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SpaceX Falcon 9 first stage has landed at LZ-1 [video] (youtube.com)
289 points by romanhotsiy on May 1, 2017 | hide | past | web | favorite | 108 comments

I see a lot of comments about how boring this is becoming. It caused a bit of excitement for me, though.

The launch and landing happened around 7 am local time, and my house is only a few miles from the landing zone. So, I'm taking my morning shower, and I hear the boom. I'm thinking "Sounds like a SpaceX landing or a rapid unplanned disassembly". Then my houseguest from out-of-town yells into the bathroom: "David, I think something just hit the house!".

Me: "No, hun, that's what a rocket landing sounds like. Go check the internet, I'm pretty sure we're okay."

Best of luck to SpaceX, and thank you for not launching (and landing) any earlier in the morning!

There's a map here of how loud it is and noise analysis:


Good business: make the hard seem easy and the nigh on impossible seem merely hard. They do these landings so well now it almost seems normal that rockets land after taking off and boosting a second stage to orbital velocity.

Nit: The first stage does not boost the second stage to orbital velocity. It boosts it to ~2,000 m/s, which is one-quarter of an orbital velocity, and one-sixteenth of the energy required for orbit.

I don't believe it's likely that we'll see recovery of an orbital velocity stage anytime soon.

Nit: The energy of an object going 2,000 m/s is 1/16th of that going 8,000 m/s, but since this is a rocket launching from Earth the energy for the rocket to get to 2,000 m/s is much greater than the energy to go from 2,000 m/s to 8,000 m/s [1].

Just look at how much larger the first stage (mass almost all propellant) is compared to the second stage (large fraction of the mass is the payload).

[1] https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation

That has nothing to do with the rocket launching from Earth (A rocket in space follows the same rules), and everything to do with the fact that rockets expend most of their energy to push their own fuel.

That fact is incredibly relevant for getting to orbit - however, it is not at all relevant for surviving re-entry, where all that matters is your kinetic energy.

The Earth part was just shorthand for the fact that the atmosphere and gravity of Earth add about 1.3–1.8 km/s of delta v to achieving the pure kinetic delta v of 7.8 km/s needed to achieve LEO [1]. The first stage adds almost all of this "extra" delta v.

I was mostly just correcting your "one-sixteenth of the energy required for orbit" statement. I agree that reentering at 7.8 km/s is much more difficult than 2.0 km/s, but the second stage is smaller and more spherical than the first stage. That might make reentering it a bit easier than if it had the shape of the first stage.

[1] https://en.wikipedia.org/wiki/Low_Earth_orbit

A better approximation to the 2nd stage's shape would be that of a cow.

(If that made no sense, it's a variation on an old freshman physics joke.)

>I don't believe it's likely that we'll see recovery of an orbital velocity stage anytime soon.

Oh, I wouldn't be so pessimistic.

"Considering trying to bring upper stage back on Falcon Heavy demo flight for full reusability. Odds of success low, but maybe worth a shot." - Elon Musk [1]


Remember, everyone said they would never land the first stage....

"...maybe worth a shot" is a pretty thin reed upon which to hang your hopes. There are a lot of reasons to not return the second stage, business as well as technical.

Sure, I agree, though it's clear Elon has made a career out of the thin reeds.

Also, if they don't do it now, it's obvious they are working on it / thinking about it. Wait five years.

> Remember, everyone said they would never land the first stage....

Everyone? That's a bit hyperbolic.

Actually almost everyone with experience in the matter said that SpaceX would never successfully reuse a first stage booster. That would be Boeing, USA, and a majority of NASA engineers. Granted many of those had an interest in seeing Space Exploration Technologies fail, but their opinion certainly holds weight.

> I don't believe it's likely that we'll see recovery of an orbital velocity stage anytime soon.

I understand it's a very different beast, but why do you think this is so much harder technologically? We bring things back from orbital velocity routinely, indeed much more frequently than anyone landed a rocket vertically prior to SpaceX.

Agreed. And with Dragon, SpaceX actually has a ton of experience with orbital reentry.

Musk said that they might attempt second stage recovery late next year for the Falcon Heavy.


