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SpaceX lands rocket at sea second time after satellite launch

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Re: SpaceX lands rocket at sea second time after satellite launch

#261

Post by 542458 »

prplhaz4 wrote: post #216
geerlingguy wrote: post #92

What's notable about this attempt (as opposed to the last) is that the first stage rocket was traveling twice as fast (4x the energy to overcome on landing), and didn't have enough propellant to do a 'boostback' burn. Instead, coming in very hot, the rocket had to use three engines (instead of one) to slow for landing. The last time this was attempted, the first stage put a nice hole in the deck of the drone ship. Se…

One of my favorite facts is that merely relighting the engine provides enough thrust to lift the rocket (at its minimum throttle of 60%). This means that it must slow to a standstill, cut the engines and hit the platform at exactly the same time or it will either start going up again or be dropped onto the platform from a less than ideal height.

This maneuver (powered descent with high deceleration right before impact) is called a "suicide burn"!

Re: SpaceX lands rocket at sea second time after satellite launch

#262

Post by aerovistae »

gist wrote: post #238

The big difference between landing at sea and on land seems to be the PR value. Otherwise a target is a target, taking any differences in weather into consideration. In fact it seems that landing at sea is actually less pressure since you don't have the same safety concerns and crash pictures (which are bad for publicity) the rocket simply disappears.

Completely incorrect.

The question to ask is, why are they bothering to land at sea?

And, if you had done any cursory research instead of just announcing that SpaceX is making a PR grab because it sounded good to you, you would have read in the abundantly available explanations that this launch was to geostationary transfer orbit, rather than low earth orbit. GEO is a lot, lot higher than LEO, which means the rocket has to be going a LOT faster to get there. This uses up a lot of fuel, leaving them very little to slow down from an even higher speed than the normal mission. Decelerating from a much higher speed takes MORE fuel than decelerating from a low speed, and they have less fuel available because so much got used up in getting to that speed.

So it's not plausible to get all the way back to the launch site. Instead they position a droneship way downrange so the rocket doesn't have to go as far back to land. But it's still going EXTREMELY fast, and managing to slow down all the way and land is an incredible accomplishment.

Re: SpaceX lands rocket at sea second time after satellite launch

#263

Post by ekun »

typon wrote: post #254
jklinger410 wrote: post #249

I find the level of criticism for SpaceX on this site to be incredible. I understand this is a place for intelligent discussion, but sometimes I feel like I can't find a single thread on this site without someone in the comments presuming they are smarter than someone else.

What is it about software development that brings out these kinds of people?

Ive noticed it in any technical field. People love to hear themselves talk and miss out on a lot by not listening to others.

Re: SpaceX lands rocket at sea second time after satellite launch

#264

Post by odonnellryan »

thrownear wrote: post #219
hoorayimhelping wrote: post #165

> P.S. Downvotes for this question? Really? There are always people on HN who love being contrarian and trying to diminish amazing things. It's like they hate seeing people excited for something and want to point out that this isn't that big of a deal. We're literally watching things happen for the first time ever, and this person's response is "what's so great about this?" while implying that people who are excited…

>diminish amazing things.. Sorry. We are living in a period where mediocrity and even complete fraudulent stuff is hailed as profound and "amazing". People with differing opinions matter, and I would say they matter more than ever. And I don't think people love being a contrarian". It is quite easy being a fanboy, but it is hard to go against popular opinion, and be a "contrarian". There is no love in being a contrar…

> Sorry. We are living in a period where mediocrity and even complete fraudulent stuff is hailed as profound and "amazing".

Like what? Even the transistor is pretty damn amazing.

It's fine to be critical, but let yourself get excited sometimes too.

Re: SpaceX lands rocket at sea second time after satellite launch

#265

Post by knowaveragejoe »

abduhl wrote: post #162
agumonkey wrote: post #153

Earlier quoted context omitted.

Based on some talks the first lunar landings were way more adventurous and lucky than what SpaceX is doing. Making a snooker trick shot is nice, announcing it and doing it twice is another thing.

What about announcing it and doing it six times? That's the number of times we landed men on the moon. Let's not try to downplay NASA's previous successes as "lucky" and "adventurous" in order to make SpaceX seem more advanced in an engineering sense.

Luck was a significant factor, however. There were _so many_ things that could have gone wrong, that is not an understatement at all. They found bugs in the AGC's software years later that could have sent 3 men to their deaths, had they occurred.

Re: SpaceX lands rocket at sea second time after satellite launch

#266

Post by thrownear »

jklinger410 wrote: post #249

I find the level of criticism for SpaceX on this site to be incredible. I understand this is a place for intelligent discussion, but sometimes I feel like I can't find a single thread on this site without someone in the comments presuming they are smarter than someone else.

>I find the level of criticism for SpaceX on this site to be incredible.

This has to be the funniest comment I have seen today. There are more than one post regarding this event with 300+ votes. Still the level of criticism for Spacex on this site is "incredible", Really?

Re: SpaceX lands rocket at sea second time after satellite launch

#267

Post by aerovistae »

jklinger410 wrote: post #249

I find the level of criticism for SpaceX on this site to be incredible. I understand this is a place for intelligent discussion, but sometimes I feel like I can't find a single thread on this site without someone in the comments presuming they are smarter than someone else.

I see little or none, <5% of discussion on this page.

Re: SpaceX lands rocket at sea second time after satellite launch

#268

Post by pilsetnieks »

mikeash wrote: post #195
sjtrny wrote: post #186

Earlier quoted context omitted.

What exactly is wrong with that discussion? I found the level of evangelical, employee circle jerking at these SpaceX events to be nauseating. And that was before they started chanting. Well done guys but it's just not necessary.

Good ol' HN. These folks are pushing the boundaries like nobody else, advancing humanity more than a thousand Facebooks or Snapchats ever could, but if they express pride in their work it's a "circle jerk."

If they chanted "SpaceX," or "Falcon 9," or "JCSAT-14" it would signify pride in their work. The "USA" chant glorifies the state/government above all else.

It's the same reason why foreigners are baffled by, for example, the Pledge of Allegiance.

Re: SpaceX lands rocket at sea second time after satellite launch

#269

Post by odonnellryan »

lmm wrote: post #229
justifier wrote: post #225

Earlier quoted context omitted.

> Runway rather than barge but that's not really an important difference. it is an important difference when you look beyond earth the moon, mars, and any future site that has yet to send robots to pave a runaway that is: 4,500 meters long, 91 meters wide, and 40 centimeters thick(o); will necessarily be vertical take off and landing (o) https://en.wikipedia.org/wiki/Shuttle_Landing_Facility

If and when SpaceX land rockets beyond Earth, that will very much be something to get excited about.

This argument makes no sense.

Re: SpaceX lands rocket at sea second time after satellite launch

#270

Post by unethical_ban »

simonh wrote: post #131
zupreme wrote: post #115

I remain confused about why SpaceX is getting so much fanfare and praise. What have they accomplished that NASA didn't already accomplish during the Apollo missions? I know SpaceX is doing it all more cost effectively, because we have better technology, but have they actually accomplished anything tangible that NASA didn't a generation ago?

The Apollo missions were one-offs. They left nothing behind that future missions could utilize. Everything was disposed of after use, even Spacelab which had a very short life and completed a specific programme of missions and then burned up. The shuttle was the first attempt at re-usability but was far too expensive to be viable. Only the space station is genuinely long term re-useable infrastructure. It's something…

The only two questions I see in your post are in the P.S. What am I missing?
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