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#1160
by
karanfildavut
on 17 Jan, 2018 18:36
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That was interesting. Can they do the refuelling testing with something safer than LOx and Kerosene? LOx and water for example?
The shrinkage issue must have been even worse for the shuttle, with LH2 and non shrinking SRBs.
That would fall under the heading of Bad idea. Water expands when it freezes (and it WILL freeze with that much LOX floating around), and can shatter the rocket or damage GSE. The thermal behaviour of liquids are usually quite unique and cannot be easily substituted. Even the particular composition of hydrocarbons will have an effect on melting point etc. which is why RP-1 is so highly specced compared to other fuels. They just gotta do what they gotta do.
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#1161
by
CyndyC
on 17 Jan, 2018 19:11
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This interesting article explains why it's been tricky getting Falcon Heavy in position to fire her engines:
https://www.teslarati.com/whats-causing-spacex-falcon-heavy-delays/
That was interesting. .......The shrinkage issue ......
A couple of people in L2 were actually able to do the math and estimate the potential contraction in centimeters and inches. Can't share the details here of course, but another plug for L2, and the posts are still on the next to last page in Discussion Thread 13. If not, w/o saying too much the easiest way to find them is by doing an advanced search for posts by Lar with keyword 'banana' (don't laugh too hard yet, that search brings up 2 posts)
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#1162
by
Semmel
on 17 Jan, 2018 19:37
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This interesting article explains why it's been tricky getting Falcon Heavy in position to fire her engines:
https://www.teslarati.com/whats-causing-spacex-falcon-heavy-delays/
That was interesting. .......The shrinkage issue ......
A couple of people in L2 were actually able to do the math and estimate the potential contraction in centimeters and inches. Can't share the details here of course, but another plug for L2, and the posts are still on the next to last page in Discussion Thread 13. If not, w/o saying too much the easiest way to find them is by doing an advanced search for posts by Lar with keyword 'banana' (don't laugh too hard yet, that search brings up 2 posts)
Ahh come on.. dont be so secretive. Lox has a dT of about -200°C from ambient. Aluminium has a
thermal expansion ratio of 13 um/m/K and Falcon first stage is about 40m high. Of the 40m its about 25m lox tank and 15m RP1 tank. So thats -200*13e-6*25=0.065m. The RP1 is at about -7°C, which causes insignificant shrinkage. So for all practical purposes, F9 first stage gets about 70mm shorter, or about 3 inches. Thats not magic. L2 is worth it anyway though.
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#1163
by
Steve D
on 17 Jan, 2018 19:51
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This interesting article explains why it's been tricky getting Falcon Heavy in position to fire her engines:
https://www.teslarati.com/whats-causing-spacex-falcon-heavy-delays/
That was interesting. .......The shrinkage issue ......
A couple of people in L2 were actually able to do the math and estimate the potential contraction in centimeters and inches. Can't share the details here of course, but another plug for L2, and the posts are still on the next to last page in Discussion Thread 13. If not, w/o saying too much the easiest way to find them is by doing an advanced search for posts by Lar with keyword 'banana' (don't laugh too hard yet, that search brings up 2 posts)
Ahh come on.. dont be so secretive. Lox has a dT of about -200°C from ambient. Aluminium has a thermal expansion ratio of 13 um/m/K and Falcon first stage is about 40m high. Of the 40m its about 25m lox tank and 15m RP1 tank. So thats -200*13e-6*25=0.065m. The RP1 is at about -7°C, which causes insignificant shrinkage. So for all practical purposes, F9 first stage gets about 70mm shorter, or about 3 inches. Thats not magic. L2 is worth it anyway though.
Would the amount of stretch from being pressurized offset that?
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#1164
by
CyndyC
on 17 Jan, 2018 20:36
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Aluminium has a thermal expansion ratio of 13 um/m/K
Aluminum Alloy ~13*10-6 in/(in F) or ~24*10-6 m/(m C)
Semmel used a different LOX tank length too, but somehow the final answers in the two threads are identical in inches
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#1165
by
rpapo
on 17 Jan, 2018 22:34
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Range conflicts and how Boca Chica will or won't share resources? MIGHT be just a WEE bit off topic?
