
SpaceX CRS-3 launch scrubbed due to helium leak - mkempe
http://new.livestream.com/spacex/events/2833937/statuses/48058415
======
gedmark
Just to set expectations, SpaceX has tried to recover the 1st stage of almost
all of its launches to date. (Using just parachutes for most of them). They've
yet to successfully recover a first stage.

Their most recent test went pretty well all things considered. For the first
time they tried a "death swoop" maneuver, turning the 1st stage 180 degrees
around as it was starting to re-enter and refire some of the engines to slow
it down. It picked up a nasty roll though and centrifuged the propellant,
cutting the engines prematurely. They recovered some debris but that's about
it.

It's hard to overstate how big a deal it will be if they pull this off. But
the odds of success are very low, given the propensity of these things to
tumble and roll on reentry.

~~~
jessriedel
Do you know how fast the Falcon 9 1st stage gets? Judging by the video
animation of their long term re-usability plan, the 1st state separates before
it achieves a velocity necessitating re-entry.

[https://www.youtube.com/watch?v=kJrFwxE3lzI](https://www.youtube.com/watch?v=kJrFwxE3lzI)

Is this video incomplete? Will both the 1st and 2nd stages will actually
require re-entry shielding?

~~~
gedmark
Just from what I've read - At 1st stage separation the F9 is going Mach 10 at
an altitude of 80km.

There's no hard and fast definition of how high/fast you need to be going for
it to count as a "re-entry", but that certainly qualifies.

~~~
jessriedel
Hey, thanks much. That's useful. For everyone else's information, low-earth
orbit is ~8km/s, or Mach 24. According to Wikipedia, "Thermal control becomes
a dominant design consideration" above Mach 10.

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

If anyone knows anything about the how the first stage is shielded, I'd be
very interested to know. In the artistic video, you can see a quick peak of
the nose of the first stage. It's colored tan/yellow like the heat shield on
the second stage, but there aren't many details. (Presumably, this was
purposefully vague.)

~~~
lholden
The orange you are seeing at the top of the bottom stage may be either a tank
or some sort of shielding for the tanks from the upper stage. I know the upper
stage looks like it will use it's own heat shield... but it will also be re-
entering from a much higher orbit.

The engines on a rocket are designed to withstand huge amounts of heat. It may
be the intent is to have the rocket re-enter engine first. I'd love to see
more information on that part of the rocket myself. Certainly interesting :D

~~~
lutorm
If you don't enter engines-first, the engines aren't pointing in the right
direction to slow the rocket down...

~~~
lholden
The engines do not burn for the majority of descent. You turn the engines
forward and make a short burn. This reduces your velocity and causes the orbit
of your ship to eventually enter the atmosphere.

Atmospheric drag is then going to provide most of your deceleration, slowing
you down to terminal velocity. You then make another burn at the very end of
the flight to slow down from terminal velocity and stop.

The second stage is a good example. After making a deceleration burn, it will
be re-orienting so that the heat shield at the top is facing the direction of
movement. It will then keep this orientation until it is safe to orient the
vehicle around for landing.

You _could_ use your engines for most of the deceleration... but it would
consume a very large amount of fuel. No point in doing so when you already
have atmospheric drag to do the work for you.

~~~
lutorm
I didn't mean the engines were on the whole way down. But if they aren't
pointing in the right direction to begin with, you need to flip the entire
70m-long stage around somewhere in the atmosphere. Even at terminal velocity
it's moving pretty fast, and I doubt it will survive going sideways at 100m/s
through the air, never mind that you need some thrusters that can even develop
enough force to flip it around.

That animation for the second stage reentry is an animation. Recovering the
second stage will be extremely difficult and, if it is ever done successfully,
I don't think it'll involve doing a 180 flip in the lower atmosphere.

------
haswell
Sadly, the launch has been scrubbed due to a helium leak.

[http://new.livestream.com/spacex/events/2833937/statuses/480...](http://new.livestream.com/spacex/events/2833937/statuses/48058415)

Next attempt will be April 18th.

~~~
pothibo
These kind of things seem to happen often. I know helium is very hard to keep
in containment due to it's atom size. Nonetheless, I wonder if there's
technologies being developed right now that could fix that once and for all.

~~~
astrodust
Do you mean it's hard to contain because you have a gas comprised of tiny
noble atoms versus hydrogen which is generally found in pairs?

