
SpaceX Soft Lands Falcon 9 Rocket First Stage - cryptoz
http://www.spacex.com/news/2014/07/22/spacex-soft-lands-falcon-9-rocket-first-stage
======
Crito
The video is pretty cool, but make sure to read the rest of the page. Most
exciting of all is this last note: _" We will attempt our next water landing
on flight 13 of Falcon 9, but with a low probability of success. Flights 14
and 15 will attempt to land on a solid surface with an improved probability of
success."_

That "solid surface" will presumably be a barge. Very exciting stuff.

Edit: The "loss of hull integrity" also answers a common question of _" why
not use parachutes"_. Even if they could land the stage softly enough with a
reasonable amount of parachutes, the stage has trouble surviving tipping over
in the ocean after landing. It needs to land and remain upright, but using
parachutes you will often get some lateral velocity that would cause a tip-
over. They need more control than parachutes can provide (and that's all
ignoring the problems of salt water).

~~~
grecy
> _" We will attempt our next water landing on flight 13 of Falcon 9, but with
> a low probability of success."_

I'm wondering why the next water landing has a low probability of success?

~~~
davidrhunt
I believe it is because of this:

> _However, our next couple launches are for very high velocity geostationary
> satellite missions, which don’t allow enough residual propellant for
> landing._

Based on the press release they plan on using Falcon Heavy for this type of
launch in the future but it sounds like that project isn't ready for primetime
yet.

~~~
grecy
I took that statement to mean they can't even attempt a landing on the next
couple of launches because there will not be enough residual propellant for
landing.

And then the next statement, I assume, refers to the next launches where they
_can_ attempt a landing.

EDIT: my assumption is confirmed here
[http://en.wikipedia.org/wiki/List_of_Falcon_9_launches](http://en.wikipedia.org/wiki/List_of_Falcon_9_launches)

Next up are flights 11 and 12, which can't be landed.

Then 13 has the "low probability of success".

~~~
greglindahl
Funny that you cite Wikipedia, which is citing... the link that this HN
discussion points to.

~~~
nkoren
Yeah, I actually made that particular edit to Wikipedia about 20 minutes
before seeing it cited as a _verification_ of that article, here. Funny to see
one of those infamous internet self-confirmation loops get established in
near-realtime...

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anovikov
What i don't understand is how are they going to solve the problem of landing
precision. The stage is passive from the retroburn (just after the stage
separation) for the several hundreds seconds it is flying back, and large part
of that trajectory is in atmosphere, and stage has a high sail factor: it is
big and, being almost empty, lightweight. So it might be dragged by wind too
far from the landing site to compensate in hover mode which is i assume only
100-200 meters or so, even if original entry trajectory is perfect. Ballistic
missile warheads for example, accumulate about 100 meters or error due to this
factor despite they are much smaller/have higher density and fly several times
as fast. A an additional short mid-flight engine burn to compensate may be a
solution but so far i haven't heard of that. Anyone has an idea?

~~~
Symmetry
I believe that's what the new grid fins they've been testing out on the
Grasshopper are for. Those are there to let the rocket steer even at the
speeds it comes in at.

[http://en.wikipedia.org/wiki/Grid_fin](http://en.wikipedia.org/wiki/Grid_fin)

~~~
toomuchtodo
They are! And they work well at both subsonic and supersonic speeds, just not
transonic speeds.

~~~
anovikov
No, these things are just for improvement of stability when descending.

But it seems that answer is aerodynamic control by partially (and
differentially) extending the LEGS. Which appears brilliantly smart and should
work. Same hardware, zero additional weight or cost, additional function.

~~~
toomuchtodo
"stability" = "steering"

------
jccooper
Better video from the first landing, despite the data corruption, than this
one, due to the ice fouling. Wonder why this one got iced? Clouds?

But even so, it certainly shows success. Can't wait to see 'em get a stage
back. That'll be amazing.

~~~
mmaunder
Icing is caused by supercooled raindrops freezing on the airframe. In this
case the spacecraft came from a very high altitude so I'd expect the airframe
to already be very cold and even if droplets aren't supercooled, they might
just freeze on the cold surface of the lens. Pireps (pilot reports) are
available globally where pilots report icing conditions they encounter. I
suspect the SpaceX engineers anticipated this possibility and decided that
they didn't want to add the extra weight and complexity of a heating or
deicing system to the lens.

