Quantcast

Gap Staging

The Rocketry Forum

Help Support The Rocketry Forum:

accooper

Well-Known Member
Joined
Oct 12, 2009
Messages
918
Reaction score
1
Where can I go on the Internet to learn about gap staging?

TIA

Andrew From Texas
 

Micromeister

Micro Craftman/ClusterNut
TRF Lifetime Supporter
TRF Supporter
Joined
Jan 19, 2009
Messages
15,074
Reaction score
38
Location
Washington DC
Why not go to the source "the Hand book of Model Rocketry" G. Harry Stine was the innovator of the method back in the 60's. Its contained in the chapter on Staging which has all ya need to know in any edition you might come across.
 

Bone Daddy

Well-Known Member
Joined
Oct 4, 2009
Messages
924
Reaction score
2
Not really much to it. I read about it in the Stine book and thought it sounded interesting enough to try. I already had a second stage in mind, so I made a booster, drilled two holes in the fore end and bam - two stage rocket with gap staging. Worked like a charm. I've used gap staging now on several rockets without a problem.

This particular beast has a 4" booster. The holes are a bit more than 1/4" from the end since my second stage - actually all my rockets - has a 1/4" overhang.

Admittedly, there was no rocket science involved. I knew the second stage was stable so I eyeballed what looked like would be a good match based on the pictures in the book. Swing test was good. I test tumbled it out of a second story window. Then off to the rocket range.

Finished 2 stage.JPG


Finished booster.JPG
 

accooper

Well-Known Member
Joined
Oct 12, 2009
Messages
918
Reaction score
1
Will gap staging work with 1/2a to D size engines?

Andrew
 

tbzep

Well-Known Member
Joined
Jan 18, 2009
Messages
1,714
Reaction score
1
Will gap staging work with 1/2a to D size engines?

Andrew
1/2A booster to D12 sustainer?

It would physically stage just like any 18mm booster/sustainer combination. In fact, the D12's large nozzle gives it a higher percentage of ignition reliability than 18mm sustainers.

However, odds are that it won't be able to boost a rocket of that weight fast enough to fly vertically and stable....unless you are wanting it to stage while still on the launch rod.
 
Last edited:

Lentamental

Well-Known Member
Joined
Jul 27, 2009
Messages
359
Reaction score
1
Pretty sure he meant that the concept of gap staging will work for 1/2A through D engines, not a 1/2A lifting a D...

Still, an interesting concept. If I could get my hands on a few A10-0 or A8-0, it could make for a seriously awesome flight with a D on top. Lifting up 10-20 feet, dropping the booster, and then shooting off for the stars.


On a similar note, is the ejection charge from a motor with a standard delay sufficient to ignite a second stage, or the ejection charge different in motors intended to be used as boosters?
I would of course make sure that the rocket would still be traveling at a high enough velocity when the second stage lights, but it could make for an awesome effect, looking like an air-start.
 

MarkII

Well-Known Member
Joined
Jan 18, 2009
Messages
8,212
Reaction score
9
On a similar note, is the ejection charge from a motor with a standard delay sufficient to ignite a second stage, or the ejection charge different in motors intended to be used as boosters?
I would of course make sure that the rocket would still be traveling at a high enough velocity when the second stage lights, but it could make for an awesome effect, looking like an air-start.
Black powder booster motors do not have ejection charges or even delays. A booster motor just contains the very hard slug of highly compressed propellant and a clay nozzle.

Although a single-stage motor that has a delay grain and an ejection charge can certainly be used in a booster stage, it cannot be used to ignite the upper stage motor. First of all, the upper stage, or sustainer, motor should be lit while the rocket is still carrying considerable momentum and speed from the boost; otherwise, the boost has been wasted, and the whole effort has been for naught. But this is exactly what would happen if you used a single-stage motor to light the sustainer. Remember that the whole purpose of the delay grain in a single-stage motor is to allow the rocket to coast to a stop at apogee, so that the ejection charge (which is designed specifically to generate gas to pressurize the airframe, which then ejects the recovery system) fires and pushes out the laundry when the rocket is nearly motionless. So having the booster motor burn a delay grain and allow the rocket to coast to a stop before igniting the sustainer would be counterproductive. It would be a total waste of the booster's energy; you would be better off not using a booster at all in that case.

I alluded above to the other big reason why you can't use a single-stage motor to ignite a sustainer: the ejection charge doesn't work that way. The purpose of the ejection charge is to produce gas (a great deal in a very short interval of time) and is not to produce flame. But flame is what you need to ignite the upper motor, and ejection charges are not well-suited for producing it. The ejection charge is set up to blow everything in front of it out of the rocket; it will do that to a sustainer just as well as it does to the recovery system. So when it fires, it will simply blow off the sustainer without igniting it.

