Nibb31

Although I have the greatest respect for SpaceX's accomplishments, quotes like this one or Musk's gibberish tweets about Mars colonies are only PR. There is no substance behind them, and nobody seriously expects launch prices to go down to $7 million or for Musk to retire on Mars. Read what I said. Percentage of the first stage in the rocket. Percentage of the rocket in the total launch cost. A percentage of a percentage. I'm sure you can figure it out. It wasn't an analogy. You keep on claiming that the rocket is the only cost of launch operations, which is wrong. SpaceX employs 3500 people, mostly high-salary engineers and technicians. It owns and maintains 3 launch sites, a test range, several regional offices, and a manufacturing facility, as well as the administrative, logistics and sourcing channels to keep them running. The cost of those is way more than ice-cream pocket change.

But that is Zvezda, which is Russian. There are plenty of US flags all over the US segment.

I've consistently said that the launch vehicle hardware is only a small part of the cost of running a launch business. And that the first stage is only a small part of the cost of the entire launch vehicle. You can twist it with your misunderstanding and bias as much as you want. The result is that saving money on the reusability does not save as much money as you think it does. Stating the contrary, like you do, is like saying that the only cost of running a taxi cab company is to buy the cars, or that the only cost of a software company is the computers. It's ridiculous. The biggest cost of running a company in the high-tech world is the employees, not the material costs. Reusing stages saves a little money on manufacturing workforce and materials, but you still need to keep the production infrastructure, the tooling, the sourcing and the facility running. Some of those savings are replaced by the extra logistics related to recovery and maintenance of the boosters. The rest of the operation stays the same. No, it can't. A 20% saving is highly optimistic.

No you haven't. You have waved away the economical and industrial factors or used wrong assumptions on how the space industry works. You keep on bringing up unrealistic figures like "90% reduction". That implies that the first stage hardware represents well over 90% of the total launch cost, which completely ignores all the other costs involved. In reality, it might represent 60% of the total rocket, while the rocket hardware itself only represents maybe 30% of the total launch cost.

Boosters are heavy, so you would need super-huge parachutes, which aren't precisely cheap. Salt water is also corrosive and damages engines, which means they would need to be stripped down and cleaned. Also, even with a parachute, a splashdown is a violent process. The Shuttle SRBs were recovered after parachuting down into the Atlantic. They were steel casings, much stronger than aluminium tanks, and they still got severely damaged and bent in the process. - - - Updated - - - It still needs to flip around at hypersonic speeds to do a retro-burn. That might be possible, but it might not. It's still another nut that needs cracking.

We don't know anything about the economics of a reusable F9 first stage yet. As I said earlier, there are fixed costs that are not proportional to the size of the rocket or launch rate. The biggest cost is the salary of the personel, not the launch hardware. Reusing hardware only saves a small part of the operation cost. The rest of the logistics, R&D, manufacturing and processing facilities, maintenance, payload integration, launch operations, mission control, etc... all remain the same. And the economics of reusing rocket stages goes against the economics of mass producing rocket stages, which has been how SpaceX has managed to reduce costs until now. The industry will need several years of experience with reuse and higher launch rates before anyone can claim that it actually saves money. Currently there is no reason to believe that the demand for orbital launches will boom because SpaceX cuts prices from $60 million to $50 million. They also need to figure out how to make it survive reentry. The central core will be flying much higher and faster than an F9 1st stage. It will need some sort of TPS, and it might be going too fast to flip around without breaking up in the air stream. Let's let them figure out recovering and reusing the easy stuff before speculating on stuff that is much more complicated. I'm not saying they can't do it, but it will require a serious R&D effort, which might not be economically worth it. There isn't much of a market for Falcon Heavy so it doesn't make much sense to spend a big effort on reusing the central core. Getting the side boosters back will already be quite an accomplishment.

I've tried switching to Linux several times, but each time, after a few days, I find myself needing that special program that I had on my Windows drive that didn't have an equivalent on Linux. After struggling for 3 days to get Sketchup working in Wine, I gave up and switched back to Windows.

What would be the point of that? If you want rocks, a robot could get them with much less effort.

You keep on waving around this 90% figure, as if SpaceX reusability will somehow reduce their launch price from $60 million to $6 million. We've already explained to you plenty of times that it doesn't work that way. The hardware is only a part of the launch costs. Most of those costs are fixed costs that do no benefit from reusability. The best SpaceX can hope for, with full reuse of the 1st stage, is 20%, which would bring the ticket price down to $50 million. Also, there will never be "full reusability" of the Falcon 9. The second stage will not be reusable. It is very unlikely that the central core of the FH will be reusable before a long time, and there will still be many payloads that won't be able to afford the mass penalty of reusability. There is no reusable FH yet. Full reusability of the central core, which goes much higher and faster than the F9 core, is pushing expectations quite a lot. Since the central core will probably have to be expendable, the FH can't be cheaper than an expendable F9.

