TNT equivalent of an exploding LOX/RP-1 rocket

Does anyone know where to find information about how this is
calculated/estimated? I seem to rememeber TNT equivalent numbers given for
Saturn-5 and the never-built NOVA?

Best wishes
Sven Grahn

Sven Grahn wrote:

Does anyone know where to find information about how this is
calculated/estimated? I seem to rememeber TNT equivalent numbers given for
Saturn-5 and the never-built NOVA?

General rule of thumb is 20% of the weight of the propellant can be
considered TNT. The propellant is more energetic than TNT, and properly
mixed would make a much bigger bang, but in any even remotely realistic
scenario, the propellants would be poorly mixed.

--
Scott Lowther, Engineer
Remove the obvious (capitalized) anti-spam
gibberish from the reply-to e-mail address

Sven Grahn wrote:

Does anyone know where to find information about how this is
calculated/estimated? I seem to rememeber TNT equivalent numbers given for
Saturn-5 and the never-built NOVA?

General rule of thumb is 20% of the weight of the propellant can be
considered TNT. The propellant is more energetic than TNT, and properly
mixed would make a much bigger bang, but in any even remotely realistic
scenario, the propellants would be poorly mixed.

--
Scott Lowther, Engineer
Remove the obvious (capitalized) anti-spam
gibberish from the reply-to e-mail address

In article ,
Sven Grahn wrote:
Does anyone know where to find information about how this is
calculated/estimated? I seem to rememeber TNT equivalent numbers given for
Saturn-5 and the never-built NOVA?

There are rules of thumb -- based on a combination of past experience and
sheer guesswork -- for the "explosive equivalent" of various propellant
combinations. It can depend on the situation, e.g. for solids, it is (or
was, my info is old) considered significant whether they are in immediate
proximity to a liquid stage or not.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |

In article ,
Sven Grahn wrote:
Does anyone know where to find information about how this is
calculated/estimated? I seem to rememeber TNT equivalent numbers given for
Saturn-5 and the never-built NOVA?

There are rules of thumb -- based on a combination of past experience and
sheer guesswork -- for the "explosive equivalent" of various propellant
combinations. It can depend on the situation, e.g. for solids, it is (or
was, my info is old) considered significant whether they are in immediate
proximity to a liquid stage or not.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |

"Sven Grahn" wrote in message ...

Does anyone know where to find information about how this is
calculated/estimated? I seem to rememeber TNT equivalent numbers given for
Saturn-5 and the never-built NOVA?


Short answer: rocket fuel mixed with oxidizer is equivalent to about
twice its mass in TNT.

Long answer:

Worst-case scenario is complete mixing of fuel and oxidizer, which
then detonate as a homogenous mixture.

I did a few calculations in Cheetah 2.0 to compare total energy
release of some propellant combinations to common explosives. Cheetah
is an equilibrium code that is intended more for detonation
calculations, so understandably it does not have many rocket
propellants in its built-in database. I can easily add RP-1 if you
provide: enthalpy of formation, elemental ratio (C:H:O:N etc.), and
initial density (g/cc).

Using the database in Cheetah, I ran LH2/LOX and LCH4/LOX. The
results of RP-1/LOX should be very close to methane/LOX (all
hydrocarbons are similar in energy release):

Ox/Fuel Mass Ratio Avg. Density Vdet Total Energy
[O:F] [g/cc] [km/s] [kJ/g]
======= ========== ============ ====== ============
O2/H2 8 (stoich) 0.426 4.81 12.6
O2/H2 6 (SSME) 0.361 5.38 12.2
O2/H2 4 0.284 6.27 11.1

O2/CH4 3.5 0.829 5.77 9.91

Common explosives:

Explosive Avg. Density Vdet Total Energy
[g/cc] [km/s] [kJ/g]
========= ============ ====== ============
TNT 1.65 6.88 4.67
PETN 1.778 8.58 5.93
RDX 1.806 8.94 5.78

Here, "Total Energy" is *not* the energy released in the detonation,
but rather the total energy if all the mechanical and thermal energy
of the detonation products is extracted by bringing products to rest
at 1 atm & 300 K. This is the energy you would measure by detonating
these propellants/explosives in a bomb calorimeter. If you are
worried about far-field blast wave damage from an accidental
explosion, this is probably the most meaningful and conservative
estimate.

As you can see, common propellants have about twice the energy release
per unit mass of TNT.
--
Andrew J. Higgins Mechanical Engineering Dept.
Assistant Professor McGill University
Shock Wave Physics Group Montreal, Quebec CANADA
http://www.mcgill.ca/mecheng/staff/academic/higgins/

"Sven Grahn" wrote in message ...

Does anyone know where to find information about how this is
calculated/estimated? I seem to rememeber TNT equivalent numbers given for
Saturn-5 and the never-built NOVA?


Short answer: rocket fuel mixed with oxidizer is equivalent to about
twice its mass in TNT.

Long answer:

Worst-case scenario is complete mixing of fuel and oxidizer, which
then detonate as a homogenous mixture.

I did a few calculations in Cheetah 2.0 to compare total energy
release of some propellant combinations to common explosives. Cheetah
is an equilibrium code that is intended more for detonation
calculations, so understandably it does not have many rocket
propellants in its built-in database. I can easily add RP-1 if you
provide: enthalpy of formation, elemental ratio (C:H:O:N etc.), and
initial density (g/cc).

