Author Topic: General Falcon and Dragon discussion (Thread 12)  (Read 285517 times)

Offline Chris Bergin

Thread 12 for general discussion on SpaceX's Falcon and Dragon vehicles. Thread 11 isn't locked for the interim, just relocated in the SpaceX "100,000 plus archive section." Allowing quotes from that thread to be posted into this new thread.

Previous threads (now over 3 million views for these 11 SpaceX threads alone):

Thread 1:
http://forum.nasaspaceflight.com/index.php?topic=19228.0

Thread 2:
http://forum.nasaspaceflight.com/index.php?topic=22769.0

Thread 3:
http://forum.nasaspaceflight.com/index.php?topic=24179.0

Thread 4:
http://forum.nasaspaceflight.com/index.php?topic=25597.0

Thread 5:
http://forum.nasaspaceflight.com/index.php?topic=28006.0

Thread 6:
http://forum.nasaspaceflight.com/index.php?topic=29476.0

Thread 7:
http://forum.nasaspaceflight.com/index.php?topic=30385.0

Thread 8:
http://forum.nasaspaceflight.com/index.php?topic=31402.0

Thread 9:
http://forum.nasaspaceflight.com/index.php?topic=32719.0

Thread 10:
http://forum.nasaspaceflight.com/index.php?topic=33598.0

Thread 11:
http://forum.nasaspaceflight.com/index.php?topic=35364.0


SpaceX news articles on this site:
Old: http://forum.nasaspaceflight.com/index.php?topic=21862.0 (links)

Then recent news articles, not linked above, as we moved to a tag group system:
All recent: http://www.nasaspaceflight.com/tag/spacex/


L2 SpaceX - Dedicated all-vehicle (Falcon to BFR/MCT) section:
http://forum.nasaspaceflight.com/index.php?board=60.0


NOTE: Posts that are uncivil (which is very rare for this forum), off topic (not so rare) or just pointless will be deleted without notice.

Offline SpacemanInSPACE

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #1 on: 02/17/2015 07:36 PM »
Amazing how many developments they have coming up for the falcon/dragon system. 1st stage resuse efforts, dragon pad abort, falcon heavy demo.... Did I miss something??
Space is worth it God Damnit!

Offline docmordrid

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #2 on: 02/18/2015 01:48 AM »
SFN is running with the LC-13 and SLC-4W landing pad leases

Link....
« Last Edit: 02/18/2015 01:48 AM by docmordrid »
DM

Offline deltaV

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #3 on: 02/18/2015 03:54 AM »
From the previous thread:

If the ISS is 180 degrees out of phase only some kind of magic propellantless propulsion is going to allow you to reach it in a few hours.

If you have about 1.6 km/s of delta-vee (or less depending on the latitude of launch site and inclination of target orbit) to waste on a worst-case plane change you can rendezvous with the ISS in one-quarter orbit (less than half an hour). There are two launch opportunities when the phasing is exactly right but the planes are a bit off; launch at the one with the smaller plane change requirement. Phasing isn't important enough to be worth investing that much delta-vee in, but if you wanted to you could do it by e.g. using Falcon Heavy instead of Falcon 9. No advanced preparation nor magic propulsion required. I'm not saying this is a good idea, just that your "magic" claim is wrong.

Offline oiorionsbelt

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #4 on: 02/25/2015 04:09 PM »
Not sure if this picture has been posted elsewhere, so in case it hasn't ....

Offline dror

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #5 on: 02/25/2015 05:19 PM »
This picture and the sight of the expanding flame during launches got me thinking, and I know nothing about it, what if the middle engine was replaced with a truncated spike?
Could it perform a bit like an aerospike engine?
Could it raise the overall ISP by even a nudge?
 :-\
"If we crave some cosmic purpose, then let us find ourselves a worthy goal. "
Carl Sagan, Pale Blue Dot

Offline RanulfC

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #6 on: 02/25/2015 05:45 PM »
This picture and the sight of the expanding flame during launches got me thinking, and I know nothing about it, what if the middle engine was replaced with a truncated spike?
Could it perform a bit like an aerospike engine?
Could it raise the overall ISP by even a nudge?
 :-\

Not really helpful as you'd lose about 147,000lbs of thrust which you need on takeoff :)

It WOULD perform "like" an aerospike because that's what it would be and there'd be some ISP improvement in general but no where near enough to make up for the lost thrust :)

Randy
From The Amazing Catstronaut on the Black Arrow LV:
British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

Offline Helodriver

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #7 on: 02/25/2015 05:54 PM »
Not sure if this picture has been posted elsewhere, so in case it hasn't ....


I know it has because I'm the one who shot originally shot it.

Taken last year at the Dragon 2 reveal event.

Here it is full size.

Online abaddon

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #8 on: 02/25/2015 05:55 PM »
This picture and the sight of the expanding flame during launches got me thinking, and I know nothing about it, what if the middle engine was replaced with a truncated spike?
Could it perform a bit like an aerospike engine?
Could it raise the overall ISP by even a nudge?
 :-\

Not really helpful as you'd lose about 147,000lbs of thrust which you need on takeoff :)

It WOULD perform "like" an aerospike because that's what it would be and there'd be some ISP improvement in general but no where near enough to make up for the lost thrust :)

Randy

Not to mention, how are you going to land the thing?

Online Lars-J

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #9 on: 02/25/2015 05:57 PM »
This picture and the sight of the expanding flame during launches got me thinking, and I know nothing about it, what if the middle engine was replaced with a truncated spike?
Could it perform a bit like an aerospike engine?
Could it raise the overall ISP by even a nudge?
 :-\

Not really helpful as you'd lose about 147,000lbs of thrust which you need on takeoff :)

It WOULD perform "like" an aerospike because that's what it would be and there'd be some ISP improvement in general but no where near enough to make up for the lost thrust :)

Randy

Not to mention, how are you going to land the thing?

