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How Not to Land an Orbital Rocket Booster [video] (youtube.com)
296 points by robin_reala 8 months ago | hide | past | web | favorite | 90 comments

I have to appreciate the humour this shows. All in the name of progress, and it certainly made me laugh.

SpaceX has somehow managed to turn landing a booster from space into something almost mundane, but it bears remembering the failures that got them there.

You try and fail. And try and fail. And try and fail. And then one day you have learned enough to try and succeed.

Learning how to NOT land it is learning how to land it.

“I have not failed 10,000 times. I have not failed once. I have succeeded in proving that those 10,000 ways will not work. When I have eliminated the ways that will not work, I will find the way that will work.”

The trick with learning how to fly, is to throw yourself at the ground... and miss. - Douglas Adams

And if you're smart, rich and lucky, you learn enough before the funding runs out. :)

The failures were all very low cost since the rockets actually completed their mission. Once reusability becomes common and lowers the price of launches, failures like those will actually be very expensive for someone else.

Relatively low cost, yes. But all those recovery efforts, offshore barges, added hardware and software cost actual money that was away from their gross margin from the rocket launches.

It was a good move regardless but don't underestimate the amount of time and money spent.

Still relatively small beans compared to the cost of the rocket. Remember, they started out simple. They did controlled re-entry burns and let the rocket fall - cost: extra fuel and 10 minutes more of data collection. Then the did a descent down to sea level and a hover before falling into the sea - cost: extra fuel, grid fins (grid fins yet?), more data collection. By the time they went for a barge landing (sorry, drone ship) they had reasonable confidence in having some success - and they hit it. By that point the long term benefits should have been clear, so further development was investment in their future.

All of this should have been done a long time ago by the established players in the industry. It sounded crazy to them, but really the cost of experimenting with re-entry should not have been much and AFAIK they never even tried.

One big obstacle to established players was the fact that a lot of existing booster stages had been optimized in such a way that they simply could not survive atmospheric reentry, lateral stress, and could not land. Both major operational US rockets, Delta IV and Atlas V, have exterior insulation (which would burn away upon reentry), relatively thin walls (meaning they're not very strong against aerodynamic buffeting or fin torque), and single engines (meaning that it's very hard to throttle down to land). Adapting these rockets for reusability testing would have meant basically redesigning them from the ground up.

Probably more importantly, the idea of landing a rocket was basically impossible until computer control got good enough to handle the descent and landing.

For sure - but it's been good enough for a while. Consider the McDonnell Douglas DC-X in 1993: https://en.wikipedia.org/wiki/McDonnell_Douglas_DC-X

DC-XA set a height record of 10,000 feet, and pretty much goes straight up and down. So it proved out most of what Blue Origin's suborbital rocket does, and the last part of what SpaceX's first stage does, but not the re-entry burn and flying a cylinder stuff.

Soviet space shuttle Buran landed automatically from space in 1988 using Soviet-made hardware and software. So I very much doubt that using recent computer chips were essential to land the rocket.

> Adapting these rockets for reusability testing would have meant basically redesigning them from the ground up.

And now they're going to have to do that anyway if they want to compete with SpaceX, so what the GP said is true, it's something established players should have done a long time ago, and they're going to be noncompetitive for a period of time as a result.

Correct - they just went down the wrong optimization road, so the incremental development program for Falcon 9 landing is nothing they could have replicated.

Yes, sure it was an impressive R&D program that piggy backed on their production runs.

But it was still an expensive program with Grasshopper test vehicles, lots of failed tests and a reduced capacity on the boosters. "Just a little extra fuel" is a great oversimplification, there's much more than that in doing an atmospheric re-entry.

But a marvelous program it has been and I look forward to seeing their future progress.

The real cost of the "extra fuel" was really in making the base rocket big enough to address the majority of the rocket without add-on boosters. Then you always have leftover fuel for more moderately sized satellites. And in terms of design simplicity that might have been worth while before considering reuse.

I recall that they spent about $1 billion in landing-related R&D before they got it to work. Definitely a lot. (Although, for comparison, a single Shuttle cost about $2 billion to build, not counting any R&D costs.)

But if that $1 billion came from their margins rather than from investment, it means they wouldn't run out of funding unless they ran out of business, which is pretty cool.

I believe that the $1 billion figure is for the entire development cost of the Falcon 9 vehicle (stages 1 and 2.)

I wonder if that'll get added to the contracts as a possible cost to the customer.

"If Rocket is destroyed while operating for any reason, Customer will be required to pay the pro-rated portion of anticipated Rocket lifetime replacement cost, or insurance deductible, whichever is higher."

