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SpaceX Crew Dragon Splashes Down After Historic Test Flight

scientificamerican.com

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Re: SpaceX Crew Dragon Splashes Down After Historic Test Flight

#41

Post by spricket »

varjag wrote: post #22
bahmboo wrote: post #14

Earlier quoted context omitted.

I live by salt water. Salt water destroys everything. Sometimes quickly but always eventually. Ok, maybe not fish.

Carbon steel hull ships traverse saltwater for many decades however.

They use cathodic protection which makes the underwater hull basically immune to corrosion. But this doesn't stop water that gets on top or inside.

Ships rust like hell. I've known some guys in the Navy and they said it was common for everything unarmored to have holes all over.

Re: SpaceX Crew Dragon Splashes Down After Historic Test Flight

#42

Post by Robotbeat »

jwr wrote: post #38
ChuckMcM wrote: post #4

This is a better article on the recovery than the one I linked from TechCrunch. I would like to reiterate the point made before which is that SpaceX is on the verge of being in a place that no company has ever been before with regard to space. The are on the cusp of having a capsule that they can send into orbit for days and then return to Earth. They already have rockets capable of putting tons of material into ever…

I wonder at which point we will start worrying about the carbon footprint of these launches, though. I didn't do the math, but it seems it might become a global factor once you get to multiple launches per week.

Not even close. A Falcon 9 has no more fuel than a 777. A few 777s per week is inconsequential in a world where there are 100,000 flights per day. Aviation is responsible for only about 3.5% of anthropogenic emissions per year. So even multiple flights per week are just a rounding error on a rounding error.

Re: SpaceX Crew Dragon Splashes Down After Historic Test Flight

#43

Post by Robotbeat »

ChuckMcM wrote: post #33
JulianMorrison wrote: post #29

Earlier quoted context omitted.

Why would they do day trips when they plan to do suborbital passenger trips. Not make going into space a bucket list item for the upper middle class, but a routine A-to-B for business class flyers. The bucket list item would be Mars.

I would assume free cash flow would be the reason. Let's assume that you could get $20M per seat on a 7 seat dragon with 2 of those seats going to crew and the other 5 going to paying passengers. You, launch them on a re-usable F9 which you currently charge $80M for a non-reusable booster flight into low orbit. Could you clear 25 - 35 million in margin on that? Could you do that for doing "nothing" special other than…

You wouldn't use Dragon, you'd use BFR/Starship: https://www.youtube.com/watch?v=zqE-ultsWt0

Re: SpaceX Crew Dragon Splashes Down After Historic Test Flight

#44

Post by Robotbeat »

neuronexmachina wrote: post #36
JulianMorrison wrote: post #29

Earlier quoted context omitted.

Why would they do day trips when they plan to do suborbital passenger trips. Not make going into space a bucket list item for the upper middle class, but a routine A-to-B for business class flyers. The bucket list item would be Mars.

SpaceX actually showed a mock-up of what point-to-point travel might look like in one of their videos.

Here: https://www.youtube.com/watch?v=zqE-ultsWt0

Re: SpaceX Crew Dragon Splashes Down After Historic Test Flight

#45

Post by lutorm »

jwr wrote: post #38
ChuckMcM wrote: post #4

This is a better article on the recovery than the one I linked from TechCrunch. I would like to reiterate the point made before which is that SpaceX is on the verge of being in a place that no company has ever been before with regard to space. The are on the cusp of having a capsule that they can send into orbit for days and then return to Earth. They already have rockets capable of putting tons of material into ever…

I wonder at which point we will start worrying about the carbon footprint of these launches, though. I didn't do the math, but it seems it might become a global factor once you get to multiple launches per week.

World CO2 emissions last year was ~ 37Gigatons of carbon. A F9 launch uses of order 100 tons of RP1, so global emissions correspond to about 370 million launches...

Re: SpaceX Crew Dragon Splashes Down After Historic Test Flight

#46

Post by XorNot »

ceejayoz wrote: post #40
jwr wrote: post #38

Earlier quoted context omitted.

I wonder at which point we will start worrying about the carbon footprint of these launches, though. I didn't do the math, but it seems it might become a global factor once you get to multiple launches per week.

https://www.smithsonianmag.com/science-nature/spacex-environ... says: > if the SpaceX’s plan for a rocket launch every two weeks comes to fruition, this amount of carbon (approximately 4,000 tonnes per year) will rapidly become a bigger problem So, that gives us a number... and it's also very weird for the Smithsonian to describe that as a "problem". 4,000 tonnes per year is about a thousand cars worth per the EPA's…

Rockets and the rocket fuel are also in the "easy to substitute" category. They'll never not be hydrocarbons, but significant work has been done on producing rocket-compatible fuels from biological sources, and the marginal increase in cost if you scaled up to industrial production is possibly going to be entirely unnoticeable considering the general purity and refining requirements of anything you load into a spacecraft.

This, similarly, is also the answer when it comes to aviation by and large. The real problems on Earth are ground transportation and electricity.

Re: SpaceX Crew Dragon Splashes Down After Historic Test Flight

#47

Post by nordsieck »

slg wrote: post #16
influx wrote: post #11

Earlier quoted context omitted.

Why did they force the requirement for saltwater splashdown?

I am curious about this as well. Was the propulsion the problem? Did they just want a water landing? Did they specifically want an ocean landing to increase the acceptable margin for error in the splash down location? Is there some specific property to the salt water like buoyancy that is important? Would a landing in fresh water like the Great Lakes (or Lake Victoria if they need something more equatorial) meet NASA…

> Would a landing in fresh water like the Great Lakes (or Lake Victoria if they need something more equatorial) meet NASA's requirements and allow the capsule to be reusable?

I'd guess that one of the big reasons they (and everyone else who does water landings) lands in the ocean, is that it is much more palatable to regulators to create an exclusion zone in the ocean, which people can easily route around.

Also, people live on the side of the lake, so there isn't much margin for error, which never warms the cockles of a regulator's heart.

Re: SpaceX Crew Dragon Splashes Down After Historic Test Flight

#48

Post by rst »

iamcreasy wrote: post #37
Tuna-Fish wrote: post #7

Earlier quoted context omitted.

They are unlikely to do this at this point. The big problem is that while the capsule will be reusable, since NASA killed the propulsive landing for Dragon 2, it now needs to splash down in saltwater and therefore is not considered safe for humans after the first use. This makes Dragon 2:s too expensive for large-scale space tourism. Unless there is suddenly a huge market for this, I think SpaceX would prefer to sell…

> NASA killed the propulsive landing for Dragon 2 Are you sure NASA was to blame for it? I remember Elon saying they are not perusing propulsive landing anymore because of the amount of resources it would take to develop and validate the design. From what I gather, it was SpaceX's decision.

Combined decision. NASA was unwilling to pay for testing propulsive landing, or allow testing on cargo missions, because the parachutes already work, and SpaceX didn't want to front the money themselves.

Re: SpaceX Crew Dragon Splashes Down After Historic Test Flight

#49

Post by Teever »

varjag wrote: post #21
huehehue wrote: post #13

Earlier quoted context omitted.

"Although water retrieval has been attempted, it is not recommended due to the adverse effect that salt water has on avionics, electronics, and structures. This approach was abandoned due to the elevated cost associated with refurbishing salt water damaged components. By avoiding water retrieval, the engines would avoid maintenance that would have resulted from the corrosive nature of the salt water and thereby exped…

This is related to rocket engines, not ballistic descent capsules.

Ballistic descent capsules such as the Dragon have rocket engines in them.
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