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View Full Version : Ares vs. Jupiter Rocket Designs


Viper Daimao
16th July 2008, 12:42 PM
I read an article at Space.com (http://www.space.com/news/ap-080714-alternative-moon-rocket.html)about a little tiff at NASA about a competing rocket design some employees have been working on off hours. They claim it is more efficient and half as expensive as the Ares rockets. They call it Jupiter.

Does anyone else know any more about this? It sounds like these guys want to stop the Ares project right when it's about to test fly and only have some calculations and blueprints if that. But are they right in their claims of superior design?

BenBurch
16th July 2008, 12:46 PM
Ares is, in my opinion, an accident waiting to happen. Solid fueled rockets are not a good idea on a man-rated vehicle. Too much can go wrong too explosively.

Viper Daimao
18th July 2008, 07:00 AM
Ares is, in my opinion, an accident waiting to happen. Solid fueled rockets are not a good idea on a man-rated vehicle. Too much can go wrong too explosively.

Do you know if the other design, Jupiter, also uses solid fuel?

BenBurch
18th July 2008, 07:21 AM
Do you know if the other design, Jupiter, also uses solid fuel?

No I do not.

Were this my call, I would launch unmanned spacecraft on big inexpensive boosters, and have a man-rated small liquid fueled booster to loft small capsules into space to meet them. Think Gemini-Titan. That was a sufficiently large system to do the job. Those capsules do not need to support people for three months, they just need to dock with the previously launched things that can.

Jimbo07
18th July 2008, 07:30 AM
Ares is, in my opinion, an accident waiting to happen. Solid fueled rockets are not a good idea on a man-rated vehicle. Too much can go wrong too explosively.

Actually, despite the infamous event of 1986, SRBs have a good safety record, numbers-wise. They are also apparently easier (less risky) to handle on the ground. That said, Soyuz has also been very successful. This is a debate that won't go away soon. That is, by my limited understanding, SRBs may not be astoundingly superior, but they are not so inferior as to render the debate moot.


Were this my call, I would launch unmanned spacecraft on big inexpensive boosters, and have a man-rated small liquid fueled booster to loft small capsules into space to meet them.

Well, that is, in theory, what's happening. Ares I will launch a crew capsule and Ares V will launch heavier unmanned payloads. The capsules themselves do not have to support the crew for six months, but they do need to remain capable of doing so in an emergency, much like the current task for Soyuz.

BenBurch
18th July 2008, 07:34 AM
Jupiter does have an SRB component; http://en.wikipedia.org/wiki/DIRECT

Travis
18th July 2008, 07:38 AM
I was under the impression that the Ares I would be liquid fueled. Is that incorrect?

BenBurch
18th July 2008, 07:51 AM
I was under the impression that the Ares I would be liquid fueled. Is that incorrect?

Yes. Its first stage is a huge solid fueled rocket.

http://en.wikipedia.org/wiki/Ares_I

Travis
18th July 2008, 08:28 AM
Yes. Its first stage is a huge solid fueled rocket.

http://en.wikipedia.org/wiki/Ares_I

Ahhh, maybe I'm thinking of an earlier proposal then.

lumos
18th July 2008, 08:31 AM
Ares is, in my opinion, an accident waiting to happen. Solid fueled rockets are not a good idea on a man-rated vehicle. Too much can go wrong too explosively.

I'll have to disagree with your statement. Solid boosters (SRB) are far safer "explosively" than a liquid fueled booster. I can't think of any solid boosters that have exploded during launch (but if you know of one, please tell me.). Solids are very safe. The Challenger accident was not caused by the explosion of the SRB but by the SRB leaking hot gases into the external tank, igniting the explosion of the external tank. The explosion was the liquid fuel (O2 and H2) used for the Shuttle main engines. Leaking hot gases such as those on the original shuttle SRBs on a spacecraft like Ares I would not endager the spacecraft nor would it explode the spacecraft.

The problem with the SRB for the first stage of Ares I is primarily structural and acoustic. The SRB could potentially "shake" the spacecraft apart due to its long, flexible structure and large vibrations. Making the spacecraft more rigid to prevent breakup due to vibration would add mass. Adding mass is bad, shaking is bad, flexibility on the launch vehicle is bad. We have a lot of tradeoffs.

Personally, I like the Jupiter concept (I scanned the proposal) and I believe that it would have been an easier, initially cheaper, but not safer, option. (due to it's commonalilty with the existing Shuttle components) Once the design (vibration/acoustic) issues for Ares I are worked out, it will be an extremely safe and efficient spacecraft.

If I were to recommend a re-design, I would try to replace the Ares I first stage SRB with a liquid fueled first stage. The 2nd stage of Ares I is already liquid (cryo O2 and H2). This would make the launch vehicle similar to the Ares V without the 2 SRBs, similar to the Saturn V, and similar to the Titan.

There were a lot of political maneuvers on the part of ATK, the manufacturers of the SRBs, to sell the SRB stage as "common" from the shuttle to Ares. Unfortunately, they are now talking about a 5.5 segment SRB compared to a shuttle 4 segment SRB. The SRB's were also not designed to launch a large mass on top of it. If you'll notice, most solids you'll see, are strap on boosters and/or mounted on the sides of a liquid fueld first stage.

jadebox
18th July 2008, 10:23 AM
I can't think of any solid boosters that have exploded during launch (but if you know of one, please tell me.). Solids are very safe.


