Author Topic: SpaceX Dragon 2 Updates and Discussion - Thread 2  (Read 707062 times)

Offline StealthGhost

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Re: SpaceX Dragon 2 Updates and Discussion - Thread 2
« Reply #1020 on: 01/26/2018 06:33 pm »
Propulsive landing has since been canceled for Dragon 2 so it’s more than likely the final version of Dragon 2 willl not have those lading leg holes drilled into the heat shield.

Also hear further delays have taken place due to safety concerns regarding the inner pressure vessel of Dragon 2. First orbital launch of Dragon 2 could take place no earlier than Q4 2018, further delays are very likely to push Dragon 2 test flight to 2019 or 2020. If all goes well more likely we will see the first human missions for SpaceX in the early 2020’s the latest.
« Last Edit: 01/26/2018 06:36 pm by StealthGhost »

Offline joek

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Re: SpaceX Dragon 2 Updates and Discussion - Thread 2
« Reply #1021 on: 01/28/2018 05:44 am »
In round 2 of COTS NASA then chose the system with least capabilities (Orbital's Antares/Cygnus) in stead of the Boeing offer. The former had no cargo return capability (Capability C) whereas the latter did have Capability C.

So yeah, bad planning on NASA's part.

One of the often forgotten reasons for rejecting proposals including Boeing and LM EELV's (both COTS-1 and -2), and one of the justifications for the approach taken by COTS, was NASA's need for an affordable medium-class LV (Delta-II replacement).  Bad planning on NASA's part?  Maybe, if viewed through a narrow lens.

Offline tyrred

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Re: SpaceX Dragon 2 Updates and Discussion - Thread 2
« Reply #1022 on: 01/28/2018 06:03 am »
Propulsive landing has since been canceled for Dragon 2 so itís more than likely the final version of Dragon 2 willl not have those lading leg holes drilled into the heat shield.

Also hear further delays have taken place due to safety concerns regarding the inner pressure vessel of Dragon 2. First orbital launch of Dragon 2 could take place no earlier than Q4 2018, further delays are very likely to push Dragon 2 test flight to 2019 or 2020. If all goes well more likely we will see the first human missions for SpaceX in the early 2020ís the latest.

SpaceX has so far, to my knowledge, only had a final version of Falcon 1.  Final version of Dragon?  This is not the capsule you're looking for.

Can you point to source of further delays of Dragon 2 due to pressure vessel concerns?  Source/citation needed, please.

Offline joek

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Re: SpaceX Dragon 2 Updates and Discussion - Thread 2
« Reply #1023 on: 01/28/2018 06:14 am »
Propulsive landing has since been canceled for Dragon 2 so itís more than likely the final version of Dragon 2 willl not have those lading leg holes drilled into the heat shield.

Also hear further delays have taken place due to safety concerns regarding the inner pressure vessel of Dragon 2. First orbital launch of Dragon 2 could take place no earlier than Q4 2018, further delays are very likely to push Dragon 2 test flight to 2019 or 2020. If all goes well more likely we will see the first human missions for SpaceX in the early 2020ís the latest.

SpaceX has so far, to my knowledge, only had a final version of Falcon 1.  Final version of Dragon?  This is not the capsule you're looking for.

Can you point to source of further delays of Dragon 2 due to pressure vessel concerns?  Source/citation needed, please.

Only recent public report mentions concerns with second stage COPV's (ASAP report 11-Jan) in the context of CCtCap, not Dragon 2 pressure vessel?


p.s. assume you mean Dragon Cargo/1 or Falcon 9, not Falcon 1.

Offline joek

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Re: SpaceX Dragon 2 Updates and Discussion - Thread 2
« Reply #1024 on: 01/28/2018 07:09 am »
I would think that there would be a simple solution. NASA could simply not have any valuable downmass for the first propulsive landing or two. NASA went years without this capability, surely they could work around a couple of flights?
I have made that argument before. To which Jim replied that all downmass on Dragon is very valuable and NASA can not allow risking it.
Dragon is the only way that science (the main reason for ISS) can get back to earth.  Every down flight opportunity is needed.