There are plenty of multi-staged rockets that use single-stage motors in the booster, but these all use some other means (an electronic timer or flight computer) to ignite the upper stage. They do this after the booster burns out, while the entire rocket is still climbing at a good clip. Then the delay and ejection charge in the booster motor is used to deploy a recovery system for the booster stage, and it fires well after the booster has separated. This is how rockets that use composite propellant (APCP) motors are staged.

MarkII
 
Last edited:

Lentamental

Well-Known Member
Joined
Jul 27, 2009
Messages
359
Reaction score
1
I realize that the rocket would have slowed down considerably after the delay. The idea would be to pick the shortest delay possible, so that it would only coast for a short period of time. Strap on boosters would be used to help it get enough initial speed so that it could still be going at a considerable clip by the end of the coast. Then, the 2nd stage would ignite, and go on its way.

The boost would not be wasted at all. The boost would have taken it up a fair ways, and given it a fair bit of speed. In fact, the sugar rocket to the moon group has a planned delay in between "stages" (really just grains) so as to let the rocket coast for a while, to keep the speed (and thus air resistance) down, so that they get higher.

Anywho, the point would be for an awesome flight show.

Still, I get your point of the difference between booster and sustainer "ejections" (or lack thereof.) Thanks for that info.
 

tbzep

Well-Known Member
Joined
Jan 18, 2009
Messages
1,714
Reaction score
1
To go into a little more detail, an ejection charge is composed of grains of BP that are lightly tamped into the motor. At ejection, these grains break up into individual small grains, giving it a ton of surface area and allowing it all to burn almost instantly, creating a lot of gas. The particles burn up before traveling very far. It's more than just flame to ignite an upper stage, because you will see a flash of flame sometimes when motors eject. It's the burning (flaming) particles with some mass to them that do the trick.

The propellant part of all motors starts out as powder, but is compressed into one solid slug and burns from one end to the other. When the booster burns through, what's left of the slug breaks into several large chunks that have enough momentum to travel up the rocket and into the nozzle of the sustainer. The chunks are also big enough that they won't burn up before getting there.

Ejection charges won't reliably ignite upper stage motors. I remember reading about someone testing it years ago and they did get ignition occasionally, but the percentage was very low. Think of it this way. Had you rather quickly pass your hand over an open flame, or had you rather get hot coals dumped on you? :y:
 

Mikus

Well-Known Member
Joined
Jan 27, 2009
Messages
644
Reaction score
3
Why not go to the source "the Hand book of Model Rocketry" G. Harry Stine was the innovator of the method back in the 60's. Its contained in the chapter on Staging which has all ya need to know in any edition you might come across.
EVERY rocketeer should own that book, imho. :2:
 

tbzep

Well-Known Member
Joined
Jan 18, 2009
Messages
1,714
Reaction score
1
EVERY rocketeer should own that book, imho. :2:
True, but the guy did ask for online sources of information. :)

BTW, I picked up an old 2nd edition that has some stuff in it that is not in the current version. It's interesting to read through what Bill has left alone and what he's changed since his Dad "wrote the book on model rocketry". :cool:
 

Mikus

Well-Known Member
Joined
Jan 27, 2009
Messages
644
Reaction score
3
Worked like a charm. I've used gap staging now on several rockets without a problem.
What kind of mess did the residue leave? I'm getting a bird with gap-staging ready to go, if our field ever dries out, and I was kinda wondering about that.
 

tbzep

Well-Known Member
Joined
Jan 18, 2009
Messages
1,714
Reaction score
1
What kind of mess did the residue leave? I'm getting a bird with gap-staging ready to go, if our field ever dries out, and I was kinda wondering about that.
I know this was directed at someone else, but you can expect residue similar to regular staging. It can leave some gunk at the vent holes, the front of the booster, and on the rear of the sustainer. The amount depends on the diameter of the rocket and the general design. Sustainer ignition can char the top of the booster if it doesn't fall away soon enough.

There is a happy medium with gap staged boosters. The vents need to be big enough and the booster needs to fit tight enough to keep the it on the sustainer until ignition, but they need to be small enough and fit loose enough to let the sustainer ignition blow them off before full thrust is achieved to prevent charring. With my son's open gap staged Aerobee, we had to work more on the fit of the booster because no air pressure builds up to separate the stages. We charred the booster a few times before we got the happy medium.
 

tbzep

Well-Known Member
Joined
Jan 18, 2009
Messages
1,714
Reaction score
1
Heh, not bashing. Just stating. :D

Oooh I bet that is interesting. Any ideas why? Safety?
I know you weren't bashing. I was just ribbing a little on you and Micro. BTW, I agree that everybody should have a copy of the Handbook. I bet Bill Stine even has a copy on his bookshelf. :cool:

It's been a while since I've read through the two, but I recall a few changes were probably made due to safety and some definitely had to do with the evolution of the hobby, product availability, etc.
 