You're right. The propellant in the SRBs is not an explosive and no solid boosters have exploded.

Several times a month, I fly rockets that use solid propellant motors made with basically the same propellant (APCP) as in the SRBs. APCP actually burns slower than typing paper. It's how quickly it produces a large volume of gas while burning - not how fast it burns - that makes it an effective rocket propellant.

A problem with solid propellants is that, once lit, there's little direct control over the thrust during the flight. But, Ares, like the Shuttle, is using solid propellant for just the first stage. The second stage can be throttled to compensate for any variations in the perfomance of the solid booster.

There's also the problem that a solid propellant booster can't be easily shut down in case of a problem. During the Challenger accident, the Range Safety Officer fired explosives placed on the SRBs which broke open the cases. The drop in pressure caused the solid propellant to stop burning. But, you can't do something like that while the booster is still near the crew vehicle.

In the case of the shuttle, abort procedures are rather limited. The shuttle has to be high enough to glide to an emergency landing. Even if the Challenger astronauts had recognized the problem, they probably would not have been high enough to make a safe abort.

With the Ares, however, its much more likely the crew would survive a problem with the booster or second stage because the escape system could pull them quickly away from the rest of the rocket.

As far as Ares vs. Jupiter, NASA's response is at:

http: // www. nasa. gov /pdf/256922main_Direct_vs_%20Ares%20_FINAL_62508.pdf

I think it's cool that people are think about this in such detail. I'd love to help design a system that will transport people to the moon then Mars. But, I think the people at NASA have some idea of what they are doing and that the problems with Areas will be worked out.

The real question is whether NASA will receive the support it needs to keep us at the forefront of manned space exploration and technology in general.

-- Roger

BenBurch
18th July 2008, 12:05 PM
lumos, look at the GPS 2R launch.

All it takes is a crack in the fuel element.

mhaze
19th July 2008, 07:33 AM
Rockets are extremely dangerous, this simple fact should be recognized. NASA becoming safety-neurotic will only repress the industry further. How to get people into space? Simple.

Open bidding.

neutrino_cannon
19th July 2008, 03:34 PM
Solid fuel rockets are fine and dandy for getting up into low orbit, but after that they're not so hot. A solid fuel rocket is a binary sort of proposition; it's either on or off, and there aren't any speeds in between. You can't turn it off once it's on either. This strikes me as suboptimal for orbital slingshots and other fancy maneuvering.

Add to that that I don't think anyone's come up with a solid fuel composition that matches even LOX/kerosene for specific impulse.

But for the first stage, I'm not entirely sure what's gained by a liquid fuel rocket. Trickier to move around on the ground, lower thrust-to-weight ratio, during the part of the mission where T/W ratios matter, and you're saving weight through superior specific impulse at the one point where that doesn't really matter.

BenBurch
19th July 2008, 05:19 PM
Solid fuel rockets are fine and dandy for getting up into low orbit, but after that they're not so hot. A solid fuel rocket is a binary sort of proposition; it's either on or off, and there aren't any speeds in between. You can't turn it off once it's on either. This strikes me as suboptimal for orbital slingshots and other fancy maneuvering.

Add to that that I don't think anyone's come up with a solid fuel composition that matches even LOX/kerosene for specific impulse.

But for the first stage, I'm not entirely sure what's gained by a liquid fuel rocket. Trickier to move around on the ground, lower thrust-to-weight ratio, during the part of the mission where T/W ratios matter, and you're saving weight through superior specific impulse at the one point where that doesn't really matter.

I just think back to the Gemini launch pad abort where the command pilot was able to shut off the Titan when it was not generating enough thrust. ( Somehow, I managed to be home sick from school for every launch. ;) )

mhaze
19th July 2008, 06:33 PM
Actually, yes, you can turn a solid rocket off. This is old stuff: Precision targeting of (range of) ICBM solid rockets was done by integrating acceleration, and blowing a hole in the casing at the exact moment when the correct amount of thrust had been provided.

Down close to the ground, in the initial launch, huge amounts of mass ejection are required. Further up, longer burn times are needed, some throttling, then pulsed burns for the final "circularization" of the orbit.

Solid rockets have exhibited reliability within an acceptable range for manned spaceflight.

I'm not sure that's saying a lot....

neutrino_cannon
20th July 2008, 12:34 AM
Wait... you turn off a solid fuel rocket by destroying the integrity of the fuel column enough that it can no longer generate thrust?

:eye-poppi

Hybrid rockets are looking better and better.

mhaze
20th July 2008, 06:39 PM
Wait... you turn off a solid fuel rocket by destroying the integrity of the fuel column enough that it can no longer generate thrust? :eye-poppi

Hybrid rockets are looking better and better.

Exactly right. Just as the main Shuttle engines disengage the ET when there is still fuel in it - it is the very accurate "DeltaV" number which is required from a stage. Future use of the past stage is nominal if not disadvantageous. This can be seen from the calculus of the basic multistage rocket equation.

