SpaceX Dragon successfully docks with International Space Station • Hacker News Board

Re: SpaceX Dragon successfully docks with International Space Station

#21

Post by tharax » Mon, Mar 04, 2013, 1:40 AM UTC

methodin wrote: post #17

Is there any significance to the fact that both major launches had problems but did not hinder a successful mission? Is that a common occurrence as far as missions go to fail (or have failures) while still gracefully completing?

I remember my statistics lecturer was fond of pointing out that NASA estimated the probability of SOMETHING failing on launch was (1). That is, because of the complexity of the project, there was always something that was missed or broken - although it could have been as simple as a bulb that was backlighting a switch might be blown, or a cupboard might have been restocked incorrectly, or a calculation for external events might be slightly off.

Re: SpaceX Dragon successfully docks with International Space Station

#22

Post by jacquesm » Mon, Mar 04, 2013, 1:40 AM UTC

methodin wrote: post #17

Is there any significance to the fact that both major launches had problems but did not hinder a successful mission? Is that a common occurrence as far as missions go to fail (or have failures) while still gracefully completing?

I think the 'fail fast' strategy shown here is a pretty good one, freeze as soon as anything is outside normal operating parameters to give you time to decide what to do (I can see Elon Musk standing over a control panel with 'Abort / Retry / Ignore buttons').

The other things that helps is to have many redundant parts. So far they've been able to steer clear of any catastrophic mishaps but given the nature of spaceflight it will be a long time before we can relax on that front. 10's of launches without serious mishap would be quite amazing, so far the statistical base is rather thin. That does nothing to detract from the achievement to date, SpaceX is nothing short of incredible.

Re: SpaceX Dragon successfully docks with International Space Station

#23

Post by gilgoomesh » Mon, Mar 04, 2013, 1:42 AM UTC

methodin wrote: post #17

Is there any significance to the fact that both major launches had problems but did not hinder a successful mission? Is that a common occurrence as far as missions go to fail (or have failures) while still gracefully completing?

Shuttle mission STS-51 suffered an engine failure but still completed successfully (although at a lower than intended orbit):

http://en.wikipedia.org/wiki/STS-51-F

STS-93 also shut down an engine (although not as dramatically):

http://en.wikipedia.org/wiki/STS-93

The answer is really: yes, minor issues happen all the time. Something as dramatic as an engine shutdown (as in CRS-1) is rare but not unheard of.

With Falcon9/Dragon -- none of these issue have resulted in failure to reach orbit or complete main objectives. If SpaceX weren't under such close scrutiny, we probably wouldn't notice the issues Dragon had on this mission.

Re: SpaceX Dragon successfully docks with International Space Station

#24

Post by DeepDuh » Mon, Mar 04, 2013, 1:48 AM UTC

ramidarigaz wrote: post #7

DeepDuh wrote: post #5

I didn't follow everything in detail this time. What was with that problem they were talking about?

The capsule's thrusters had a blockage which prevented them from maneuvering and deploying the solar panels. They managed to clear the blockage just fine.

Interesting. Did they release informations on how they solved that? Also, don't they have some built in redundancy for the thrusters?

Re: SpaceX Dragon successfully docks with International Space Station

#25

Post by InclinedPlane » Mon, Mar 04, 2013, 1:55 AM UTC

opminion wrote: post #20

InclinedPlane wrote: post #10

Earlier quoted context omitted.

Cost is an unknown except to SpaceX. Price (i.e. cost to the consumer) is easier to figure out but a little more complicated for reasons I'll explain later. The easiest direct comparison would be to the ESA's ATV. Each ATV launch costs around $900 million in amortized development costs plus vehicle costs plus launch costs. But, it delivers 6,595 kg of cargo, which puts the delivered cost of cargo at about $132/gram.…

The $132/g vs $127/g price would make sense, all other things being equal (which are not, ok), if SpaceX were pricing in a duopoly, right?

If I take your meaning correctly, yes.

For SpaceX the actual costs they experience are quite low compared to their competition. For example, they don't use rad-hardened CPUs, nor do they use vxworks. This alone saves them millions of dollars. However, it makes sense for them to offer their services as close to the competition's prices as possible, because it maximizes their profits. You see the same thing on their launch services.

Re: SpaceX Dragon successfully docks with International Space Station

#26

Post by InclinedPlane » Mon, Mar 04, 2013, 2:00 AM UTC

ramidarigaz wrote: post #15

InclinedPlane wrote: post #10

Earlier quoted context omitted.

Cost is an unknown except to SpaceX. Price (i.e. cost to the consumer) is easier to figure out but a little more complicated for reasons I'll explain later. The easiest direct comparison would be to the ESA's ATV. Each ATV launch costs around $900 million in amortized development costs plus vehicle costs plus launch costs. But, it delivers 6,595 kg of cargo, which puts the delivered cost of cargo at about $132/gram.…

Wow. I had no idea the ATV was so expensive. As a side note, your comments in space-related threads are always awesome. Do you work in the industry?