I have a feeling someone is working there right now to come up with a quick
and dirty deicing system - considering how disappointing this video is. The
fluid system the Cirrus SR22 uses comes to mind.

~~~
infogulch
I think some kind of disposable multi-layered lens cover that peels off
automatically would work well. Pretty cheap, and easily replaceable. Effective
against more than just ice.

~~~
discodave
I propose a revolutionary solution: a lens cap.

I'm assuming that they only need the video from when they get close to landing
so the lens cap can be ejected once the rocket is low enough in the atmosphere
that icing is not a problem.

~~~
eyeareque
or some kind of heating element would work, too.

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larrydag
I've been super impressed with how efficient SpaceX is in getting launches
into orbit. I did a visual comparison to the Space Shuttle program. It looks
like SpaceX will overtake the Space Shuttle launch efficiency by the end of
the year.

[http://snag.gy/wUTD7.jpg](http://snag.gy/wUTD7.jpg)

sources:

[http://en.wikipedia.org/wiki/List_of_space_shuttle_missions](http://en.wikipedia.org/wiki/List_of_space_shuttle_missions)

[http://en.wikipedia.org/wiki/List_of_Falcon_9_launches](http://en.wikipedia.org/wiki/List_of_Falcon_9_launches)

~~~
tnorthcutt
That graph might be a little more intuitive if you swapped the axes, FWIW.

~~~
hughes
Definitely. Also choose colours that aren't almost identical.

~~~
Dylan16807
The blue and black don't look very close to me, and they're pretty color-blind
safe. Odd.

~~~
m_mueller
Don't underestimate the damage of bad screens, bad screen settings and people
blaming the source rather than their setup.

~~~
jfoster
Even just laptop screen brightness or glare can play a huge role here. I know
it's offtopic, but if anyone is aware of a guide or methodology for picking
colors that will be less susceptible to this problem, I would love to see it.

~~~
Someone
'Cheat' and use something else to differentiatie between the two, in addition
to color (line thickness, line dash, markers)

You probably should always do that, as you won't know where your chart will be
used (printed in black and white, very lossily converted to JPEG, whatever)

------
andrewtbham
> Flights 14 and 15 will attempt to land on a solid surface with an improved
> probability of success.

Anyone know when flight 14 is scheduled?

~~~
HarryHirsch
Where do you find a solid surface to land on except in Russia and China? You
would like to fly across water or at least unpopulated areas in case a problem
develops during flight and range safety needs to go for self-destruct. The
USA, Europe, India and Japan all do that, because no one wants a re-run of the
Long March desaster in 1996.

Flying back the opposite direction is no good because you are fighting the
rotation of the Earth and are paying with extra fuel to carry the fuel needed
to go back, besides coastlines are always the most densely settled areas of
any country.

I can't imagine that the economics will work out, but perhaps someone else has
genuine numbers to prove me wrong.

~~~
washedup
SpaceX owns some land in southern Texas. It seems that the initial idea is to
have a spaceport in Brownsville, TX, and use Cape Canaveral, FL, as the
landing location. In the mean time, they can practice by using floating
platforms in the Atlantic.

[http://www.faa.gov/about/office_org/headquarters_offices/ast...](http://www.faa.gov/about/office_org/headquarters_offices/ast/environmental/nepa_docs/review/documents_progress/spacex_texas_launch_site_environmental_impact_statement/media/SpaceX_Texas_Launch_Site_Draft_EIS_V1.pdf)

~~~
Shivetya
oh I am sure there are a few islands out there both inhabited and not so much
that would present some opportunities. Much easier to deal land on something
that isn't moving up and down, let alone side to side.

~~~
washedup
If launched from Texas, would they have to move side to side to land the first
stage in Florida?

~~~
Shivetya
my apologies for not be clearer, while the movement of the Earth is a concern
I was replying to the idea of trying to land on a floating platform which I do
not see as feasible. Both from the standpoint of trying to find such a small
location to the fact it is not going to be a stable landing area because of
wave action

~~~
coob
Would an old oil rig work?

------
nickhalfasleep
"it fell over, as planned"... great attribution of the fundamental nature of
gravity.

But mad props to SpaceX for working towards recycling their boosters.