Some new hybrid designs may provide sufficient impulse, fuel burn rate limits total thrust.

neutrino_cannon
20th July 2008, 09:22 PM
Exactly right. Just as the main Shuttle engines disengage the ET when there is still fuel in it - it is the very accurate "DeltaV" number which is required from a stage.
So throttleability of solid fuel boosters is basically a non-issue; the delta-v required for each leg of the mission is nailed down hard enough that the rockets can be made to exactly the right size (with a little wiggle room on top).

Future use of the past stage is nominal if not disadvantageous. This can be seen from the calculus of the basic multistage rocket equation.

Agreed, no need to drag along dead structural weight.

Some new hybrid designs may provide sufficient impulse, fuel burn rate limits total thrust.

IIRC some of the newer hybrid propellant combos have better Isp than solids.

mhaze
20th July 2008, 09:59 PM
So throttleability of solid fuel boosters is basically a non-issue; the delta-v required for each leg of the mission is nailed down hard enough that the rockets can be made to exactly the right size (with a little wiggle room on top).
Agreed, no need to drag along dead structural weight.
IIRC some of the newer hybrid propellant combos have better Isp than solids.
Yeah, you got it. Isp isn't that big a deal though for 1st stage, it's massive mass ejection that counts - speed is low to some machs on 1st stage - nozzle is thus inefficient ...

Look for more simple hybrids on private ventures, that's where the action will be.

lumos
21st July 2008, 10:00 AM
lumos, look at the GPS 2R launch.

All it takes is a crack in the fuel element.

Do you have a link to the investigation? I can't find anything useful on Google other than video and short comments.

It looks to me that while the failure may have been "triggered" by an SRB structural failure, the explosion is from the liquid fuel, including nitrogen tetroxide/hydrazine.

Structural failure is bad for any mechanism.

jadebox
21st July 2008, 10:41 AM
Wait... you turn off a solid fuel rocket by destroying the integrity of the fuel column enough that it can no longer generate thrust?

No, not at all. You just release the pressure in the casing and the propellant stops burning. The pressure release causes the temperature to drop low enough that the APCP no longer burns.

The rocket motors I use have enclosures at each end that are designed to fail if the pressure in the motor gets too high. This is intended to prevent the motor casing from rupturing if, for example, the rocket's nozzle gets clogged. I've witnessed a couple of cases where the rocket motor has failed like this during ignition. The most dramatic was about a month ago when a motor failed in my "Akavish" spider-themed rocket (see video (http://www.payloadbay.com/video-7934.html)). Apparently there was a crack in the propellant core which caused the motor to over-pressurize. The aft enclosure failed, causing the motor to shoot up through the motor mount, taking off the top of the rocket. When I went to recover the pieces, I found the propellant core intact. It looked like it hadn't been used since at all it stopped burning as soon as the enclosure failed.

Problems like the one I experienced are, fortunately, rare. I suspect that the propellant core I used had been damaged during handling before I bought it. It was bought second-hand (which I will avoid in the future!).

NASA x-rays the propellant cores used in the Shuttle to detect any cracks or bubbles that might cause a problem. That's a bit beyond my budget.

-- Roger

neutrino_cannon
22nd July 2008, 10:29 PM
Yeah, you got it. Isp isn't that big a deal though for 1st stage, it's massive mass ejection that counts - speed is low to some machs on 1st stage - nozzle is thus inefficient ...

It is possible to optimize the nozzle for the low-altitude pressure and high-mass low velocity throughput. Not sure how much you would gain from higher Isp at launch though; they did can the variable-geometry nozzle on the shuttle, after all.

Look for more simple hybrids on private ventures, that's where the action will be.

I liked the cut of theSpace X Falcon 1 rocket, even though it was liquid-propelled. I agree that we'll be seeing more simple, private rockets.


The rocket motors I use have enclosures at each end that are designed to fail if the pressure in the motor gets too high. This is intended to prevent the motor casing from rupturing if, for example, the rocket's nozzle gets clogged. I've witnessed a couple of cases where the rocket motor has failed like this during ignition. The most dramatic was about a month ago when a motor failed in my "Akavish" spider-themed rocket (see video (http://www.payloadbay.com/video-7934.html)). Apparently there was a crack in the propellant core which caused the motor to over-pressurize. The aft enclosure failed, causing the motor to shoot up through the motor mount, taking off the top of the rocket. When I went to recover the pieces, I found the propellant core intact. It looked like it hadn't been used since at all it stopped burning as soon as the enclosure failed.

Cool video, thanks.

Do you think that the pressure-relief valve concept would scale well?

DrRocket
23rd July 2008, 04:51 PM
[QUOTE=jadebox;3872087]You're right. The propellant in the SRBs is not an explosive and no solid boosters have exploded.[Quote]

In point of fact all solid propellants are explosives. The most common space launcher propoellants are class 1.3 explosives, which the propellants used in some high performance ICBM stages are class 1.1 explosives. There have been a couple of accidents that might be called explosions. C4 rockets experiences such a failure. And there was a Delta II that ruptured the case shortly after launch, although that failure was attributed to damage to the case.