Might be worth looking at the need for "valuable" downmass today (CRS1 Dragon only) vs. what will be available with CRS2+CCtCap (CRS2 Dragon berth and dock, and Dream Chaser + CCtCap Dragon and CST-100).

Don't have access to my archives at the moment, but given CRS2 and CCtCap requirements, should be simple to determine whether CRS2+CCtCap assets would satisfy "valuable" downmass needs and leave room for less valuable downmass on propulsive landing Dragon.  (E.g., disposal downmass on Dragon would be appropriate for testing propulsive landing.)

Online Comga

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Re: SpaceX Dragon 2 Updates and Discussion - Thread 2
« Reply #1025 on: 01/29/2018 12:52 am »
They can try testing propulsive landing in concert with parachutes during a splashdown.

Not feasible.  They don't work together.
Would, in principle, work for a Soyuz-style cushion. In fact, they once showed this in a CGI sequence at some talk somewhere (landing in the desert).

But anyway, full propulsive landing almost certainly isn't going to happen because it's require adding in the ballast sled again, requiring a significant redesign. So there's not really any point in trying a test like that  unless they want to land in the desert Soyuz-style.

Is that necessarily true?
SpaceX needs the ballast sled to effect precision propulsive landing.
Statements from SpaceX say that their geographic accuracy with the current parachute landing is something like a mile or two.
That's plenty accurate for someplace like east of Edwards.  When I had the value I laid out a circle that size at the end of the longest runway at Edwards, and it fit with margin.
So they should be able to use semi-propulsive landing, Soyuz style, without the sled.
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Online Comga

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Re: SpaceX Dragon 2 Updates and Discussion - Thread 2
« Reply #1026 on: 01/29/2018 01:44 am »
They can try testing propulsive landing in concert with parachutes during a splashdown.

Not feasible.  They don't work together.

They don't but are you saying it's impossible?
Could SpaceX not program the Dragon 2 capsule to slow it's descent under the parachutes?
If the SuperDraco's offset the capsule's mass by half it would slow the descent by about a third, wouldn't it?
That would go a long way to demonstrating braking.
The next step would be sensing the water (or ground) and braking to a halt.
There are many ways to sense the height above ground, some through a window.
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline IanThePineapple

Re: SpaceX Dragon 2 Updates and Discussion - Thread 2
« Reply #1027 on: 01/29/2018 01:46 am »
They can try testing propulsive landing in concert with parachutes during a splashdown.

Not feasible.  They don't work together.

They don't but are you saying it's impossible?
Could SpaceX not program the Dragon 2 capsule to slow it's descent under the parachutes?
If the SuperDraco's offset the capsule's mass by half it would slow the descent by about a third, wouldn't it?
That would go a long way to demonstrating braking.
The next step would be sensing the water (or ground) and braking to a halt.
There are many ways to sense the height above ground, some through a window.

Pull a Soyuz and puff the engines RIGHT before splashdown to make it extra-smooth.

Online Comga

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Re: SpaceX Dragon 2 Updates and Discussion - Thread 2
« Reply #1028 on: 01/29/2018 01:59 am »
They can try testing propulsive landing in concert with parachutes during a splashdown.

Not feasible.  They don't work together.

They don't but are you saying it's impossible?
Could SpaceX not program the Dragon 2 capsule to slow it's descent under the parachutes?
If the SuperDraco's offset the capsule's mass by half it would slow the descent by about a third, wouldn't it?
That would go a long way to demonstrating braking.
The next step would be sensing the water (or ground) and braking to a halt.
There are many ways to sense the height above ground, some through a window.

Pull a Soyuz and puff the engines RIGHT before splashdown to make it extra-smooth.

Obviously, but rather they could be ramped up, rather than "puffed", to bring the velocity to near zero as the height approaches zero, like the first stages.  Keep the acceleration under very strict limits. 
Better than "pulling a Soyuz", which has been described as pretty violent and none too pleasant.
But which, nevertheless, is the way we now bring American astronauts home from the ISS.
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline IanThePineapple

Re: SpaceX Dragon 2 Updates and Discussion - Thread 2
« Reply #1029 on: 01/29/2018 02:00 am »
They can try testing propulsive landing in concert with parachutes during a splashdown.

