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Even in this video you can see the inherent safety of liquid fuel rockets over solid fuel. (although this is a hypergolic rocket, not like the cryogenic fuel r

by jlgreco 13y ago

Even in this video you can see the inherent safety of liquid fuel rockets over solid fuel. (although this is a hypergolic rocket, not like the cryogenic fuel rockets that we typically use for people.) The launch vehicle started breaking up and became engulfed in flames, but it didn't blow up per-se until it hit the ground. Solid fuel rockets do not tend to be so considerate; see the Challenger or Delta II 7925. Lots of things can go wrong on a liquid fuel rocket (engine shutoffs, fires, vehicle breakup, etc) but on solid fuel rockets you basically only have one failure mode: "pop". With a proper launch escape system, most failure scenarios of a liquid fuel rocket should be quite survivable. You can build working launch escape systems for solid fuel rockets too, but that is a worse situation. IANARS

ajross 13y ago
I don't see how your point follows. A similar deviation with a solid fuel rocket would have resulted in basically the same event (an impact with the ground of a fueled, burning rocket at T+25s), no? There are indeed safety reasons to prefer liquid fuel, but I don't see that this events provides any new evidence.
- HeyLaughingBoy 13y ago
  He's saying that a solid-fuel rocket would likely have exploded before even hitting the ground.
  - jlgreco 13y ago
    Yeah, pretty much. The rocket was already engulfed in flames and disintegrating before it hit the ground; were it a solid fuel rocket it would have blown way sooner.
  - huhtenberg 13y ago
    This implies that solid rocket fuel is inherently susceptible to detonation, while liquid fuel is not. Even if it's true, it seems counter-intuitive.
    - jlgreco 13y ago
      It seems intuitive enough to me. Solid fuel is basically "pre-mixed". That's why this Proton rocket didn't blow up until it slammed into the ground, even though it was rapidly falling apart and completely consumed in fire. The speed at which it burns is basically the extent to which that fuel and oxidizer is mixed. Consider a bucket of kerosene. Gasoline doesn't have it's own oxidizer, it uses the air for that. If you light the bucket on fire then it will burn slowly for quite a while, but if you then grab the bucket and fling it into the air then the fuel and oxidizer will mix and you'll have a rather decent fireball on your hands. If you mix the fuel with an oxidizer first (say, ammonium nitrate....^), then you are going to have a bad situation the moment it catches; no need to shake it up. The other major sort of engine, a hybrid engine, is even safer than either solid or liquid rockets. This is because the fuel and the oxidizer are separated and unmixed like in liquid fuel rockets but additionally the fuel is not going to be able to rapidly mix with the oxidizer if it hits the ground or something (since it is a giant chunk of basically rubber or paraffin or whatever.) ^ ...and now I'm on a watchlist.
      - HeyLaughingBoy 13y ago
        Nah. The employees at the local Tractor Supply or Fleet Farm coulda told us the same thing ;-)
- jlgreco 13y ago
  I don't think the rocket would have made it to the ground burning had it been solid fuel, it probably would have blown when it started to break up above the ground. That liquid fuel, although hypergolic, isn't going to massively explode unless mixed (hitting the ground did a good job of that). With solid fuel rockets your oxidizer and fuel are already packed and mixed together in an ideal ratio; it is an inherently shittier situation. In either case, in this situation, the crew would be long gone. The real problem comes when the failure of the launch vehicle comes with less notice. When you start designing solid fuel manned rockets you end up making mistakes like this: http://articles.orlandosentinel.com/2009-07-18/news/new_1_nasa-constellation-program-rocket-ares-i http://articles.orlandosentinel.com/2009-07-18/news/new_1_na...
  - hahainternet 13y ago
    I think that you're mistaken. Almost always when you see a rocket explode in mid air that is due to the range safety officer detonating its onboard explosives. Lets face it, any large structural breakup that breeches the tanks of a hypergolic fuel is going to cause a huge explosion regardless.

by jlgreco 13y ago

ajross 13y ago

I don't see how your point follows. A similar deviation with a solid fuel rocket would have resulted in basically the same event (an impact with the ground of a fueled, burning rocket at T+25s), no? There are indeed safety reasons to prefer liquid fuel, but I don't see that this events provides any new evidence.

HeyLaughingBoy 13y ago
He's saying that a solid-fuel rocket would likely have exploded before even hitting the ground.
- jlgreco 13y ago
  Yeah, pretty much. The rocket was already engulfed in flames and disintegrating before it hit the ground; were it a solid fuel rocket it would have blown way sooner.
- huhtenberg 13y ago
  This implies that solid rocket fuel is inherently susceptible to detonation, while liquid fuel is not. Even if it's true, it seems counter-intuitive.
  - jlgreco 13y ago
    It seems intuitive enough to me. Solid fuel is basically "pre-mixed". That's why this Proton rocket didn't blow up until it slammed into the ground, even though it was rapidly falling apart and completely consumed in fire. The speed at which it burns is basically the extent to which that fuel and oxidizer is mixed. Consider a bucket of kerosene. Gasoline doesn't have it's own oxidizer, it uses the air for that. If you light the bucket on fire then it will burn slowly for quite a while, but if you then grab the bucket and fling it into the air then the fuel and oxidizer will mix and you'll have a rather decent fireball on your hands. If you mix the fuel with an oxidizer first (say, ammonium nitrate....^), then you are going to have a bad situation the moment it catches; no need to shake it up. The other major sort of engine, a hybrid engine, is even safer than either solid or liquid rockets. This is because the fuel and the oxidizer are separated and unmixed like in liquid fuel rockets but additionally the fuel is not going to be able to rapidly mix with the oxidizer if it hits the ground or something (since it is a giant chunk of basically rubber or paraffin or whatever.) ^ ...and now I'm on a watchlist.
    - HeyLaughingBoy 13y ago
      Nah. The employees at the local Tractor Supply or Fleet Farm coulda told us the same thing ;-)
jlgreco 13y ago
I don't think the rocket would have made it to the ground burning had it been solid fuel, it probably would have blown when it started to break up above the ground. That liquid fuel, although hypergolic, isn't going to massively explode unless mixed (hitting the ground did a good job of that). With solid fuel rockets your oxidizer and fuel are already packed and mixed together in an ideal ratio; it is an inherently shittier situation. In either case, in this situation, the crew would be long gone. The real problem comes when the failure of the launch vehicle comes with less notice. When you start designing solid fuel manned rockets you end up making mistakes like this: http://articles.orlandosentinel.com/2009-07-18/news/new_1_nasa-constellation-program-rocket-ares-i http://articles.orlandosentinel.com/2009-07-18/news/new_1_na...
- hahainternet 13y ago
  I think that you're mistaken. Almost always when you see a rocket explode in mid air that is due to the range safety officer detonating its onboard explosives. Lets face it, any large structural breakup that breeches the tanks of a hypergolic fuel is going to cause a huge explosion regardless.