[Quote]Several times a month, I fly rockets that use solid propellant motors made with basically the same propellant (APCP) as in the SRBs. APCP actually burns slower than typing paper. It's how quickly it produces a large volume of gas while burning - not how fast it burns - that makes it an effective rocket propellant.[Quote]

The propellant used in the shuttle SRBs is called a PBAN propellant, named for the binder. It is a mix of PBAN, aluminum, ammonium perchlorate and a few other minor ingredients, including some iron oxide to catalyze burning. The burn rate is considerably faster than most paper. Space booster propellant burn rates, at 1000 psi are typically on the ordre of 0.35 in/sec radially outward from the surface which is largely the centerbore.



[QUOTE]A problem with solid propellants is that, once lit, there's little direct control over the thrust during the flight. But, Ares, like the Shuttle, is using solid propellant for just the first stage. The second stage can be throttled to compensate for any variations in the perfomance of the solid booster.[QUOTE]

This is basically true, althought the grain is shaped to provide a pre-planned pressure-time profile that is appropriate to the mission



There's also the problem that a solid propellant booster can't be easily shut down in case of a problem. During the Challenger accident, the Range Safety Officer fired explosives placed on the SRBs which broke open the cases. The drop in pressure caused the solid propellant to stop burning. But, you can't do something like that while the booster is still near the crew vehicle.[QUOTE]

This is also true but not as important as you think. You can't shut down a liquid rocket either, at least as an abort mechanism. If you shut down the engine, then the rocket crashes back to the ground. No current rocket has an engine out capability, although Space X claime to be developing one.

[QUOTE]In the case of the shuttle, abort procedures are rather limited. The shuttle has to be high enough to glide to an emergency landing. Even if the Challenger astronauts had recognized the problem, they probably would not have been high enough to make a safe abort.[QUOTE]

The current shutele has no abort options once it has left the pad and until after SRM burnout and separation.

[QUOTE]With the Ares, however, its much more likely the crew would survive a problem with the booster or second stage because the escape system could pull them quickly away from the rest of the rocket.[QUOTE]

That is the plan. The escape propulsion is provided by solids with a very high burn rate.

jadebox
24th July 2008, 08:10 AM
In point of fact all solid propellants are explosives.

No. APCP is definitely not an explosive. If APCP exploded, it would be useless as a rocket propellant.

APCP is listed as an explosive by the BATF, but that is currently being challenged in court. And, APCP is flammable, and, therefore, was once classified as "Class 1.3" for shipping by the DOT. They've changed their system of classification, but APCP, quite rightly, is still treated as a hazardous material for shipping.

But, APCP burns much too slow to be an explosive. The ATF's own testing showed that APCP in a rocket motor burned at about 5 mm per second. In testing by the ATF, bond paper burned about ten times faster. A true explosive would burn at a rate at least 200 times faster than that.

-- Roger

jadebox
24th July 2008, 08:17 AM
Space booster propellant burn rates, at 1000 psi are typically on the order of 0.35 in/sec radially outward from the surface which is largely the centerbore.

According to the ATF's testing, paper burns at up to about two inches/second -- about five times the rate you quote for the solid propellant.

-- Roger

jadebox
24th July 2008, 08:22 AM
There have been a couple of accidents that might be called explosions.

"Explosions" are not necessarily caused by explosives. If you blow up a balloon too much, it will "explode" but that doesn't make air an explosive.

If a solid rocket motor overpressurizes, the casing can explode from the pressure. But, that's not because the propellant is explosive. And, a nice thing about most solid propellants is that they only burn under pressure. If a motor casing fails, the propellant stops burning. That's not true of most liquid propellants.

No matter what kind of booster is under them, however, the astronauts in Ares will be much safer than in those the shuttle simply because there is a reliable launch abort system available.

-- Roger

mhaze
24th July 2008, 08:36 AM
APCP is not an explosive.

BenBurch
24th July 2008, 08:44 AM
Neither is steam;

http://upload.wikimedia.org/wikipedia/commons/thumb/8/8c/Boiler_explosion_1850.jpg/640px-Boiler_explosion_1850.jpg

jadebox
24th July 2008, 11:09 AM
Neither is steam;


Sorry? Did anyone suggest that it is?

-- Roger

neutrino_cannon
24th July 2008, 11:38 AM
I think the distinction can best be drawn between different classes of explosives; deflagrants, that being most propellants in all but the most exotic engines, which burn from a quickly-propogating flame front, and detonations, which burn from the pressure wave and have a much faster pressure spike.

jadebox
24th July 2008, 12:32 PM
I think the distinction can best be drawn between different classes of explosives; deflagrants, that being most propellants in all but the most exotic engines, which burn from a quickly-propogating flame front, and detonations, which burn from the pressure wave and have a much faster pressure spike.

But, not everything that deflagrates is an explosive. In fact, most things that burn with a flame deflagrate, but aren't explosive.

In the case against the ATF, the Court of Appeals ruled that the ATF had not set standards for what separates a non-explosive which deflagrates from an explosive. The ATF replied that it is the rate at which the substance burns and attempted to show that APCP burns at a comparative rate to other substances on their explosives list.

