35

Well, I can refer you to the Range Safety Wikipedia entry: Two switches were used, ARM and DESTRUCT. The ARM switch shut down propulsion for liquid propelled vehicles, and the DESTRUCT ignited the primacord surrounding the fuel tanks. In the case of manned flight, the vehicle would be allowed to fly to apogee before the DESTRUCT was transmitted. This would ...


27

It would be possible to design a check valve chain of high reliability of closing, but it would restrict flow and start to increase the risk of one valve sticking shut. You would probably also need pressure sensors between the valves to determine system state, so you end up with a large number of pipe to fitting joints that are potential leaks and a bunch of ...


22

Thrust termination is the goal of Range Safety in the event of an errant rocket. Rendering the boosters inert is considered secondary, when possible. The Range Safety Officers don't rely on the current positions of the vehicle to decide to terminate, but instead are looking at the IIP (Integrated Impact Point) on a map. The IIP is the point where the ...


14

Boil-off of methane is piped to a Flare Stack and burned off so it won't be vented unburned into the atmosphere. You can see a good picture of the flarestack on the right in the image of Starhopper fueling below: (Image credit: NasaSpaceflight.com (bocachicagal) Update Mar 4 2021: SpaceX no longer uses a flare stack. About six months ago they installed a ...


12

Apparently the battery is only prone to explode while used. So when turning the satellite off, the risk appears to be mitigated sufficiently (I expect the battery to be discharged. A battery storing no energy can't cause an explosion, as an explosion is simply the uncontrolled and rather sudden release of said energy). This means the main risk of a GEO ...


9

As a rule of thumb, no rocket fuel (or oxidizer) will ever be able to detonate on its own. For the simple reason that the maximum flame front propagation through it needs to be slower than the fluid speed through the injectors, otherwise the flame would propagate back into the tanks. NO, no-one has ever managed to pump flammable fluids faster than their ...


7

Hydrazine has a lot of spectral structure in the microwave regions (see paper), as does dinitrogen tetroxide (sorry, only paper I have is paper). This means that they’re pretty good at absorbing and reemitting, hence reflecting, microwave radar energy. Reflections are what the radar displays Off hand, hydrazine has such a thicket of strong lines that it’s ...


7

At low temperatures, the activation energy for pure CH4 O2 oxidization is about 170kj/mole. (See figure 1 here) That’s about 1.8eV per atomic reaction. 1.8eV can be provided by 688nm red light, or any shorter wavelength. So generally, visible light can initiate reactions. I can’t quantify how many photons/cm2 it’ll take to start a runaway reaction from ...


7

Many entries in this 1957-2015 Catalogue of Launch Vehicle Failures mention stage numbers. By my tally, the blame for launch failure goes to the first stage 42 times; the second, 60; the third, 36. If you restrict the reasons for failure to those that might apply to Falcon 9 (one entry is a Falcon 9, btw), or if you discriminate between explosions and less ...


6

I suspect Scott Manley doesn't have better access to sources than we do. All he can do is interpret what he sees using his knowledge of the field. In cases like this, it's tempting to gather any news you can, but everyone is laboring under the same lack of information. When an accident happens, there's only one source you can trust: the official accident ...


6

It was probably the launch of Apollo 16 with about 41.9 TJ. Apollo 16 carried the most fuel of the Apollo missions with a fuel mass of 1,439,894 + 160,551 + 43,727 (+ a little for LM?) = 1,644,172 pounds = 745,784 kg. They used RP-1/LOX for the first stage and LH2/LOX for the second and third stage. The N1 total mass was lower than Saturn V and it used RP-...


6

I was a missile tech on a SSBN in the '70s and worked on the Poseidon C3 SLBM. This missile had six "Thrust Termination Ports" arranged around the periphery of the second stage motor dome. Each TTP was a 10" diameter fiberglass tube angled outward from the motor dome to the side of the missile with det-cord at each end. When commanded by the ...


6

National Geographic reports that the 2014 Antares explosion carrying a Cygnus v4 for the Cygnus CRS Orb-3 mission "knocked two spectators off the bed of their pickup truck and another off her dock. The blast broke windows and imploded doors in buildings close to the launch site", which both shows that something did indeed knocked over and windows got blown ...


