181–190 of 216 posts
Am I the only one who was surprised by how violently the rocket exploded when it fell to its side?
One second, you're chilling out at -207 C with your bros and some kerosenes, maybe even stopping off in near space--then, out of nowhere your containment vessel is compromised and you're evicted.. expected to just phase change and mix with all those common atmospherics.
I think I'd react the same way.
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Flotation devices attached to the booster = extra payload Yes, but how much extra fuel does the rocket have to carry to land? That's a ton of extra payload as well.
Estimates I've heard say 15% loss of payload mass for a barge landing, 30% for land.
Any ideas why it's higher on land? Seems like it wouldn't differ that much.
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The Falcon 9 isn't totally reusable not does it plan to be. It still has a non-recoverable second stage so it's not quite to the point of a SSTO.
A reusable SSTO would be a very difficult project, given that noone's even built an expendable SSTO yet.
is there a reason they can't like come to a stop over the water and then land in it and just expand some floats?
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A reusable SSTO would be a very difficult project, given that noone's even built an expendable SSTO yet.
If you're going to build an expendable rocket designing it as a SSTO doesn't really make sense. With a single stage you can't shed the extra weight of the engines and rocket that got you out of the atmosphere and have to have engines that work both in atmosphere and in vacuum.
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Seems way harder for way lower returns to recover the second stage. Only 1 engine instead of 9, and you're recovering from orbital velocity which opens up several new cans of worms. Would they need heat shielding? The extra weight there might blow away any cost savings from recovering the engine.
Heat shielding is needed, as well as extra landing engines that work outside of vacuum, since the second stage engine would destroy itself under atmospheric pressure. It's easy to see how quickly you start to get dimishing returns, but it would be cool if they could pull it off.
https://en.wikipedia.org/wiki/Atmospheric_entry#Inflatable_h...
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If you're going to build an expendable rocket designing it as a SSTO doesn't really make sense. With a single stage you can't shed the extra weight of the engines and rocket that got you out of the atmosphere and have to have engines that work both in atmosphere and in vacuum.
I agree. I'm just saying it's easier to make an expendable than a reusable one, because you don't have to allocate mass to return systems.
SpaceX actually got very close to sticking this landing. Sea conditions were reasonably rough, with 3-meter waves. It's also the first time SpaceX launches in fog, IIRC. Everything about the landing except the stuck leg seemed to be perfect. So IMHO, the fact that the rocket exploded is not the most pertinent fact about this experiment. The main piece of news is that SpaceX is exceedingly likely to be able to recover…
http://www.surfline.com/forecasters/blog/12_foot1.gif
(source: http://www.surfline.com/surf-science/wave-heights---forecast...)
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There's a pragmatic difference between recovering the booster over some period of time, vs literally parking the booster right where it took off & ready to re-launch within hours/minutes.
I can't see re-launching withing hours any time in the foreseeable future. Even once they're proven reusable each booster will need significant inspection and likely maintenance before being ready to re-launch.
Initially, yes of course. But if they manage to launch a stage 100 times and it always passes inspection and etc, etc etc it's not impossible that eventually you'll get to the point where you only inspect every 2 launches, every 3 launches, every 5 or 10 launches.
Once the ride to orbit costs: $100million/X + $Ymillion + $Zthousand
where X is the number of reuses
Y is the second stage cost
Z is the fuel, launch fees, refurb, etc
There's an experience curve (https://en.wikipedia.org/wiki/Experience_curve_effects) that shows you how much you'll save as you build more and more units and it's entirely possible that the (expendable) second stage could eventually get very cheap to the point where you don't want to spend $1 million (or whatever) going over the rocket for every launch.
If you're launching priceless (or very, very expensive) fancy space telescopes that cost tens of billions then the cost of a failed launch is very, very high. But if you're launching a bunch of food and you can lob another shot next week if it fails, and everything else is cheap enough, it might someday make sense.
Before you ask me if I'm crazy, please understand that airplanes do exactly this; you have to get your engines overhauled every few thousand hours and I'm sure there are inspections, but they don't tear the plane down and rebuild it after every flight. Once systems get reliable enough, that's a thing.
