
SpaceX’s Pad Abort Test - ggonweb
http://www.spacex.com/news/2015/05/04/5-things-know-about-spacexs-pad-abort-test
======
ghayes
At the Kennedy Space Center, NASA had an interesting abort procedure for
astronauts still on the ground at the launch site: an underground Rubber Room
which astronauts could slide down into.

[0] [https://scriptunasimages.wordpress.com/2012/11/23/inside-
nas...](https://scriptunasimages.wordpress.com/2012/11/23/inside-nasas-rubber-
room/)

[1]
[http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/2011001...](http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110012275.pdf)

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greglindahl
And to contrast this with the Orion capsule abort system: Crew Dragon's abort
thrusters will eventually used for landing, while Orion's (much heavier) abort
system is jettisoned 120 seconds into flight.

See
[https://en.wikipedia.org/wiki/Orion_%28spacecraft%29#Launch_...](https://en.wikipedia.org/wiki/Orion_%28spacecraft%29#Launch_Abort_System_.28LAS.29)
and
[https://en.wikipedia.org/wiki/Orion_abort_modes](https://en.wikipedia.org/wiki/Orion_abort_modes)

~~~
anovikov
Even if they are not used for landing, main thing is that they use same fuel
tanks as those used by Draco thrusters for orbital propulsion and deorbit, so
no weight is wasted (weight of the Super Draco engines themselves is not that
big). Overall payload loss for the abort system is about same as if using the
escape tower (ca. 800kg if i do my math right), but escape burn is possible
throughout the ascent, not just in the first 3 minutes, and there is no
additional safety risk from it (if escape tower failed to separate, astronauts
will be doomed, here there is no such risk).

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simonh
I know the SuperDraco's are designed to eventually enable a soft-landing back
on Earth. In this case they are only being used for the abort, and the landing
will be by Parachute, presumably the powered landing approach isn't ready for
testing yet. I understand the initial manned launches will use parachutes for
landing as well.

What I'm wondering is, will they eventually carry enough fuel to both be able
to do an abort, and then do a powered landing, if required? I assume so, since
at that point the only cost in terms of weight to be able to do the abort as
well as the landing would be the weight of the fuel for the abort itself.

Also if the capsule will be capable of an abort at any stage in the ascent,
what preparations will be in place to allow for capsule recovery? Presumably
it could come down anywhere along the line of flight, up to the point at which
it achieves orbit. That could include the middle of Africa, and maybe even the
Indian Ocean. Imagine a second stage engine failure.

None of these are criticisms of the system, it's fantastic engineering and
potentially a huge win over current options. Excuse me while I got and watch
Gravity again (while switching off the part of my brain that knows from KSP
how orbital rendezvous work).

~~~
snops
>What I'm wondering is, will they eventually carry enough fuel to both be able
to do an abort, and then do a powered landing, if required?

Even if it could, its important to note that the abort system would only be
used when something has gone drastically wrong, potentially an explosion,
which means you can't garuntee Dragon will be undamaged. In that case, would
you trust a complex powered landing, or a simpler parachute landing where you
have triple redundancy?

In addition, SpaceX launch on the coast and the rocket flies over the sea, so
an abort may end up with a sea landing. I haven't seen any concepts from
SpaceX showing a powered dragon landing at sea, and it would presumably
require a pretty calm sea state, while parachutes would work in any weather.
You could see similar problems with a powered landing on unfamiliar land, for
instance trying to "land" on a tree canopy.

~~~
jessriedel
Why would parachutes work better at sea? Just like a rocket, the parachute
stops providing useful upwards force as soon as the capsule touches
water/ground. The only thing I can think of is that it is probably easier to
add landing air bags to a capsule descending by parachute than by rocket, but
that's really only useful on land.

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Retric
Parachutes work better at sea than land; water becomes far softer as you
reduce speeds. Also, a powered landing on a 30 foot wave seems like a rather
complex problem not to mention buildings etc. Worse, powered landings have
little redundancy where a sea landing with 2/3 of your parachutes is not a
major issue.

I suspect a larger issue is seawater is not something you want anywhere close
to delicate equipment. But, for an emergency landing that's not much of a
concern. Anyway, I suspect these are designed so if either the powered landing
or the parachutes work the landing is survivable even if the craft is damaged.

~~~
simonh
The super-dracos are on the sides of the capsule, not the bottom, so should be
able to provide thrust all the way down to surface contact on land and sea.
Also the vehicle can suffer the loss of a thruster without compromising it's
abort or landing capability.

I don't really see that parachutes in 30ft waves are going to be all that much
beter than anything else, but don't manned launches have fairly strict weather
condition safety requirements? I'm pretty sure that would include sea states
in any conceivable abort landing zone.

One final advantage is that the vehicle can use the thrusters to manoeuver
prior to landing, potentially avoiding problematic terrain. In theory you
could probably designate a series of preferred abort destinations that are
within the vehicle's operational envelope for different stages of the flight.
So instead of ending up anywhere along a line, there would be a series of
preferred landing zones along or near the line.

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jessriedel
Thanks for the good point about manoeuverability when landing on bad terrain
during an unplanned emergency.

> don't manned launches have fairly strict weather condition safety
> requirements? I'm pretty sure that would include sea states in any
> conceivable abort landing zone.

