blackhawk887 Ars Tribunus Angusticlavius
9y
19,694
100% TNT equivalent is crazy. Even 25% is probably twice a reasonable figure. The FAA uses 14% for LOX/hydrogen and 10% for LOX/kerosene. Hydrogen is more than twice as energetic per mass of methane, and kerosene about 80% as energetic as methane.

LOX and liquid methane are miscible, unlike the other combinations, but there aren't any plausible scenarios where you'd get better mixing than a rocket falling back on the pad shortly after liftoff, which both kerolox and hydrolox are also perfectly capable of doing. //

mattlindn Ars Centurion
7y
231
NASA's current blast range evacuation area ranges from 3 to 4 miles as shown in the diagrams in this article (I measured it on google maps).

It's worth mentioning that the privately run Rocket Ranch down in South Texas where people can pay money to get closer to the Starship launches is only 3.9 miles from the launch site. The people who watch from the Mexico can get as close as 2.4 miles.

Where most people (including myself) watch(ed) from, South Padre Island, is almost exactly 5 miles away.

So yeah this seems kind of excessive. //

Jack56 Ars Scholae Palatinae
7y
672
For the nth time, a fuel-oxidiser explosion is not a detonation. It is a deflagration. They are far less violent. An intimate mixture of gaseous oxygen and methane can detonate but liquid methane and liquid oxygen cannot mix intimately - are not miscible - because methane is a solid at lox temperatures, especially the sub-cooled lox which Starship uses. A detonation takes place in under a millisecond. Deflagrations are fires. I’m not saying it wouldn’t be bad but comparisons with an energetically equivalent mass of TNT are way out of line. //

mattlindn Ars Centurion
7y
231
Jack56 said:

For the nth time, a fuel-oxidiser explosion is not a detonation. It is a deflagration. They are far less violent. An intimate mixture of gaseous oxygen and methane can detonate ....

Didn't think about this, but yes you're correct. The boiling point of Oxygen is 90.2 K and the melting point of Methane is 90.7 K. If you mix the two together, before any Methane can melt all the oxygen has to boil off. Though there should still be some local melting given the outside air temperatures are MUCH warmer than the liquid oxygen.

Though at the same time given the temperatures are so close together I don't think much Methane will freeze before an explosion happens. So maybe the point is moot? //

SpikeTheHobbitMage Ars Scholae Palatinae
3y
1,745
Person_Man said:

I have to imagine a fully fueled stack with optimal mixing for the biggest explosion would probably be the largest non nuclear explosion ever.

Most of Starship's propellant is oxygen. The full stack only carries 1030t of methane (330t on Ship, 700t on SuperHeavy). Methane also has a TNT equivalent of only 0.16. Using the omnicaluclator, I get 1030t of methane* = 164.8t of TNT. That doesn't even make the top 10 list.

*omnicalculator lists natural gas, which is mostly methane. //

blackhawk887 Ars Tribunus Angusticlavius
9y
19,694
mattlindn said:

Didn't think about this, but yes you're correct. The boiling point of Oxygen is 90.2 K and the melting point of Methane is 90.7 K. If you mix the two together, ...

Mixing with oxygen should depress the freezing point of methane. For example, if you take water at its freezing point, and mix it equally with alcohol that is itself, say, 10 degrees colder than the freezing point of water, the resulting mix will be well below 0 C but will not contain any frozen water.

Also, you can mix butane and water under a little pressure, even though at atmospheric pressure butane boils a half-degree below the freezing point of water. They aren't miscible, but that's just because of polarity - they are happy to both be liquids at the same temperature and a little pressure.

Methane and LOX are considered miscible and were even considered for monopropellants at various mix ratios. The mixture is reportedly a bit shock sensitive though. //

SpikeTheHobbitMage Ars Scholae Palatinae
3y
1,745

Mad Klingon said:
For the many debating using eminent domain to expand launch facilities, that would likely be the simple part of the issue. Most of that area is considered sensitive wildlife area and dealing with the current piles environmental regulations and paperwork could take decades for a major expansion. Look at all the grief SpaceX gets when they build on the relatively bland bit of Texas coast they are currently using. It would be much worse at the Florida site.

One of the great legacies of Apollo was we got a well built out area for launching stuff before most of the environmental legislation was passed.

One of the great legacies of Apollo was that the exclusion zone around Cape Canaveral preserved enough of the wetlands in good enough condition to become a protected nature reserve.