Falcon 9 dimensions: measuring photos

[Hobbes-22]

I'm building scale models of the Falcon 9, for this purpose I'm trying to get reasonably accurate dimensions of the rocket.

This has proven non-straightforward, as SpaceX doesn't publish more than the total length and diameter, so no data for the individual stages.

I've measured several photos to get the following data, adding photos until I had a set that was reasonably consistent with each other. For the v1.2 data I used 4 photos.
I used simple software to get one reference dimension on the photo (the stage diameter, which is well-known at 12 ft), then derived other dimensions from the reference. I don't have access to photogrammetry software, which should be able to compensate for distortion. So that would be one avenue to improve on this data.

For F9 v1.2:
Total length: 70 m
first stage (full length of the stage incl. engines) 40,5 m
interstage 6,7 m
2nd stage 9,3 m (length of the outer skin visible on a stacked rocket, so excl engine)
These are ±0.5 m due to distortion in the photos I used.


For F9v1.1:
first stage (full length of the stage incl. engines) 41 m
interstage 6 m
2nd stage 8,3 m
Dragon trunk 2,8 m
These are ±1 m due to distortion in the photos I used.

For F9v1.0:
first stage (full length of the stage incl. engines) 31 m
interstage  6,4 m (although some flights used longer interstages)
2nd stage 4,6 m
These are ±1 m due to distortion in the photos I used.

Now, these data differ by several meters from the info found on Spacelaunchreport.

I've put this post in the SpaceX general section as the info may be useful for other purposes.

[meekGee]

I take it you measured that 12' diameter in several spots up and down the rocket, to determine the perspective and lens?

[Hobbes-22]

No. I just measured at one point, I don't know how to compensate for the distortion manually.

I did try to select the photos with the least distortion (e.g. photos taken from far away using a telephoto lens)

[meekGee]

No. I just measured at one point, I don't know how to compensate for the distortion manually.

I did try to select the photos with the least distortion (e.g. photos taken from far away using a telephoto lens)

That will help, but I can't tell you how much off you are...

Out of curiosity, what's the difference in the diameter between the lowest and highest point?

[Hobbes-22]

in one photo, the diameter measurements are 258 mm (just above the landing legs) and 289 mm (stage separation interface)

[meekGee]

And what is it midway in between (that'll tell you how linear the distortion is.)

[dglow]

Suggest you PM user okan170, who does many of NSF's excellent CG renders.

[DOCinCT]

There is also the large rendition off of the SpaceX Falcon 9 page
http://www.spacex.com/sites/all/themes/spacex2012/images/falcon9/falcon9-render.png
no perspective issues

[old_sellsword]

There is also the large rendition off of the SpaceX Falcon 9 page
http://www.spacex.com/sites/all/themes/spacex2012/images/falcon9/falcon9-render.png
no perspective issues

I wouldn't rely on that too heavily as it doesn't appear to be accurate, just look at the location of the grid fins in reference to the interstage.

[GWH]

Spaceflight 101 might have some helpful dimensions: http://spaceflight101.com/spacerockets/falcon-9-ft/

[Lars-J]

...I used simple software to get one reference dimension on the photo (the stage diameter, which is well-known at 12 ft), then derived other dimensions from the reference. ...

It's not quite that simple. Is 12 ft the interior tank diameter or the exterior? And does it include whatever exterior layers that are added on top of that? An inch here and there will skew your numbers.

[Hobbes-22]

Spaceflight 101 might have some helpful dimensions: http://spaceflight101.com/spacerockets/falcon-9-ft/

It looks like they use the same data as Spacelaunchreport, which doesn't agree with my measurements.

[Hobbes-22]

There is also the large rendition off of the SpaceX Falcon 9 page
http://www.spacex.com/sites/all/themes/spacex2012/images/falcon9/falcon9-render.png
no perspective issues

SpaceX's own renders were the first data point I tried to use and had to discard. For the v1.0 rocket, the renders were off by several meters.

