people and equipment.

[mkempe]

This was an experiment. The goal is to land on terra firma, not [mare incognitum].

[mapt]

For Falcon 9 though, the first stage contributes so much of the dV that it is not particularly feasible to land it at the launch site - by the time it separates, it's moving at several kilometers per second away from the launch site towards the horizon. That opens up the question of where the launch/landing site pair is bound to be. A ship-based landing system, such as a semisubmersible oil drilling rig (only ~$1B used!) with a landing pad built onto it, would seem to be close to optimal for the F9 specifically.

The Falcon Heavy's 2 side boosters, on the other hand, will separate much earlier in the flight - they are likely to be much more practical to land at the launch site, particularly for direct geosynchronous payloads that allow a lot more vertical / near-vertical burn time in relation to horizontal.

[grinich]

Citation? Usually the flight plan is to increase altitude (less atmospheric drag) before increasing angular velocity to full orbit.

Elon's been pretty explicit that F9 stage 1 will land back on the pad, or very close by.

[mapt]

See this thread for estimates on the dV of the different stages of these launch platforms for a full-capacity payload: http://forum.nasaspaceflight.com/index.php?topic=30685.0;all

It costs about 8km/s to get into low orbit from an atmosphere-less Earth. From our planet it costs about 9.4-1.0km/s because of aerodynamic and gravity losses. Those aerodynamic and gravity costs, and the Hohmann Transfer from groundlevel to orbit (trivial for LEO, more for GTO) are the only parts of the equation one can address while burning vertically to stay over the launch site.

Assuming 10, If the first stage only has to contribute 2km/s, it can address aerodynamic and gravity losses (while thrusting vertically), and then leave the second stage to boost for the horizon and achieve full orbit all on its own.

At 4-5km/s first stage contribution, it doesn't look like this is possible unless the payload is very undersized, leaving the second stage with enough dV to go from 'rising out of the upper atmosphere vertically' to 'circular orbit' all on its own.

The mass is a free variable, a greater vertical component is practical in GTO (and I don't have the modelling skills to say how much), and the second stage may launch fully fueled for F9R contra to the existing pattern, so I can't be 100% sure whether F9R will be a practical return-to-launchsite option for lightweight GTO payloads.

[HarryHirsch]

They'll still need to verify all systems and components before a second launch

That. You need to re-qualify the engine after each launch. The cost of labour far exceeds the cost of materials, you need to strip and re-build the thing, and you ask yourself just how much money you can save through re-using the first stage. I don't think it's much.

[grinich]

On traditional launch vehicles, yes. Shuttle was definitely this way. And I'm sure SpaceX will initially do a complete disassemble and inspection to gather more data about the wear and tear.

But the Merlin engines have been designed from the start to be reusable and dependably reignitable, whether at sea level or upper atmosphere. They're pretty amazing-- essentially the pinnacle of +50 years of engine design. Tom Mueller is a huge badass. :) http://en.wikipedia.org/wiki/Merlin_(rocket_engine)

And check out that bad boy roar: http://www.youtube.com/watch?v=wkdReoxGHG8

I don't have a link on hand, but Elon has said multiple times that the majority cost of the Falcon-9 is the raw material. One of the reasons they've been able to drop the price significantly is by using more efficient manufacturing techniques, requiring less material and creating less waste. (e.g. stir-friction welding)

It's also worth noting that Falcon-9 can still complete a mission with one (and perhaps two?) engine failures, which gives quite a more comfortable margin of error. There's a big difference between "perfect" and "near perfect" when it comes to engineering these things. ;)

[jessriedel]

> I don't think it's much.

SpaceX disagrees. They expect to cut the cost of launch by 1 order of magnitude

https://en.wikipedia.org/wiki/SpaceX_reusable_launch_system_...

[ef4]

> you need to strip and re-build the thing

That's how politically-designed boondoggles like the shuttle work. It's not inevitable, if you actually spend the engineering effort on reliability and repeatability.

If NASA operated an airline, they would probably be tearing down and rebuilding every jet engine after every flight, and a ticket would cost $100,000.

[XorNot]

I said this in another thread, but part of the issue is failure intolerance.

Sure - for human payloads I'd want to be damn sure my process is good, like, hundreds to thousands of missions deep before I trusted it.

But that's totally unnecessary for an unmanned payload! If the cost of launch drops enough, you can fully justify launching 2x the payloads if you expect maybe 1 in 10 failures due to the mode of launch.

I suspect it's possible to do a damn site better then that, but for NASA its never been an option. If it's reusable, they can't let a mission fail because they'll only get punished and funded according to the failures, even if they specced everything expecting 1 mission to possibly not go off right.

[001sky]

This is true for a sub-set of unmanned payloads.

Space-X is great for the sub-set of things that don't require insurance, and don't therefore need to use corner-case mil-spec stuff with the corner case pricing.

For others, the cost of losing a $1-2B bird on top of a $100m/cheap rocket is shitty math. Nobody is going to insure the top of it, so ultimately the "waste" is akin to a form of insurance.

Everybody knows this already, so I'm not sure how sympathetic a hearing it is going to get. It will be great PR though to hopefully spurn <designs> that fit the new framework...and thus expand the market for space-x and hopefully limit the superflous use of corner-case technology for mundane/run-of the mill applications (at the tax payer's expense).

[XorNot]

Right, but part of the reason we launch hugely expensive satellites is because launching a rocket is hugely expensive.

That calculus changes if your rocket launches start to get cheaper. It changes by a lot if your rocket launches have reasonable but predictable failure modes - which is something you get from volume.

As it is, rocket launches are relatively infrequent and expensive - which means its impossible to figure out the amortization of costs, and its not worth building a 10m satellite if your launch costs 100m (since if you can raise the latter, you can almost certainly get more for a better satellite too).

[001sky]

^^^ Yes, this is exactly the 'white space' for Space-X.

[ef4]

The $2B satellite is equally absurd, and only costs that much for the same reasons that the launch costs $400M. Everything is bespoke and produced in the maximal number of congressional districts, with no meaningful competitive pressure to drive prices downward.

And the two expenses buoy each other: if launches were inexpensive, you could spend a lot less on fault-tolerance in the payloads, because you could just launch a lot more payloads or even support on-orbit repair infrastructure.

[rjurney]

You really think SpaceX loads aren't insured? This seems impossible.

[HarryHirsch]

If you look at previous launches of new designs you will see that the first few flights are invariably not commercial, they carry research spacecraft. These are the qualification flights; until the vehicle has a good track record the satellite operator won't find anyone to insure their bird.

Now the Falcon 9 is an all-new design, and their track record isn't all that shiny - there is a history of missing the target orbit by a fairly significant margin. It's going to be downvoted, but it had to be said.

I wouldn't be surprised if this flight went without insurance.

[lotsofmangos]

SpaceX appear to have gone with failure tolerance. Their first stage is practically a raid array.

[sitkack]

Teardown and rebuild doesn't increase your safety margins, they reduce it. If I rebuilt my Toyota every 10k miles I'd have a lot more breakdowns.

[cfreeman]

The Merlin engine was designed from the beginning to be re-useable. They don't have to be "stripped and rebuilt" after each launch. They have already fired engines on the test stand for multiple mission durations with no problems.

[oh_sigh]

So, have you done more analysis on this than SpaceX has?

You should send them this post of yours so they stop wasting all that money! I bet they never thought of what you said.

[mikeash]

Unlike NASA's adventures with the space shuttle, SpaceX is a for-profit business with a goal of making money. They wouldn't be pursuing reusability if they didn't think it would increase their ability to make a profit.