~~~
rbanffy
Helium atoms are also smaller than Hydrongen atoms and that makes it even
easier for Helium to find its way around the smallest joints and seals.

~~~
krasin
>Helium atoms are also smaller than Hydrogen atoms

How is that?

Hydrogen atom is one proton + one electron [1], and "Helium is composed of two
electrons bound by the electromagnetic force to a nucleus containing two
protons along with either one or two neutrons, depending on the isotope" [2]

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

[2]
[http://en.wikipedia.org/wiki/Helium_atom](http://en.wikipedia.org/wiki/Helium_atom)

~~~
bri3d
In a Chemistry 101 sort of way:

Helium has more protons, thus more nuclear charge. Its valence electrons are
in the same shell but are being "pulled closer" by the protons, so the total
diameter of nucleus + electron shell is "smaller."

The reality is, of course, much more complex. Here's Physicsforum (generally a
good source) teaching more:

[http://www.physicsforums.com/showthread.php?t=306457](http://www.physicsforums.com/showthread.php?t=306457)

~~~
krasin
Thanks for the explanation. Now, it makes sense to me.

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Gravityloss
If the first stage reusability works fine and cost per flight goes down a lot,
then it starts making sense to optimize the upper stage and spacecraft for
lower cost per flight as well. (Because now, even if the first stage flight
was free, the launch would still cost a huge amount of money.)

In manned flights to low earth orbit, since the spacecraft reenters, at least
that part could be reused.

The second stage is hard to reuse because it flies so far downrange
horizontally and reenters at very high speed. The engine also can't run low in
the atmosphere, meaning somehow different recovery than for the first stage.

The parts of the spacecraft that are not heat shielded (service module) will
be sacrificed, but in the future the whole spacecraft might be a monolithic
entity or even part of the second stage and do its mission and reenter and
land as a whole.

~~~
jcampbell1
The first stage has 9 motors, and the second stage has 1. Recovering the 2nd
stage seems incredibly difficult involving lots of compromises for a
relatively small benefit. I'd invest engineering effort into making the first
stage motors not require much re-manufacturing between flights. The cost
savings are going to come from a first stage that is re-fill and go, vs
completely disassemble the motors and rebuild and replace parts.

~~~
Crito
Also, although the first stage is quite large and has 9 engines, when it
finally touches down it uses only the center engine, throttled down. Even
using just that one engine, it produces too much thrust to hover (grasshopper
can hover, but grasshopper is heavier than a returning F9 first stage).

The second stage is meant for use in a vacuum so it's expansion nozzle is much
larger, so perhaps that extra weight would balance things out a bit, but I
suspect that the second stage would have a massive thrust/weight ratio when
reentering almost empty. Makes things more challenging, even if the engine
does work in atmosphere correctly.

~~~
Gravityloss
AFAIK the second stage merlin with the big nozzle would have flow separation
and would shake itself apart if fired at low altitude. IIRC The concept videos
have shown separate smaller DRACO landing engines. Also used with Dragon for
soft touchdown?

~~~
Crito
Ah yes, you're right. The concept video shows them using the second stages
main engine for a deorbiting burn, then using a heat shield for reentry, then
using [dracos/superdracos?] to touch down.

------
geerlingguy
There's also a good thread with links, updates and commentary over on Reddit:
[http://www.reddit.com/r/spacex/comments/22zo8c/spacex_crs3_l...](http://www.reddit.com/r/spacex/comments/22zo8c/spacex_crs3_launch_updates_and_discussion/)

Launch time is 20:58:44 UTC (16:58:44 EDT), and of note, this launch will be
deploying over a hundred femtosats, and will be SpaceX's first attempt at
first stage vertical landing (over water).

------
rbanffy
I imagined the launch control announcing the abort with a chipmunk voice...

------
wolf550e
live updates with video:

[http://www.spaceflightnow.com/falcon9/009/status.html](http://www.spaceflightnow.com/falcon9/009/status.html)

NASA live stream (higher resolution than above):

[http://www.ustream.tv/nasahdtv](http://www.ustream.tv/nasahdtv)

SpaceX live stream:

[http://www.spacex.com/webcast/](http://www.spacex.com/webcast/)

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coreymgilmore
This is like "guess and check" method, just on steroids for rocket scientists.
30-40% sounds like a good enough percentage to me.

If I remember correctly, it wasn't until the space shuttle solid rocket
boosters that NASA managed to recover a 1st stage. SpaceX is a lot younger.

