
SpaceX Plans to Land Next Falcon 9 on Solid Ground - paulsutter
http://www.defensenews.com/story/defense/air-space/space/2015/04/15/spacex-ground-attempt-reusable-landing-sea/25827625/
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Cshelton
I think now that they have proven they can 'hit the hole', almost spot on,
they'll be able to get approval to go for a try on cleared land space. It
sounds like to me, landing on land would be ideal; less expensive and less
risk with stabilization and rough waters.

~~~
anigbrowl
Landing is an awful lot harder than taking off, it seems to me; a single
engine rocket with stabilizing jets is a bit like trying to land a pogo stick
- possible, but inherently problematic. I know this must seem stupidly
obvious, but I wonder if a better design for a reusable launch vehicle isn't 4
engines connected by a frame with the payload in the center, basically a
chair.

Yeah, it sounds horribly unwieldy with a bunch of structural challenges, but
the thing is it's self-stable in a way that a vertical column can never be. A
few years ago the wisdom was that small (remote control) helicopters could
only be flown stably with a coaxial main rotor. Quadcopters would work in
theory, but everyone figured 4 motors on an frame was going to be even more
complex to mange and that the stresses on the frame would likely weaken it too
much, the power-to-weight ratios wouldn't work out and so on and so on. Now
everyone is using quadcopter configurations because they are much easier to
control and not actually that difficult to build.

My naive opinion is that output has never quite been consistent enough from
rocket to rocket to make the idea of bolting multiple rockets together seem
worthwhile unless they were all part of a single fuselage; one of the four
would always be putting out too much or too little power and the whole
contraption would fly off course in short order. but since the SpaceX rockets
depend on liquid rather than solid propellant, and very precise pumping is not
that big of an engineering challenge these days, it seems like it should be
worth experimenting with on a small scale.

~~~
Lorento
It's always tempting with difficult control problems to imagine why not just
do what feels stable? Why not just hold it in place with something? Why not
make it shorter and wider? For an example of why not - compare a turtle to a
human. The human is inherintely unstable and its vital organs are exposed
through weak flesh. If we lose control of our unstable balance, we die when
our head hits the ground. The turtle is naturally stable and armor plated! But
which one is really best at surviving?

~~~
Tharkun
Given that turtles can live for hundreds of years...you tell me ;-)

~~~
unmole
Tortoises, not turtles.

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mrfusion
I don't think they can completely give up on the barge though. As I understand
it they'll always need barge landings for the Falcon Heavy core?

Maybe they're just itching to get a success on their pelt.

~~~
acadien
I agree, as others have said the dynamics of a barge is a necessary challenge
to prove the technology. But they need some more positive press, maybe a gif
that doesn't end in an explosion hehe.

On a side note the colloquialism 'success on their pelt' is totally new to me,
I've always heard it as 'success under their belt'.

~~~
js2
I don't believe there is any such idiom. The idiom is "under one's belt",
meaning to succeed at something. I have never heard, nor can I locate via
Google, any similar idiom using the word "pelt".

~~~
acadien
Yeah I suspected it was a typo or something, but I kind of like it...

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Already__Taken
> next attempt to land

Not the next F9 launch. They won't have legs the payload needs all the fuel.
Next launch after that is a Dragon test so it isn't that one either. Maybe
June we'll see that.

Those ULA comments at the end are very odd and contradictory.

~~~
benkuykendall
According to their events page, 22 July will be the first attempted (to use
their phrasing) ``land landing''.

[http://spacexstats.com/upcoming.php](http://spacexstats.com/upcoming.php)

~~~
ehmmm
That is not an official SpaceX website.

 _This website is not in any way associated with SpaceX._

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TeMPOraL
> _" Just purely the boat moving, even in a low sea state, it's hard to
> imagine that vehicle is going to stay vertical," Shotwell said. "That
> vehicle is big and tall, compared to the itty-bity-greater-than-a-football-
> field-size ship."_

Is this a new development? This contradicts both a lot of things I read over
the Internet (granted, those were not official SpaceX statements) and the
apparently still ongoing plans to build a second barge.

~~~
jsolson
If it's actually that serious a problem (and I'm not a rocket scientist, so I
don't know), it suggests a solution: stabilize the landing bed on the ship
relative to the sea. Perhaps have the bed float above the ship
electromagnetically such that you can control the field strength applied to
any part of the platform dynamically as the ship bucks underneath it.

There might be a reason that people don't let me design large mechanical
systems...

~~~
ohitsdom
Elon Musk actually joked/hinted (in a tweet) that they were making
modifications to the barge similar to the flying SHIELD helicarrier.

