I think they are a long way from deciding on an Ariane 6 design, its really still at the proposal stage at the moment, and hey if the Skylon works it could be the Ariane 6...

1. There is no such requirement for launch vehicle. A liquid booster can have the same characteristics and be better than a solid in other areas.
http://www.sworld.com.au/steven/pub/lrb.pdf

2. Liquid boosters like the original design of the shuttle and what NASA intended to replace the SRB's in the late 90's.

Yes, it is worse
a. Because they are extremely heavy lifts
b, They are sensitive to stray voltages and static electricity.
c. The hazard does not go away once they are stacked. It is there the whole time.
d. The VAB used to have hundreds of offices for the Saturn V stage contractors. These offices can't be used for the shuttle or any SDLV, because of the solid motors.

LOX and LH2 are only hazardous during the countdown, when no one is on the pad anyways.

There are no precautions on the pad for an unloaded liquid booster. In fact, Atlas has its kerosene on board and it is benign.

Face it. Your point is wrong. Solid first stages for spacelaunch is not a trend.

And there's even more behind the curtains, as could be expected. The rest is "...but then I'd have to kill you" area.

But the general remark is true that technologies are being tested at the moment, and that -partially due to these tests, partially due to the early stage of the design phase in general- the Ariane 6 design is far from fixed at the moment. It could still go almost any direction. Including the solids direction.

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c: just ask the survivors of the 2003 Alacantara accident. Solids don't magically become safe the moment they're stacked.

Other things to consider:
Solid rocket segments have strictly limited lifetimes. You've got strong oxidizers mixed in with a polymer binder and various plasticizers...it's not stable, certainly not more so than RP1. And they are non repairable. Crack, chip, bubble, any defect from manufacturing or later handling that makes a segment slightly suspect...that segment is junk. This is not just an issue of waste, but ties back into the safety issue...you must dispose of these expired or damaged segments. If you were to base an entire space program off these things, you would have a quite significant quantity of these.

Also consider the hazard experienced should the vehicle need to be un-stacked. If there's problems encountered on the pad and the vehicle needs major work, a liquid fueled vehicle can have its tanks drained and be made safe, solid boosters need to be disassembled and the segments removed to a distant location. There's the direct hazards of handling the solid rocket components that this involves, and there's the risk of damaging the segments in handling, which would require shipping the damaged segments for disposal and shipping in replacement segments.

Solids are good for compact, low-delta-v, high-thrust applications. Launch escape systems, ullage motors...their disadvantages are greatly reduced and their advantages are far more important. As a primary source of delta-v for an orbital launch of any but the tiniest payloads, however...they're simply a terrible idea.

Solid rockets, although they have their disadvantages, are not nearly so bad as that makes it sound cjameshuff. The propellant used for most modern SRBs (ammonium perchlorate composite propellant) is quite stable, and is good for >20 years post manufacturing. It is somewhat like a dense pencil eraser in consistency, and is not prone to cracking (though if it does crack, it must be detected and disposed of, as a crack can easily cause a very impressive failure). The propellant is pourable when made, and with modern manufacturing techniques, the number of faulty segments is quite small.

The propellant is also quite difficult to light - it is not at all prone to accidental ignition. It is basically completely static insensitive, and it is not prone to shock ignition either. I have lit APCP with a lighter before, and it can take >5 seconds of direct flame contact before the propellant will ignite.

The main issue with older motors is simply that the outer layer of the propellant will slightly oxidize, making it more difficult to light and lower thrust while that layer is burned off (<0.2 seconds after ignition in most cases). If stored properly, this is minimal even over many year periods, so there really isn't any issue with storage.

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Dead And Alive

SRB segments fell of a wagon last year in a train crash, yet no kaboom.

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Shock ignition of SRB propellants is very rare, but it has happened before. In 1990, a Titan IV SRB segment ignited when it was accidentally dropped about 20m while preparing for a static test at Edwards AFB.

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Dropping an SRB 20 meters is quite an "oops" day!

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Having spent some time working around engine test facilities (mostly aviation gas turbines), I will say they're all quite impressively large. iirc, the USAF's test facility (AEDC, in Tullahoma, Tennessee) routinely tests large rocket motors in deep pits, with the exhaust pointing vertically up. This way if something breaks the engine will try to drill through the planet instead of going on a ballistic trajectory towards (inevitably) Graceland.

yes.. having the rocket part below ground level has it's advantages... instead of spreading the test stand all over if somebody goofs on the fuel mix, and makes it go "boom" instead of "swooooosj"
you instantly get a nice new swimming pool, or at least a hole to dump all the wreckage into before building a new stand.