Not feasible.  They don't work together.

They don't but are you saying it's impossible?
Could SpaceX not program the Dragon 2 capsule to slow it's descent under the parachutes?
If the SuperDraco's offset the capsule's mass by half it would slow the descent by about a third, wouldn't it?
That would go a long way to demonstrating braking.
The next step would be sensing the water (or ground) and braking to a halt.
There are many ways to sense the height above ground, some through a window.

Pull a Soyuz and puff the engines RIGHT before splashdown to make it extra-smooth.

Obviously, but rather they could be ramped up, rather than "puffed", to bring the velocity to near zero as the height approaches zero, like the first stages.  Keep the acceleration under very strict limits. 
Better than "pulling a Soyuz", which has been described as pretty violent and none too pleasant.
But which, nevertheless, is the way we now bring American astronauts home from the ISS.

Ok then, so throttle up the engines semi-slowly before splashdown, and touch down very softly.

Offline Nomadd

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Re: SpaceX Dragon 2 Updates and Discussion - Thread 2
« Reply #1030 on: 01/29/2018 03:04 am »
 It's not so simple. As soon as the engines slow the capsule down the parachutes will lose lift in a way that's not easy to predict. The only good way is to cut away from the chutes before you use the engines.
« Last Edit: 01/29/2018 03:05 am by Nomadd »
Those who danced were thought to be quite insane by those who couldn't hear the music.

Offline AncientU

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Re: SpaceX Dragon 2 Updates and Discussion - Thread 2
« Reply #1031 on: 01/29/2018 01:40 pm »
Or maybe just use the propulsive landing as designed and parachutes as back-up... nah, better to jury-rig something. :(
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Offline IanThePineapple

Re: SpaceX Dragon 2 Updates and Discussion - Thread 2
« Reply #1032 on: 01/29/2018 01:46 pm »
Or maybe just use the propulsive landing as designed and parachutes as back-up... nah, better to jury-rig something. :(

Well, you don't really need landing legs for landing in the ocean...

Offline deruch

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Re: SpaceX Dragon 2 Updates and Discussion - Thread 2
« Reply #1033 on: 01/29/2018 08:49 pm »
It's not so simple. As soon as the engines slow the capsule down the parachutes will lose lift in a way that's not easy to predict. The only good way is to cut away from the chutes before you use the engines.

For this reason, a possibly better choice to achieve testing of the SDs on returns would be to try the same sort of minor usage prior to any parachute deployment.  But, this increases the risk that you destabilize the capsule.  Basically, there ain't no such thing as a free lunch.  If SpaceX's customer isn't willing to accept a higher than otherwise necessary risk to its returning cargo--regardless of whether we think the potential returns make such a relatively minor risk well worth it--the only way for them to test it would be with a fully self-funded, dedicated test.  Something that they've clearly decided is not worth the expenditure given they no longer view further development of the capsule shape as being on their long term path forward.
Shouldn't reality posts be in "Advanced concepts"?  --Nomadd

Offline speedevil

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Re: SpaceX Dragon 2 Updates and Discussion - Thread 2
« Reply #1034 on: 02/07/2018 12:21 am »
I read that Spacex had removed the landing legs from the Dragon2 so no landing on solid surfaces as it would damage the heat shield, that includes ships. However it appears Spacex are attempting to catch the F9 fairing in what appears to be a net hung between 4 arms on a fast ship at sea. If they can do this then they may very well attempt to catch a Dragon2 with a net. Stopping the Dragon2 from entering the sea would save money on referb time. I have no evidence for this but it seems logical and could save Spacex money and achieve at least some of the original promise of Dragon2.

I would say, not a chance! First you need precision landing (800m doesn't cut it), second it is several magnitudes heavier than a fairing half (how big/strong would the net have to be?), third if it missed and hit the side of the ship, the crew could die.


- hah.