I disagree. We don't do stuff just because we can. There are plenty of things we can do, but we don't because it would be a waste of resources or downright stupid. Individuals might be driven by ego, but as a species, we are driven by survival. My opinion is that all human achievements come down to improving our safety and our comfort and those of our children. We are a species of hunter-gatherers. From the first nomadic human tribes to today's immigrants, humans have only explored and migrated because they wanted to improve their odds of survival or their standard of living. Humans went to the Moon to win points in the Cold War because having the edge over the enemy was seen as a matter of survival. Immigrants settled in the New World because they were in danger in their home countries or sought a better life. For the moment, space does nothing to improve our safety or our comfort. In fact, it's quite the opposite of a better life out there. Which is why we have so much trouble justifying space exploration. The only thing we can do is to keep on learning about the universe until we find a reason to go there.

It would still need a heat shield for reentry, avionics, RCS for attitude control, and complex logistics to operate mid air recovery downrange in Europe or Africa (depending on the launch innclination), with all the ITAR strings attached. All in all, it would still be much more complex than flying back the first stage. A single mass-produced Merlin engine is supposed to be pretty cheap compared to the rest of the rocket so I'm not sure that it makes sense to go to huge extremes to get it back. I can't help thinking that it might be better to redesign the whole vehicle. Maybe you could make a reusable "Super Dragon" that would combine the second stage with the orbital vehicle, on top of a wider-base, lower-CG, reuse-friendly 1st stage. It would be a whole new launcher, a bit like a 2-stage version of DC-X, but it would be a great way to evolve SpaceX's current technology.

Well, then you might not want to get into an argument with people who have been following space new for years. The point of reusability, as shown in all their old PR since they started working on reusability, implies flying back to the launch site, which is done by an RTLS burn after separation. It has been admitted that reusability carries some heavy penalties: - Additional fuel for the RTLS burn and landing (but remember that the stage is nearly empty at this point) - A trajectory that is steeper, which adds less horizontal velocity in order to minimize the above - A dV penalty that is transferred to the upper stage because of the suboptimal trajectory - Additional avionics and attitude control systems to flip back the stage - Additional weight for landing gear Everybody recognizes that because of those penalties, the max payload of a reusable Falcon 9 will be several tons lower than a non-reusable Falcon 9, with something like 7 tons to LEO instead of 11 tons. So, only the smaller payloads will be able to benefit from the discount of a using a reusable first stage, but it is still within the margins of the launcher. - - - Updated - - - I doubt we will ever see 2nd stage reusability on the Falcon at this point. Maybe on SpaceX's next generation rocket, but it is a much tougher nut to crack than getting the 1st stage back.

News: SpaceX is a corporation too. In fact, they employ 3500 people, which makes them bigger than ULA, and their biggest customer is the US Government.

What a load of rubbish (and never trust an opinion blogger with 1980's haircut and a moustache). There are plenty of things that government does better than private enterprise. Defense, police, or healthcare for example... scientific research and rocket science too. There would be no space industry at all if the government wasn't paying for it. But this is rolling off into the tangent of politics, which is frowned upon here, so let's not go there. You're the one who claimed that Falcon 9 has a 40% structural safety margin (whatever that means), not me, so I was responding to that. If it's true, then they have 40% too much structure, which is a waste. I don't know if it's true, It was just a tongue-in-cheek comment to what you said.

You discuss.

A hull that it basically a very thin aluminium tube that supports multiple tanking/detanking cycles, several tons of vertical load, thermal cycles varying from cryo fuel loading to hypersonic friction, aerodynamic loads, and landing empty at potentially non-vertical angle. It's much more complex than an airplane's airframe and with much tougher weight constraints.

It's a pretty common fallacy that government=expensive and private=cheap. SpaceX is cheap because they have a vertical organisation and it is started from a clean sheet with cost optimization in mind. There are many private companies that use various levels of subcontractors and have a long history of heavy organization. It has nothing to do with private<>government, but it's all about organization. If your margins are too high, you are wasting money, not optimizing. But you misread my post. I wasn't saying that SpaceX products were low quality. I was saying that the Falcon 9 design is optimized for low-cost, not for reusability. Those are contradictory requirements. A paper cup is optimized for low-cost, and it works well for what it's designed for (it satisfies all requirements, which is the definition of quality). Try sticking it in a dishwasher to reuse it, and it doesn't work so well.