When their own testing revealed how slowly APCP burns, they decided to compare it's burn rate to the "burn rate" of safety fuse. Safety fuse is, of course, designed to burn very slowly along its length. Nevertheless, the burn rate they calculated for the fuse is still faster than the rate at which APCP burns.

Of course, none of this has anything to do with the topic since both Ares and the Jupiter proposal use solid-propellant boosters.

-- Roger

mhaze
24th July 2008, 12:40 PM
Excuse me, but we are not in this forum seriously going to discuss whether something is an explosive or not based on its inclusion or exclusion in a list of proscribed materials by a government regulatory agency of a certain country.

I submit a question of this sort should be answered by looking at the definitions of the words and the scientific processes involved.

Lawyers and or politicians do not define science and do not define explosive.

jadebox
24th July 2008, 01:11 PM
Lawyers and or politicians do not define science and do not define explosive.

Although, there is a legal definition of an explosive (a substance "the primary or common purpose of which is to function by explosion"), I emphasized the scientific defintion (a substance which burns rapidly or undergoes detonation). I showed that solid rocket propellants do not meet that definition, because they don't burn rapidly or detonate.

Oh ... and I have tried, twice, to steer the conversation back on topic ...... :-)

-- Roger

DrRocket
24th July 2008, 02:02 PM
Space booster propellant burn rates, at 1000 psi are typically on the order of 0.35 in/sec radially outward from the surface which is largely the centerbore.

According to the ATF's testing, paper burns at up to about two inches/second -- about five times the rate you quote for the solid propellant.

-- Roger

Ever to try to burn compacted rolled up paper at 2 inches per second.?

DrRocket
24th July 2008, 02:09 PM
If by APCP you mean ammonium perchlorate composite explosive, then you are not even close to correct. It generally does not detonate, but it is a class 1.3 explosive. And I can assure you that the procedures for manufacturing it treat it as an explosive material. And I really don't care what the ATF says. I have been involved in the manufacture of literally millions of poinds of this stuff. The AP itself is actually detonable, though usually not considered sensitive. However the detonation of the Kerr McGhee plant that made AP ought to be enough of a demonstration.

The difference between rapid deflagration and full Chapman Jouguet detonation is well-known. But the difference would be lost on a nearby observer. Rapid deflagrations can create enough havoc and overpressure to satisfy almost anyone. I have seen enough results of both to not want to be very near either one.

APCP is not something that I would recommend be handled by amateurs. Particularly amateurs who think it is safe.

mhaze
24th July 2008, 02:12 PM
Although, there is a legal definition of an explosive (a substance "the primary or common purpose of which is to function by explosion"), I emphasized the scientific defintion (a substance which burns rapidly or undergoes detonation). I showed that solid rocket propellants do not meet that definition, because they don't burn rapidly or detonate.

Oh ... and I have tried, twice, to steer the conversation back on topic ...... :-)

-- RogerYes, we are in agreement. The legal definition is quite irrelevant for the purposes of discussion of solid rocket propellants. Our solid rocket boosters are not going to blow up because of some lawyer's snakelike thoughts, or some regulatory agency idiot bureacrat typing some words into a list of "bad stuff".

Side comment back to OP: I think we could argue that highest reliability and safety in multistage manned rocket launch would be the product of rapid turn around schedules a la Soyuz - doing the same thing over and over for decades - not trying to innovate, keeping everything as simple as possible.

For these purposes, NASA is diametrically opposed to safety, reliability, and the other factors of interest - whatever product they push out to the pad.

neutrino_cannon
24th July 2008, 02:14 PM
Hey, you should listen to the ATF; they have a lot of experience burning stuff.

Just how were these tests conducted anyhow? Was the burning paper under pressure?

And while we're at it; would there be any advantage to detonating rocket fuel? I'm thinking of something analogous to the air-breathing pulse detonation engines that there's so much interest in of late.

DrRocket
24th July 2008, 02:18 PM
Although, there is a legal definition of an explosive (a substance "the primary or common purpose of which is to function by explosion"), I emphasized the scientific defintion (a substance which burns rapidly or undergoes detonation). I showed that solid rocket propellants do not meet that definition, because they don't burn rapidly or detonate.

Oh ... and I have tried, twice, to steer the conversation back on topic ...... :-)

-- Roger

You are utterly wrong. Class 1.1 solid rocket propellants do detonate and are actually high explosives. Such propellants are in use as we speak. In large rocket motors. Burn rates on such propellants are in the range of ).5 inches per second. Detonation velocities of the same propellants are thousands of meters per second. Burn rate has nothing to do with detonation rates or detonability.

Class 1.3 propellants generally are not considered to detonate -- which means that detonation waves tend to damp out, the propellants have a large critical diameter, or even that the hole in the witness plate was ragged rather than clean. They are explosives. APCP propellants quite obviously contain AP (ammonium perchlorate) AP is detonable.

People who think that APCP propellants are safe are themselves dangerous.

Accidents involving either the manufacture of APCP propellant or rocket case ruptures are quite impressive. And dangerous.

BenBurch
24th July 2008, 02:30 PM
Sorry? Did anyone suggest that it is?

