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Author Topic: SpaceX (general discussion)  (Read 228815 times)

Offline cluttonfred

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Re: SpaceX (general discussion)
« Reply #15 on: September 13, 2012, 12:23:48 pm »
All very helpful, Randy, thanks.
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Offline FutureSpaceTourist

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Re: SpaceX (general discussion)
« Reply #16 on: September 21, 2012, 11:26:41 pm »
Grasshopper has done a very brief initial hop. Blink and you'll miss it!


RGClark

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Re: SpaceX (general discussion)
« Reply #17 on: September 30, 2012, 12:12:10 am »
 The new Falcon 9 v1.1 will have its engines arranged in an octagonal arrangement:

Untested Rocket Boosts SpaceX Revenue Nearly $1 Billion.
By Amy Svitak
Source: Aviation Week & Space Technology
September 17, 2012
Quote
...Another change, she says, involves the rocket's nine Merlin 1D engines, which will be positioned in an octagonal configuration, rather than the “tic-tac-toe” placement on the current Falcon 9.
“You actually want the engines around the perimeter at the tank, otherwise you are carrying that load from those engines that are not on the skin,” she says. “You've got to carry them out to the skin, because that is the primary load path for the launch vehicle."
http://www.aviationweek.com/Article.aspx?id=/article-xml/AW_09_17_2012_p40-495349.xml&p=2

 See this thread on NasaSpaceflight for how this engine arrangement might look:

SpaceX Falcon 9 v1.1.
http://forum.nasaspaceflight.com/index.php?topic=28882.msg956757#msg956757

 This could have another advantage in that the octagonal arrangement of the engines makes possible the use of an aerospike in the center, if the center engine is removed.
 This would give the first stage engines Merlin Vacuum type performance, raising the Isp from the ca. 311 s of the Merlin 1D to the ca. 340 s of the Merlin Vacuum.
 This would result in a marked improvement in payload.


  Bob Clark

Offline Byeman

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Re: SpaceX (general discussion)
« Reply #18 on: September 30, 2012, 11:19:53 am »

 This could have another advantage in that the octagonal arrangement of the engines makes possible the use of an aerospike in the center, if the center engine is removed.
 This would give the first stage engines Merlin Vacuum type performance, raising the Isp from the ca. 311 s of the Merlin 1D to the ca. 340 s of the Merlin Vacuum.
 This would result in a marked improvement in payload.

Wrong for multiple. Not for a first stage booster and also in this case.  Another case of an armchair rocket scientist who doesn't know what what he is talking.

A.  The loss of thrust from the missing engine would reduce performance by much more than the gain
B.  The added mass of the aerospike would offset performance
C.  There is no basis/data/proof for the claim that the final ISP would be 340.
D.  The aerospike would make the vehilce incompatable with the existing launch pad and associated infrastructure.

There is no advantage to the suggested change

RGClark

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Re: SpaceX (general discussion)
« Reply #19 on: October 03, 2012, 12:23:46 am »

 This could have another advantage in that the octagonal arrangement of the engines makes possible the use of an aerospike in the center, if the center engine is removed.
 This would give the first stage engines Merlin Vacuum type performance, raising the Isp from the ca. 311 s of the Merlin 1D to the ca. 340 s of the Merlin Vacuum.
 This would result in a marked improvement in payload.

Wrong for multiple. Not for a first stage booster and also in this case.  Another case of an armchair rocket scientist who doesn't know what what he is talking.

A.  The loss of thrust from the missing engine would reduce performance by much more than the gain
B.  The added mass of the aerospike would offset performance
C.  There is no basis/data/proof for the claim that the final ISP would be 340.
D.  The aerospike would make the vehilce incompatable with the existing launch pad and associated infrastructure.

There is no advantage to the suggested change

 For A.) that would depend on the degree that the aerospike increases the Isp. You would also reduce dry mass on the reduced engine mass. For an aerospike engine formed from multiple chambers arrayed around a central spike, you also don't use full nozzles. The greatly shortened nozzles will also reduce dry mass.
 Prior studies on aerospikes showed close to optimal performance for a given engine chamber pressure by using the aerospike:

THRESHOLD.
Pratt & Whitney Rocketdyne's engineering journal of power technology.
Nozzle Design.
by R.A. O'Leary and J. E. Beck, Spring 1992

http://www.pwrengineering.com/articles/nozzledesign.htm


  Bob Clark

Offline Byeman

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Re: SpaceX (general discussion)
« Reply #20 on: October 03, 2012, 06:42:12 am »

 This could have another advantage in that the octagonal arrangement of the engines makes possible the use of an aerospike in the center, if the center engine is removed.
 This would give the first stage engines Merlin Vacuum type performance, raising the Isp from the ca. 311 s of the Merlin 1D to the ca. 340 s of the Merlin Vacuum.
 This would result in a marked improvement in payload.

Wrong for multiple. Not for a first stage booster and also in this case.  Another case of an armchair rocket scientist who doesn't know what what he is talking.