Micromeister

Micro Craftman/ClusterNut
TRF Lifetime Supporter
TRF Supporter
Joined
Jan 19, 2009
Messages
15,074
Reaction score
38
Location
Washington DC
To go into a little more detail, an ejection charge is composed of grains of BP that are lightly tamped into the motor. At ejection, these grains break up into individual small grains, giving it a ton of surface area and allowing it all to burn almost instantly, creating a lot of gas. The particles burn up before traveling very far. It's more than just flame to ignite an upper stage, because you will see a flash of flame sometimes when motors eject. It's the burning (flaming) particles with some mass to them that do the trick.

The propellant part of all motors starts out as powder, but is compressed into one solid slug and burns from one end to the other. When the booster burns through, what's left of the slug breaks into several large chunks that have enough momentum to travel up the rocket and into the nozzle of the sustainer. The chunks are also big enough that they won't burn up before getting there.

Ejection charges won't reliably ignite upper stage motors. I remember reading about someone testing it years ago and they did get ignition occasionally, but the percentage was very low. Think of it this way. Had you rather quickly pass your hand over an open flame, or had you rather get hot coals dumped on you? :y:

Several decades of research by many in the hobby and professional rocketry on the subject have provided inconclusive results; We DO NOT KNOW what causes upper stage ignition, but it's fairly obvious staging would not be nearly as reliable as it is, if it were left to random chance a chunk of burning propellant to hit those small nozzle openings alone to do the job.

It is not only possible to use a standard delay/ejection charge motor to reliable ignite upper stage motors It can be very helpful in some long coast phase optimum mass models IF and I say again IF all the math as been done and choosing a motor delay combiniation that matches up with the most high speed forward coast time of the model. This was done this year at Naram winning the event.

Back to igniting those upper stage motors; It could be any one or combination of Heat, Radiation, and hot particulates that bring the cold BP up to combustion temperature. I'm presonally in the heat & radiation camp bringing the BP up to temp as these travel more or less in a straight line where particulates are more subject to pressure (Burst or burn through) release changes and venting.
Exactly how it works remains a mystery but as all have stated a couple times Staging and more to the thread authors point Gap Staging work very will with all BP Booster/sustainer combinations up to gap of about 12".
Some say they've had success with larger gaps but everything I've done, read, seen or heard of being successful more than once (repeatability being key) has been within that distance range:)
Personally I like to keep my gap as short as possible but have had repeated successful staging with gaps as long as 8 inches.
I firmly agree Everyone should have a least one Handbook of Model Rocketry, An endless source of factual knowledge and proven techniques. Much of what is picked up "On-line" is neither.
 

Bone Daddy

Well-Known Member
Joined
Oct 4, 2009
Messages
924
Reaction score
2
My recipe for vent holes:

1) make two marks 180o apart

2) draw a straight line and make a mark at 1/2"

3) insert spent engine into the body tube, past the mark

4) using a drill press with a 3/16" bit I drill one hole

5) rotate body tube and drill second hole.

note: it is possible to drill both holes if you have a cradle to hold the body tube straight and prevent it from rotating.

6) clean up the holes with an exacto knife.

7) apply super glue around the edges of the hole.

The booster pictured has 10 flights under its belt.

With my many hobbies, I find a drill press to be indispensable. I use a cheap and inexpensive drill press from Northern Tool. Not a precision tool, but it gets the job done.

Mark the body tube post.jpg


Insert spent motor post.jpg


Drill holes post.jpg


Clean up with exacto knife post.jpg


finished hole post.jpg
 

Bone Daddy

Well-Known Member
Joined
Oct 4, 2009
Messages
924
Reaction score
2
I use a sleeve to protect the inside of the booster from the hot gases when the sustainer ignites. (This too is adapted from the Good Book. They use bond paper rather than a body tube.)

1) Insert spent motor until it rests against the thrust ring.
2) mark the motor at the top of the body tube.
3) transfer the mark to a second piece of body tube.
4) cut the body tube off at the mark.
5) slit the body tube
6) insert in booster and mark vent holes (keep the overlapping seam away from the vent holes.
7) remove the sleeve.
8) tape to spent motor and drill holes using a 1/4" bit
9) trim a tad more than 1/4" from the top of the insert to account for motor overhang from sustainer
10) insert and line up holes.
11) test fit sustainer and booster, trim if needed.
12) ready to go.

These cuts, holes, etc. do not need to be perfect. Just needs to get the job done.