[Hobbes-22]

...I used simple software to get one reference dimension on the photo (the stage diameter, which is well-known at 12 ft), then derived other dimensions from the reference. ...

It's not quite that simple. Is 12 ft the interior tank diameter or the exterior? And does it include whatever exterior layers that are added on top of that? An inch here and there will skew your numbers.

12 ft is the exterior diameter without insulation. The DragonLab factsheet shows the inner diameter of the trunk as 142".
Most of the photos I have don't have the resolution to measure down to 1", so I have to accept some noise in my measurements (hence the ±0.5 m).

[DOCinCT]

There is also the large rendition off of the SpaceX Falcon 9 page
http://www.spacex.com/sites/all/themes/spacex2012/images/falcon9/falcon9-render.png
no perspective issues

SpaceX's own renders were the first data point I tried to use and had to discard. For the v1.0 rocket, the renders were off by several meters.

There are some good side shots of F9 v1.1 from Vandenberg launch site, not too bad on perspective; and yes, those do show the correct positioning of the grid fins.
Also there are the large resolution images in the SpaceX gallery on their website

[edkyle99]

I'm building scale models of the Falcon 9, for this purpose I'm trying to get reasonably accurate dimensions of the rocket.

This has proven non-straightforward, as SpaceX doesn't publish more than the total length and diameter, so no data for the individual stages.

For what it is worth, I have been looking at this question, measuring multiple photos, looking at illustrations, etc., and have conjured the attached drawing which shows my current estimates for dimensions in inches.  Multiply by exactly 0.0254 to convert to meters.  Very much plus or minus, of course, especially on the lengths.  I've only focused on v1.2/Block 3 so far.

EDIT:  I'm removing this drawing from this message.  I'll provide updated drawings a subsequent message in this thread that will include v1.1 and, eventually, v1.0. 

 - Ed Kyle

[edkyle99]

A question to discuss.  I am attaching an image of the first stage/interstage connection area on a v1.2.  Where, I wonder, does the first stage upper LOX tank bulkhead attach to the cylindrical tank wall?  I've drawn some options.  I doubt it is right at the interstage connection (the line of fasteners), because I expect a "skirt" at the top of the stage itself, but I don't know.

 - Ed Kyle

[old_sellsword]

A question to discuss.  I am attaching an image of the first stage/interstage connection area on a v1.2.  Where, I wonder, does the first stage upper LOX tank bulkhead attach to the cylindrical tank wall?  I've drawn some options.  I doubt it is right at the interstage connection (the line of fasteners), because I expect a "skirt" at the top of the stage itself, but I don't know.

 - Ed Kyle

We've never seen a skirt at the top of a first stage tank, only at the bottom. Although I agree with you that putting all those rivets through the bulkhead connection sounds like a bad idea, I'm interested in what the solution is.

I've attached a couple pictures that might help. The first one is v1.1 stages in construction showing the metal skirts on the bottom of the tank. I'm not sure which end the second one is or even what version of F9 it is.

[cambrianera]

A question to discuss.  I am attaching an image of the first stage/interstage connection area on a v1.2.  Where, I wonder, does the first stage upper LOX tank bulkhead attach to the cylindrical tank wall?  I've drawn some options.  I doubt it is right at the interstage connection (the line of fasteners), because I expect a "skirt" at the top of the stage itself, but I don't know.

 - Ed Kyle

We've never seen a skirt at the top of a first stage tank, only at the bottom. Although I agree with you that putting all those rivets through the bulkhead connection sounds like a bad idea, I'm interested in what the solution is.

I've attached a couple pictures that might help. The first one is v1.1 stages in construction showing the metal skirts on the bottom of the tank. I'm not sure which end the second one is or even what version of F9 it is.

Second picture is F9 1.0: carbon composite skirt on the bottom of RP-1 tank.

[edkyle99]

Here's an image from Wiki of what are likely v1.1 stages at Hawthorne in 2014, showing the top part of the first stage.  I'm starting to believe that the tank wall is right up near where the interstage begins.

 - Ed Kyle