SpaceX Dragon successfully docks with International Space Station | Hacker News Reader

SpaceX Dragon successfully docks with International Space Station

arstechnica.com

223 pointsiProject36 comments

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.

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.

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.

The human body is basically code 2 all the time. It's just that it can fix itself, until you get code 3.

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.

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.

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.

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.

I'm sure there's a lot of information that could paint a more complete picture, but here's a start.

According to NASA[1], a shuttle launch cost $450 million on average. Their contract with SpaceX covers 12 launches for $1.6 billion[2], or roughly $133 million per launch. SpaceX also received $75 million from NASA to develop a crewed version of the Dragon capsule.

I'm sure NASA has made other payments to SpaceX over the years, but even if those payments totaled a couple billion it's still cheaper than 12 Shuttle launches just to supply the ISS.

According to Wikipedia[3], the Falcon 9 rocket itself costs half as much as an Atlas V.

[1] http://www.nasa.gov/centers/kennedy/about/information/shuttl...

[2] http://www.space.com/13012-nasa-unveils-private-space-taxi-c...

[3] http://en.wikipedia.org/wiki/Comparison_of_orbital_launch_sy...

If a shuttle launch and a Dragon launch have the same utility, what you say is true, but the shuttle can carry a lot more cargo. For example, the Dragon is nowhere near large enough to carry a full space station module. I'm not sure that this renders what you said false, but there's a lot more to it than this.

That's a bit of a red herring. In terms of specific utility for cargo delivery / return they are actually fairly comparable, in cost at least. Dragon will probably pull ahead as they load it with more cargo in later flights using the upgraded Falcon 9 v1.1.

In terms of space station modules, any new modules are more likely to be delivered in standalone launches from an expendable vehicle (such as the Falcon Heavy). Although, the SpaceX CRS-8 mission is expected to deliver the Bigelow Expandable Activity module, but it's a fairly tiny module.

The $450 million / flight cost for a Shuttle is a fantasy, it's a hypothetical sort of best-case cost. Over the lifetime of the program the actual cost was $1.5 billion.

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.

In comparison, the Dragon is on a fixed price contract (about $133 million per vehicle) which includes launch and operations and whatnot. This particular Dragon is delivering 1050 kg of supplies (677 kg within the pressurized part of the spacecraft, the rest within the unpressurized "trunk"). This comes out to a cost to NASA of $127/gram.

Which, admittedly, is not Earth shattering. However, this flight will also be returning 1370 kg of equipment back to Earth, including highly valuable scientific experiments and such-like. And Dragon is currently the only vehicle capable of doing so. On the whole this makes Dragon more than worthwhile.

However, this is still only the 2nd operational Dragon resupply mission, and they will continue to increase the amount of cargo delivered as they become more confident in the vehicle and especially as the Falcon 9 v1.1 becomes operational (which will happen in the next flight) which will add about 4 tonnes of additional payload capacity. If fully utilized it could bring the cost of cargo deliveries to ISS down to around $30-$50/g. Also, there is definitely an element of subsidizing the development of new systems in the CRS contract terms, though even so they're reasonably cost effective.

Edit: to compare to the Shuttle, on an MPLM mission the Shuttle could deliver about 15 tonnes of supplies and equipment and cost around $1.5 to $2 billion per launch (the higher figure due to the extremely low flight rate near the end of the Shuttle program), which works out to a cargo delivery cost of around $100/g, though the Shuttle could also return significant amounts of cargo.

Edit2: I inadvertently omitted the cost of the MPLM modules themselves from the calculation above, although including them would be difficult since most of them were built by the Italian Space Agency as payment in kind for ISS access, overall they would only affect the cost figures by less than 20%. Also, fun fact: the MPLMs were named for famous Renaissance artists, or ninja turtles, here's NASA's logo: http://en.wikipedia.org/wiki/File:Multi-Purpose_Logistics_Mo...

Very interesting, thank you.

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.

Nicely laid out, of course the "coolness" thing here is that the marginal cost of getting additional cargo is $25 - $30 per gm. Less if you can go with a non-returnable module.

But the thing that really gets me excited is that "you" being the person trying to get stuff into orbit, not having to go to NASA or Boeing to do so. If the only thing between something on the ground and something in orbit is a well defined amount of money, it is possible to compute the ROI for sending something to the L1 point for example.

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.

Dragon uses vxworks: http://www.spacex.com/downloads/dragonlab-datasheet.pdf second page, under Flight Software

Thanks for the correction, that's interesting. It's a testament to the utility of vxworks, I suppose, which costs a few hundred thousand dollars per client. Even so, not using rad-hardened CPUs still saves them millions, especially when you factor in backup hardware, test units, etc.

It's probably because it is:

- Certified (for military use maybe?)

- It gets out of the way when needed

- Lots of people experienced in it

"Even so, not using rad-hardened CPUs still saves them millions"

Yes

> However, it makes sense for them to offer their services as close to the competition's prices as possible, because it maximizes their profits.

This is an important lesson that I learned the hard way with my first startup.

Not only does it maximize their profit, but it also helps reduce the risk of setting off a price war. In my case, we went into the ISP industry in '95 with a price about 1/3 of the larger competition in Norway. What we did not realize - being completely fresh to business - was that these guys did not price their service that way because their costs were that high, but because the market at a time (which was not yet regular consumers) could bear it and their margins were high.

So when we and a couple of other small ISPs launched with so much lower prices in autumn of '95 it too two days, and the big incumbent ISPs followed suit, and eventually pushed the prices much further down. We stuck it out a year before we sold our dial up customer base and focused on hosting and consulting when it was clear that the big providers at that point had seen that their big price drops were well timed for a big growth in the consumer segment and decided they were willing to sustain big losses to take market share.

It took several years before the market segment returned to profitability for anyone, and by then most of the small providers were out of the picture...

You really don't want to rock the boat too much if you can instead build up a war chest, unless you're extremely well funded and/or know for a fact that you can not only beat the competition on price, but can also survive if they decide taking losses for a while is worth it if they can get rid of you.

>... 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.

Previous thread on SpaceX costs: https://news.ycombinator.com/item?id=3857904

I think a big congratulations is due for SpaceX; one is an aberration, two is on it's way to being normal. So congrats to them for moving towards a normalization of privatized space operations.

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?

3 of 4 thruster packs experienced the issue; they need 2 of 4 to open the solar panels and 3 of 4 to dock with the ISS. From what I understand they got all 4 working again using the "water hammer" effect to clear the blockage, but I'm not sure how accurate that is.

Imagine it's your job to fiddle around remotely with fuel pump electronics (or whatever may create that water hammer) within a time window of maybe 20 minutes or else you've just sunk a 100M investment somewhere in the ocean. Must be lots of fun o.O

There's plenty of excitement for me just tweaking a live production server, not sure my heart could cope with what you just described.

I remember it being something about check valves in the oxidizer pressurization system. I don't recall where I read that, but it's probably not too hard to dig up (I'm just lazy).

I wonder what biological samples taken from the crew means.

It probably means what you think: urine, blood, saliva, fecal matter... Whatever a scientist or doctor on the ground might need to analyze.

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