Minor nit: the Falcon Heavy demo flight (with upper stage recovery attempt) is set for late THIS year, it's just that Musk puts the odds of successful upper stage recovery fairly low: https://twitter.com/elonmusk/status/847882289581359104

Musk is "fairly confident" to have upper stage reuse operational by sometime next year: http://www.space.com/36412-spacex-completely-reusable-rocket...

Musk is notorious for doubling down on bets when the first bet seems like it most likely will succeed. I would bet you we'll see upper stage recovery within 1 or 2 years, with reuse of that stage within 2 to 4 years. (Particularly if SpaceX doesn't suffer another major failure within the next 2 years... Failures are always a significant possibility in this business given enough launches.) That counts as pretty darned soon.

Slightly different but yeah. The falcon has a single pre-orbit stage. The heavy has two pre-orbit stages. So it'll end up being three falcon engines stitched together with decouplers. Part of the way to orbit, the outside two decouple and return the to launch pad. Some time after that, the center engine decouples and lands on a barge. None of those will be going at orbit velocity though.

But Musk has now said they are going to try upper stage reuse for Falcon Heavy. Not just the boosters: http://www.space.com/36412-spacex-completely-reusable-rocket...

Thing is you just need heat shielding, really. A de-orbit burn well have a rather small dV, say, 50m/s or so. Then let the atmosphere do almost all the work... the stage just needs to survive, and then do a suicide burn landing just like the stage 1.

If you're doing the suicide burn with the main engine, you have to flip inside the atmosphere (while supersonic), and also need to lose large chunks of the nozzle (not just to get it out of the way of landing legs, but because firing the engine in the atmosphere would otherwise generate turbulent flow within the nozzle which would tear the thing apart). If you're using a different engine, then you've added a whole lot of extra weight from the engine itself and its plumbing (and tankage for its fuels if, like the Dragon 2 Superdracos, it's not burning LOX and Kerosene).

So, adapting the first-stage recovery strategy is not an obvious slam dunk -- in fact, it might very well be worth considering alternatives involving parachutes if you can get the thing intact through re-entry. (Note that the Falcon 9 v1.0 first stages on which they actually tried parachute recovery are believed to have not gotten that far -- they reportedly broke up before the parachutes even deployed.)

Oh, I'm not saying it'd be easy, just that the dV needed to get the stage down is <<< the dV to get it up.

The devil is in the details, of course.

Will, it's 1/16th the kinetic energy required for the stage to get to orbit, but not 1/16th of the total kinetic energy needed. Most of the s2 mass is fuel, of which very little is taken to orbital velocity.

You're absolutely right, I totally got that wrong. Thank you for the correction.

One thing I really like about HN as compared with many other web sites is it will often happen that someone will admit they were wrong.

NROL-76's mission patch[0] seems rather mundane. NRO patches are normally a bit more cryptic and bizzare.

I wonder how many people at SpaceX are cleared to know what the payload is. What are the finer points of payload integration in such a situation?

Does Elon even know what his own company just launched?

[0] https://en.m.wikipedia.org/wiki/List_of_NRO_launches#/media/...

The general philosophy of classified information is that it's revealed on a need-to-know basis. Except for a few crude simplifications at the lowest level, there is no fixed heirarchy where you've just given all the info you want below some level. The folks at SpaceX, including Musk, probably got exactly the minimal amount of classified info they needed to safely launch the thing into orbit, e.g., the orbital parameters, its weight and exterior features, its robustness to vibrations and the like, the electronic interface for monitoring its health, etc.

NRO-39's patch (the one in the wiki article) caused a small controversy - the tentacles enveloping the world seemed like pretty poor taste in light of Snowden. They probably decided that their PR team needed to see them first from then on.

To be fair, some of the patches for the NRO missions seem weirdly aggressive, with a bunch of different animals all clutching the earth. They've had bird claws (presumably an American eagle), a tiger, a three-headed bird monster, and even a big green dragon. It's odd that tentacles were somehow considered worse taste.

