SpaceX Dragon CRS-6 Launch Webcast
nasa.gov
nasa.gov
T+17m: Not a successful landing today.
Edit: "Looks like Falcon landed fine, but excess lateral velocity caused it to tip over post landing" @elonmusk
https://twitter.com/elonmusk/status/588076749562318849
Update: Photo @ https://twitter.com/elonmusk/status/588082574183903232/photo...
Actually -- make the hole a steel cavity projecting below the waterline, with smooth sloped sides. Thus a miss hits the cavity side and the rocket slides down. Put thrusters at the top of the rocket to push against the pitch torque when the thing contacts the cavity. Drop your struts from the top of the rocket on to the barge.
Now you've got a lower center of mass and wider "legs". You will for sure bang up the side of the rocket, but so what, it is the engines that you really want to recover. (Hmm, actually it will be the rocket exhaust that hits the well first anyway, does pressure in the well from the rocket exhaust help at all? Might slow down the descent, might increase the pitch torque.)
The ultimate goal is to land on a flat pad, so adding stuff now moves away from that goal.
Can't wait to see the recovered barge video.
From my armchair observations, it looks like they just need to tweak some constants in their control algorithm to avoid control-induced oscillation. This is the first time that the rocket has reached the ship while still under control (the first landing attempt ran out of hydraulic fluid and went out of control, and of course the second not-quite-attempt didn't have the ship there so it probably wasn't as obvious what was going on) and I imagine there's a fair amount of "oh, duh, how did I overlook that?" going around SpaceX headquarters now that they've finally seen it in action all the way to the end.
Won't be easy, but if anyone can do it, it's SpaceX.
Odds of rocket landing successfully today are still less than 50%. [1]
"This is just a complete guess..." <-- reasonable
"Bayesian analysis tells us..." <-- smells of assSee "If It’s Worth Doing, It’s Worth Doing With Made-Up Statistics": http://slatestarcodex.com/2013/05/02/if-its-worth-doing-its-....
http://lesswrong.com/lw/sg/when_not_to_use_probabilities/
(Note that I think that starting with a good 50/50 coinflip and revising it based on evidence in this case is reasonable, I just think it's nice to have a reasoned opposing opinion sometimes.)
If you've never done something before you really have no idea if it's going to work, and in rocket launch everything that occurs after the last failure is a complete unknown in terms of failure modes.
Now, if he'd made successful flyback stages before, or it was a relatively routine thing for the industry he might have a good enough feel to assign a ballpark number. But that's not the situation.
In the link you provided he uses computer failure as an example, where a person who is familiar with computers does have some information - I've owned my current rig for three years and it's never failed. If you told me you thought it has a 50% chance of failure next month I can pretty confidently say that's an overestimate.
But it's useless to pull numbers out of the air for something as complicated as SpaceX is trying to do.
Nobody has ever landed a rocket before. But we don't expect the rocket to turn into an alarm clock or suddenly develop antigravity. In fact, we have quite reasonable expectations on what behaviors the rocket will exhibit. We might, for instance, expect the rocket to crash more than we expect it to land. What else does that say rather than p(crash) > p(land)?
(Of course, this may well come down to "probability as ratio" vs. "probability as anticipation", which is probably a matter of preference.)
For an estimate one needs to gather up what evidence and information is available; make a judgment on how well understood the system is, and its components; determine how predictable the behavior of the system has been in the past; figure out how close what is attempting to be done is to any previous testing or operations; and so on. Then take all of that and make an informed estimate of the likelihood of something occurring.
That's what an estimate is, a statement about how well a system seems to be understood and the probability of some event occurring. An estimate can build in uncertainty in the understanding of the system quite easily, by simply making a more cautious or pessimistic assumption.
SpaceX designed and built these rockets. They've flown them numerous times. They've done test flights exploring landing operations. They've done re-entry flights and landing attempts multiple times. All of these things increase confidence in understanding how the rocket operates under different conditions during landing, making it possible to come up with a reasonably informed estimate of the probability of a successful landing over a given number of attempts.
Perhaps they are wrong, perhaps they have made a key error in their modeling, who knows. That's why these are estimates, because there's always the possibility for unknown variables to affect outcomes. But to say that there is no basis for SpaceX's estimates is patently ridiculous.
So inspiring what mankind is capable of when we work together.
Optimistic that in the distant future we will be eligible.
http://www.latimes.com/business/la-fi-spacex-employees-lawsu...
Not following the legally required procedure is bad, though.
The problem is that companies following the "fire at least 10% every year in every department" Jack Welch philosophy tend to let some good people go. It's a management philosophy that just assumes that there's no such thing as a really good team, full of worthwhile players.
Its an attitude that works better in professional sports, where hyper-competitiveness is more often an asset than a liability. The knock-on effects of a bunch of coworkers trying to outdo one another to make the cut seem as though they'd make for a crappy work environment, which I believe is what VieElm was talking about.
http://www.vanityfair.com/news/2012/07/microsoft-downfall-em...