5

Project Highwater SA-2 and SA-3 were test flights of of the Saturn I booster. Their S-I first stage launched normally, then the remaining fuel was detonated after engine cutoff: The S-IB Stage Propellant Dispersion System (PDS) will sever each of the nine propellant tanks and disperse the propellants if flight termination becomes necessary. Two exploding ...


5

Some rockets (especially hybrids) use nitrous oxide oxidizer, which exothermically decomposes into nitrogen and oxygen and is capable of detonation. This is not just a theoretical hazard, Virgin Galactic experienced an explosion during a cold-flow injector test in 2007 that killed 3 people and injured 3 more. Acetylene is typically handled as a solution in ...


5

Partial answer: Volume 2 of a March 1981 study (links below) by the DOD gives the External Tank explosive force on the pad as equivalent to 54,000 pounds of TNT. Rationale for the calculation is described in the paper. If you want to read some interesting predictions about what would have happened if one SRB came off during first stage, etc, etc, these ...


5

Weather radar is not specifically measuring clouds or water in the atmosphere. What is measured is the amount of microwaves in the 5 GHz range reflected by anything in the atmosphere. This can be water droplets, but as well be insects, birds or any other kind of droplets, like propellant that didn't stay where is was supposed to be.


5

I'll just start with some things that came to my mind. Not planning to provide a complete list here. You can look at the craft itself prior to and shortly after launch. Was there any leakage or jets of propellant where there shouldn't be any? For example, smoke was visible during the final launch of the space shuttle Challenger. Comparing the video to a ...


4

How strong would the blast yield be? Probably not very. Rocket explosions usually consist of an initial small blast that blows the fuel in one direction and the oxidizer in the other. The fuel ignites, but since it's not mixed with the oxidizer, it burns at the interface between the fuel and the surrounding air, and doesn't generate much of a shock wave. ...


4

Just to mention one facet of this multifaceted problem, any electrical field potential that exists (i.e. items that aren't on a common bias electrically) can and usually will at some point create an arc (spark) when it discharges. Coupling and de-coupling of interfaces, feedlines, etc especially would be a danger if their electrical fields are uneven. Also, ...


4

A firefighter on the scene reported that a number of train rail cars, and ground support tanks were burned and blew up in the process. Could be one of any of those.


3

Liquid oxygen contains contains 4000 times more oxygen than normal air (by volume). A lot of materials that are almost inflameable in normal air may burn in liquid oxygen. Even pure oxygen at a pressure of 200 bar is a dangerous thing. Even stainless steel tubes did burn due to a steep pressure rise of the oxygen inside. Even an asphalt floor may be ...


3

During the moon race, a soviet N-1 rocket exploded seconds after liftoff. This is ranked as one of the largest conventional explosions with an approximate yield of 1 kt of TNT. Upon impact of the base of the N1 with the pad, the vehicle exploded, destroying launch pad 110 east, which would take over 18 months to repair. [...] At T+23 seconds ...


2

The first stage filters out a lot of the mistakes. Pretty much the entire stack is tested to some extent during the first stage. This includes the hardware being subject to vibration and force as well as software for guidance etc. They are also subject to the most environmental factors, which are harder to predict and test than isolated hardware. They are ...


2

From an addendum to SpaceX environmental impact statement, submitted sometime in 2019-2020: When the test vehicle is still connected to the ground systems, the methane would be transferred back to the methane tanks. If the vehicle is connected to the ground systems and tests are performed without engine ignition, the methane would be transferred to the ...


1

To augment @Mark's excellent answer let's remember Elon Musks tweet yes. This seems instant from a human perspective, but it really a fast fire, not an explosion. Dragon would have been fine. I can't find a perfect one-liner to quote, but something like An explosive charge is a measured quantity of explosive material, which may either be composed solely ...


1

The Intelsat 708 accident did a significant amount of damage to a village in China. On February 15, 1996, the Long March 3B rocket failed during launch, veering off course immediately after liftoff and crashing into a village near the launch site (probably Mayelin Village).1 An enormous explosion destroyed most of the rocket and killed an unknown number ...


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