After reading up on some of the patches and their hidden meanings, the octopus could have been largely symbolic. For example, there could have been 8 components of the mission and the octopus has 8 arms. Something like that. Here's some background on why I think that might be possible:

"The patches’ relative obscurity changed in 2000, with the launch of a payload known as NROL-11. The mission patch depicted what appeared to be owl eyes peering down at the Earth, where four arrow-shaped vectors, two per orbit, made their way across Africa. Three of the vectors were white, and one was dark. Based solely on studying the design, civilian satellite watcher Ted Molczan hypothesized that the patch showed a failed satellite (the dark vector), and that the newly launched satellite would take its place.

Sure enough, after the launch a new satellite appeared just where Molczan predicted. Pearlman, who reported on the story at the time, says that NRO at first told him “no comment” when he contacted them. About 30 minutes later they called him back and asked him not to publish the story. Pearlman told them no dice, and in the end, the NRO spokesman told him that the patches were just morale-builders for those who work on the launches."


>It's odd that tentacles were somehow considered worse taste.

Anticnidarianism is alive and well.

Why you would expect good taste from war-mongers and military-industrial profiteers, I can't fathom. This sort of gauche pageantry is par for the course from those groups who consistently are getting away with heinous activities they deem too scary for the rest of us mere mortals to know about.

Furthermore I believe the front tentacle is touching Iran.

What happens if SpaceX wants to do business with a foreign government? Is that permitted?

Of course, that would presume that a foreign entity would trust a US company for sensitive payloads in the first place, but just a thought I had as corporations become multi-national, global entities.

They already had international customers. The list of previous and future missions is at http://www.spacex.com/missions

No explicit foreign governments in the list and I don't know if there is any kind of inspection of what gets sent to orbit.

Watch the whole stream, it was beautiful. There was a view from ground all the way from separation to landing.

This is the first time, I think, we got to see the charred surface of the first stage. I wonder what kind of processing is involved to make the stage usable again?

Do they just put it through a car wash and re-fill for next time?

Is everything reusable on the first stage?

We've certainly seen gunked up stages after landing -- and a lot of the gunk isn't charred paint (or thermal coating), but soot from the rocket exhaust in the re-entry burn, which they can just clean off.

Agreed. We've seen lots and lots of primary missions, but the truly revolutionary thing, the booster landing, we never followed this close.

Most of that is soot, not char (i.e. it's "dirt" that has stuck to the rocket, not the actual material on the outside of the rocket charring).

Anecdotal: I believe musk said that the charred outside was surprisingly only in need of a fresh coat of paint.

In a funny way, i'd be happy if it got to a point where they just sent the dirty/charred rockets back up.

"It's a rocket - of course it's going to get dirty!"

Wouldn't be surprised if it's similar to the coatings placed on the launch pad stabilizers. The paint is meant to char because it acts similar to a ceramic preventing damage to the underlying metal. There's a good youtube video of this on the moon launches where the tail fin hold downs char, but don't warp.

The grid fins have paint like that, which is why they catch on fire.

They're aluminium underneath the paint - and that also melts a bit on a high speed GTO reentry, hence the likely switch to titanium grid fins in the future.

The booster footage was amazing. Incredible to see just how much it flies through its own exhaust on the re-entry burn!

And I was surprised just how close to the second stage it still looked when the secondary engines started up.

I can't even imagine trying to steer a rocket to turn it around, with an open top, while it's in the exhaust of another rocket! It's amazing.

True story! The landing was fantastic, no doubt, but this footage is a thing of pure beauty: https://www.youtube.com/watch?v=EzQpkQ1etdA&feature=youtu.be...

I enjoyed watching Blue Origin's landing as well (https://youtu.be/9pillaOxGCo) and from their video it looks like engine restart is at five thousand feet with full burn at one thousand. Do we have similar numbers for Space X?

I am curious what threshold differences there are between teams, both are doing amazing work.

btw, this portion of the return where they did the entry level was most impressive for space x (https://www.youtube.com/watch?v=EzQpkQ1etdA&t=1145s)

SpaceX rockets have to shed a lot more velocity the numbers are not comparable.

At around T+8 minutes it's really obvious how the rocket is actually gliding at an angle as it comes down, to steer itself towards the landing site. A cylinder might not make a great glider, but it has significant lift especially at these velocities.