-- Roger

Point is a pressurized vessel can go kaboom even if what pressurizes it is not in any way an explosive.

mhaze
24th July 2008, 02:53 PM
You are utterly wrong. Class 1.1 solid rocket propellants do detonate and are actually high explosives. Such propellants are in use as we speak. In large rocket motors. Burn rates on such propellants are in the range of ).5 inches per second. Detonation velocities of the same propellants are thousands of meters per second. Burn rate has nothing to do with detonation rates or detonability.

Class 1.3 propellants generally are not considered to detonate -- which means that detonation waves tend to damp out, the propellants have a large critical diameter, or even that the hole in the witness plate was ragged rather than clean. They are explosives. APCP propellants quite obviously contain AP (ammonium perchlorate) AP is detonable.

People who think that APCP propellants are safe are themselves dangerous.

Accidents involving either the manufacture of APCP propellant or rocket case ruptures are quite impressive. And dangerous.

From our friend Wikipedia.org (note the last sentence)...
In ballistics (http://en.wikipedia.org/wiki/Ballistics) and pyrotechnics (http://en.wikipedia.org/wiki/Pyrotechnics), a propellant is a generic name for chemicals used for propelling projectiles from guns and other firearms.
Propellants are nearly always chemically different from high explosives (http://en.wikipedia.org/wiki/High_explosive) as used in shells (http://en.wikipedia.org/wiki/Shell_%28projectile%29) and mines to produce a blasting effect. However, some explosive substances can be used both as propellants and as bursters, as for example gunpowder (http://en.wikipedia.org/wiki/Gunpowder), and some of the ingredients of a propellant may be similar, though differently proportioned and combined, to those of an explosive.
A very typical propellant burns rapidly but controllably and non explosively, to produce thrust (http://en.wikipedia.org/wiki/Thrust) by gas (http://en.wikipedia.org/wiki/Gas) pressure (http://en.wikipedia.org/wiki/Pressure) and thus accelerates (http://en.wikipedia.org/wiki/Accelerate) a projectile (http://en.wikipedia.org/wiki/Projectile) or rocket (http://en.wikipedia.org/wiki/Rocket). In this sense, common or well known propellants include, for firearms (http://en.wikipedia.org/wiki/Firearm), artillery (http://en.wikipedia.org/wiki/Artillery) and solid propellant rockets (http://en.wikipedia.org/wiki/Solid_rocket):


Gun propellants, such as:

Gunpowder (http://en.wikipedia.org/wiki/Gunpowder) (black powder)
Nitrocellulose (http://en.wikipedia.org/wiki/Nitrocellulose)-based powders
Cordite (http://en.wikipedia.org/wiki/Cordite)
Ballistite (http://en.wikipedia.org/wiki/Ballistite)
Smokeless powders (http://en.wikipedia.org/wiki/Smokeless_powder)


Composite propellants (http://en.wikipedia.org/wiki/Composite_propellant) made from a solid oxidizer (http://en.wikipedia.org/wiki/Oxidizer) such as ammonium perchlorate (http://en.wikipedia.org/wiki/Ammonium_perchlorate) or ammonium nitrate (http://en.wikipedia.org/wiki/Ammonium_nitrate), a rubber such as HTPB (http://en.wikipedia.org/wiki/HTPB) or PBAN (http://en.wikipedia.org/wiki/PBAN), and usually a powdered metal (http://en.wikipedia.org/wiki/Metal) fuel (http://en.wikipedia.org/wiki/Fuel) such as aluminum (http://en.wikipedia.org/wiki/Aluminum).
Some amateur (http://en.wikipedia.org/wiki/Amateur_rocketry) propellants use potassium nitrate (http://en.wikipedia.org/wiki/Potassium_nitrate), combined with sugar (http://en.wikipedia.org/wiki/Sugar), epoxy (http://en.wikipedia.org/wiki/Epoxy), or other fuels / binder compounds.
Potassium perchlorate (http://en.wikipedia.org/wiki/Potassium_perchlorate) has been used as an oxidizer, paired with asphalt (http://en.wikipedia.org/wiki/Asphalt), epoxy (http://en.wikipedia.org/wiki/Epoxy), and other binders.

Propellants that explode in operation are of little practical use currently, although there have been experiments with Pulse Detonation Engines (http://en.wikipedia.org/wiki/Pulse_Detonation_Engine).

DrRocket
24th July 2008, 04:53 PM
...
Propellants that explode in operation are of little practical use currently, although there have been experiments with Pulse Detonation Engines (http://en.wikipedia.org/wiki/Pulse_Detonation_Engine).

In current applications propellants are not intended to explode. That does in no way change the fact that the propellants are explosives, and in the case of class 1.1 solid propellants in fact high explosives. Explosives are capable of undergoing combustion in more than one mode. The explosives used in solid rockets undergo relatively slow combustion when used as designed. However, they are capable of much more rapid combustion. In some cases the can exhibit true detonation. Been there, done that, it isn't pretty.

Even the class 1.3 propellants, ones such as you mentioned that use HTPB or PBAN as the binder are explosive. They do not detonate under normal circumstances, basically meaning that they have a large critical diameter. But if one breaks up, and a lot of surfeace area is exposed the rapid deflagration will seem like an explosion to anyone in the vicinity.

