How far back would you want to be?...BFR safe distances for GSE...

[John Alan]

Ok...I'm messing with an idea here in this thread...
https://forum.nasaspaceflight.com/index.php?topic=43936.msg1733771#msg1733771

Assuming the worst and BFR/BFS has an "Amos-6" type event on the pad...
It's bigger...A LOT more prop... taller... but taking all that into account (4200+ tonnes of prop going off)
How far back should other nearby (well made cat 5 rated) structures be to avoid major damage...
(minor is deemed ok...dented or dinged but functional...with patches if holed by small debris )
And yes I am talking things... People are more easily damaged in the blast wave and would be further back.

My working number at this time is... over 150 meters back (500+ feet)
To little?... to much?...Thoughts on that value?

Now that we know the 2017 version specs (basically)... Time to discuss what a RUD event might look like...

Opinion and speculation... Or facts with numbers to back it... are welcome... 

[StvB]

That value of 150m sounds very low. Need some time to think about an answer, though.

edit: this is an interesting chart for a ballpark:

[StvB]

So, adding on to my original post above. A NASA memorandum titled preliminary investigation of blas hazards of RP-1/LOX and LH2/LOX propellant combinations states the following in its summary.

The development of large launch vehicles has created major problems
in the siting of test stands and launch pads. Thus, RP-1/LOX vehicles
are sited by using a TNT equivalent of 20 percent for quantities up to
500,000 pounds and an equivalent of 10 percent for any excess over
that amount; LH2/LOX vehicles are sited using a TNT equivalent of 60
percent.

link to .pdf: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19650014066.pdf

I don't know what the values are but you say 4,200 tonnes, so 9,259,415 pounds put it in excess of the 500,000 pound mark. Not sure if Methalox fits closer to LH2 or RP-1 in this regard, but even if you put it at the 10% equivalent TNT by mass, it's about 900,000 pounds meaning the DHS chart says you want to be far away. No idea if this analysis puts it in the ballpark, but I think 150m is cutting it close.

[envy887]

There's a HUGE difference between people and ground support equipment. Some GSE will be right on the pad. The integration facility might be 200-300 meters away, and even that might be fine if it's built for a Cat 5 storm. Critical personnel will be in hardened structures 2 or more miles away. Spectators will be at least 5 miles away.

[guckyfan]

There's a HUGE difference between people and ground support equipment. Some GSE will be right on the pad. The integration facility might be 200-300 meters away, and even that might be fine if it's built for a Cat 5 storm. Critical personnel will be in hardened structures 2 or more miles away. Spectators will be at least 5 miles away.

5 miles, that would be the distance to South Padre Island. If that is enough they might actually be able to launch from their Boca Chica site.

[John Alan]

There's a HUGE difference between people and ground support equipment. Some GSE will be right on the pad. The integration facility might be 200-300 meters away, and even that might be fine if it's built for a Cat 5 storm. Critical personnel will be in hardened structures 2 or more miles away. Spectators will be at least 5 miles away.

Yes... and to make the situation crystal clear (read the linked thread)
In the situation in that thread... closest high dollar asset (besides the launch mount) is the Prop Farm 150 meters away behind a blast wall...
And two free standing (but anchored to the ground) moveable structures 220 meters away

Also - assuming a Green Field or shallow off shore new built complex...
Leave any current locations out of this please... Boca Chica or 39a (for now)
But yes... Boca is just in the scope at 5 miles to open site tourists...

Two so far think maybe ok... any more?

[Lars-J]

There's a HUGE difference between people and ground support equipment. Some GSE will be right on the pad. The integration facility might be 200-300 meters away, and even that might be fine if it's built for a Cat 5 storm. Critical personnel will be in hardened structures 2 or more miles away. Spectators will be at least 5 miles away.

Yes... and to make the situation crystal clear (read the linked thread)
In the situation in that thread... closest high dollar asset (besides the launch mount) is the Prop Farm 150 meters away behind a blast wall...
And two free standing (but anchored to the ground) moveable structures 220 meters away

Also - assuming a Green Field or shallow off shore new built complex...
Leave any current locations out of this please... Boca Chica or 39a (for now)
But yes... Boca is just in the scope at 5 miles to open site tourists...

Two so far think maybe ok... any more?

Perhaps... I... should...  be... using... less... periods. 

[John Alan]

Perhaps... I... should...  be... using... less... periods. 

Ha... sorry, but it's my style for online posting... It may be annoying, I know... 

[Nomadd]

1.7 miles.

[wannamoonbase]

There's a HUGE difference between people and ground support equipment. Some GSE will be right on the pad. The integration facility might be 200-300 meters away, and even that might be fine if it's built for a Cat 5 storm. Critical personnel will be in hardened structures 2 or more miles away. Spectators will be at least 5 miles away.

5 miles, that would be the distance to South Padre Island. If that is enough they might actually be able to launch from their Boca Chica site.

There's a HUGE difference between people and ground support equipment. Some GSE will be right on the pad. The integration facility might be 200-300 meters away, and even that might be fine if it's built for a Cat 5 storm. Critical personnel will be in hardened structures 2 or more miles away. Spectators will be at least 5 miles away.

5 miles, that would be the distance to South Padre Island. If that is enough they might actually be able to launch from their Boca Chica site.

This is the biggest problem I see with trying to do BFR from BC, the safety distance needed.

I think the only logical place for BFR is LC39.  It's distance from populated areas was chosen for a reason all those decades ago.  The reason would still seem to stand, it's just being applied 50+ years later.

[John Alan]

1.7 miles.

I take it that is centerline Boca Chica launch pad to your location/property there?... 

[launchwatcher]

That value of 150m sounds very low. Need some time to think about an answer, though.

edit: this is an interesting chart for a ballpark:

Not sure how comparable this is.

Explosives start with fuel and oxidizer well mixed and combustion happens very quickly, while a liquid fueled rocket has a large mass of fuel and a separate large mass of oxidizer; in a RUD, the rate of combustion would be limited by how quickly the fuel can get in contact with an oxidizer (the contents of the oxidizer tank or the surrounding air), or the oxidizer can get in contact with a fuel (either the contents of the fuel tank or the much less massive structure of the vehicle).   

The large spherical tank at SLC40 is about 350-400 feet from the pad center and was fine after the rapid combustion of about 500t of kerolox.   Your table lists a safe distance for buildings of around 320 feet for a ~1/4 ton bomb and 400 feet for ~1/2 ton. 

with the 2017 BFR takeoff mass of around 4400t, and making completely unwarranted assumptions about linearity and equivalent power of kerolox and metholox... that would scale to a safe distance for structures somewhere just under the 860 feet for a 10,000lb bomb...

Similar tanks at LC39A - and the SpaceX hangar - look like around 1400-1500 feet from the pad.

[garcianc]

I keep thinking that a lot of the old ideas that NASA had are still relevant:



and then there is this:

[Lars-J]

I keep thinking that a lot of the old ideas that NASA had are still relevant:

Can you explain - How is a movable exhaust deflector relevant to this?