
SpaceX nails triple booster landing after satellite delivery - support_ribbons
https://www.bbc.com/news/av/science-environment-47903788/spacex-nails-triple-booster-landing-after-satellite-delivery
======
DennisP
This really looks good for launch costs long-term.

The Heavy costs $90 million per reusable launch with a 64,000 kg payload, or
$1400 per kilogram.[1]

Current versions of the Falcon 9 and Heavy can fly ten times with virtually no
refurbishment between flights.[2] The only part they throw away is the $7.5
million upper stage.[3] Their expendable cost is $150M and they haven't really
started reusing yet, so if they actually reuse each rocket ten times, they
have a lot of room to lower prices; ten launches would be $($150M - $7.5M) +
($7.5M * 10) = $21.75M per launch, or $334/kg for the rocket itself. Launch
cost won't be quite that low because they also have labor, fuel, and so on,
but it looks like they can get well under $1000/kg just with the Falcon Heavy.

The larger and fully-reusable BFR should do even better.

[1]
[https://en.wikipedia.org/wiki/Falcon_Heavy](https://en.wikipedia.org/wiki/Falcon_Heavy)

[2] [https://www.space.com/spacex-falcon-heavy-triple-rocket-
land...](https://www.space.com/spacex-falcon-heavy-triple-rocket-landing-
success.html)

[3] [https://www.nextbigfuture.com/2019/04/spacex-
recovered-6-mil...](https://www.nextbigfuture.com/2019/04/spacex-
recovered-6-million-fairings-so-falcon-heavy-will-
be-92-reusable.html#more-155979)

~~~
baq
the fully reusable falcon heavy can IIRC only lift about 8000kg to LEO.
expendable is volume-limited but if you want to lift a concrete block, you can
:)

~~~
JshWright
Reusable is 8000kg to GTO, not LEO. LEO performance in fully reusable
configurations is 30+ tons.

~~~
DennisP
So assuming 32 tonnes it's $668/kg for the hardware (assuming full payloads).

Probably also have to build in enough slack for occasional failed landings,
but we don't know yet what the failure rate will be after the kinks are worked
out.

~~~
JshWright
You'd be hard pressed to fit 32 tons inside Falcon Heavy's fairing. It's far
more likely to be volume constrained than mass constrained when flying to LEO.

~~~
grey-area
That could bring satellite costs down a lot though - if launches are cheap and
not weight limited a cheap steel frame satellite with heavy solar panels
becomes feasible - all the old rules about building to optimise weight and not
price go out the window.

I wouldn’t be surprised if spacex also enter the satellite building business
after mass producing starlink.

~~~
DennisP
And that makes solar power satellites more feasible, especially with the BFR.

Musk has expressed skepticism, famously asking "what's the conversion rate?"
The answer is that microwave transmission is 40% efficient with today's
technology. This isn't bad considering that average daily sunlight in geosynch
is five times higher than on the ground,[1] and you don't need much storage or
backup.

The early SPS designs were hugely expensive monolithic beasts, but current
designs use lots of identical parts (of several varieties) that self-assemble
in orbit, so you get economies of scale with factory production.

A year ago I read the book _The Case for Space Solar Power_ [2], which broke
down the costs in detail. With pre-SpaceX launch costs they got 15 cents/kWh,
including manufacturing and ground stations. I plugged in the BFR cost Musk
was claiming (I think I used $50/lb) and got about 4 cents/kWh.

[1]
[https://en.wikipedia.org/wiki/Solar_irradiance#Irradiance_on...](https://en.wikipedia.org/wiki/Solar_irradiance#Irradiance_on_Earth's_surface)

[2] [https://www.amazon.com/Case-Space-Solar-Power-
ebook/dp/B00HN...](https://www.amazon.com/Case-Space-Solar-Power-
ebook/dp/B00HNZ0Z96)

~~~
nostrademons
Hmm, what's the cost to put solar panels in heliocentric orbit? Dyson spheres
anyone?

------
bbojan
Not only that, but apparently they recovered both fairings:
[https://www.google.com/url?sa=t&source=web&rct=j&url=https:/...](https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.teslarati.com/spacex-
falcon-heavy-fairing-recovery-
starlink/amp/&ved=2ahUKEwjojrSJwsrhAhVkiOAKHdmCDVYQyM8BMAB6BAgFEAQ&usg=AOvVaw1M3yDSNH7xzYKQG9Hcdd1Z&ampcf=1)

So 5 out of 5...