EDIT: My broader qualm is this. If you've got hundreds of open req.s, but fail a candidate based on a quiz that you know the candidate doesn't know (but which aligns with one specific job posting), you're maybe doing hiring wrong.
All at the time when I'm rejecting other offers expecting to have a chance to talk to SpaceX.
Regardless, I greatly admire the company's ambition and goals. The methane powered Raptor engine for the MCT is just sheer insanity. I love it. SpaceX inspires many of us, young and old.
https://www.youtube.com/watch?v=C9I55o8hQgs
Admittedly, he also replicated all the other possible failure modes too. Turns out landing on barges is hard.
Perhaps a barge full of Tesla batteries and electromagnets could grab and hold it as it comes in?
Yes! Amazingly, although the nozzle looks just like a bell-shaped piece of sheet metal, it in fact uses "regenerative cooling" which means the nozzle is full of small pipes which wind back and forth like a radiator. The rocket fuel is passed through these pipes before combustion, resulting in a heat exchange which is doubly beneficial, keeping the nozzle (relatively) cool and also heating up the rocket fuel so it combusts more efficiently.
> the exhaust into the vacuum looks like a messy grey cloud, not the bright cone I might have expected
Yep, since there is no atmospheric pressure squeezing it into a cone shape, the exhaust just kind of flies everywhere!
Edit: Apparently it's not what I hoped, http://www.reddit.com/r/spacex/comments/2swnth/how_well_does...
'saved' and 'safed' are pretty similar on stream...
Not sure what FTS means but hopefully its capture was a success!
FTS is the flight termination system. I believe that is a self destruct mechanism in case things go very wrong. They arm it before liftoff and disable it after it's well over the ocean.
Meaning switched off from being armed.
Fun fact: if the F9 first stage had traditional fins at the bottom, they wouldn't be able to do this. The vehicle would tumble in the upper atmosphere and end up either nosediving into the ground or breaking up.
Don't believe me? Go get the KSP demo and try it for yourself! The demo is pretty ancient, but it is free: https://kerbalspaceprogram.com/demo.php
Well of course all this sounds easy, but KISS principles apply I suppose. Still, I could see this happening at some point in the future ..
https://www.youtube.com/watch?v=u656se4e34M
And here's extended video of the last section (I think from a different launch):
Landing a rocket on a barge involves dealing with gravity, wind resistance, air currents and the crazily unstable centre-of-gravity of a large vertical tube balancing on some rockets.
Landing on a moving target shouldn't be that hard except you get (almost) zero weight budget, you're relying on atmospheric braking which means intense heat, and at the end you're hoping the engine doesn't malfunction.
In case it wasn't clear there, the real challenge here is using something that wasn't designed for landing - it was designed for liftoff - to do the landing.
Musk is probably just happy it hit the barge, and tried to slow down some. We'll find out later if it:
a) ran out of fuel
b) misjudged the position and velocity of the barge at the moment of impact
c) landed at the intended speed because there were technical concerns that kept it from landing any slower
d) something else entirely
But keep in mind, the stage landed on the barge. That means it can be salvaged! Pretty cool, if you ask me.
KSP doesn't really have an equivalent, but you can compare it to trying to land on the moon using a solid rocket fuel engine. (The difference with SpaceX is that at least they can turn it off.)
Gilly is the smallest body in the program, so its gravity is so weak you can leave orbit with your space suit's thrusters.
Minmus suicide burn with a Mainsail could probably compare.
My guess is that it primarily an issue of time. When you are trying to dock with the ISS, you are effectivly in a 0g environment, so you can take as much time as you want. This means that you can cancel out your relative velocity at a safe distance and crawl your way towards the ISS at whatever speed you like.
When you try to land on a barge, you essentially need to do a suicide burn, where you wait until the last second to fire your engines enough so that you have zero relative velocity at the instant you hit the barge [0].
Added to this is the fact that landing is largly an afterthought.They would not build, let alone launch, the rocket before they were confident it could dock. However, because the marginal cost of a landing attempt is (relativly) low, they decided that it is cheaper to attempt landings with low confidence and get data instead of attempt to engineer a perfect landing with high confidence before they attempt anything.
[0] If I recal correctly, their margin of error is stopping within one second of hitting the barge.
one second means 10m/s impact; that sounds like quite a lot for a freaking rocket. can you by any chance remember were did you get that from?
Let's say you're driving along the highway and come up on another car. Try to get behind him and gently nudge his bumper. (Don't try this in real life.) Not too hard, right? That's docking with the ISS.
Now, do the same thing, except he's stopped on a steep downhill slope, and you're going 70MPH. You can use your brakes, but you have to push them pretty hard if you push them at all. If you come to a stop too early, the hill will accelerate you into his bumper. If you start on the brakes too late, you'll hit too hard. You have to time it precisely.
That's more or less landing on the barge, except you also have to steer in two dimensions, and you're coming it at more like 700MPH.