A lot of the cost of the ATV comes from the development cost and the low number of missions (for clairty I've amortized that cost through the missions planned up to 2014 in the above). Even so it costs about half a billion dollars just to build and launch each one. To be fair, the ATV is able to transfer propellant to the station which is something that only it and the Progress vehicles can do.

For myself, I'm merely an enthusiastic amateur, I've been studying spaceflight closely since I was a child and I've come to pick up a few tidbits of trivia along the way.

Re: SpaceX Dragon successfully docks with International Space Station

#27

Post by tsotha » Mon, Mar 04, 2013, 2:09 AM UTC

InclinedPlane wrote: post #10

eliben wrote: post #2

It would be interesting to see the total cost of this mission, and compare it to the total cost of similar NASA missions in the past.

Cost is an unknown except to SpaceX. Price (i.e. cost to the consumer) is easier to figure out but a little more complicated for reasons I'll explain later. The easiest direct comparison would be to the ESA's ATV. Each ATV launch costs around $900 million in amortized development costs plus vehicle costs plus launch costs. But, it delivers 6,595 kg of cargo, which puts the delivered cost of cargo at about $132/gram.…

>... though the Shuttle could also return significant amounts of cargo.

Just how much is a matter of some dispute. At one time a plan to return Hubble was under consideration, but even though the shuttle was supposedly designed to handle cargo that large, NASA finally decided it would be too dangerous.

Re: SpaceX Dragon successfully docks with International Space Station

#28

Post by InclinedPlane » Mon, Mar 04, 2013, 2:20 AM UTC

methodin wrote: post #17

Is there any significance to the fact that both major launches had problems but did not hinder a successful mission? Is that a common occurrence as far as missions go to fail (or have failures) while still gracefully completing?

There's pretty much always going to be something that goes wrong, although sometimes it's not as important as other times.

To bring in some historical examples. On Apollo 11 there were two major problems. The first was that the chosen launch site was actually filled with enormous spacecraft-wrecking boulders so Armstrong had to fly the LM to a more suitable landing site (and almost ran the thing out of fuel doing it). The second was that a circuit breaker used for arming the ascent engines on the LM got broken during an EVA and the astronauts had to improvise by using a felt-tip pen to activate it. On Apollo 12 the launch vehicle was struck by lightning on ascent and the computers got a bit frazzled, but luckily someone in mission control (John Aaron) knew how to get the system back under control. During Apollo 13's launch severe POGO oscillations in the center engine on the Saturn V first stage almost tore the engine off the rocket (flexing the huge thickness of solid metal that supported the engines by 3 inches) before it was shut-down automatically, and later an Oxygen tank on the CSM exploded during flight. During Apollo 14 it took nearly 2 hours to dock the CSM and the LM (normally this took maybe 10 minutes), there was also a problem with a short-circuit in a switch which forced a software rewrite to be able to land on the moon, and then the landing radar altimeter didn't work and had to be rebooted.

I could go on but I think you get my point.

Re: SpaceX Dragon successfully docks with International Space Station

#29

Post by InclinedPlane » Mon, Mar 04, 2013, 2:22 AM UTC

tharax wrote: post #21

methodin wrote: post #17

Is there any significance to the fact that both major launches had problems but did not hinder a successful mission? Is that a common occurrence as far as missions go to fail (or have failures) while still gracefully completing?

I remember my statistics lecturer was fond of pointing out that NASA estimated the probability of SOMETHING failing on launch was (1). That is, because of the complexity of the project, there was always something that was missed or broken - although it could have been as simple as a bulb that was backlighting a switch might be blown, or a cupboard might have been restocked incorrectly, or a calculation for external e…

This is the way complex systems work, pretty much. The more systems and sub-systems you need to have running the more likely it is that one will have something wrong with it. And when you add in redundancy and extra capacity you actually increase the chance of something going wrong, you just reduce the chance of it having such a negative effect on the mission.

Re: SpaceX Dragon successfully docks with International Space Station

#30

Post by neurotech1 » Mon, Mar 04, 2013, 2:30 AM UTC

tharax wrote: post #21

methodin wrote: post #17

Is there any significance to the fact that both major launches had problems but did not hinder a successful mission? Is that a common occurrence as far as missions go to fail (or have failures) while still gracefully completing?

I remember my statistics lecturer was fond of pointing out that NASA estimated the probability of SOMETHING failing on launch was (1). That is, because of the complexity of the project, there was always something that was missed or broken - although it could have been as simple as a bulb that was backlighting a switch might be blown, or a cupboard might have been restocked incorrectly, or a calculation for external e…

They had a shuttle mission where everything was nominal, even the toilet kept working the whole mission.

But yeah, space flight is like that. Then again its relatively rare for a jet fighter to consistently return Code 1, no faults. Usually its Code 2 with minor fixes required pretty regularly. Code 3 is an abort.