Like how UPS charges customers who have packages in the truck when they're involved in accidents?

I think the rental car model makes more sense. If your payload breaks the rocket, you're liable for it. I think this is Already the case with much rocket insurance.

I haven't heard of that. But I have seen UPS charge customers when their package gets run over by their trucks. "You should have packed it more securely"

Except for the Grasshopper fail, that must have hurt. But yes, their overall approach was genius.

As there is a definite Monty Python feeling to the video, I'd suggest this is appropriate: https://youtu.be/aNaXdLWt17A?t=20s

Did the Month Python music and quotes gave it away?

Congratulations on... noticing the same thing I did?

the road to wisdom - well, it's plain and simple to express: To err and err and err again but less and less and less

It's incredibly reassuring that ACTUAL rocket scientists have the same problems as people learning how to play Kerbal Space Program.

The part that made me laugh the most, however, was that Scott Manley had the top comment (when I looked, anyway).

For those who don't spend their off hours accidentally blowing up green videogame astronauts, or stranding them on distant planets, Scott Manley has the single most extensive tutorial series for Kerbal Space Program.

I can't help thinking that the captions would make excellent Culture ship names.


ROU Sticky Throttle Valve

Edit: In case anyone is wondering about about the connection to the Culture, the SpaceX "Autonomous spaceport drone ships" are named after Culture ships:


Just Read the Instructions


Of Course I Still Love You

Was there ever a ship called It's just a scratch ? That's sounds like a good name too.

Apparently not according to:


Rather like 'Look, that's not an "Explosion"' as well... :-)

Edit: I'm hoping that the first manned ship on Mars will be "The Ends of Invention".... ;-)

> Edit: I'm hoping that the first manned ship on Mars will be "The Ends of Invention".... ;-)

Problem with Mars landings is the high turnaround time - while you can see what failed and fix it in a matter of days to weeks on Earth, with Mars you're looking at months to years of having another attempt.

Wonder how they'll get it done - practice on Moon first?

The Moon is not a super useful analog. It lacks any sort of atmosphere. Mars has just enough atmosphere that you have to deal with it, but not enough of one to be especially useful (parachutes buy you a little, but not much).

In fact, some of the best data and tests we have about landing big things on Mars come from SpaceX's first stage booster landings. The burn that the first stage does at the edge of space to slow down is in an environment very similar to that of the Martian atmosphere.


The Moon isn't a useful analogy precisely because the Martian atmosphere does make a significant difference. Just not enough to allow parachute-only soft landings. I've seen the 'thick enough to be annoying, too thin to be useful' meme before but it doesn't really match reality.

For example Pathfinder decelerated from 7.3km/s to 0.4km/s purely using it's aeroshell, before it even deployed the parachutes[0]. Now 0.4km/s is still pretty fast, but a saving of 6.9km/s dV is absolutely enormous.

Red Dragon was only possible because, with modifications to the capsule aerodynamics, the Martian atmosphere would brake the capsule enough for it to soft-land on the SuperDracos. There's no way a Dragon could usefuly soft-land on the Moon. It's just way too heavy for it's size. All that thick capsule hull is just dead weight for an airless environment. Given it's high dry mass the rocket equation demands huge amounts of fuel to compensate. The parameters are all wrong for the Moon because it's designed to use atmospheric drag to do most of the work.


Good points. I've always taken the spirit of that saying to be more like "thick enough to have to deal with, too thin to be enough".

On the moon, you don't have to worry about reentry at all, so no need for a heat shield or any sort of aerodynamic protection, just some way to do a propulsive landing.

On earth, you need the heat shield and some aero considerations, but you can land safely with parachutes alone.

On mars, you need to deal with reentry but also some sort of propulsive landing system for anything of reasonable size.

It's great and useful for smaller probes but as we've sent larger and larger probes the thin Martian atmosphere has been less and less useful. One of the major issues is that the mass keeps going up but the surface area of the heat shields we can reasonably bring along doesn't scale as well. There's some hopes in inflatable technologies though.

That is a good point. Red Dragon was only feasible by adding an asymmetric sled under the capsule to provide lift, so it could spend significantly longer braking through the atmosphere. Also the ITS video and presentation shows it using it's lifting body design to maximise time up in the atmosphere. At that scale straightforward aeroshells don't cut it, but you can still get a useful effect.

The error we're doing is trying for things to be perfect: sending our best people on our best ships to a possible death.

We should do it like old times: get team B, C, D and E and send multiple ships. Even with 75% failure we get one success. And the best are still alive on earth to advise those in space.

Same problem with health in space: we send people in peak Earth physical condition. Perfectly adapted to 1G with no radiation. Why don't we try sending people with what are considered physical defect on earth there and see if they're better adapted to space?