~~~
JshWright
This is a _completely_ different sort of recovery though. The Shuttle SRBs
just fell into the ocean under parachutes. The F9 first stage will be
'landing' under its own power (after decelerating itself to reduce aerodynamic
stresses).

~~~
wolf550e
Also, the SRBs were not "rapidly reusable", they were not simply refueled or
merely refurbished. They went in sections back to Utah for essentially re-
manufacturing. It was more expensive to reuse the SRBs than to buy new ones,
but the decision was made to reuse because of prestige.

~~~
Retric
I suspect it had less to do with prestige than jobs. A large chunk of the
initial SRB cost was raw materials, more of the refurbishing costs was
manpower. Congress critters dislike direct welfare but but put a fig leaf on
it an call it a middle class job and there practically in love.

------
simonh
I obviously don't know what I'm talking about, but my main concern is the
landing legs. Building deploy-able landing legs strong enough to handle a
landing but light enough to make the concept viable isn't going to be easy.

The leg frame on Grasshopper looks massively over-engineered, which is fine
for a test vehicle but would be far too heavy for an actual launch vehicle. We
have still to see the final leg design, and the ones in the CGI mockup video
look, to my untrained eyes, very skinny. Grasshopper has proved the basics of
the maneuvering and landing capability, but there's still a fair way to go.

~~~
jobu
Even once they get the landing perfected, my concern would be the wear-and-
tear of even a single launch of the rocket. It has to reduce the success
probability of the next launch by some percentage.

~~~
mikeash
You can sell the subsequent launches more cheaply and use them for payloads
that are more expendable.

I believe the plan is that the first launch of a new first stage would be used
for manned missions (once they get to that point) and then subsequent launches
would be used for satellites and such. Presumably going for cheaper and
cheaper satellites as it ages.

~~~
curtis
If we really are going to start launching manned missions to Mars then most of
the payloads launched from earth are going to just be propellant. If you have
a failure with a used rocket that's just carrying propellant as its payload,
then you're pretty much out just the cost of the propellant. This is probably
oversimplifying things a bit, but still.

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unreal37
Interesting, it's going to land vertically in water as if it was on land. Low
chance of success (30-40%)

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dm2
Is this one of their Grasshopper rockets?

Apparently the name Grasshopper was just the name of the rocket during the
tests, because I can't find that term used anywhere.

[http://www.nasaspaceflight.com/2014/02/spacex-
crs-3-landing-...](http://www.nasaspaceflight.com/2014/02/spacex-
crs-3-landing-legs-plan-first-stage-recovery-ambitions/)

~~~
InclinedPlane
No, this is a fully operational regular launch which will deliver cargo to the
ISS. But it will have sufficient extra payload capacity to allow for this test
(which will test some but not all of a reusable flight profile of the first
stage including a controlled deceleration and hover burn but only over the
ocean).

~~~
dm2
So this rocket is fully capable for vertical landing, they're just doing it
over the ocean for safety reasons?

That's awesome. Such a short time from initial testing to actual use.

I wonder if they have a buoy or something for it to target.

~~~
arrrg
Considering where they launch I don’t think landing anywhere but in the ocean
is an option.

They launch from the coast to the east (taking advantage of the Earth’s
rotation), meaning when the first stage shuts off it will be somewhere over
the Atlantic, on a ballistic trajectory further eastward. Since the goal is to
be re-useable without losing too much payload capability I really don’t think
they can have much fuel to spare at that point. To decelerate and come to a
hover, sure, that’s the goal, but to actually decelerate, accelerate in the
opposite direction, decelerate again and come to a hover? That would be
ridiculous.

SpaceX will need to launch from somewhere else to end up over land when the
first stage shuts off.

~~~
m_mueller
Please note: This is pulled out of my a.. ahem KSP knowledge, but: The first
stage of an orbital rocket doesn't yet have a very high horizontal velocity -
because of wind resistance it's best to go more or less straight up until a
certain height has been reached. Therefore most of the first stage velocity
can be killed just using gravity and letting it decelerate to terminal
velocity before firing the engines again. The 2nd stage is where recovery
becomes much more costly per ton. Thus, recovery capabilities might lead to
new designs, such as more lightweight second stages or even two stage
orbiters.