You might be right, but note that all the shuttle abort landings sites were on
land at a handful of locations, in part because the shuttle was a glider (so
it had a decent amount of unpowered range) and in part because landing the
shuttle somewhere that wasn't planned was nearly impossible (since it needed
such a huge flat expanse to land). Therefore, you only needed to have a good
weather simultaneously at a few locations.

For the Dragon, however, the lack of gliding ability and the ability to land
anywhere in an emergency makes it infeasible to wait for simultaneously good
weather everywhere, simply because it might end up anywhere along it's flight
path in an emergency. So you probably need to be able to handle bad weather.

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jonlucc
> Buster the Dummy already works for a great show you may have heard of called
> MythBusters. Our dummy prefers to remain anonymous for the time being.

I'd love to know what the SpaceX test dummy's name is, but for now I'm going
to assume it's Edison.

~~~
eps
Unlike MythBusters, SpaceX is likely to have more than one dummy and, unlike
Nasa^H^H^H^HESA they tend not to make cutesy circus out of their projects,
e.g. avoid things like "Oh, hai, Twitter, I'm the Rosetta probe! Yuppie!"

So I suspect dummies will remain anonymous.

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codeulike
SpaceX named their recovery sea vessels 'Just Read The Instructions' and 'Of
Course I Still Love You', after the Iain M Banks sci-fi Culture ships.

~~~
madaxe_again
I wonder which of their vessels will win GCU Grey Area for its name.

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lotsofmangos
If Elon launches a space vessel named 'Grey Area', I either want to be on it,
or in a bunker.

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donpdonp
Thanks for this post. It makes clear this 'pad abort test' is really a test of
the amazing SuperDracos which could constitute their own launch system!
SuperDracos are partially 3D metal printed and can fire months after being
fueled.

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

~~~
greglindahl
Not just partly: from that Wikipedia article:

"It was announced in May 2014 that the flight-qualified version of the
SuperDraco engine is fully printed, and is the first fully printed rocket
engine. In particular, the engine combustion chamber is printed of Inconel, an
alloy of nickel and iron, using a process of direct metal laser sintering, and
operates at a chamber pressure 6,900 kilopascals (1,000 psi) at a very high
temperature. The engines are contained in a printed protective nacelle to
prevent fault propagation in the event of an engine failure."

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zachrose
> Crew Dragon will accelerate from 0 to nearly 100 mph in one second. The
> entire test is less than two minutes long, with Dragon traveling over one
> mile in the first 20 seconds alone.

That sounds totally insane, and yet at 4.5 g's was what the Apollo crews
experienced on a successful launch.

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jccooper
That's actually fairly mild, as these things go.

The Apollo lunar missions experienced max G forces of 6.5-7.2g during reentry.
(The Earth orbital missions only went to about 3.3g.) See:
[http://history.nasa.gov/SP-368/s2ch5.htm](http://history.nasa.gov/SP-368/s2ch5.htm)

Alan Shepard freaking flew Mercury 3 by hand during a 11.6g reentry.

Ejections seats are 12-14g or worse.

Of course, max G is only part of the equation; duration is the other. You can
handle really high forces if they aren't for long. Given the short duration
and lack of need to keep the occupants awake they could go a lot harder. I'm
actually a little surprised it's so gentle.

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ceejayoz
One of the Soyuz
([http://en.wikipedia.org/wiki/Soyuz_7K-T_No.39](http://en.wikipedia.org/wiki/Soyuz_7K-T_No.39))
hit 21.3g on re-entry.

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Animats
Mercury escape tower used when booster loses control, 1961.[1] Unmanned launch
with a dummy.

[1]
[https://www.youtube.com/watch?v=Vp9BnBDKa0s](https://www.youtube.com/watch?v=Vp9BnBDKa0s)

~~~
hcrisp
Apollo's launch escape system was tested using a rocket called Little Joe II,
which started spiraling unexpectedly due to a gyro problem causing the rocket
to fail. Fortunately the escape system worked as intended. [1]
[https://youtu.be/AqeJzItldSQ](https://youtu.be/AqeJzItldSQ)

~~~
ceejayoz
I wonder how many of those observing realized it wasn't part of the scheduled
test. What a lucky disaster!

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smoyer
As a general comment, I love watching SpaceX (for several reasons). The almost
monthly stream of announcements, flights and "firsts" reminds me of watching
the Apollo program progress as a young child. Then I was limited to seeing
what NASA happened to put on television since I couldn't read for the early
parts of the program. I'm finding reading briefs like this much more exciting
as an engineer.

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smegel
SpaceX's first manned flight is going to be a momentous occasion.

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klum
Nice explanation of what's going on. I've always thought there was an
opportunity for much more of this kind of thing during the previous launches--
explaining the process to those of us who really have no idea.

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burd691
I know SpaceX is looking to make space flight more like commercial flight.
Given that commercial airliners don't have anything like this in their design,
shouldn't the goal be to get space flight to the same failure rate as
commercial flight? Thus eliminating the need for an abort system?

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cyrus_
Once they are that reliable, I'm sure SpaceX could consider removing the abort
system to save on weight. Though I assume that the SuperDracos are designed to
also be used in space / on Mars.

~~~
greglindahl
And for landing back on Earth, just not initially:

[http://www.spacex.com/news/2014/05/30/dragon-v2-spacexs-
next...](http://www.spacex.com/news/2014/05/30/dragon-v2-spacexs-next-
generation-manned-spacecraft)

