Incredible photo of S1 almost landing on the barge!
http://livestream.com/spacex/events/3959775/images/83962965
SpaceX Dragon CRS-6 Launch Webcast
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Re: SpaceX Dragon CRS-6 Launch Webcast
#62Could someone explain why it's (apparently) so much harder to land on a barge than it is to dock with the ISS?
Just wild guesses here but anyone who has played Kerbal Space Program knows that while docking is no piece of cake, it happens slowly and you can back off and try again until you run out of fuel.
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.
Re: SpaceX Dragon CRS-6 Launch Webcast
#63Such good motivation to want to be an even better programmer / engineer / scientist. So inspiring what mankind is capable of when we work together.
You guys know we are looking for software people, right? http://www.spacex.com/careers
The HR screen was a bit off. I applied as a Python developer and was given a purely C memory-leak multiple-choice quiz. Sort of annoying, considering I told the recruiter explicitly that I don't know C.
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.
Re: SpaceX Dragon CRS-6 Launch Webcast
#64Could someone explain why it's (apparently) so much harder to land on a barge than it is to dock with the ISS?
IANARS (I am not a rocket scientist).
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.
Re: SpaceX Dragon CRS-6 Launch Webcast
#65Looks like Falcon landed fine, but excess lateral velocity caused it to tip over post landing -@elonmusk https://twitter.com/elonmusk/status/588082574183903232
Scott Manley did precisely this in KSP the other day, trying to replicate the barge landing:
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.
Re: SpaceX Dragon CRS-6 Launch Webcast
#66Could someone explain why it's (apparently) so much harder to land on a barge than it is to dock with the ISS?
Just wild guesses here but anyone who has played Kerbal Space Program knows that while docking is no piece of cake, it happens slowly and you can back off and try again until you run out of fuel. 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 ca…
"Looks like Falcon landed fine, but excess lateral velocity caused it to tip over post landing" -- https://twitter.com/elonmusk/status/588082574183903232
Re: SpaceX Dragon CRS-6 Launch Webcast
#67Earlier quoted context omitted.
Just wild guesses here but anyone who has played Kerbal Space Program knows that while docking is no piece of cake, it happens slowly and you can back off and try again until you run out of fuel. 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 ca…
"Looks like Falcon landed fine, but excess lateral velocity caused it to tip over post landing" -- https://twitter.com/elonmusk/status/588082574183903232
Ok! So basically, it was d) something else entirely. :)
Re: SpaceX Dragon CRS-6 Launch Webcast
#68Could someone explain why it's (apparently) so much harder to land on a barge than it is to dock with the ISS?
Just wild guesses here but anyone who has played Kerbal Space Program knows that while docking is no piece of cake, it happens slowly and you can back off and try again until you run out of fuel. 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 ca…
In addition, even one engine on the F9 first stage, throttled down to its minimum, generates way too much thrust for the vehicle to do a gentle landing. They have to do a suicide burn --- they fall towards the launchpad unpowered and then at the last possible moment light up the engine, and hope that when they come to a halt they've landed. There is no margin for error.
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.)
Re: SpaceX Dragon CRS-6 Launch Webcast
#69Earlier quoted context omitted.
Just wild guesses here but anyone who has played Kerbal Space Program knows that while docking is no piece of cake, it happens slowly and you can back off and try again until you run out of fuel. 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 ca…
In addition, even one engine on the F9 first stage, throttled down to its minimum, generates way too much thrust for the vehicle to do a gentle landing. They have to do a suicide burn --- they fall towards the launchpad unpowered and then at the last possible moment light up the engine, and hope that when they come to a halt they've landed. There is no margin for error. KSP doesn't really have an equivalent, but you…
In KSP, I would compare it to landing on Gilly (Eve's moon) with a solid rocket booster.
Gilly is the smallest body in the program, so its gravity is so weak you can leave orbit with your space suit's thrusters.
Re: SpaceX Dragon CRS-6 Launch Webcast
#70Could someone explain why it's (apparently) so much harder to land on a barge than it is to dock with the ISS?
Gravity :)