
SpaceX successfully tests parachute for bringing astronauts back [video] - salmonet
https://www.washingtonpost.com/video/business/technology/spacex-successfully-tests-parachute-for-bringing-astronauts-back-to-earth/2016/01/28/5f5e3d52-c5d3-11e5-b933-31c93021392a_video.html
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ChuckMcM
The more interesting test for me was the hover tests
([https://www.youtube.com/watch?v=07Pm8ZY0XJI](https://www.youtube.com/watch?v=07Pm8ZY0XJI))
I keep doing back of the envelope calculations to see if a Dragon2 has enough
fuel capacity to land and return from the lunar surface. Granted there is
limited ability to leave and re-enter the capsule but it would make for an
interesting capability.

If I recall correctly the "land on land" scenario for dragon has it using
parachutes most of the way down, then doing a drop and land at the end.

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JshWright
Far more important than the parachutes is the atmosphere. Even without
parachutes, the atmosphere is responsible for almost all of the deceleration
the capsule experiences. The atmosphere takes it from orbital velocity
(~30,000 m/s EDIT: ~8,000m/s (km/h->m/s conversion fail)) and slows it down to
the terminal velocity of the capsule (~100 m/s). The capsule only has to take
care of that last bit from terminal velocity down to 0 m/s.

On the moon, there is no atmosphere, so the capsule would have to handle all
the deceleration from lunar orbital velocity (~2,000 m/s) to 0. So, in
ballpark figures, you're looking at 20 times more 'delta V' (change in
velocity) that the capsule would have to accomplish in order to land on the
moon. It takes _way_ more fuel to manage that.

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baq
if you replaced the dragon's trunk with a booster, it should be enough. i'm
pretty sure it's not feasible, but in KSP world totally would work.

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zardo
I doubt Falcon Heavy could throw enough mass to make it work. Dragon is just a
poor vehicle to send to the moon. It should work for landing a few tons on
Mars though (one way).

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greglindahl
FH is 117 MT to LEO vs Saturn V 140 MT, Dragon is bigger/heavier than the
Apollo capsule, and the even smaller LEM was the thing that landed on the
Moon.

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endymi0n
Nevertheless, quick back-of-the-envelope calculation should make an Apollo-
style operation completely viable. Launch Dragon into orbit, Launch a fully
loaded second stage without payload into orbit with a second FH and dock with
the Dragon, Command Module style, then use the second stage for lunar orbit
insertion and back. Should do the trick, even with a much heavier capsule.

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JshWright
Using more than one launch is very much not an 'Apollo-style' operation. One
of the major features of the Apollo program is that is used a single launch,
which distinguished it from all the other competing proposals at the time.

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douche
I will never be able to look at a video of a space flight again without
thinking of how it would be achieved in Kerbal Space program.

Four Mk2R Radial Mount Parachutes, I think...

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jewel
If anyone here hasn't played Kerbal Space program, try out the demo. It's less
of a game and more of a space rocket simulator, with a real physics engine. I
learned a lot by playing it.

I'm not in any way affiliated with the game, but can say with certainty that
the overlap of HN readers and people who would enjoy the game is very high.

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kincardine
It's also less of a simulator and more of a total brain takeover.

When I first started playing all I could think about (as I was trying to get
work done) were trans-munar injections and free-return trajectories.

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stuxnet79
I bought the game but still haven't played it yet. How much of a timesink is
it? Could it be enjoyed in 30min to an hour playing sessions?

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Buttons840
Yes, you can leave the game in almost any state and then pick up where you
left off later. The only exception is suborbital flights, but getting to orbit
takes 3 to 5 minutes max.

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douche
For the first couple hours, you're going to be reverting to
launch/construction every five minutes anyway when you mess up and crash or
realize you didn't build your rocket correctly to do what you want to do.

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TrevorJ
First couple of hours? That's still how I play 90% of the time.

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vecter
I'd appreciate it if someone could explain to me how dangerous it is to use
multiple parachutes instead of one. It sounds like it provides more
reliability in case the one parachute fails, but it also seems there would be
a risk of the parachutes becoming entangled. I personally have no
understanding of the engineering or a sense of those risks.

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krschultz
This was pretty low risk considering that they have been landing the cargo
Dragon capsule under parachute for a few years now. The crew Dragon capsule
probably has slightly different weight & balance characteristics but the
system hasn't changed that much.

