Author Topic: Dragon Landing Accuracy D1 vs D2  (Read 3062 times)

Offline Wolfram66

Dragon Landing Accuracy D1 vs D2
« on: 01/13/2018 05:25 PM »
What is the Landing accuracy of Cargo Dragon D1 vs Crew/Cargo Dragon D2 ? I always wondered why SpaceX splashes Down where they do in the Pacific. If they are to transport returned science to Texas, why not land in Gulf of Mexico?

Offline Jim

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Re: Dragon Landing Accuracy D1 vs D2
« Reply #1 on: 01/13/2018 05:30 PM »
Trunk/service module disposal

Offline kevinof

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Re: Dragon Landing Accuracy D1 vs D2
« Reply #2 on: 01/13/2018 05:39 PM »
what Jim is saying is that it's not just the Dragon that returns but also the trunk, which you have no control over. You need somewhere reasonably big to dump the trunk into without fear of hitting anything (except the water).

What is the Landing accuracy of Cargo Dragon D1 vs Crew/Cargo Dragon D2 ? I always wondered why SpaceX splashes Down where they do in the Pacific. If they are to transport returned science to Texas, why not land in Gulf of Mexico?

Offline Flying Beaver

Re: Dragon Landing Accuracy D1 vs D2
« Reply #3 on: 01/13/2018 06:18 PM »
Dragon 2 is splashing down off of Cape, Hence the new crane on Go Searcher.

https://www.facebook.com/photo.php?fbid=1857957254214877&set=pcb.10156132176541318&

Maybe two de-orbit burns? first, one to dispose the truck further out in the Atlantic, and then a second to shorten up the trajectory for the capsule?

From the LZ-1 Pad 2/Dragon Processing Facility EIA.

Quote
"the Dragon capsule would splashdown off the coast of Florida where
vehicle recovery would occur."

http://forum.nasaspaceflight.com/index.php?topic=36513.msg1627861#msg1627861
Watched B1019 land in person 21/12/2015.

Offline biosehnsucht

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Re: Dragon Landing Accuracy D1 vs D2
« Reply #4 on: 01/13/2018 07:18 PM »
Could you not do a first deorbit burn and then drop the Trunk/SM so that it lands in the middle of the drink, then tweak your orbit accordingly to pick a different location for the Dragon? The prop is all in the Dragon itself, isn't it? As long as you don't plan to boost yourself back to orbit and sit there for a long time before de-orbiting for real... how long can D1/D2 operate without the Trunk/SM ?

Offline Flying Beaver

Re: Dragon Landing Accuracy D1 vs D2
« Reply #5 on: 01/13/2018 07:25 PM »
Could you not do a first deorbit burn and then drop the Trunk/SM so that it lands in the middle of the drink, then tweak your orbit accordingly to pick a different location for the Dragon? The prop is all in the Dragon itself, isn't it? As long as you don't plan to boost yourself back to orbit and sit there for a long time before de-orbiting for real... how long can D1/D2 operate without the Trunk/SM ?

Dragon's truck (both 1 and 2) is used for power generation (solar) and heat dispersal (radiators). Both very important on orbit.

You want to know your coming home before you throw it away.
Watched B1019 land in person 21/12/2015.

Offline Elmar Moelzer

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Re: Dragon Landing Accuracy D1 vs D2
« Reply #6 on: 01/13/2018 10:24 PM »
Hope this is not too off topic, but I always disliked the fact that Dragon2 still has a trunk that is disposed off for landing. I think that an integrated trunk would not only safe money but would also result in a more buoyant craft that should theoretically already slow down higher in the atmosphere and thus would - to my understanding - put less stress on a TPS.
« Last Edit: 01/13/2018 10:25 PM by Elmar Moelzer »

Offline nacnud

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Re: Dragon Landing Accuracy D1 vs D2
« Reply #7 on: 01/13/2018 10:34 PM »
..but I always disliked the fact that Dragon 2 still has a trunk that is disposed of for landing...

Hence BFR/BFS
« Last Edit: 01/15/2018 12:05 AM by nacnud »

Offline Wolfram66

Re: Dragon Landing Accuracy D1 vs D2
« Reply #8 on: 01/14/2018 12:05 AM »
Trunk/service module disposal
Thanks Jim, that makes sense.

Q) What is the Landing ellipse accuracy? Are there EI & atmospheric  guidance changes between D1 & D2 ?  ???