Getting it out of the exhaust of that other rocket is probably job one...

Coming down on its jets, the way God and Robert Heinlein intended!

What is truly amazing is that this is becoming normal.

I said it on Twitter.. F9 stuck the landing 1 minute before I had to walk out the door with my 5yo daughter and she was really happy to see it. Then through the bus window as it was pulling away, she made rocket-taking-off hands that went up to space... and then came back down and landed again. I'll be able to tell her about how nice that was to see someday :)

Got a lot of frisson reading this comment. I just can't understand the people who love to criticize Musk as a charlatan and PR mastermind because either way, true or untrue, he and his engineers are doing undeniable good in inspiring the next generation of scientists.

Yeah, it is strange. A charlatan is someone who is lying and has no intent on following through on their unrealistic plans.

Musk clearly isn't a charlatan as he's trying his very best to make his unrealistic plans a reality, and has already succeeded tremendously.

Is Musk crazy? He might be. But he's earnestly crazy.

I think a lot of the criticism has come from moves he made on the business side, like having SpaceX buy SolarCity bonds.

Worked out pretty well for SpaceX.

At what point do you say "he's made so much money for us that we'll give him at least one major fuckup before we start trying to reign him in."?

The criticism is SpaceX, Tesla, and SolarCity are so tied together financially they'll all go down if one does. As an outsider I don't really care how Musk arranges his financial house. However, if I had a financial stake in SpaceX I'd be pretty upset to see my money getting invested in another company for Elon Musk's benefit.

Seems to me is that what is for Elon's benefit is to all our benefit.

That's up to SpaceX's private owners, now isn't it?

Yes it is. That was part of the postulation. I don't know how things are drawn up - they may not have had a choice.

> I just can't understand the people who love to criticize Musk as a charlatan and PR mastermind

As you hear opinions from a larger and larger group, the ideas start more and more to resemble noise, distributed according to some statistical law.

My understanding is that the idea Musk is a charlatan is being orchestrated by the Koch brothers because they are in the oil business, and he is promoting renewable energy.


It can't be both per objective reality, but per history it can be both because it is subject to revision.

I see no evidence that Musk is doing anything other than working as hard as he can to bring innovation forward. If 1 in 10 business heads had his drive this century someone on Mars be commenting on this now.

Why do you dislike him?

> he and his engineers are doing undeniable good

I think they do indeed a lot of good - however, launching a classified military spy satellite is not one of it, in my opinion.

Bookmark this comment for her!

The more boring these "rocket successfully lands" stories get, the more exciting they paradoxically become.

That never gets old :-) and I thought the external views were really awesome as well. On the previous return of SES-10 which was a geosync mission, previously SpaceX had said that the booster was unrecoverable in those situations given the additional boost that it gave the payload (so started from a higher altitude) but they tried it, and got it back anyway. Watching the grid fins nearly burn off from re-entry friction was a the most interesting bit of that one.

As far as I'm concerned these gravity assisted landings are technologically superior voodoo magic. The combination of materials, software and physics to accomplish the improbable.

I do like how these landings are becoming more routine. They're making it seem like a piece of cake now. I don't think I'll get as excited again until the Falcon Heavy maiden launch.

Is it just me or is this first time they've caught video of stage separation from the ground?

Beautiful video in any case. It's fun to see the first stage engine cut off, separate, flip over, and the second stage accelerates away.


Didn't they say it was classified? I think just before the separation of the rocket and payload, they said something about what it was.

13:38 in the video "Falcon X is delivering the, National Reconnaissance office's satellite to orbit right now"

There's nothing secret about that. It's a satellite and it's for the NRO. What's secret is what it does, and what its orbit will be. (Once it gets to its final orbit, I guess there are amateur satellite trackers that will figure it out, but not until then).

The webcast host may not (I'd guess he probably doesn't) know what the satellite does or its final orbit. He does mechanical design. I'd bet they keep that information compartmentalized within SpaceX so only the operations personnel who need to know would know.

We know that it's either very light or it's a low orbit, otherwise spacex would have done a water landing.

I'd bet nobody at SpaceX knows what it actually does even though they might take a good guess based on the orbit.