~~~
taneq
I guess salt water isn't that much of an issue after all?

~~~
jessriedel
Yea, I wish we'd get a more detailed explanation of the accounting on this.
For all I knew it was totally plausible that fairings would be destroyed by
sea water, and it was also plausible there'd be no damage. The part that
confuses me is why they would spend so much effort trying to catch them with
Mr. Steven if they are in fact serviceable after a swim. Maybe the idea is
that salt-water refurbishment-and-reuse saves a bit of money compared to
expendable, but mid-air-catch would have saved more but turned out to be too
difficult?

~~~
wazer5
I think their customers would be more comfortable with (re)using a Caught
fairing, so that was Plan A. Also not all fairings are the same. Most have
acoustic blankets and other components that need to maintain strict ratings.
Remember, many payloads are more expensive than the rocket and the fairing
requirements are usually margined-up by the satellite manufacturer to avoid
blame for failure.

------
martythemaniak
There's a great media thread on reddit where people post their own photos and
videos:
[https://www.reddit.com/r/spacex/comments/bbhz9a/rspacex_arab...](https://www.reddit.com/r/spacex/comments/bbhz9a/rspacex_arabsat6a_media_thread_videos_images_gifs/)

Here's a great video of the entire flight and landing of the side boosters in
one shot, made with custom tracking software:
[https://www.youtube.com/watch?v=cEZZkEXAD6Q](https://www.youtube.com/watch?v=cEZZkEXAD6Q)

~~~
hcrisp
The boostback burns in that video are amazing. Lots of dynamics in what looks
like a shock-induced interface of the rocket exhaust and hypersonic
atmosphere.

------
mhandley
Nice video capturing the sonic booms from the booster landings here:
[https://twitter.com/jefffwilliams/status/1116486329284595717](https://twitter.com/jefffwilliams/status/1116486329284595717)

~~~
misterprime
Yep, shared that with the office and family. That's amazing. It really does
feel like the future.

------
raehik
Big fan of making technical spacecraft manoeuvres sound like cool skateboard
tricks.

~~~
trollied
I'm more impressed by the booster landings though :-)

Seeing a launch/landing in-person is on my bucket list.

~~~
Joe-Z
I saw the live stream yesterday and when the two side boosters landed side-by-
side synchronously it was almost as if it was out of a movie. We are living in
the future!

~~~
qmarchi
On this launch, it looks like they offset the timings to reduce the chance of
tipping over.

If you get time, go look for the first FH booster landings. The timing is
almost perfect and the long exposure images looked beautiful.

~~~
pedrocx486
>On this launch, it looks like they offset the timings to reduce the chance of
tipping over.

On reddit a lot of people enphasised that it was to avoid interference. Which
interference, no one knows.

~~~
that_jojo
Incorrect. _Gift that you give to me_ , no one knows,

------
joeblau
Every single time I watch a successful SpaceX launch I get chills and also get
so excited. Congrats to everyone who has worked on this.

------
goshx
I was at Kennedy Space Center's Apollo/Saturn V viewing site for this launch
and it was amazing. If you ever have the opportunity to be there for a Falcon
Heavy launch, do yourself a favor and go. It's quite an experience and totally
worth the money.

~~~
ambicapter
Yeah, if you have a week of free time. I planned to go this weekend but
chickened out at the last second-turned out in my favor since they launched
yesterday, four days after the original date.

~~~
goshx
Yes, there may be delays or they may postpone the launch. I went on Wednesday
and decided to stay one more day for yesterday's attempt and I am so glad I
did. It was worth it.

------
hoorayimhelping
Here's the video cued up to the booster landings:
[https://youtu.be/TXMGu2d8c8g?t=1643](https://youtu.be/TXMGu2d8c8g?t=1643)
with the main core landing a few minutes later.

If it's not obvious, the main core landing was much harder this time around,
because of how fast it was going due to the two boosters imparting a lot of
extra speed on it before they separated. If you think about it, it'll have
somewhere between 1x and 3x the velocity of a normal Falcon 9 core

~~~
gnode
It doesn't necessarily make it harder. There's a burn to slow the booster down
for re-entry, and having the side boosters do a lot of the work means more
fuel / delta-v can be saved to slow the core booster.

The FH is apparently capable of 8,000kg in a reusable GTO launch (
[https://en.wikipedia.org/wiki/Falcon_Heavy#Capabilities](https://en.wikipedia.org/wiki/Falcon_Heavy#Capabilities)
), and this satellite was only 6,000kg. So it looks like there would be plenty
of fuel available to slow the core down well below the survivable maximum.

~~~
ravedave5
It's the same steps but it is harder, the center booster was going faster than
any other core that has been recovered. The recovery itself was ~300 miles
further out than any other recovery.

Swinging a bat at a 10mph ball is the same technology as swinging at a 90mph
one. I don't think anyone would say that they were equally as easy.

~~~
gnode
My point is that it's less a question of technical difficulty / tolerance, but
more fuel / delta-v / mass cost.