This thread is rarely on topic.
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#1166
by
Jesbus
on 18 Jan, 2018 10:07
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We've been so eagerly waiting for the static fire, only to see it be postponed again and again. To calm the nerves I made a Falcon Heavy simulator:
http://falconheavy.space
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#1167
by
Pete
on 18 Jan, 2018 10:58
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We've been so eagerly waiting for the static fire, only to see it be postponed again and again. To calm the nerves I made a Falcon Heavy simulator: http://falconheavy.space
No earth-shattering Kaboom?
Are you sure this is an accurate sim?
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#1168
by
Semmel
on 18 Jan, 2018 11:49
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Aluminium has a thermal expansion ratio of 13 um/m/K
Aluminum Alloy ~13*10-6 in/(in F) or ~24*10-6 m/(m C)
whoopsy.. yeah, I should have looked at the temperature. I ignored the micro inch / inch because the unit of length doesnt matter since the expansion ratio is linear. But I forgot to look at the temperature. Good call!
Also, I didnt remember the number in the L2 thread and I didnt look it up. Its actually funny that we got the same result, given that I made a factor of 2 error. I am pretty sure the lox tank and temperature difference are somewhat correct though.
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#1169
by
ZachS09
on 18 Jan, 2018 12:34
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We've been so eagerly waiting for the static fire, only to see it be postponed again and again. To calm the nerves I made a Falcon Heavy simulator: http://falconheavy.space
Wow. I've never seen such clickbait like this.
It won't even let me proceed to prop-load, static fire, or even launch!
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#1170
by
AbuSimbel
on 18 Jan, 2018 13:00
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We've been so eagerly waiting for the static fire, only to see it be postponed again and again. To calm the nerves I made a Falcon Heavy simulator: http://falconheavy.space
Wow. I've never seen such clickbait like this.
It won't even let me proceed to prop-load, static fire, or even launch!
So you think Falcon Heavy is clickbait?
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#1171
by
wannamoonbase
on 18 Jan, 2018 14:09
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We've been so eagerly waiting for the static fire, only to see it be postponed again and again. To calm the nerves I made a Falcon Heavy simulator: http://falconheavy.space
Wow. I've never seen such clickbait like this.
It won't even let me proceed to prop-load, static fire, or even launch!
So you think Falcon Heavy is clickbait?
It's had me clicking for almost 7 years now. So yeah.
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#1172
by
spacenut
on 18 Jan, 2018 14:10
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The wait has been l o n g. Hope is flys without any problems.
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#1173
by
shuttlefan
on 18 Jan, 2018 19:35
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So, per the update thread the vehicle has been lowered to horizontal. Does this indicate a delay to tomorrow's static fire?
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#1174
by
wannamoonbase
on 18 Jan, 2018 19:48
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The wait has been l o n g. Hope is flys without any problems.
Agreed, seeing the pictures of if vertical on the pad the last couple of weeks has made it hit home just how big of a monster this vehicle is for SpaceX.
This is no small accomplishment.
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#1175
by
ChrisGebhardt
on 18 Jan, 2018 19:56
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So, per the update thread the vehicle has been lowered to horizontal. Does this indicate a delay to tomorrow's static fire?
Not in and of itself, no.
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#1176
by
RocketLover0119
on 18 Jan, 2018 21:08
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Is it possible they went horizontal because of the atlas launch just to protect from a worst case scenario event?
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#1177
by
yokem55
on 18 Jan, 2018 21:18
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Is it possible they went horizontal because of the atlas launch just to protect from a worst case scenario event?
I was wondering this myself. But I'm thinking unless they roll it back into the HIF, it may not be at any lower risk than if it was vertical.
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#1178
by
Lar
on 18 Jan, 2018 23:14
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I expected them to have rolled it back to the HIF, so if they didn't I'm a bit surprised. I agree that horizontal but outside isn't necessarily any more secure from debris than vertical.
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#1179
by
RocketLover0119
on 18 Jan, 2018 23:18
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Atlas scrubbed, so, now we wait for ULA to reschedule, if rescheduled to tommorow, no SF, if a different day, tommorow a SF will be attempted.