A.  The loss of thrust from the missing engine would reduce performance by much more than the gain
B.  The added mass of the aerospike would offset performance
C.  There is no basis/data/proof for the claim that the final ISP would be 340.
D.  The aerospike would make the vehilce incompatable with the existing launch pad and associated infrastructure.

There is no advantage to the suggested change

 For A.) that would depend on the degree that the aerospike increases the Isp. You would also reduce dry mass on the reduced engine mass. For an aerospike engine formed from multiple chambers arrayed around a central spike, you also don't use full nozzles. The greatly shortened nozzles will also reduce dry mass.
 Prior studies on aerospikes showed close to optimal performance for a given engine chamber pressure by using the aerospike:

  Bob Clark

Wrong again.  More regurgating internet engineering nonsense. 
Your premise was just to remove the center engine and use the remaining 8 in an aerospike.
It is ludrious to think just because they made a octocal engine arrangement it is more conducive to aerospike


Offline FutureSpaceTourist

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Re: SpaceX (general discussion)
« Reply #21 on: March 10, 2013, 02:48:58 pm »
On Thursday, 07/03/2013, SpaceX did their latest Grasshopper test and flew to 80m:

http://www.youtube.com/watch?&v=2Ivr6JF1K-8#!

Yesterday, in a keynote interview at the South by Southwest (SXSW) conference in Austin, Texas, Elon Musk said:

Quote from: http://www.newspacejournal.com/2013/03/09/more-on-grasshoppers-johnny-cash-hover-slam-test/
What you saw there was essentially testing the terminal guidance and landing capability of the rocket. With each successive test, we want to go higher and further and improve the technology to the point where we’re doing transitions all the way through hypersonic and back, hopefully later this year.

Hypersonic flight that lands ... that'll be quite a video!

Offline fredymac

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Re: SpaceX (general discussion)
« Reply #22 on: April 21, 2014, 12:16:30 pm »
Falcon 9 1st stage hovers over the Atlantic ocean after boosting the Dragon capsule to the ISS on Sunday.  Vehicle is hovering around 9 meters above the water.  There is a video at the Spacex Youtube website showing the Falcon 9R (re-useable) undergoing first powered hover flight.  Boeing and Lockheed are probably quoting Inigo Montoya about now:  "I wonder if he's using the same wind we are using?"
 

Offline sferrin

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Re: SpaceX (general discussion)
« Reply #23 on: April 21, 2014, 01:26:51 pm »
"DARPA Hard"  It ain't what it use to be.

Offline Orionblamblam

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Re: SpaceX (general discussion)
« Reply #24 on: April 21, 2014, 04:09:39 pm »
Falcon 9 1st stage hovers over the Atlantic ocean after boosting the Dragon capsule to the ISS on Sunday.  Vehicle is hovering around 9 meters above the water.

As sferrin pointed out, that's not even close to an accurate description of that photo (wrong flight, wrong side of the continent, and very wrong altitude... it's not hovering above water, but Way Up There restarting an engine). And so, inquiring minds want to know: where did *your* description come from? Seems odd that it would be so wrong and yet so specific.
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Offline fredymac

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Re: SpaceX (general discussion)
« Reply #25 on: April 22, 2014, 02:52:14 am »

My bad.  I did an image search for a water landing of the Falcon 9 and this picture showed up.  I had never seen it before and assumed it was for Sunday.  The caption mentioned the specifics on hovering.


Spacex doesn’t release its’ photos right away (and they don’t have to since this is privately funded).  This is what comes of not wanting to wait for the official release.  Elon Musk had tweeted that the booster had indeed made a successful re-entry and this picture dovetailed with that.  Lesson learned.  Official release or multiple sources.


Offline Byeman

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Re: SpaceX (general discussion)
« Reply #26 on: April 22, 2014, 06:02:15 am »
Boeing and Lockheed are probably quoting Inigo Montoya about now:  "I wonder if he's using the same wind we are using?"

Why?  There hasn't been any real break through yet.  Boeing and Lockheed are very secure.

Offline sferrin

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Re: SpaceX (general discussion)
« Reply #27 on: April 22, 2014, 06:40:20 am »
Boeing and Lockheed are probably quoting Inigo Montoya about now:  "I wonder if he's using the same wind we are using?"

Why?  There hasn't been any real break through yet.  Boeing and Lockheed are very secure.

Let them rest on their laurals.  More market for SpaceX when (not if) they get the machine humming.
 
"DARPA Hard"  It ain't what it use to be.

Offline VH

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Re: SpaceX (general discussion)
« Reply #28 on: April 22, 2014, 03:14:06 pm »
Once SpaceX gets the details worked out for their first stage recovery process and starts to do it on land no one will be able to touch them on cost. I am looking forward to SpaceX's next evolution.


Private space is showing it is the way to go. And it is made in America to boot.

Offline sferrin

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Re: SpaceX (general discussion)
« Reply #29 on: April 22, 2014, 06:30:44 pm »
Once SpaceX gets the details worked out for their first stage recovery process and starts to do it on land no one will be able to touch them on cost. I am looking forward to SpaceX's next evolution.

I could see lobbyist-fed politicians outlawing land recoveries, "for the children". 
"DARPA Hard"  It ain't what it use to be.