In the beginning they said that the payload is confidential too, not just the destination. Rewatch it ;)

"satellite" is not a description of the payload.

Yes, that's why there was no video or telemetry from the second stage in the webcast like they usually have. Its existence is not classified, but lots of details are. You won't find any photos of the satellite, and there are no official numbers as to how heavy it was (although you can guess an upper limit from the fact that the first stage did an RTLS landing) or what orbit it went into (which is why there was no second-stage telemetry displayed).

It's worth noting that the very existence of the National Reconnaissance Office was classified until 1992, although it leaked out to the public in the 70s. They're a bit less secretive now.

What part of that is classified? It's public knowledge that this mission was for the NRO (the payload was officially called "NRO-76"), and the fact that it's a satellite is... self-evident?

Another great achievement. I am OK with this becoming a regular boring affair.

Wow! What amazing work being done by SpaceX.

What was the payload?

I believe it was an NRO spy satellite.

Amazing video from the ground this time. Link to the webcast at the time of separation. https://youtu.be/EzQpkQ1etdA?t=1211

Thanks! We updated the link from https://twitter.com/SpaceX/status/859006000136769536.

You almost forget that it was an NRO spy sat payload.

We detached this subthread from https://news.ycombinator.com/item?id=14237002 and marked it off-topic.

No, they didn't forget to add that extra detail which adds nothing to their post.

I thought it was a pretty important detail. It shows that the government thinks they are competent enough and competitive enough to succeed at this. Since this launch was successful, they've sent spacecraft to the ISS, and they are launching a GPS satellite pretty soon, the government is going to have them do more launches. The government is a huge customer with lots of satellites and lots of money.

This is the first military payload but they have landed and recovered the first stage several times. I guess the NSA should do more technical demos because no one seems to find this NRO tech unethical if it's coupled with an amazing technical display.

Wonder if they took the octopus of the patches

People can very much dislike NRO spy satellites and, at the same time, be excited about Musk's end goals for SpaceX.

Life is complex and paradoxical. We do the best we can.

You don't have to wonder:


For all the patches, wiki has us covered of course: https://en.wikipedia.org/wiki/List_of_NRO_Launches

Looks like only NROL-39 had the octopus.

Do you feel that Google Maps imagery is similarly unethical?

But, wouldn't it be interesting if one of the reasons we had such great ground coverage was somehow related to the NRO being a customer?

I guess the better coverage of the first stage is that they landed in land and not in a small ship in the middle of the sea. It's more difficult to put cameras in the sea and keep a good connection.

I think it's indirectly related. Probably, the satellite has a low orbit to have a better sight, and they don't expect to have the satellite for too long so care about some drag. So the rocket has more fuel to a return to land maneuver.

Also, it was very strange that they cut the transmission so soon. Usually they continue with the second stage and they highlight many times that the main mission is the satellite and they transmit as much of the satellite as possible in case they have an RUD. This time they closed the transmission as soon as the first stage landed.

Anyway, an amazing transmission.

> Also, it was very strange that they cut the transmission so soon.

That's an NRO requirement.

Yes, to keep the position secret in theory. Though I bet Russian and Chinese space surveillance radars will pick up it's orbit the first time it passes over their territory and amateurs will find out where it is eventually too.

Yep. Same reason the cheering crowd at SpaceX was much smaller than a usual launch - only folks with clearance allowed in.

I wonder how much was that, and how much was the fact the launch window opened at 4am.

Pretty sure the NRO wasn't want anyone to know which direction and how high up that satellite was heading.

Or its mass. You can determine that by the second stage acceleration.

They couldn't/wouldn't show footage of the 2nd stage, so more attention for the 1st stage. Fine by me, it was amazing to watch

Couldn't, it's a NRO launch which are very secretive. Usually the most description you get out of an NRO launch is that it's for the NRO and a video from the ground of the launch.

The first stage is such an attention whore. It usually gets most of it anyways, this time it punted the first stage entirely off the show.

I wouldn't be too surprised if that view was something they'd had before but didn't use because you had the more interesting second stage feed during a normal launch. Today they couldn't show anything from stage 2 because it was an NRO launch and there's a lot of secrecy around what those even look like.

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