In the case of a bat swing, to bat the ball faster, your muscles need to be
stronger, and the ball and bat need to withstand greater pressures. In the
case of a vehicle travelling through space / thin atmosphere, it only needs
more fuel to burn to slow it down. Analogously, you don't parallel park a car
from 70mph, having travelled somewhere on a highway.

Here's a graph a booster's speed over time, showing the reentry burn:
[https://i.stack.imgur.com/xFYIh.png](https://i.stack.imgur.com/xFYIh.png) (
from [https://space.stackexchange.com/questions/20246/what-is-
this...](https://space.stackexchange.com/questions/20246/what-is-this-debris-
on-the-crs-10-reentry-at-t630) )

------
narrator
Can we finally stop having sci-fi films in which the whole outcome of the
movie is solely determined on some heroic manual flying of a spaceship while
simultaneously using manually aimed weapons like it's World War II?

~~~
bergoid
The Apollo 13 astronauts would like to share a couple of anecdotes with you.

~~~
jniedrauer
Apollo 13 (the movie) had plenty of careful checklist readbacks and minimal
explosions or shaky cameras. Most scifi is more like Michael Bay in space. See
Gravity for a more egregious example of a movie that tries to play itself off
as "hard scifi" but ends up just being an over the top action movie.

~~~
TremendousJudge
Yeah, The Martian is like, the hardest sci-fi book I've ever read, but I found
the film adaptation... lacking

------
rjf72
I find this, and SpaceX, so inspiring. It's easy to feel that technology just
moves itself forward. After all there are billions of people on Earth with
people working on a countless array of different problems. And each day things
seem to move forward, almost inexorably so. And so it's easy to feel that the
value of the individual is really relatively low.

Yet imagine a world where Elon did not exist and thus SpaceX did not. Much of
what he's done is stuff that we could have been working on decades ago. For
some time we were. NASA as early as the 70s had already laid out plans for a
Mars expedition including a tremendous space ship that would be assembled and
fueled in orbit to take 5 man crew on a 600 day manned expedition to Mars,
including landing of rovers similar to the moon.

Those plans got canned by Nixon, and space never really recovered. Not only
did we not "inexorably advance" in space, we regressed. Today we're struggling
to do a manned flyby of the Moon - when we went to having barely put a man in
orbit in 1962, to putting a man on the moon in 1969. The point of this is that
technology does not advance by itself, let alone inexorably so. I think it's
extremely likely that had SpaceX not come to exist, it's entirely possible
that we would still be effectively where we were at near the turn of the
century.

Progress of our species, in spite of there being billions of us, is still
dependent upon the individual. And SpaceX's plans have very much followed the
old quote of Gandhi, "First they ignore you, then they laugh at you, then they
fight you, then you win." But of course we've not yet won. As remarkable as
this achievement is, it's but the starting line for where we need to be. And
that line will not move forward unless we move it forward. But "we" does not
mean waiting for somebody else to do so. As SpaceX and Musk have demonstrated,
it's ultimately up to the individual to get up and move that line forward --
for the betterment of all.

~~~
chasd00
if you want to talk inspiring, consider Gwynne Shotwell. She's tasked with
turning Musk's crazy ideas and timelines into reality. I can't imagine a
tougher job and she's killing it.

~~~
TremendousJudge
I always read about Musk like he does the whole thing on his own. Never read
about all the engineers that work their asses off to achieve these results

~~~
sharcerer
The way I see ot, ot goes both ways. He has taken a lot of shit for
Tesla,SpaceX so obviously when something good happens then too he gets a lot.
The dynamic is a bit similar to actors/actresses in movies. If it flops,
nobody is blaming the makeup artist,dialogue writer. Btw, i do find some
things related to Elon's life overglorified(those parts do not involve
SpaceX,Tesla) BTW, read this thread about Tom Mueller.
[https://mobile.twitter.com/mekkaokereke/status/1081619342377...](https://mobile.twitter.com/mekkaokereke/status/1081619342377156608?lang=en)

Really inspiring. This thread got picked up by many news sites. I just googled
"spaceX engineer lumberjack" to find this.

------
maxerickson
Large existing discussion at
[https://news.ycombinator.com/item?id=19639965](https://news.ycombinator.com/item?id=19639965)

~~~
oska
For some reason the discussion in this thread is far better than the earlier
one you linked.

------
plutonorm
I wonder how they do the booster landings?

Is it precise modelling and standard control algorithms, or something more
exotic like neural networks?

~~~
sonium
It's done using convex optimization

[https://www.nap.edu/read/23659/chapter/10#39](https://www.nap.edu/read/23659/chapter/10#39)

~~~
amelius
How is "booster landing" mapped to a convex optimization problem?