Contrary to popular belief, SSME's weren't completely refurbished after each flight. They were designed for reusability, which is why they were so expensive. They were removed and rotated after each flight so that they could be serviced and tested, and then got a full refurbishment after X flights. There is no reason to believe that Merlins will need to be fully refurbished after each flight. I'm more concerned with mechanical stress and fatigue on the tanks and legs. An invisible crumple in a cylinder can fragilise the structure. I think that even if they get the landing part fixed, it will be a while before they will be flying reused stages.

Because rockets launch East, and East of KSC is the ocean. KSC was built specifically on the East coast so that rocket bits would fall into the ocean instead of on people. The first stage naturally comes down approx 300 km East of the launch site. If you want to bring it back to the launch site, you're going to have to perform an RTLS (return to launch site) burn that reverses the trajectory to send it 300 km back, which of course is going to cost much more propellant and therefore a larger mass penalty. This is something that nobody has done yet, and they need to master the precision of the burn by landing in the ocean before attempting a real RTLS. They don't want the rocket to land in the middle of the KSC Visitor Center or a rocket fuel factory.

Yes they did. See post #48

I agree, but this is where SpaceX's approach reaches its limits. In engineering, you design something to meet a set of requirements. You make trade-offs on some points because other points are more important. Yet the requirements for the Falcon 9 as a low-cost mass-produced launcher and as a robust reusable launcher are contradictory. The Falcon 9 was designed from scratch and optimized to be cheap and mass-produced. It has relatively cheap and light tanks and the factory is geared to mass-produce up to 400 engines per year, which is nearly one new Falcon 9 rocket every week. Now, they are bolting additional stuff onto a cheap disposable rocket to make it reusable, which it wasn't optimized for from the start. The result is the bolt-on legs, the high CG, stretched tanks, and additional hardware added at the top of the stage that makes it even more top heavy. The other result is manufacturing overcapacity that is going to idle and lose money if they start massively reusing core stages. The Falcon 9 is a very clever design as cheap launch vehicle, and it has done a lot to lower the cost of access to orbit, but I'm not sure that it's the most robust design to base a reusable rocket on. If you were designing a reusable booster from scratch, you would integrate all of this stuff into a design that is optimized for different trade-offs than a disposable booster. You could afford to make it sturdier and more expensive, because you would only build them in small numbers. You could afford more expensive tooling for a conical shape because the trade-off in cost would be worth it. You wouldn't need to constrain the width to road tunnels for to lower mass-transportation costs, because transport from the factory to the launch site would be exceptional. It would be designed from the start with landing in mind, with a wide footprint and low CG, instead of bolting legs onto tall thin tank. In the end, this is a bit like turning a bicycle into a motorbike. Sure, it can be done if you bolt enough extra stuff onto it, but it will never be as good as a motorbike designed from scratch as a motorbike. Yes, it's hard, but I think they might be making it harder than it needs to be.

The vertical velocity problem seems to be solved. It's just a matter or timing the suicide burn so that the vertical speed and altitude curves intersect at zero. It's a pretty easy mathematical problem and the landing looked ok from that point of view. What looked wrong here, was that the rocket was coming in at an angle, with too much horizontal velocity, and then tried to right itself by overcompensating. It might be due to the wind, but it looks like a PID/oscillation problem to me. Ideally, any horizontal velocity should have been dealt with before the final descent. The cause of the tipover seems to be that a leg collapsed or failed to deploy. They need to investigate whether that was due to a fragility in the design or the result of the messy landing, or a bit of both. It does illustrate that vertical landing is a complex problem, and it might be a while before it can be done confidently enough to reuse stages or carry humans. In a sense, I'm happy that Dragon V2 will be landing on parachutes for the foreseeable future. I also wonder if it wouldn't have been easier to design the Falcon 9 with a wider but shorter core stage (like the DC-X or Rombus concepts) instead of this long thin top-heavy design. Even with most of the weight at the bottom, there's still a limit to how low you can get the CG, especially as the Falcon 9 now has all the grid fin mechanisms, the helium tanks and the RCS thrusters on top.

The ultimate goal, is refuel and restack. It will be a long time before we get to that routine though. And fast-turnaround only makes sense if there are high launch rates. When you have one launch per month and a factory that is built to churn out 400 engines per year, there is no point in fast-turnaround.

It has GPS plus inertial data. That's more than enough for precise positioning. It doesn't need weather or wind data, it just compensates automatically. When you're driving your car on the motorway, you don't need wind predictions to keep your car on the road. If your car is pushed sideways by the wind, you just steer it back on the road to compensate.

It's a shame he didn't correct the camera positioning. It's a bit too jumpy to be watchable.