~~~
TeMPOraL
Heh, for some reason I always felt there's a connection between (Marvel's
Cinematic Universe) SHIELD and SpaceX.

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dayyan
Here's a much better quality video of the previous attempt:
[https://www.youtube.com/watch?v=rAzwuEmZcmE](https://www.youtube.com/watch?v=rAzwuEmZcmE)

~~~
benihana
That thrust vectoring!

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flountown
Are there any articles or press out there that describe the stabilization tech
used on the barge?

A lot of the things when looking through Google seem to focus on the
challenges of guiding the rocket but not stabilizing the platform.

I guess it tends to be a non-issue since it seems their plan all along was
landing it on land, but I'd be really interested to see the design story that
went into the barge.

~~~
mbell
There is nothing special about the barge stabilization, it's off the shelf
marine tech. A few azimuth thrusters controlled by a station keeping system.

The only unusual thing about it is that the azimuth thrusters are a lot more
powerful than would normally be put on a barge that size to give it better
positional control in rough seas.

~~~
flountown
I know this was a few days ago, but I forgot to check back. The reason I ask,
is that this company [http://seakeeper.com/](http://seakeeper.com/) used to be
a customer of mine. It seems like an extremely cool concept and I know it
works for smaller vessels and the company is currently developing larger
solutions for the government and oil industries.

~~~
mbell
This is what the SpaceX barge uses:

[https://www.thrustmaster.net/out-drive-propulsion-
unit/porta...](https://www.thrustmaster.net/out-drive-propulsion-
unit/portable-dynamic-positioning-system/)

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51Cards
I saw this on the planned launch schedule a few days ago. The date mentioned
there is 22 July 2015. I was surprised they were getting clearance to try so
soon since they haven't quite nailed sea landings yet. I guess it could be
argued they have seem to have the navigation part down pretty well though,
minimizing the odds they will drop this in a neighbourhood.

~~~
ErrantX
I guess the important part is that they've proven they can hit the target.
Thats the risky part of testing over land. One assumes that it's a recognised
risk that at the point of actually landing there is a risk of explosion, and a
land-based site will account for that.

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sergiosgc
Does this mean they'll be launching from another facility? Right now, the
trajectory goes over to the sea, and bringing the first stage back to dry land
is expensive. They'd have to launch far away from the east coast.

~~~
ridgeguy
There's a Falcon 9 launch from Vandenberg scheduled for July 22. VAFB is a
large coastal installation with lots of room for a return to land.

schedule: [http://spaceflightnow.com/launch-
schedule/](http://spaceflightnow.com/launch-schedule/)

read near the end of this story for a statement that booster return to land is
planned for the July 22 launch:

[http://www.nasaspaceflight.com/2015/03/spaceport-america-
spa...](http://www.nasaspaceflight.com/2015/03/spaceport-america-spacex-
reusability-testing/)

~~~
themgt
Sounds like a July 22nd party in Cape Canaveral is in order?

~~~
timfrietas
Vandenberg is actually in California :)

~~~
themgt
I meant a landing party! :) (I may be wrong about where they intend to land,
but see -
[https://en.wikipedia.org/wiki/File:New_Landing_Complex_1_sig...](https://en.wikipedia.org/wiki/File:New_Landing_Complex_1_sign_at_old_Launch_Complex_13_\(16619020720\).jpg))

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hahamrfunnyguy
Instead of moving the rocket to meet the platform, would it be feasible to
employ some stabilization mechanism so that the barge stays relatively level
and the rocket doesn't have to correct as much?

~~~
GeneralMayhem
If the goal is to recover a rocket from LEO, yes. If the goal is to use this
as a training mission to land a rocket on another planet, then no.

~~~
Narishma
Landing on another planet with the rocket's first stage?

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classicsnoot
Someone may have asked this already, but why not use some kind of system
similar to "mobile" oil rigs? The kind that float into place, partially
submerge, then tether to the sea floor? Seems like the best of both worlds to
me...

[edit]...It could also serve as the launching platform. In this way the
launch/recovery pad could be floated to the rocket, boarded and built, moved
into position near the equator, then launch and recover.

~~~
ptio
That's what Sea Launch used[1].

Note that the drone ship doubles up as a recovery vehicle to ferry back the
stage to land. Also a sea launch platform will be a permanent structure while
the drone ship's purpose is to be a test platform for landing on land.

[1]
[http://en.wikipedia.org/wiki/Sea_Launch](http://en.wikipedia.org/wiki/Sea_Launch)

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chinathrow
I just love the term "flight termination system". It sounds so much better
than "self destruction system" :)

~~~
travelton
Anyone know how this flight termination system works? Obviously it self-
destructs. But, under what parameters? Does Mission Control send the signal,
or does the rocket determine this on its own?