Quote
We've got a special boat to catch the fairing, like a catcher's mitt. It's like a giant catchers mitt in boat form.
 It's gonna run around and catch the fairing.
Kinda fun.
I think you might be able to do the same thing with dragon so if NASA wants us to, we could try to catch dragon.
Made for the fairing, but it would work for dragon too.
When talking about fairing recovery, Musk talks about Mr Steven, and that it could do Dragon recovery :)
« Last Edit: 02/07/2018 12:27 pm by speedevil »

Offline yg1968

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Re: SpaceX Dragon 2 Updates and Discussion - Thread 2
« Reply #1035 on: 02/07/2018 03:55 pm »
That was an interesting comment. But technically, it's actually up to SpaceX to decide how they land Dragon2. It's harder to certify something that hasn't been done before but it is possible. It might be a good idea to try this with cargo Dragon2.

Offline speedevil

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Re: SpaceX Dragon 2 Updates and Discussion - Thread 2
« Reply #1036 on: 02/07/2018 04:05 pm »
That was an interesting comment. But technically, it's actually up to SpaceX to decide how they land Dragon2. It's harder to certify something that hasn't been done before but it is possible. It might be a good idea to try this with cargo Dragon2.
I consider it vanishingly unlikely this'd happen.

The whole issue with 'try this with Cargo Dragon2' has been that it appears that they have no 'spare' missions to allow spacex to try wacky stuff on, as downmass turns out to be a problem due to the way the contracts shook out.
This means that in order for SpaceX to prove this, they'd likely have to do it on their own missions, and ...

Online butters

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Re: SpaceX Dragon 2 Updates and Discussion - Thread 2
« Reply #1037 on: 02/07/2018 04:09 pm »
That was an interesting comment. But technically, it's actually up to SpaceX to decide how they land Dragon2. It's harder to certify something that hasn't been done before but it is possible. It might be a good idea to try this with cargo Dragon2.

It might be a good idea, but given NASA's opposition to trying propulsive landing with cargo Dragon 2, I doubt they'd let SpaceX do it. Let's face it: the commercial crew program is a dead-end for SpaceX. NASA won't let SpaceX do what they need to do to make Dragon 2 useful for anything other than ISS missions, so that's all it will ever do. The commercial part of the commercial crew program is dead.

Offline su27k

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Re: SpaceX Dragon 2 Updates and Discussion - Thread 2
« Reply #1038 on: 02/07/2018 04:20 pm »
That was an interesting comment. But technically, it's actually up to SpaceX to decide how they land Dragon2. It's harder to certify something that hasn't been done before but it is possible. It might be a good idea to try this with cargo Dragon2.
I consider it vanishingly unlikely this'd happen.

The whole issue with 'try this with Cargo Dragon2' has been that it appears that they have no 'spare' missions to allow spacex to try wacky stuff on, as downmass turns out to be a problem due to the way the contracts shook out.
This means that in order for SpaceX to prove this, they'd likely have to do it on their own missions, and ...

Not necessarily, the problem with propulsive landing test is that for some reason it couldn't be done with the help of helicopters or cargo planes, it requires a real launch which makes it super expensive to even do one test. But parachute landing can be tested by dropping Dragon from helicopter or cargo planes, there's no need for "spare" mission or their own missions, just using whatever test method they're using for qualifying the parachute should be enough.
« Last Edit: 02/07/2018 04:22 pm by su27k »

Offline yg1968

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Re: SpaceX Dragon 2 Updates and Discussion - Thread 2
« Reply #1039 on: 02/07/2018 07:33 pm »
That was an interesting comment. But technically, it's actually up to SpaceX to decide how they land Dragon2. It's harder to certify something that hasn't been done before but it is possible. It might be a good idea to try this with cargo Dragon2.
I consider it vanishingly unlikely this'd happen.

The whole issue with 'try this with Cargo Dragon2' has been that it appears that they have no 'spare' missions to allow spacex to try wacky stuff on, as downmass turns out to be a problem due to the way the contracts shook out.
This means that in order for SpaceX to prove this, they'd likely have to do it on their own missions, and ...

Not necessarily, the problem with propulsive landing test is that for some reason it couldn't be done with the help of helicopters or cargo planes, it requires a real launch which makes it super expensive to even do one test.

Do we know this for a fact? Dragonfly did not involve any F9 launches.

https://en.wikipedia.org/wiki/DragonFly_(rocket)

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