SpaceX (Vol. 2)

[Robmarriott]

I just think that they could say “we are scheduled to test ‘x’ or ‘y’ on this date, weather permitting”, even if they said it a few hours before. People having to do detective work and speculate from road closures etc just seems a really weird way to do business to me.

[Beati Dogu]

That would be nice, but the reality is that they run to their own schedule and they’re under no obligation to release anything that isn’t required by law. Road closures, planning permission applications, test fires and launches basically.

If they had a more public friendly approach then it would also likely encourage the mainstream media to start hanging around more often. Definitely not great PR to have those clueless buffoons reporting their usual “ErMeGeRd, sPaCeX BiLlOnNaIRe DoNe bLoWn StUFf Up AgAiN, HuRr HuRr HuRr !”

[Robmarriott]

Good point, hadn’t thought about the media angle.

[Beati Dogu]

Booster static fire coming up. It has 3 Raptor engines fitted.

Success:

Edited by Beati Dogu on Tuesday 20th July 01:24

[Flooble]

3 engines being all they can test on the little stands?

So now they'll have to fit the other "X" number of engines, move it to the orbital launch stand (if the FAA hasn't made them knock it down) and then do another static fire there?

Or will they just scrap this static-test booster now?

[annodomini2]

Flooble said:

3 engines being all they can test on the little stands?

So now they'll have to fit the other "X" number of engines, move it to the orbital launch stand (if the FAA hasn't made them knock it down) and then do another static fire there?

Or will they just scrap this static-test booster now?

Fundamentally, we don't know, SpaceX hasn't published anything.

[Hill92]

annodomini2 said:

Flooble said:

3 engines being all they can test on the little stands?

So now they'll have to fit the other "X" number of engines, move it to the orbital launch stand (if the FAA hasn't made them knock it down) and then do another static fire there?

Or will they just scrap this static-test booster now?

Fundamentally, we don't know, SpaceX hasn't published anything.

Elon tweeted after the static fire that they might try 9 engines on booster 3 depending on progress with booster 4.

[Beati Dogu]

3 engines with no water suppression was pretty loud.

https://youtu.be/xV30bdrr1HI

Now imagine it with 11 times as many engines.

[MartG]

Short video of the test

https://www.youtube.com/watch?v=6VrglzVbElA

Multi angle

https://www.youtube.com/watch?v=Bk1nvyuDBZ0

Edited by MartG on Tuesday 20th July 10:21

[nuttywobbler]

The sight and sound of 33 raptors firing will be quite spectacular. And terrifying.

[Dog Star]

nuttywobbler said:

The sight and sound of 33 raptors firing will be quite spectacular. And terrifying.

I really do wonder what the consequences for
- the launch site
- the construction site (high bay etc)
- Boca Chica village
- Brownsville
will be if a fully fuelled Starship stack goes off on the pad or just after takeoff.

That's going to be a very very big bang indeed.

[Beati Dogu]

It would trash the launch site a little, but everywhere else should be fine.

This is the SN4 test tank explosion to give you an idea:

https://www.youtube.com/watch?v=mGfrOCjxzps


You can see the blast wave in the humid air. The sound takes a while to reach the camera.

[Dog Star]

Beati Dogu said:

It would trash the launch site a little, but everywhere else should be fine.

This is the SN4 test tank explosion to give you an idea:

https://www.youtube.com/watch?v=mGfrOCjxzps


You can see the blast wave in the humid air. The sound takes a while to reach the camera.

Yes, I’ve seen all these explosions over the development period. I don’t think they’re all that relevant.

Now let’s consider what might happen with several thousand tons of propellant. Let’s use an N1 as a starting point…

[Flooble]

http://www.russianspaceweb.com/n1_5l.html

40 km for "some" damage, but 5km for significant damage.

[Dog Star]

Flooble said:

http://www.russianspaceweb.com/n1_5l.html

40 km for "some" damage, but 5km for significant damage.

That's going to make for some pretty big lawsuits - flying glass and so forth.

[Flooble]

That's why they have the alert notices - no doubt they will distribute those more widely to cover off the risk.

I would not be surprised to see other suppression systems in play as well - water curtains are effective at absorbing a lot of sound energy. Or they'll just balance the risk and cost of payouts ...

[CraigyMc]

My sums may be wrong, but I think a fully fuelled starship booster exploding would be in the same rough class as an A bomb going off.

The brisance would be much lower (the resulting shockwave would not be as destructive) but the overall energy release is in the right range to be comparable with a Hiroshima-sized A bomb.

[rxe]

CraigyMc said:

My sums may be wrong, but I think a fully fuelled starship booster exploding would be in the same rough class as an A bomb going off.

The brisance would be much lower (the resulting shockwave would not be as destructive) but the overall energy release is in the right range to be comparable with a Hiroshima-sized A bomb.

Well it is 1200 tonnes of propellant, so it will be in the kiloton range .... I know kilotons are measured in TNT, but it will be in the same ballpark. I think the impact would depend on exactly how it happened, but a well mixed vapour cloud explosion can be a really big bang. I think Flixborough involved 15 tonnes of cyclohexane, but was equivalent to a 0.25 kiloton weapon.

Worst case of the thing breaking up as it launches and dumping the contents of the fuel tanks over 100 meters could easily be in the 10 KT range.

[CraigyMc]

rxe said:

CraigyMc said:

My sums may be wrong, but I think a fully fuelled starship booster exploding would be in the same rough class as an A bomb going off.

The brisance would be much lower (the resulting shockwave would not be as destructive) but the overall energy release is in the right range to be comparable with a Hiroshima-sized A bomb.

Well it is 1200 tonnes of propellant, so it will be in the kiloton range .... I know kilotons are measured in TNT, but it will be in the same ballpark. I think the impact would depend on exactly how it happened, but a well mixed vapour cloud explosion can be a really big bang. I think Flixborough involved 15 tonnes of cyclohexane, but was equivalent to a 0.25 kiloton weapon.

Worst case of the thing breaking up as it launches and dumping the contents of the fuel tanks over 100 meters could easily be in the 10 KT range.

TNT's not actually all that energy-dense by weight compared to hydrocarbons, so whatever number of kilotons of methane there is, there will be a multiple of that in terms of kT of TNT equivalent. 10kT may actually be about right.

I'm not sure how to calculate for the lower reactivity given the temperature of the supercooled methalox involved -- it's not just about the energy in the material, it's about how fast it reacts too, but yep. A-bomb sized.

Edited to add: the booster is 3300 tons. The starship that sits on top is 1200.

Edited by CraigyMc on Friday 23 July 15:51

[Beati Dogu]

Back in the day they worked out that a full stack Saturn V had the same potential explosive power as around 0.6 kilotons of TNT (the Hiroshima bomb was about 15 kt). Interestingly the most energetic stage was not in fact the big kerosene powered first stage, but the smaller, hydrogen powered second stage.

However, this potential yield was if it exploded perfectly, which was unlikely to happen. In reality, only a fraction would have actually ignited - about 3-400 tons worth of TNT they reckoned. Enough to tear it to bits in a shower of unburnt kerosene and gas.

This was born out later out by the Soviets, when the Soviet N1 rocket fell back 100 meters and exploded on the pad. Only about 15% of the fuel ignited and observers reported it still raining down unburnt kerosene over half an hour after the explosion. Still, a blast equivalent to 150 tons of TNT is not to be messed with. The pad was trashed and it broke windows over 30 miles away.