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Crew Dragon Docks with ISS

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Re: Crew Dragon Docks with ISS

#241

Post by dingaling »

simonh wrote: post #172
computerex wrote: post #160

Earlier quoted context omitted.

Whilst I agree with the general sentiment, the Space Shuttle was the single most capable spacecraft that has ever flown. You are not being fair in measuring it simply on the basis of how much mass it could put in Orbit.

It was an amazing vehicle and highly capable in some way, but severely constrained in others. The main problem is it was almost completely useless for any missions or activities beyond LEO. In theory you could use it to put up a small boost stage for a light interplanetary probe, but its cargo capacity was a bit small for that, and there’s just no point using a whole shuttle to do it. Now that we have Falcon 9 and He…

The Shuttle was never designed to support Lunar missions so that's a red herring.

It was designed to recover satellites and bring them back to Earth safely as part of its military mission. Nothing Space X is offering has such a capability.

Different vehicles for different roles.

Re: Crew Dragon Docks with ISS

#242

Post by red2awn »

gfodor wrote: post #130
tnli wrote: post #29

Earlier quoted context omitted.

Elonville, Musktown?

I put like 90% liklihood we'll have a nation state named "Musk" on Mars in 50 years.

A nation in 50 years sounds like an Elon timescale. More likely a small settlement of <100 people for research and exploration.

Re: Crew Dragon Docks with ISS

#243

Post by oldgradstudent »

computerex wrote: post #160
bane wrote: post #15

SpaceX runs basically as a giant R&D program that also happens to accomplish useful things as byproducts of its approach (with the miracle of insurance to cover costs if things get explody). Every flight is data for incremental improvement. If you think of all SpaceX has ever done was try to get to this point, with somewhere around 80 flights on the Falcon 9, but for a variety of mission buyers (NASA, USAF, Commercia…

Whilst I agree with the general sentiment, the Space Shuttle was the single most capable spacecraft that has ever flown. You are not being fair in measuring it simply on the basis of how much mass it could put in Orbit.

The shuttle was a fiasco.

It was ridiculously expensive. It was unsafe. And everybody knew that before it flew the first mission.

http://www.iasa-intl.com/folders/shuttle/GoodbyeColumbia.htm...

Re: Crew Dragon Docks with ISS

#244

Post by OctaviusCrassus »

stevens32 wrote: post #225
OctaviusCrassus wrote: post #163

Unbelievable what Elon Musk has been able to create for humanity. So grateful for him and this administration. Looking forward to see more free market ingenuity

Free market doesn't seem correct here since the government is the customer.

Govt is 100% funded from the free market

Re: Crew Dragon Docks with ISS

#245

Post by simonh »

dingaling wrote: post #241
simonh wrote: post #172

Earlier quoted context omitted.

It was an amazing vehicle and highly capable in some way, but severely constrained in others. The main problem is it was almost completely useless for any missions or activities beyond LEO. In theory you could use it to put up a small boost stage for a light interplanetary probe, but its cargo capacity was a bit small for that, and there’s just no point using a whole shuttle to do it. Now that we have Falcon 9 and He…

The Shuttle was never designed to support Lunar missions so that's a red herring. It was designed to recover satellites and bring them back to Earth safely as part of its military mission. Nothing Space X is offering has such a capability. Different vehicles for different roles.

The contention was that it was the most capable spacecraft ever flown, without qualification and no reference to LEO, so I think pointing out that it's domain of operations was actually very limited is reasonable.

The shuttle was very well deigned for what it was intended to do, that's quite right, it's just a shame it was never used to perform one of it's primary tasks. However it also doomed the manned US space programme to operate exclusively in LEO for the vehicle's lifetime.

Re: Crew Dragon Docks with ISS

#247

Post by simonh »

GuB-42 wrote: post #235
simonh wrote: post #172

Earlier quoted context omitted.

It was an amazing vehicle and highly capable in some way, but severely constrained in others. The main problem is it was almost completely useless for any missions or activities beyond LEO. In theory you could use it to put up a small boost stage for a light interplanetary probe, but its cargo capacity was a bit small for that, and there’s just no point using a whole shuttle to do it. Now that we have Falcon 9 and He…

My understanding is that Falcon rockets are not optimal beyond LEO. They can do it of course, Falcon Heavy could launch a car in the general direction of Mars. But they are limited by their use of kerosene in their 2nd stage and its low specific impulse compared to hydrogen. BFR and it's Raptor engines are better suited for that purpose. But we don't have a BFR yet.

That's true Hydrolox is by far preferred for upper stages, particularly for interplanetary missions. However Heavy is so powerful it compensates quite well for it's compromises in that area. It can still boost double the payload to Trans-Mars Injection than Delta IV Heavy and more again than Atlas(1).

(1) As Dom Toretto always says, American Muscle beats Import every time ;)

Re: Crew Dragon Docks with ISS

#248

Post by mattowen_uk »

haunter wrote: post #17

Currently they have problems with the voice between ISS and Dragon. There is a huge interference and they can't read it. Funny enough we the viewers hear it loud and clear

They were trying to get the 'Hard wire' link working - which is the direct cable link between the ISS and Dragon. What we were all hearing, was the 'Big Loop' which is comms via Mission Control, SpaceX, Dragon, and the ISS - which carries a couple of seconds delay.

What got me, was that the whole boarding process was held up for over 30 minutes, because NASA couldn't progress past their 'hard wire' item on their checklist.

They eventually switched to RF (radio) direct link between the ISS and Dragon to be able to progress past that checklist item - later on the hard wire audio was fixed and working.

Re: Crew Dragon Docks with ISS

#249

Post by mcpherrinm »

pfdietz wrote: post #182
kbenson wrote: post #171

Earlier quoted context omitted.

> Simply evolving the Saturn 1B (which was cheaper, per lb of payload to orbit, than the Saturn V) could have easily beaten the Shuttle's economic performance. I don't know how much it applies, but sometimes evolving something requires switching out components for other ones, which are more expensive. Not everything scales. Marketing isn't the only reason why 50% more capability often costs 100% more. I imagine with…

We have an example of a better component, that is otherwise very similar: the first stage engines of the Saturn IB and the Falcon 9: H-1: https://en.wikpedia.org/wiki/Rocketdyne_H-1 Merlin: https://en.wikipedia.org/wiki/SpaceX_Merlin The Merlin has considerably higher specific impulse and thrust/weight ratios. It also has very fast throttling, a necessity for vertical landing. And, it's remarkably cheap (less than $1…

There is a typo in the H-1 link It should be: https://en.wikipedia.org/wiki/Rocketdyne_H-1

Re: Crew Dragon Docks with ISS

#250

Post by mortehu »

yellowapple wrote: post #20
cbhl wrote: post #13

Earlier quoted context omitted.

First three times I tried doing it by eye and ended up hopelessly lost. Needed to pull out my trigonometry to figure out how to line up the capsule to get the Y/Z aligned...

I got it on the first try, but only because I've got 600+ hours of Kerbal Space Program under my belt (where docking is much harder when you consider that docking in KSP entails actually getting to the target and doing it with imbalanced RCS thrusters that I placed on the craft willy-nilly; SpaceX's online docking sim was a breeze in comparison). Trick was to get rotation aligned first, then worry about translation.…

If you do rotation then translation, you're either going to waste fuel or time. Just aim for the target and get within 20 meters before doing any of that, and the amount of translation you'll have to do is minimal. It's like traveling on the hypotenuse instead of the other two sides of a right triangle.
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