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The SRMU was tested vertically in the old F-1 engine test stands, with the nozzle pointed down.

Sounds like a " Not in my back yard " issue, and with good reason.

Dan

A long time ago, in an engine manufacturer now far away, they had an engine part company with itself and rain heavy, hot chunks of metal through (among other things) the roof of a guy's RV and a nearby sail loft.

Hi, My My, that was Not a good day at all !!! Sure makes a nasty impression on a decent sail loft.
Somedays, you meet all kinds of different people.

Augustine himself says there is

Nothing says that cannot be done at a later point for Ares V's strap-ons at some point.

Here's an Aviation Week article about a new all solid-fueled booster that Japan is going to build. The booster is designed to put 1.2 tons into LEO, require little in the way of ground infrastructure, and to get the cost down to $30 million per launch. Solids have their advantages but also their limitations.

To be built by IHI Aerospace, the ASR is Japan's proposed future launcher for medium scientific payloads. JAXA also is studying a further development that would cut costs partly by using a fuel that could be melted and formed into a solid engine at less than the boiling temperature of water. That follow-on rocket could be available for commercial use, according to ASR project leader Yasuhiro Morita.

Studies of the ASR began in 2007 and the agency has now completed its concept design, done the preliminary design review and is about halfway into more detailed development work.

The point of the project is to cut costs. The ASR would lift 1.2-ton satellites to low orbit, a third less than its predecessor M-V, at around a third of the cost per launch. At $80 million a shot, the M-V was enormously costly, partly because it was launched only seven times in nine years, the last in 2006. The agency says Japan's space scientific effort suffered from that high cost.

For the ASR, "the purpose is to significantly reduce the time and labor needed for ... assembly and checkout of the rocket and to make the associated ground support system and facilities as compact as possible," Morita says. The target cost is $30 million per launch.

With Japan now 'committed' to getting serious about space-based solar power, this could (possibly?) really help keep construction costs down a bit

http://news.yahoo.com/s/afp/japanspa...olartechnology

Alex

Didn't someone on here say thet no one else is going in the direction of solids?

It sounds like solids have come of age.

I know you would post something related to this and you would come to the wrong conclusion, again. This is a solid rocket replacing another solid rocket. This is not a trend. There is a place for them, but they are not replacing liquid stages. There was SCOUT and it was replaced by Pegasus, Taurus and Minotaur. But then again Falcon 1 can do the same job.

The role of solids has not increased and only decrease. This and Ares I is not indicative of the whole space launch arena. Titan IV solids were replaced by liquid cores strapon boosters on the DIV and AV. Delta II solids were replaced by single core DIV and AV. Ariane 6 is doing away with the Ariane V solids. Ares I is a reduction in solids from the shuttle. Ares I also going away because it is an expensive solid.

Your basic premise is wrong. Nothing has changed in solid motor technology. They are same as they were in the 1960's. There is nothing that has changed nor has their usage. They serve the same roles.
Do some research or work in the business before make unsubstantiated claims. But still don't make unsubstantiated claims.

Just for comparison, they are aiming at 1.2 tons to LEO at $30 million target cost - may or may not come to that. For comparison, Falcon 1e is targeted at 900 kg to LEO and less than $15 million, but let's round it up.

On one side you've got an LV with $25 million per ton and arguably a harsher environment for the payload, on the other side you've got $17 million per ton.

Anyway, to infer from this small launcher that a big one such as Ares is the right decision is ignoring all the arguments made over and over such as scalability, costs, handling difficulty etc.

The most powerful all-solid propellant booster today is probably the Taurus with a LEO payload of about 1.3 metric tons. There are reasons why no one is building 10+ ton capacity all solid boosters and it isn't "tradition." Solids require much less support infrastructure at the launch site but liquids scale much better to large boosters due to higher efficiency among other reasons.

not to mention that for an all solid rocket the payload ratio is horrible.
However the Weight to thrust ratio is excellent.
each to it's own uses. solids wont go away anytime soon. and neither will liquid propelled rockets.

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LOL, I think you meant to say thrust-to-weight ratio.

I wrote the response below as a response to a post made by ugordan, but it is appropriate here again:

Solids are better than Liquids (will be)

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If this somewhat dated article about the Vega is accurate, it's still a relatively low to medium lifter with a LEO zero degree inclination capacity of 2.3 metric tons. There is a need for boosters in that weight class but I've yet to hear of anyone trying to build a large booster that's all solid propellant powered. The relatively low Isp of solid propellants seem to limit their scalability to larger booster designs.

Well, as said...

So one of the design plans for Ariane 6 has it all solids except for the upper stage. So while that's not "all" solid powered, the vast majority of that design is.

Attached Images

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