Offline deruch

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Re: Dragon Landing Accuracy D1 vs D2
« Reply #9 on: 01/14/2018 01:01 AM »
Hope this is not too off topic, but I always disliked the fact that Dragon2 still has a trunk that is disposed off for landing. I think that an integrated trunk would not only safe money but would also result in a more buoyant craft that should theoretically already slow down higher in the atmosphere and thus would - to my understanding - put less stress on a TPS.

Every single space capsule (except shuttle, if you're being loose with "capsule") has disposed of the "service module" before reentry, which tells me that this is likely either a much harder problem than you imagine, totally unworkable for some reason, or just not at all worth it.  My first guess would be that if you were going to try to do that, you would have to reengineer the trunk to support much higher loads than it currently sees and you would therefore lose significant performance for not that much gain.  Not to mention that it would totally change the gumdrop profile of the capsule, etc.  Also, you would have to figure out some sort of garage door operation to access unpressurized payloads in the trunk that are now behind your heat shield.
Shouldn't reality posts be in "Advanced concepts"?  --Nomadd

Offline the_other_Doug

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Re: Dragon Landing Accuracy D1 vs D2
« Reply #10 on: 01/14/2018 01:12 AM »
Hope this is not too off topic, but I always disliked the fact that Dragon2 still has a trunk that is disposed off for landing. I think that an integrated trunk would not only safe money but would also result in a more buoyant craft that should theoretically already slow down higher in the atmosphere and thus would - to my understanding - put less stress on a TPS.

Every single space capsule (except shuttle, if you're being loose with "capsule") has disposed of the "service module" before reentry, which tells me that this is likely either a much harder problem than you imagine, totally unworkable for some reason, or just not at all worth it.  My first guess would be that if you were going to try to do that, you would have to reengineer the trunk to support much higher loads than it currently sees and you would therefore lose significant performance for not that much gain.  Not to mention that it would totally change the gumdrop profile of the capsule, etc.  Also, you would have to figure out some sort of garage door operation to access unpressurized payloads in the trunk that are now behind your heat shield.

Close, but not quite -- Mercury had no service or support module, just a retrofire pack that was pretty much guaranteed to completely burn up coming in.

That said, Gemini flights landed in the Atlantic, mostly.  Their adapter sections had high-pressure tanks and such that likely survived entry.  And they could not be de-orbited in a targeted fashion, as they had to be dumped just to expose the retros.  Of course, back in the 60s, I suppose you were supposed to be flattered if a piece of space junk came down on your house... :D
-Doug  (With my shield, not yet upon it)

Offline woods170

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Re: Dragon Landing Accuracy D1 vs D2
« Reply #11 on: 01/14/2018 06:28 PM »
Hope this is not too off topic, but I always disliked the fact that Dragon2 still has a trunk that is disposed off for landing. I think that an integrated trunk would not only safe money but would also result in a more buoyant craft that should theoretically already slow down higher in the atmosphere and thus would - to my understanding - put less stress on a TPS.

That would seriously complicate the spacecraft.
Remember, Dragon was developed when SpaceX "didn't really know what they were doing" (their quote) with regards to designing a spacecraft.
So they chose to go KISS (Keep It Simple Silly).
They had bid COTS for both pressurized AND unpressurized cargo. Unpressurized had to go outside the pressure vessel, which in itself was based on existing-and-proven outer mold lines (again: KISS).
That led to the trunk as we see today.

Crew Dragon (aka Dragon 2) is still adhering to the KISS principle. The trunk from Cargo Dragon is beautiful in its simplicity so it was kept unaltered. Prime focus for Crew Dragon is focused on its primary function: fly crew. You don't go wasting money on something that doesn't need changing.

Offline kevinof

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Re: Dragon Landing Accuracy D1 vs D2
« Reply #12 on: 01/14/2018 06:33 PM »
except for the Solar panels which will no longer be folded, and instead be part of the walls of the trunk. But then , that's making it simpler again.

...
Crew Dragon (aka Dragon 2) is still adhering to the KISS principle. The trunk from Cargo Dragon is beautiful in its simplicity so it was kept unaltered. Prime focus for Crew Dragon is focused on its primary function: fly crew. You don't go wasting money on something that doesn't need changing.

Tags: cargo COTS CRS SpaceX Dragon Crew