Very carefully, balancing on the truncated spike. ;)

No, I don't think aerospike is worth it for a first stage, since most of its thrust expended deep in the atmosphere.

Offline Jim

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #10 on: 02/25/2015 06:04 PM »
Also, that spike would be very narrow and hence not much to "push" on

Offline oiorionsbelt

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #11 on: 02/25/2015 06:17 PM »
Thanks Helodriver.
 What is IPA? International Pale Ale? :)
It's between E9and E8

Offline SpacemanInSPACE

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #12 on: 02/25/2015 08:21 PM »
Next Dragon leaving Hawthorne according to Spacex twitter, likely CRS-6.

Bout time for a new mission thread Chris!  ;D

https://twitter.com/SpaceX/status/570673437770948608
Space is worth it God Damnit!

Offline kch

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #13 on: 02/25/2015 08:30 PM »
Thanks Helodriver.
 What is IPA? International Pale Ale? :)
It's between E9and E8

Very close:

http://en.wikipedia.org/wiki/India_Pale_Ale

 ;D

Offline spacenut

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #14 on: 02/25/2015 08:39 PM »
What if they used an aerospike engine on the second stage and it served double duty as a heat shield for second stage return?  Would that affect overall performance?

Offline ISP

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #15 on: 02/25/2015 09:06 PM »
What if they used an aerospike engine on the second stage and it served double duty as a heat shield for second stage return?  Would that affect overall performance?

There is no advantage in placing an aerospike engine on the second stage. A conventional bell nozzle does better.

Aerospike engines are meant to mitigate under/over expansion of the exhaust of a rocket in the atmosphere, since that (slightly) decreases performance. This happens because the air pressure decreases at altitude, and a nozzle can only work "efficiently" at either sea-level or vacuum. It's why, for every rocket engine, the Isp tends to be higher in a vacuum than at sea level.

A traditional bell nozzles does fine in a vacuum; an aerospike would quickly become inefficient.

Offline inventodoc

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #16 on: 02/25/2015 10:43 PM »
This picture and the sight of the expanding flame during launches got me thinking, and I know nothing about it, what if the middle engine was replaced with a truncated spike?
Could it perform a bit like an aerospike engine?
Could it raise the overall ISP by even a nudge?
 :-\

I'd like to applaud the creative thinking of this post as well as the interesting assessment by others afterwards.

Offline spacenut

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #17 on: 02/25/2015 11:57 PM »
I wasn't thinking of efficiency, but a method of returning the 2nd stage using the aerospike as a heat shield so the second stage could be reused. 

Online deruch

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #18 on: 02/26/2015 06:29 AM »
Has anyone heard anything about NASA directing SpaceX to redesign Dragon to be able to carry water for the ISS?  This was the first I've seen about it:

http://spaceflightnow.com/2015/01/15/nasa-hopes-to-replace-cargo-lost-on-antares-failure-this-year/

Quote
Gerstenmaier said the Antares launch failure proved the value of having at least two suppliers capable of sending cargo to the space station. It also shows why NASA selected two companies — Boeing and SpaceX — to fly astronauts to the complex.

“You don’t put all your critical spares on one vehicle,” Gerstenmaier said. “If you can split between two vehicles or three vehicles, from a redundancy standpoint then you can effectively utilize your redundancy.”

He said NASA already directed SpaceX to redesign its Dragon cargo capsule to carry water to the space station, a capability that only Orbital’s Cygnus spacecraft was previously able to handle.

“We thought we had enough redundancy so we didn’t have to make design changes to carry water on both vehicles, but now, in hindsight, we need to make a design change,” Gerstenmaier said. “We accepted some non-redundancy items to keep costs down, now we know we need that redundancy.”

How does that work exactly?  Is NASA on the hook to pay for any vehicle changes they request?  It would be one thing if Elon said, "Hey, we're changing Dragon a bit so that it can freight water to the station."  But, if the article is to be believed, Gerstenmaier said NASA is ordering it.  Does the CRS contract allow them to do so?  Does it have a mechanism to deal with the costs of changing the vehicle to meet new customer requirements?

I think it's a good idea btw.

How does that need a redesign? It can transport all that other stuff. Couldn't they just put some containers in there?

The work (and the cost associated with it) is not for the water redesign per-se.

Its mostly for paperwork, to document and certify how the (probably bags of) water will be stowed, secured and moved in and out, and to ensure safety, mass-distribution, leak risk and handling etc.

When the mass of the paper > the mass of the water, they'll be good to go  :P

Does anyone have an estimate on a reasonable timeline for completion of the work so Dragon can do water deliveries to the ISS?  Could it be finished in time for the upcoming CRS-6?  It was mentioned in the pre-EVA briefing that they were targeting CRS-6 for mid to late April now.  Might that slip (from 4/8) be related to the time needed to finish the "design changes" (assuming that most of the work was study and documentation as opposed to physical changes).  SpaceX just tweeted out pics of the finished Dragon capsule ready for shipping to the Cape (see link below), so I don't imagine that a delayed capsule is the hold up.

http://forum.nasaspaceflight.com/index.php?topic=36892.msg1337723#msg1337723

 
Shouldn't reality posts be in "Advanced concepts"?  --Nomadd

Offline dror

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #19 on: 02/26/2015 06:59 AM »
Can water be transported in a special container in the unpressurised trunk?
I believe that was the method in ATV.
Seems like a waste of much needed volume to put it in bags inside the small capsule.
"If we crave some cosmic purpose, then let us find ourselves a worthy goal. "
Carl Sagan, Pale Blue Dot

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