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JshWright
There are a few changes with this parachute system. Notably, it uses 4 chutes,
rather than 3 (which is the number used by the current cargo Dragon, and how
many the Crew Dragon test article used for the pad abort).

All in all though, you're right, this was mostly just a checkbox that needed
to get checked off.

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ChuckMcM
Josh, do you know if is there anywhere that confirms the 204s ISP number for
the superdraco thrusters? And what the fuel mass is for that?

EDIT: yes its a typo, I mean 240s

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delibes
The citation for the wikipedia page (240s ISP) gives an exhaust velocity of
2,300m/s :

[https://en.wikipedia.org/wiki/SuperDraco#cite_note-
DragonFly...](https://en.wikipedia.org/wiki/SuperDraco#cite_note-
DragonFlyEAI201403-4) \- page 12 of the PDF.

So taking a rough 2300/9.8 gives about 235s

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ChuckMcM
Yes I read that (and the spaceflight insider article
([http://www.spaceflightinsider.com/organizations/space-
explor...](http://www.spaceflightinsider.com/organizations/space-exploration-
technologies/spacexs-superdraco-engine/)), all numbers that are derived by
third parties.

So while I do not doubt that the numbers for that vehicle and that test are
accurate, I keep hoping to find actual data _from SpaceX_ on the performance
of the production rocket slated for use in the production Dragon Module.

I understand that SpaceX plays this information close to its vest given the
competition with Boeing for Commercial Crew and perhaps Blue Origin should
SpaceX ever decide to sell rockets for sub orbital tourist jaunts[1]. Anyway
I'm just interested in more _official_ specs so that I can have more
confidence in my understanding of their capabilities.

[1] If you think about it, they have all the hardware, an F9r with a Dragon
Crew mounted on top, they boost up to 100km, separate, the Dragon gets a nice
ballistic arc for that weightless feeling and then both the booster and the
capsule go back and land back at the pad for re-use.

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sopooneo
Why do the parachutes chords angle to the side in the air? It seems like after
a little while in constant wind, it would end up hanging vertically, while
falling at an angle.

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lobster_johnson
Good, relevant discussion here:
[https://m.reddit.com/r/askscience/comments/3xs6mg/how_do_lar...](https://m.reddit.com/r/askscience/comments/3xs6mg/how_do_large_triple_parachutes_like_those_used_on/)

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lmm
Needs [video] tag.

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Tharkun
Youtube link:
[https://www.youtube.com/watch?v=4PG438XSarg](https://www.youtube.com/watch?v=4PG438XSarg)

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novlean11
SpaceX with their reusable stuff is definitely changing the whole space
industry. We might have an option to fly out there in our life time without
being a millionaires.

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stuxnet79
Yes, I just finished Elon Musk's biography and it seems the objective is to
get the price down to between $500,000 to a million for getting a single
person to Mars. Extremely ambitious, but if it does happen, I will sell my
house plus whatever hard assets I will own at the time and take my trip one-
way to Mars.

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jernfrost
I thought a lot about that too. A lot of people think that seems nuts of
course to move to such a barren hostile world. But there is a certain appeal
to do something advances human civilization. On earth you are just one small
cog on the big wheel. You don't matter that much to the well being of earth
civilization. But on Mars every single colonist would matter a lot for the
future of that colony.

Even if one dies earlier on Mars, it would seem better to live a short life
with purpose than a long without purpose.

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meric
What about Antarctica? Sure it's not a different planet, but you will be doing
things that advance human civilisation and every person on Antarctica matters.

EDIT:

There's a lot of scientific research going on down there. [1]

In Antarctica you can participate in research that can reduce the possibility
of such a catastrophe in the first place.

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

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adrianN
I regularly check job offerings in Antarctica, but the openings are few and
the competition is fierce. I think you'll have a really hard time getting a
job there unless you already work for an organization that does research
there.

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rglover
Slow, steady progress is a beautiful thing.

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karanbhangui
I have a document I keep notes in for major life lessons or principles for
myself. I've added your perfect quote under the principle for mastering the
value of time and compounding:
[https://www.dropbox.com/s/4hdwbj0igcyivcd/Screenshot%202016-...](https://www.dropbox.com/s/4hdwbj0igcyivcd/Screenshot%202016-01-29%2000.37.59.png?dl=0)

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rglover
Ha! That's awesome, thanks for the inclusion :)

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backtoyoujim
who owns washington post and spacex?

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Ankaios
The Post is owned by SpaceX's competitor, Jeff Bezos.