> Why don't we try sending people with what are considered physical defect on earth there and see if they're better adapted to space?

That sounds interesting actually. What if we sent up some handicapped people, or people with amputated limbs? Missing legs might be a burden on Earth, but a benefit in space.

Nice catch. I have read several of the culture books and didn't put that together. Going to read Player of Games next now!

Player of Games is good, but I suspect you'll be disappointed if you're coming from more complex titles like Matter or Use of Weapons. Excession is one of my favorites that's not quite as dense as the rest of his work.

Massively off topic, of course.

To continue offing the topic: Use of Weapons greatly irritated me. You spend all this time getting to know the guy through flashbacks, then at the end Banks pulls a bait and switch "No it was really the other guy all along!" The book makes no sense with that ending.

Quite the contrary, it does make far more sense with that ending. The whole book is centered around that.

It is, by far, my preferred Culture book and the one that apply the best today.

Nice compilation, definitely some segments I don't remember seeing before.

With those out of the way though... they've attempted 10 landings so far this year and all have been successful. Third flight of a reused booster is planned for early next month.

...and fingers crossed for seeing all three cores from the Falcon Heavy test-flight making successful landings.

> definitely some segments I don't remember seeing before.

I'm bummed there isn't a better video of the March 2016 SES-9 failure (the only shot in this video is the droneship on the horizon).

That was the landing that punched a hole in the deck of the droneship.

My god, finally something that explodes as easily as all cars do in the movies.

Haha, it's a running joke in our family that American cars are made from TNT. Cars on British TV just crash, they don't explode.

I thought the same thing when that rocket slowly tipped over and still completely self-destructed. I understand rocket fuel is volatile, but wow.

Everything burns around liquid oxygen.

Are we sure those are not intentionally/automatically triggered explosions?

The grasshopper flight that flipped sideways then exploded was blown up by the flight termination system. The rest of them are just pressurized tanks of propellant rupturing in the presence of fire and/or red-hot metal.

Landed orbital rocket boosters are all alike; every unlanded orbital rocket boosters is unlanded in its own way.

"I didn't want to be the CEO of SpaceX, I wanted to be a Lumberjack." - Elon Musk

Skidders and trucks in the mud vs rockets and barges. Same difference. The toys he gets to play with are just different. Probably way less dick jokes, facial hair and steel toe boots on a SpaceX job-site though.

> Probably way less dick jokes, facial hair and steel toe boots on a SpaceX job-site though.

You don't think these folks are wearing safety tipped shoes and cracking dirty jokes from time to time?


There's an direct relationship between ease of oversight and joke PCness.

Twenty dudes in the middle of nowhere turning trees into a piles of logs are gonna be way more fun to hang around with than a team who's supervisor's supervisor could easily drop by.

Follow some people who work odd hours on Snapchat/IG. Way more screwing around happens on 3rd shift than 2nd or 1st.

IMO the morale boost of allowing people to screw around (relatively speaking) during normal operations offsets the material decrease in productivity because people are more willing to work hard in cases where you need maximum productivity.

On other threads about Uber and SoFi I think they call that a "frathouse culture" which must be cleansed by fire.

> I think they call that a "frathouse culture" which must be cleansed by fire.

The culture needed varies based on the nature of the work.

What works in an office doesn't necessarily work on a jobsite and vise versa. Even then it varies by the nature of the job. The typical "condom full of acetylene" would probably not go over well in a workplace that specializes in something highly regulated.

Huh. I can have fun at work without telling dick jokes.

It generalizes to other jokes and behavior that would be seriously pushing it in a SV office workplace setting.

"Oh, Elon! I thought you were so manly!"

It reminds me of the collection of failures film in the Redstone and Mercury projects. That said, it also shows how closely managed the release of this video was, after all when you just had a tweet from Elon and no pictures and lots of questions, all you got were crickets.

I am glad they finally made it out, if only in partial form, for folks to see. Landing is hard, and there was a lot of things that didn't work. And it is way more open than Blue Origin and their less successful flights.

They make it look so easy now.

In 20 years time we will be saying in amazement "you mean they used to just throw away the boosters after each launch?".

Bravo spaceX.

I remember first hearing about it and thinking it was science fiction, unable to really be achieved.

Glad to be wrong.

April 2015; this one looks good enough... then it explodes too.

It had a _lot_ of lateral movement at touchdown. A "sticky" valve slowed the engine's response to throttle commands. That led to a feedback loop as it got further and further behind (you can see it gimbaling significantly back and forth).

But it was almost slow enough to not explode.