Pulse detonation engines are basically advanced replacements for jet engines and use liquid fuel and with a detonation pulse in a gaseous mixture of fuel and oxidizer. The objective is to produce a particularly efficient thermodynamic cycle. That cycle does seem to be applicable to rockets.


This is a case burst, propellant fracture and rapid deflagration of many of the fragments. The test stand was destroyed.http://www.capcomespace.net/dossiers/espace_US/lanceurs_US/titan/titan%204%20explosion%20aout%201998.jpg

neutrino_cannon
24th July 2008, 10:18 PM
Pulse detonation engines are basically advanced replacements for jet engines and use liquid fuel and with a detonation pulse in a gaseous mixture of fuel and oxidizer. The objective is to produce a particularly efficient thermodynamic cycle. That cycle does seem to be applicable to rockets.


Do rocket bipropellants just mix efficiently enough that there's no need to screw with the current power cycle? Why don't turbines work that well? Just the vagaries and complexities of mixing air and aerosolized fuel, and harvesting power from it at the same time?

And just for point of comparison, what are the chances that the ignition goes wonky and the fuel/oxidizer mixture and a liquid fuel rocket explodes? Or the fuel containment gets a leak? Or the o-rings in the lines get screwed up?

Is there actually any sort of rocket that can't explode?

jadebox
25th July 2008, 06:34 AM
Okay ... let's try common sense examples ....

If you insist that a solid rocket propellant like APCP is an explosive, please describe how you could make it explode. I don't think there is any way to that.

If you take a chunk of APCP and ignite it in the open on the ground, it'll smoulder, make a lot of smoke, and glow brightly. But, it won't explode. (This is how we dispose of unused propellant grains.)

If you encase APCP in a sealed container and ignite it, the container may burst due to the pressure, but as soon as that happens, the APCP will stop burning. It won't explode. (This scenario happens when a nozzle of a rocket motor gets clogged.)

You could attach a real explosive to the APCP and detonate the explosive. All that would happen is that the APCP will break up. It won't explode. (NASA tested this for the Shuttle's SRBs and, unfortunately, demonstrated it for real after the Challenger accident.)

Possibly, you could grind it up, but it wouldn't be rocket propellant any more. That would be like saying aluminum is an explosive because aluminum powder is.

-- Roger

mhaze
25th July 2008, 07:51 AM
Okay ... let's try common sense examples ....

If you insist that a solid rocket propellant like APCP is an explosive, please describe how you could make it explode. I don't think there is any way to that.

If you take a chunk of APCP and ignite it in the open on the ground, it'll smoulder, make a lot of smoke, and glow brightly. But, it won't explode. (This is how we dispose of unused propellant grains.)

If you encase APCP in a sealed container and ignite it, the container may burst due to the pressure, but as soon as that happens, the APCP will stop burning. It won't explode. (This scenario happens when a nozzle of a rocket motor gets clogged.)

You could attach a real explosive to the APCP and detonate the explosive. All that would happen is that the APCP will break up. It won't explode. (NASA tested this for the Shuttle's SRBs and, unfortunately, demonstrated it for real after the Challenger accident.)

Possibly, you could grind it up, but it wouldn't be rocket propellant any more. That would be like saying aluminum is an explosive because aluminum powder is.

-- Roger

Yes, I'll add to your list gasoline and or kerosene. RP1 is rocket fuel, so we are dealing with a rocket fuel.

By Dr. Rocket's criteria, these are explosive (keep in mind we all know that the vapor is explosive) but we are all well aware of gasoline, what it is and is not, and it is not "an explosive" by any contemporary use of the word.

Aluminum powder? Again by Dr. Rocket's criteria, it would be an explosive. Yet anybody with a slight familiarity with the subject knows that it is the particle size which is critical in this issue - in fact aluminum powders are so graded.

APCP can like anything cause an overpressurization of a container and that container can structurally fail, in which case parts of metal go flying off, and people can and have gotten hurt. That does not make it an explosive material.

RE detonation engines, a 10 pound thrust motor will cause people 10-30 miles away to be calling the sheriff about the racket. So they are not likely to be used for thrust purposes....

I understand from Jadebox that the classification of the APCP chemical as "explosive" has been challenged in court formally. Dr. Rocket should have no need to repeat himself regarding the 1.1 and 1.3 clasifications (which I presume are the challenge) because it is obvious that we are aware of those and do not dispute that those clasifications, which are/have been formally challenged, exist as this time.

jadebox
25th July 2008, 08:33 AM
... the 1.1 and 1.3 clasifications...

Those were DOT classifications. I believe the DOT has switched to using similar UN classifications now. APCP was classified as 1.3 because, during transport, it should be handled in the same manner as the explosives which were included in the 1.3 class.

The National Association of Rocketry and the Tripoli Rocketry Association are not challenging the DOT's classification of APCP. They are challenging the inclusion of APCP in the Bureau of Alcohol, Tobacco and Firearms's list of explosives. The challenge is being made on several grounds, but the main one is that APCP is simply not an explosive in its intended use as a rocket propellant.