~~~
m_mueller
I had a laugh at that as well. Idiocracy seems near if things like that need
to be mentioned in press releases.

~~~
elements
The shuttle SRBs floated vertically after splashdown, so I don't know why
someone would be dumb for thinking the Falcon 9 booster might do the same.

------
ilaksh
The hardest part is not running out of fuel on the way down. Old-school
science fiction often assumed something like nuclear power where that wouldn't
be a concern. Seems like for many years most people haven't even attempted
this full recovery/landing thing because of fuel and weight issues.

Has SpaceX really cracked that problem? What portion of flights on this
smaller rocket can do it? It says some missions won't have enough fuel left
over.

Will the Falcon 9 Heavy be able to do all or almost all missions with a
landing and full recovery at the end? How much fuel will Heavy have left on
average after a return? Theoretically it would not wait until the last
possible second to start slowing, and therefore use up almost all of the fuel
in order to give the descent a larger margin of error and also reduce the
possibility of damage, I assume.

~~~
jpgvm
Until now most information out of SpaceX has suggested it needs roughly 30%
propellant left in the first stage of Falcon 9 to attempt a retrieval.

Numbers are not yet known for the 2nd stage retrieval or Falcon Heavy. One
could probably assume a similar number for the first stage but possibly a bit
less given the Falcon Heavy's higher thrust/weight ratio.

~~~
m_mueller
From what I've read they need 30% _additional_ fuel at launch (as in a 30%
bigger first stage) - that's different than needing 30% left in the rocket
after separation. The reason being that to have X [kg] of fuel at Y [m]
altitude you'll need (1 + Z(Y)) * X [kg] of fuel at launch, with Z being some
function of Y. My gut tells me they'll need 15-20% max for retrieval, the 30%
+ is just to get it up there. Source: Play KSP.

~~~
jpgvm
Ahh good catch, thanks for the additional insight.

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russell
I did see a launch north over my town, about 80 miles north of Vandenberg. It
looked like the path was over the ocean all the way. The first stage was still
burning, so it was pretty spectacular.

Edit: oops. This was supposed to be a reply to the comment below about
launches from Vandenberg being mostly to the south.

------
crb
Will there be a video of the landing, as seen from Earth?

Is the rocket currently aimed "at the Atlantic", or are they operating with
the precision they need to land back where they took off from: and in that
case, do they have a camera pointing at the landing point from a ship?

~~~
dba7dba
Probably no video from the earth.

We won't be getting it for awhile. But I think maybe in about a year or 2 we
will get to see the video.

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Jacky800
I wish there is someone in the medical domain equivalent to Elon Musk.

~~~
mtm
Elizabeth Holmes is taking a stab at it:
[http://seattletimes.com/html/businesstechnology/2024121844_v...](http://seattletimes.com/html/businesstechnology/2024121844_valleyphenomxml.html)

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lefrancaiz
Why does the rocket tipping over cause a loss of hull integrity? Does that
mean that it actually exploded, just from going horizontal?

~~~
icegreentea
Probably not exploded, just that the lateral stresses that the rocket is
designed for.

Rockets have to withstand a lot of different types of forces (axial, all sorts
of vibrational, probably hoop type stresses), but massive lateral shocks
aren't really one of them.

~~~
mbell
> Probably not exploded

I don't know about that:
[https://twitter.com/elonmusk/status/488718649515986944](https://twitter.com/elonmusk/status/488718649515986944)

Even with minimal fuel, the tanks are still highly pressurized, a loss in hull
integrity would result is a rapid depressurization of those tanks. It may not
have been a fiery explosion, but I would bet it made a hell of a bang.

------
sargun
I'm curious as to why SpaceX, or their competitors haven't utilize Sky Cranes,
a la Mars Science Laboratory:
[http://en.wikipedia.org/wiki/Mars_Science_Laboratory#Sky_cra...](http://en.wikipedia.org/wiki/Mars_Science_Laboratory#Sky_crane_landing)
\- basically, it seems to be a powered parachute.

~~~
danielweber
The sky crane will probably never be used again. It was an engineering marvel
but the requirements that brought it into being were a management nightmare.
(Requirements to not use any carbon-based propellant directly on the surface
of Mars, which probably got violated anyway because you can still see blast
marks from the sky crane where MSL landed.) And it was only useful for one
very particular mass window -- much lighter and it wouldn't be useful, much
heavier and it couldn't work.