~~~
kd0amg
_This is pulled out of my a.. ahem KSP knowledge_

My understanding (from watching Scott Manley's KSP videos) is that Kerbin's
atmosphere is amazingly thick near sea level and that a real-world rocket
should start its gravity turn much lower.

~~~
XorNot
KSPs out of the box drag model is also quite unsophisticated so you end up
with a lot more then you otherwise would.

------
hyp0
This would be awesome! Can you imagine seeing that thing land! Like the
numerous very cool test flghts, up-down, but for real...

This is an incredibly significant step, and crucial for the long-term vision
of cheap space-travel through reusable vehicles.

------
rkarachinsky
FYI, the launch itself will be at 4:58pm ET.

~~~
nawitus
Apparently that's 4:58pm in EDT, or 16:58 in EDT, or 20:58 in GMT (nearly
UTC).

~~~
aninhumer
The difference between UTC and GMT is that GMT used to also refer to
astronomical time (UTC-12), so UTC is preferred for clarity.

They are otherwise identical, so "nearly" is just confusing here.

~~~
nawitus
Wikipedia states that GMT doesn't have a precise definition: "The term
Greenwich Mean Time (GMT) does not have a precise definition at the sub-second
level, but it is often considered equivalent to UTC or UT1. Saying "GMT" often
implies either UTC or UT1 when used within informal or casual contexts. In
technical contexts, usage of "GMT" is avoided; the unambiguous terminology
"UTC" or "UT1" is preferred."

~~~
aninhumer
You are correct, and I should have been more precise in my criticism.

Nonetheless I think describing GMT as "nearly UTC" isn't particularly helpful,
since it's not defined accurately enough to be wrong. Furthermore, EDT is
defined in terms of UTC, so there's no reason to mention GMT at all.

~~~
nawitus
I think I mentioned GMT for it's familiarity. I think "nearly UTC" is fitting,
as it's close to UTC even though it's not precisely defined.

------
callesgg
Seams to me that a braking parachute could help enormously with the fuel
economy of the landing.

~~~
JshWright
Not really... you'd still have to do the earlier burns to slow the stage down
enough that it doesn't break up in the atmosphere, and the burn to boost it
back to the launch site. The parachutes would just save the final 'hover slam'
burn, but the terminal velocity of a practically empty first stage is already
pretty low, and the complexity of a parachute system wouldn't be offset by the
minimal savings in speed reduction.

~~~
bronson
Plus, if you're aiming for a target on the ground, the atmospheric effects
(wind) on a parachute would be severe.

You'd probably burn as much fuel recovering from the parachute's meandering
miles off target as you would just slowing the ballistic final leg. (not sure
though, -ENOMATH)

~~~
rbanffy
IIRC, they actually considered it, but the parachute, plus its pyros and extra
equipment were heavier than the extra fuel for braking.

Parachutes are very useful when you don't have engines powerful enough to slow
you down, but the whole purpose of this is the controlled landing of nine very
powerful engines.

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api
This is IMHO bigger than Apollo. The moon missions were an expensive one-shot,
while this has the potential to truly open the frontier.

~~~
tensenki
You think that recovering a rocket is bigger than landing on another planet?
I've actually re-written this comment a couple times because I'm honestly not
trying to say your opinion is stupid, but I cannot fathom how you have come to
this conclusion.

~~~
syncsynchalt
(To put some words in the commenter's mouth) he's saying that a 90% cut in
launch costs would be bigger than Apollo. In those terms, it's a defensible
argument.

~~~
saalweachter
I think it might be defensible, but I'm not sure it's correct. The question
isn't really "is it easier to put a man on the Moon today than it is build a
reusable rocket which cuts cost by 90% today", it's "was it easier to put a
man on the moon in 1960 than it is to build a reusable rocket which cuts costs
by 90% today".

The Apollo program was conceived in 1960, before either the suborbital flight
of John Glenn or the earlier orbital flight of Yuri Gagarin. Before we had
successfully built and tested a rocket capable of putting a single man in
space, we started a space program with the goal of putting a man on the Moon,
which would in the end involve launching a three-man spacecraft, with
sufficient fuel to carry it to the Moon, manually reconfiguring it in flight,
flying it for three days through the void, entering orbit around the Moon,
detaching a portion of the spacecraft to land upon the Moon under manual
controls, bouncing around the Moon in space suits, goddamn driving around the
Moon in little cars (later missions), flying the space craft back into lunar
orbit, rendezvousing with the orbiting spacecraft and manually re-docking,
flying the ship back three days to Earth, and re-entering the Earth's
atmosphere and landing safely.

And they did it in under 10 years. SpaceX turns 12 this year.

