I’m sure it’ll be the same way they got it there: on a big truck. Part of the reason the Falcon 9 is so tall and skinny is so that it can be transported by road. They made sure that the diameter is low enough that it will pass under the bridges it needs to. The payload fairing is wider, but it splits in two and they can put it on a diagonal so that it still meets the height/width requirements.
I was surprised to see people walking around the vehicle so quickly after landing. I would have guessed that they’d wait a while before declaring it safed. Maybe there was so little LOX left that it boiled away almost immediately. The remaining propellant–kerosene and pressurized nitrogen–are fairly minimal hazards. There are no nasties like hypergolics, fortunately.
At any rate, they must need a hell of a crane to get it tipped over. At the pad, they have their custom-build strongback to lift it up; I’m really not sure what they’ll use here.
Yes, but at launch, the whole stack weighed about 540 tons. The returned 1st stage, with the fuel tanks empty, weighs only 19 tons or so. I think a conventional mobile crane can handle this.
OK, it’s cool that the landing was technically possible and that it was successful. But how much does it save? I recall NASA overselling the hell out of the savings of the reusable shuttle and its reusable boosters, so let’s say you use the first stage 100 times. Between the extra cost to build in the capability to land and the cost of refurbishing after every use, what percent of the launch cost can be saved by using this?
Excellent question. I’d be interested in learning those things, too.
However, I doubt that Musk has gotten this far in the process without crunching the numbers on how much it will cost to refurbish the reusable components. Yeah, they said the same thing about the shuttle, and each turn around wound up taking a lot more work than they planned. But, we’ve learned an awful lot since then. For one thing, their first stage uses 9 motors (didn’t know that until last night) to the shuttle’s 3. I imagine it’s easier to tear down the smaller motors, and components like the pumps and seals probably aren’t stressed nearly as much as they were on the shuttle.
So, yeah, the business case still has to prove itself, but the tech is fucking awesome!
I’ve been wondering about this as well. It turned out the extensive effort required to refurbish the shuttles’ rocket boosters made the savings pretty negligible.
I’m not so sure about that. Musk himself has a tendency to make overly optimistic promises. Every model of Tesla produced so far has missed its promised launch date at least once, and that affordable Tesla that was supposed to be out by now still hasn’t left the drawing board as far as anybody knows.
Good points; maybe their projections will turn out to have been too optimistic. But they’ve come closer to making this work than anyone else has, and the tech is still fucking awesome.
So, just to make sure I’ve got this right. At separation the first stage is about 11 km downrange and moving at 7-8 kilometers per second is what I think I heard on the video. Then, after separation, it orients itself using cold gas thrusters and initiates a burn to start heading back to the launch site. How much extra fuel does it need to reverse it’s downrange velocity and come back to the launch pad? If they are going to have to transport it over the road back to the factory anyhow, why not launch it from 22 miles further inland and have it land downrange?
From the image, you can see that its more like 70 km downrange at MECO (Main Engine Cut-Off), and gets up to 130 km before the burn is complete. Also, it’s going more like 6000 km/h, or 1.7 km/s at that time (8 km/s is for orbit).
SpaceX’s previous efforts have been to land on an ocean barge. They’ve failed but for reasons unrelated to it being over water. They’ll probably try barge landings again at some point, and will virtually have to if they want to land the center core of the Falcon Heavy. I’ll be going way faster than this one and they won’t be able to afford a full burnback.
Unfortunately, I don’t have figures on the propellant fraction they have to reserve for this maneuver. It’s surprisingly little, however–at that stage in flight, almost all the mass is in the upper stage. Once the upper stage is gone, it’s just a soda can with a few drops of fuel left in it. It doesn’t take a huge amount to slow down and land. It’s in the ballpark of a 30% hit on total rocket performance.
I saw a graph once of performance figures for the Saturn V; lines for altitude, speed, mass, etc. as a function of time. I wish I could find it again, the numbers were jaw-dropping. The one I remember the most is mass. The rocket is about 3,000,000 kg at launch, and I think it was below 1,000,000 when it separates the first stage, in less than 3 minutes. If you don’t throttle the engines down, you’ll have 3x the acceleration (and 3x the Gs) as you did at liftoff.
I saw something similar on the webcast last night. There were numbers in the upper right showing speed and altitude. When the second stage fired the speed number was increasing pretty slowly. And then it started speeding up as the fuel was burned and the mass decreased.
Yep. The Falcon 9 second stage has about 180,000 pounds of thrust. With full tanks, the stage weighs around 220,000 lbs, so it starts off at somewhat under 1 gee. Empty, though, it’s more like 15,000 pounds–that would be 12 gees without throttling down! They’ll never let it get that high, of course, but it’s a pretty crazy difference from start to finish.
Kerbal Space Program teaches this principle very effectively.
I don’t know about cost effectiveness and yada yada blah blah, but that was incredibly cool! Is it overstating this to compare it with first stepping on the moon?
(edit: I feel like I just watched something really, really noteworthy- is why I ask.)