Using the database in Cheetah, I ran LH2/LOX and LCH4/LOX. The
results of RP-1/LOX should be very close to methane/LOX (all
hydrocarbons are similar in energy release):

Ox/Fuel Mass Ratio Avg. Density Vdet Total Energy
[O:F] [g/cc] [km/s] [kJ/g]
======= ========== ============ ====== ============
O2/H2 8 (stoich) 0.426 4.81 12.6
O2/H2 6 (SSME) 0.361 5.38 12.2
O2/H2 4 0.284 6.27 11.1

O2/CH4 3.5 0.829 5.77 9.91

Common explosives:

Explosive Avg. Density Vdet Total Energy
[g/cc] [km/s] [kJ/g]
========= ============ ====== ============
TNT 1.65 6.88 4.67
PETN 1.778 8.58 5.93
RDX 1.806 8.94 5.78

Here, "Total Energy" is *not* the energy released in the detonation,
but rather the total energy if all the mechanical and thermal energy
of the detonation products is extracted by bringing products to rest
at 1 atm & 300 K. This is the energy you would measure by detonating
these propellants/explosives in a bomb calorimeter. If you are
worried about far-field blast wave damage from an accidental
explosion, this is probably the most meaningful and conservative
estimate.

As you can see, common propellants have about twice the energy release
per unit mass of TNT.
--
Andrew J. Higgins Mechanical Engineering Dept.
Assistant Professor McGill University
Shock Wave Physics Group Montreal, Quebec CANADA
http://www.mcgill.ca/mecheng/staff/academic/higgins/

"Andrew Higgins" wrote in message
om...
"Sven Grahn" wrote in message
...

Does anyone know where to find information about how this is
calculated/estimated? I seem to rememeber TNT equivalent numbers given
for
Saturn-5 and the never-built NOVA?


Short answer: rocket fuel mixed with oxidizer is equivalent to about
twice its mass in TNT.

Long answer:

Worst-case scenario is complete mixing of fuel and oxidizer, which
then detonate as a homogenous mixture.
...
As you can see, common propellants have about twice the energy release
per unit mass of TNT.

But it should be noted that the explosion of a bi-propellant rocket is
actually quite unlike the detonation of a high explosive, since the energy
release is limited by the mixing of the fuel and oxidizer and cannot
detonate all at once. The example of the Challenger illustrates this quite
well. Despite ripping up in a hypersonic airstream, which probably
accelerated the mixing (I would think), it did not generate a high pressure
blast wave, which would have pulverized the cabin instantly. The astronauts
are thought to have survived all the way down to the ocean surface.

For monopropellant engines, its a different matter.

Carey Sublette

"Andrew Higgins" wrote in message
om...
"Sven Grahn" wrote in message
...

Does anyone know where to find information about how this is
calculated/estimated? I seem to rememeber TNT equivalent numbers given
for
Saturn-5 and the never-built NOVA?


Short answer: rocket fuel mixed with oxidizer is equivalent to about
twice its mass in TNT.

Long answer:

Worst-case scenario is complete mixing of fuel and oxidizer, which
then detonate as a homogenous mixture.
...
As you can see, common propellants have about twice the energy release
per unit mass of TNT.

But it should be noted that the explosion of a bi-propellant rocket is
actually quite unlike the detonation of a high explosive, since the energy
release is limited by the mixing of the fuel and oxidizer and cannot
detonate all at once. The example of the Challenger illustrates this quite
well. Despite ripping up in a hypersonic airstream, which probably
accelerated the mixing (I would think), it did not generate a high pressure
blast wave, which would have pulverized the cabin instantly. The astronauts
are thought to have survived all the way down to the ocean surface.

For monopropellant engines, its a different matter.

Carey Sublette

"Carey Sublette" wrote in message
.net...
But it should be noted that the explosion of a bi-propellant rocket is
actually quite unlike the detonation of a high explosive, since the energy
release is limited by the mixing of the fuel and oxidizer and cannot
detonate all at once. The example of the Challenger illustrates this quite
well. Despite ripping up in a hypersonic airstream, which probably
accelerated the mixing (I would think), it did not generate a high
pressure
blast wave, which would have pulverized the cabin instantly. The
astronauts
are thought to have survived all the way down to the ocean surface.


Technically, Challenger did not "blow up". NASA's frame-by-frame analysis
of the launch video shows that the ET collapsed when the O2 tank was
punctured by the nose of the SRB (which had pivoted around the forward
attach point after the aft burned through). This resulted in the sudden
release of a lot of gas at cryogenic temperatures, which immediately
condensed all of the atmospheric water in the area. The result looked like
a cloud of white smoke, but there was no evidence of combustion of the LH2.
There's a small orange/yellow fireball visible in part of the cloud that's
thought to be the detonation of the hydrazine from the OMS tank when it came
in contact with the condensation (hydrazine and water don't get along well),
but even that failed to set off the LH2. If there had been an LH2
explosion, there probably wouldn't have been a cloud (the combustion product
is water vapor).

The real damage was done by the supersonic slipstream, which shredded the
orbiter's airframe as soon as it started to tumble.

For monopropellant engines, its a different matter.

Depends. If you're talking about a monopropellant/catalyst (like hydrogen
peroxide and silver), there won't be any explosion. If you're talking about
a solid rocket like the Shuttle SRBs, the energy release is proportional to
the surface area of the combustion zone; if something happens to shatter the
propellant mass (creating a sudden, dramatic increase in the size of the
combustion zone), you'll get an explosion, but unless you've pulverized the
propellant, it'll still be a fairly small fraction of the total propellant
available (of course, the rest of the propellant will rain down as flaming
chunks, which happened in Guyana). The SRB fuel is supposed to have the
consistency of a pencil eraser, which I'd guess would be fairly hard to
shatter.