Back on topic ....

As I said earlier, there are many problems with using solid rocket boosters on manned rockets. Although, they've proven very reliable for the Shuttle, there are challenges that NASA will have to overcome to use them for Ares. The "pogo" problem is especially serious.

I would guess that the SRBs on the Shuttle exhibit the same "problem," but that the configuration of the rocket dampens the effect so it isn't really a problem. If this is true, the Jupiter proposal would seem to have already licked that problem. So, that would be a point in Jupiter's favor - at least until NASA's engineers figure out how to fix the problem.

-- Roger

mhaze
25th July 2008, 08:48 AM
Those were DOT classifications. I believe the DOT has switched to using similar UN classifications now. APCP was classified as 1.3 because, during transport, it should be handled in the same manner as the explosives which were included in the 1.3 class.

-- Roger
I stand corrected. It is a frikking alphabet soup of classifications, overlaid with multiple contradictory government agency regulations and vagueness. Again, however, we cannot consider a regulatory classification as a scientific definition.

DrRocket
25th July 2008, 08:20 PM
...

Back on topic ....

As I said earlier, there are many problems with using solid rocket boosters on manned rockets. Although, they've proven very reliable for the Shuttle, there are challenges that NASA will have to overcome to use them for Ares. The "pogo" problem is especially serious.

...
-- Roger

Pogo is a problem that is unique to liquid rockets. There is no such problem with solids. The closest solid rocket phenomena is something called acoustic burning instability, but that has not been much of an issue since the early Minuteman days with propellant based on casting powder.

There is currently a minor issue being discussed for Ares 1 with involving what is being called thrust oscillation. But in this case the issue has arisen largely from analytical studies that indicate a large structural response on the core vehicle to a very small hypothetical pressure oscillation in the the solids. It is based on pressure oscillations seen in the 4-segment SRBs with an amplitiude on the order of 1 psi. Acoustic and dynamics analyses of rockets at this early stage in a program are notoriously inaccurate and this issue will probably not be resolved until some real test data is available.

DrRocket
25th July 2008, 08:34 PM
Okay ... let's try common sense examples ....

If you insist that a solid rocket propellant like APCP is an explosive, please describe how you could make it explode. I don't think there is any way to that.

If you take a chunk of APCP and ignite it in the open on the ground, it'll smoulder, make a lot of smoke, and glow brightly. But, it won't explode. (This is how we dispose of unused propellant grains.)

If you encase APCP in a sealed container and ignite it, the container may burst due to the pressure, but as soon as that happens, the APCP will stop burning. It won't explode. (This scenario happens when a nozzle of a rocket motor gets clogged.)

You could attach a real explosive to the APCP and detonate the explosive. All that would happen is that the APCP will break up. It won't explode. (NASA tested this for the Shuttle's SRBs and, unfortunately, demonstrated it for real after the Challenger accident.)

Possibly, you could grind it up, but it wouldn't be rocket propellant any more. That would be like saying aluminum is an explosive because aluminum powder is.

-- Roger

I don't know how you dispose of propellant grains, but when we disposed of excess propellant at work,many hundreds of pounds of APCP. we lit it on the burning grounds and generated an huge fire and a giant cloud of white smoke. It burned quite nicely thank you very much and did not go out.

When we disposed of actual propellant grains we did it by splitting the motor case with a shaped charge to render the motor non-propulsive. with the nozzle removed of course, and let it burn to completion in an open pit. The motor in that case does not extinguish but burns to completion, albeit at a lower burn rate, due to lower pressure, that what one sees in a motor firing.

If you want to create what an amateur would certainly call an explosion, though not a ture detonation, you only need to rupture the case while under pressure and thereby fracture the grain. The result is a huge increase in surface area, a massive generation of gas, and destruction of most nearby structure.

Or you can have an accident while mixing the propellant and have an ignition in the mixer. The result of that is blow the roof off the building (they are designed to do that and have extraordinarily thick concrete walls surrounded by sand) and send a rather large fireball skyward with an associated very lound noise, that again most amateurs would call an explosion.

Now these are not full Chapman Jouget detonations, but people can and have been killed by these non-explosions. A mixer explosion is what put United Technologies out of the solid rocket business, and a second accident wth that propellant killed a contract maintenance worker who was working on the damaged mixer.

Once again, people who think these propellants are innocous don't know what they are talking about and are dangerous to themselves and those around them.

DrRocket
25th July 2008, 08:38 PM
Here is picture of a motor with APCP propellant. This is not a detonation. But one could reasonably call it an explosion. It leveled the test stand, and that was a pretty stout test stand.
http://www.nasa.gov/pdf/221186main_toft_checkpoint_report.pdf.

BenBurch
25th July 2008, 08:43 PM
I think you pasted in the wrong link, Dr. Rocket.

-Ben

DrRocket
25th July 2008, 09:19 PM
I think you pasted in the wrong link, Dr. Rocket.

-Ben

I certainly did, but if perhaps people were interested in the thrust oscillation issue on Ares 1 they might have found the mistake interesting. Here is the link that I intended to post.


http://www.pr.afrl.af.mil/archive/titan/titan_iv_mishaplg.jpg