The 9 Merlin engines are designed to life the fueled and loaded rocket into space, and it's hard to design these engines for a wide range of thrusts - meaning big penalties in weight, performance, efficiency, etc. Thus, when you're dealing with just the first stage, nearly empty of fuel, even minimum thrust from one engine will accelerate it up pretty hard. It can't hover because of this, so they have to take the rocket falling down with considerable velocity and fire the engine at exactly the right time so that when it passes through zero vertical velocity, it's on top of the barge with no lateral velocity either, and then shut it off at exactly that moment.
Then fuel is a whole 'nother factor. There isn't much of it at landing time, and it probably still makes up a lot of the weight of the stage. So you also have to handle the weight constantly decreasing and any motion of the fuel, and not run out before your landing burn.
You need a huge amount of precise control, and your only tools for the job are a vastly over-powered rocket engine, a stage body not exactly designed for stable aerodynamic flight, and some teeny little hydraulic fins. It's gotta be a minor miracle that they can hit the barge at all, and not with some massive destroy-everything velocity.
In mutual freefall, on orbit, it's possible to take as much time as you want, reducing relative velocities as much as you want, and keep things gentle.
When landing on the Earth (or a barge) you can only control speed so much before you run out of fuel, so you're stuck with high speeds, high accelerations, and large forces. The margins are much thinner and you have an extremely limited amount of time to get things done.
Additionally, the landings are an R&D program being carried out for very little cost, the ISS cargo trips are a commercial service being bought at around $130 million per flight, so the engineering resources available to either are considerably different. If SpaceX could plow hundreds of millions of dollars just into developing the operational capability of landing their rockets they'd likely have done it many times by now.
and then:
"Stage separation confirmed. Good luck stage 1"
and "We have stage 1 boostback startup" then a little while later "stage 1 boostback shutdown" (sounded good)
"stage one entry burn has started" then "stage one entry shutdown"
"stage one is transonic"
"stage one landing burn has started"
"LOS of stage one"
(From reddit: waiting for stage one confirm..... Waiting for tweet from Musk)
officially waiting for word from the landing ship... webcast over.
(From reddit: "We falcon punched the barge" )
(From reddit: "Rumors that the Falcon 9 booster landed on the drone ship, but not softly. At this point, who knows.")
(From reddit: Not a successful landing today.)
Musk Tweet: "Ascent successful. Dragon enroute to Space Station. Rocket landed on droneship, but too hard for survival."
All things considered I'd still call what happened today a good sign.
If this was some pure R&D project, today's events would probably be a major setback. But SpaceX still made a healthy profit on this launch even with the bang at the end. That's the genius of their approach, and it's why I think they'll succeed where others have failed.
The paradox is that making reusability easier would make it harder, because you'd have to get it right from the start, and spend a lot more money developing it, and ensure you can reuse each vehicle many times to make up for the increased cost.
So instead of inventing something new, they started with something known to work, and then adapted it. Because it's cheap, you can keep tweaking it in live tests and not worry too much when you break the stuff.
People often compare this stuff to the Space Shuttle, since that's the one example of a reusable rocket that actually flew, and it was never cheaper than expendable launchers. Imagine what would have happened if the Shuttle had crashed on its first two landing attempts. The program would have been dead before it got anywhere. Now imagine what would have happened if the Shuttle had been so cheap that they could build and launch one for $60 million, instead of $2 billion per orbiter and $500 million per launch (and imagine that somehow they could be lost without killing anybody). It would have been an enormous success even if a bunch had crashed.
This is a good example of both "worse is better" and the MVP concept. The Falcon 9 is not the best design for a reusable launcher that one could put together, I could list easily half a dozen optimizations that would lead to a vastly superior reusable vehicle, for example. But by going the expendable mode first route, and building a dead simple vehicle (2 stage LOX/Kerosene, a 60+ year old design) they've been able to iterate, do full-scale testing, and earn income. Income is the life blood of any operation, so being able to bring in profits early made it easier for SpaceX to invest in rocket R&D. And by using the expendable -> reusable route they're able to gain a lot of confidence in the behavior of their rocket as well as get multi-million dollar test vehicles to play with, all financed by their customers.
Their PR is very well-run, and not only will they not show a live video for something that they aren't sure is going to go right, they'll also have a plausible technical excuse for why they can't do it.
Not that I have anything against running your PR well, just admiring it.
(Note that the seeming ease with which they send live video back from the rocket during the launch tells us nothing. It's relatively easy to receive high-bandwidth data from a rocket above the horizon to a tracking station with a big dish that it can point at the rocket.)
I sympathise: they don't want to be associated with failure. But on the other hand, there were an awful lot of people, including me, who would have been utterly fascinated to see a first-hand view of the failure modes.
I'd still love to see the crash footage.
There is no higher compliment for a rocketry company than to be considered boring.
That said... I'm waiting for the first stage landing footage. squee
https://mobile.twitter.com/elonmusk/status/58807674956231884...
https://mobile.twitter.com/elonmusk/status/58808257418390323...
Weather is 60% "go" ... Lightning and clouds still a concern
Schedule:
PDT ET GMT BST
* Webcast: 12:50 15:55 19:50 10:50
* Liftoff: 13:10 16:10 20:10 21:10