Once it tipped over, it was going to explode. You can see the cold gas thruster at the top trying desperately to keep it upright, but it was just too off-axis, and had too much lateral momentum.

Now I would like to see them attach 7 boosters together in a hexagonal pattern and get them all to land safely.

The Falcon Heavy is basically attaching 3 boosters together in a line. Unfortunately for your vision, the Falcon Heavy boosters separate and land one-by-one as individual boosters.

Your idea does make some intuitive sense. While lifting the single booster and even with just one of 9 engines turned down to minimum throttle, when the payload is gone and the tanks are near empty there's an enormous excess of power. The minimum thrust-to-weight ratio is still like 2:1. This means you have to run a "hoverslam" profile which reaches zero velocity precisely at the deck, otherwise you'll take off again. And it means you come in terrifyingly hot and fast, resulting in the explosions in the linked video.

With 7 boosters strapped together, you'd think there could be a more appropriate ratio of power and mass, which would enable a more controlled, sedate, hover-and-land profile. If the current 40% throttled down single-engine, single-booster TWR is 2:1, 3 engines would give you a 0.86:1 to 2.14:1 TWR. They could even turn on 3 engines at the outer corners in an equilateral triangle, and use both gimballing and differential thrust to control your descent.

It should be easy. You'd just get some struts and select hexagonal symmetry...oh wait, no, that's KSP. In reality, landing 7 boosters at once with a near-unity TWR would be much more expensive in terms of fuel. You want a hoverslam profile that's almost too fast to control, because then you can get your payload higher and faster. Right now, with the single 9-engine booster, they sometimes burn 3 of the 9 engines to land (giving a >6:1 power-to-weight ratio). They do this when they're short on fuel because for every second that they are airborne, they're suffering a 9.8 m/s hit to their delta-V. They want to come down as fast as possible to minimize time in the air.

my plan would be to separate the boosters too, you just need them stuck together at launch.

or another plan would be to keep them together all the way to mars, and you have a habitation unit above the boosters which is their combined surface area.

when you launch the habitation unit you can later land another one next to it the to tile them together.

They seem very fragile?

The one at 0:49 exploded just from tipping over.

Perhaps because they're huge i guess.

They are literally thin walled fuel tanks with some rocket engines strapped to the bottom. A soda can dozens of meters tall would be an appropriate analogy.

They're probably only built to withstand forces associated with a nominal launch to save on weight; being able to withstand tipping over is unnecessary if you can avoid tipping over in the first place.

Every pound of weight you add to the rocket is a pound of payload that you can't put into space.

It's not technically 1:1 on the first stage. It varies a bit from launcher to launcher, but it's in the ballpark of 4:1 (you lose a pound of useful payload for every four pounds you add to the first stage).

Your point is spot on though. Don't waste mass to account for failure modes that you can just avoid in the first place by landing upright.

> They seem very fragile?

They're extremely fragile. In fact, they're stored pressurized because laying on their side would damage them without the pressure keeping the walls rigid.

My understanding is that they don't need pressurization while being stored, but do need it to withstand flight loads. This is in contrast to, for example, the older Atlas rockets, which had to be pressurized constantly and would collapse otherwise.

Of course I can't find any authoritative source on this, although there are a lot of random internet folks like myself repeating the claim. And I guess I'm throwing one more on the pile here.

You're correct - the Atlas (ICBM as well as the current Centaur second stage) design that requires constant pressurization is known as a balloon tank.[0] SpaceX doesn't use balloon tanks, but it does pressurize tanks with nitrogen during transport to keep the tank walls rigid and prevent damage.

[0] https://en.wikipedia.org/wiki/Balloon_tank

Why nitrogen? Is air too corrosive?

I unfortunately can't find an authoritative source, either, but I recall a /r/SpaceX discussion where it was stated that hurricane prep includes maintaining power because they're (lightly) pressurized at all times.

I wonder if they might maintain pressurization to increase strength in the event of some mishap, but it's not an instantaneous disaster if pressurization is lost.

I recall reading that they have equipment to maintain pressurization while the boosters are trucked to the launch site as well, so it's not just flight loads, in any case.

Yeah, they aren't balloon tanks (which absolutely require pressurization), but they do keep them pressurized as it improves their structural stability.

They're pressurized with nitrogen generally, just to keep them clean and dry inside. They're quite capable of standing or lying down while unpressurized though.

Huge and thin. Proportionally, the walls are thinner than a soda can's.

There’s now a high res version at https://www.youtube.com/watch?v=bvim4rsNHkQ . Could a mod update the URL for this story?

Direct link to video for fullscreen view:


that's only the first minute. robin_reala has a full-length youtube version that's also high definition.

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