~~~
theoh
Lars Blackmore, who works for SpaceX, has a page about the techniques that are
used here:

[http://www.larsblackmore.com/losslessconvexification.htm](http://www.larsblackmore.com/losslessconvexification.htm)

See also: [https://www.aa.washington.edu/facultyfinder/behcet-
acikmese](https://www.aa.washington.edu/facultyfinder/behcet-acikmese)

~~~
dom96
Can anyone give a ELI5 (for developers) of how this technique works?

~~~
theoh
The control parameter space for the rocket is non-convex because, for one
thing, it can't be throttled down close to zero thrust. You can think of the
parameter space as having a hole in it. An optimal control algorithm might
want to make very delicate low-thrust corrections, but that's not possible.

This technique is based on "the idea of relaxing the nonconvex control
constraints to a convex set in such a way that the optimal solution to the
relaxed problem is guaranteed to be the optimal solution to the original
problem."

By "relaxing", what they mean is that the new model (the convex set) actually
contains some parameter values that aren't achievable, but OTOH it is
geometrically susceptible to being analyzed by an efficient optimization
technique. So it's a clever replacement of a hard problem with an easier one.
The complex bit, which I don't understand, is how they show that this
replacement will always give the same value as if they had solved the (real)
hard problem, i.e. that the solution will never actually use the "illegal"
parameter values.

Maybe someone else can give more insight.

~~~
CarVac
I read a paper on this—it's convex because any optimal trajectory will have
the engines at full throttle whenever they're on, so they just fill up the
parameter space, confident that illegal values will never be required.

~~~
chasd00
can you link to the paper please?

~~~
theoh
I don't know which paper they mean, but here's a relevant paragraph from one
of the papers available from Blackmore's page:

"In this paper, we unify the convex optimization approaches of [1], [2], [17]
and extend them to handle thrust pointing constraints. While convexifying the
problem with nonconvex thrust pointing constraints, we develop a geometrical
insight into the problem that establishes a connection with “normal systems”
[18]. A normal linear system is defined in the context of optimal control
theory where the system is said to be normal with respect a set of feasible
controls if it maximizes the Hamiltonian at a unique point of the set of
feasible controls. In the case when the set of feasible controls is convex, a
system being normal implies that the Hamiltonian is maximized at an extreme
point of the set [18]. Our convexification result has a similar geometric
interpretation since it establishes lossless convexification by ensuring that
the Hamiltonian is maximized at the extreme points of a projection of the
relaxed set of feasible controls. This set is then shown to be contained in
the original nonconvex set of feasible controls, thereby estab- lishing that
we can obtain optimal solutions of the original nonconvex problem via solving
its convex relaxation."

------
usermac
I wonder what emergency procedure is in place in case the landing is off-
course. Does it blow itself up?

~~~
fabian2k
As far as I understand, the Flight Termination System is safed before the
landing burn. It's more dangerous to have it potentially still active after
landing. So at this point it can't blow itself up anymore.

Until the last moment it also doesn't target the barge itself, but slightly to
the side. Only very shortly before landing does it correct the target to the
actual landing position. So in most cases it would simply hit the water
instead of anything else when there is a major issue.

~~~
Klathmon
If you watch the livestream for yesterday's falcon heavy launch on youtube the
second camera angle is a rendering showing trajectory, and you can actually
see the center core adjusting closer and closer to the droneship with each
step as it gets more confident that it's able to land safely.

------
ineedasername
Can someone explain why reusable mode can't lift as much?

~~~
JshWright
Because it has to reserve fuel for landing.

------
andy_ppp
Am I going mad I only see two booster landing in the video?

~~~
benplumley
On the live stream, the video feed cut out for the landing of the third
(middle) booster.

~~~
ben_bai
This almost always happens. It's really hard to keep a stable satellite
connection, while a 150ft. booster is blasting the deck with the exhaust from
3 firing rocket engines.

~~~
JshWright
It doesn't fire all three engines down to the deck. The landing burn starts
with one engine (in order to have more control authority when the two outboard
engines start up), then two more engines get lit, then they shut down shortly
before the actual landing (reducing the TWR makes the landing a bit easier).

------
Timpy
The way the text appears with a downward-drawing red line really steals my
attention. There are rockets on screen and I kept having my eyes avert to the
fragmented text in the bottom left corner. I had to watch the video twice to
keep my eyes on the rockets. I'm thinking of the UI/UX implications, subtle
and effective.

~~~
senko
It's just a newsflash, the rockets themselves are a backdrop.

For the real thing, watch the SpaceX video directly from YouTube:
[https://youtu.be/TXMGu2d8c8g?t=1181](https://youtu.be/TXMGu2d8c8g?t=1181)