~~~
david-given
My understanding is that there's a bunch of automated triggers --- e.g. if the
vehicle leaves its flight corridor, it's supposed to get terminated. That
doesn't necessarily mean that it goes bang; for a vehicle like the F9,
shutting down all the engines is fine in most circumstances.

However, there is _also_ a Range Safety Officer with a hand on a big red
switch (or at least, a metaphorical hand on a metaphorical switch). They're
the final authority on whether the vehicle lives or dies.

The shuttle may or may not have had a self-destruct system in the orbiter
itself; I'm finding conflicting references. The SRBs and tank certainly did;
the RSO pushed the button after Challenger disintegrated on launch to stop the
SRBs flying away.

Yes, pushing the button while the SRBs and tank were attached to the orbiter
would have killed the crew. Being the RSO is a job for very sober, very
thoughtful people.

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soheil
Mojave Desert seems like a good candidate. I'd let them use my land
[http://www.ysoheil.com/2014/08/soheils-
village.html](http://www.ysoheil.com/2014/08/soheils-village.html)

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elchief
What was the % cost reduction in being able to land the boosters again? I read
it somewhere a while back but can't find it. It was pretty significant if I
recall. TIA.

~~~
mikeash
The first stage accounts for about 75% of the total cost of the Falcon 9, so
best case would be a 75% cost reduction. Any refurbishment needed before
flying again would reduce that, as well as whatever fixed costs there are for
a launch, like fuel, salaries for on-site workers, consumable launch pad
equipment, or whatever. Refurbishment is the big wild card. If the rocket is
ready to go again with no work then it could come close to that 75% reduction.
If it requires extensive work before it can fly again then it could be a lot
smaller.

~~~
elchief
Sweet, thx. That's a pretty big game-changer.

~~~
mikeash
Indeed. SpaceX is already one of the cheaper launchers out there, and cutting
their price by 1/2 or 3/4ths would be a huge deal. You can see why everyone is
so interested in their crazy barge landing project.

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solve
Shouldn't be that surprising. Military has been blowing up missiles and
detonating bombs on land at military testing sites for decades.

~~~
branchan
Yes but normally these missile and bombs are all isolated to these remote
areas. Imagine the rocket is launched from Florida, it might need to fly over
populated areas to reach its 'land' landing area, which is different.

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brianobush
How about an oil rig like structure at sea?

~~~
rtkwe
Those are expensive structures. Also there probably aren't spares lying around
that can be tasked and moved into the range.

~~~
msandford
Right now there are plenty of spares that can be had for cheap. With oil at
$50/bbl and offshore being more expensive than onshore, you can be sure that
there are jack up rigs (the kind you want) available. Here is a listing:
[http://www.worldoils.com/searigs/](http://www.worldoils.com/searigs/)

This is an old rig which you could probably get for less than scrap value
since it's going to take a bunch of effort to break it down into things which
you could actually re-melt.
[http://www.worldoils.com/searigs/jackuprig101.php](http://www.worldoils.com/searigs/jackuprig101.php)

Looking here, depending on where you park it that gets you anywhere from a
couple of miles offshore up to say 100 or more. It depends on the topography
of the ocean's floor.
[http://maps.ngdc.noaa.gov/viewers/bathymetry/](http://maps.ngdc.noaa.gov/viewers/bathymetry/)

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arman0
Dumb question: why can't they land (drop) into a large pool filled with some
inert liquid?

~~~
iSnow
Probably because a rocket engine is pretty hot on landing, so the thermal
shock upon contact with the liquid would deform it or cause cracks.

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jayfuerstenberg
Land the rocket on some flame-proof air bags. It doesn't have to land
vertically does it? Let it fall over gently if need be.

~~~
laggyluke
No flame-proof airbags are available on Mars.

AFAIK most of SpaceX's design decisions are based around this.

~~~
saganus
But can't the vehicle carry them to Mars? Kind of like the airbag system for
one of the rovers, can't remember which one (Curiosity?)

Or even better, how about getting it to land sideways on purpose? I don't see
how that would be more difficult than doing it upright.

~~~
noir_lord
Imagine the material that a coke can is made off.

Now imagine a cylinder made of that material 3-4 times wider than a barrel and
20-30ft high.

That's why you can't land them sideways they'd just crush themselves.

~~~
saganus
I guess you are right. It wouldn't make sense to make a rocket that can
withstand vertical AND horizontal forces. That would be like launching a brick
I guess.

Thanks for the pointer.