No drill press? No problem. Just use an exacto knife to make your holes.



good book also. They use bond paper, i like the body tube.

Mark insert post.jpg


Drill insert post.jpg


Trim to fit post.jpg


insert ready to go post.jpg


Sustainer and booster post.jpg
 

MarkII

Well-Known Member
Joined
Jan 18, 2009
Messages
8,212
Reaction score
9
Several decades of research by many in the hobby and professional rocketry on the subject have provided inconclusive results; We DO NOT KNOW what causes upper stage ignition, but it's fairly obvious staging would not be nearly as reliable as it is, if it were left to random chance a chunk of burning propellant to hit those small nozzle openings alone to do the job....

Back to igniting those upper stage motors; It could be any one or combination of Heat, Radiation, and hot particulates that bring the cold BP up to combustion temperature. I'm presonally in the heat & radiation camp bringing the BP up to temp as these travel more or less in a straight line where particulates are more subject to pressure (Burst or burn through) release changes and venting.
Don't forget the sudden release forward of the thrust chamber pressure, acting as a piston to drive the remaining propellant straight at the sustainer's nozzle. With dozens, perhaps even hundreds, of flaming bits of propellant being flung at the nozzle throat with some force, I would think that the odds of at least one bit (and probably more like many bits) entering the nozzle ought to be pretty good. Think about a couple of analogues: flash pan ignition and the so-called spider ignition aid for clusters. Both methods require that when a small quantity of black powder is burned, enough flaming bits or sparks will randomly work their way across a gap and into the nozzles of a set of motors positioned nearby to achieve near simultaneous ignition of every one of those motors. Pulling that off seems, at first glance, like it would be a pretty tall order, with a high failure rate. Yet that's exactly what happens; both methods are known to be quite reliable. It seems reasonable to conclude that a similar process takes place within the enclosed confines of a stage gap (or even in a totally open gap, such as in Intruder's Aerobee), where the sparks or bits only need to find their way into one nozzle (while getting a big push from behind, to boot). The standard description of this process seems like a no-brainer to me.

MarkII
 
Last edited:

tbzep

Well-Known Member
Joined
Jan 18, 2009
Messages
1,714
Reaction score
1
It is not only possible to use a standard delay/ejection charge motor to reliable ignite upper stage motors It can be very helpful in some long coast phase optimum mass models IF and I say again IF all the math as been done and choosing a motor delay combiniation that matches up with the most high speed forward coast time of the model. This was done this year at Naram winning the event.
How was this allowed? Using a sustainer motor as a booster is against the NAR safety code, therefore should not be allowed in any NAR event.

2. Motors. I will use only certified, commercially-made model rocket motors, and will not tamper with these motors or use them for any purposes except those recommended by the manufacturer.
 

tbzep

Well-Known Member
Joined
Jan 18, 2009
Messages
1,714
Reaction score
1
but it's fairly obvious staging would not be nearly as reliable as it is, if it were left to random chance a chunk of burning propellant to hit those small nozzle openings alone to do the job.
I disagree with you there because it's more like a shotgun blast of many propellant chunks than a random piece. Static firing a booster motor at night will shed some light (pun intended) on it. Folks that have patterned shotguns know that you can get 100 or more shot in a fairly small circle at 40 yards, but all you need is one shot for a kill. In the hands of a decent shooter, a person shooting clay targets at 40 yards will be near 100%. Reliability of staging is fairly close to 100% when done correctly and I suspect it is because there are many small particles that get blasted at the nozzle of the sustainer.

On to testing...

It's hard to believe that a test couldn't be devised to at least give us a very good idea if a split second of direct radiation is enough to ignite an upper stage. We need the burning temperature of BP and the ability to expose the nozzle end of a motor to a heat source of equal value and similar wavelength for a split second.

Hot gases should be fairly easy to test also and at least give us a good idea on its ability to ignite an upper stage. All we need to do is give the gases a short but indirect path so that burning particles don't reach the motor. A short three or four inch path through a very simple baffle would be similar to the same distance of gap staging. We can assume that some heat will be absorbed by the baffle, but probably no more than would be absorbed by a foot of straight body tube and we know that gap staging is fairly reliable out to that distance if done correctly. The temperature could be measured to make sure it's reasonably close so that we can be sure that the baffle isn't absorbing too much heat from the gases.

I'm sure folks have tested this in NAR R&D before, but with today's cheap and available technology, a person should be able to gather some better data in a modern R&D project. Regardless, this makes for good discussion. :)
 

Micromeister

Micro Craftman/ClusterNut
TRF Lifetime Supporter
TRF Supporter
Joined
Jan 19, 2009
Messages
15,074
Reaction score
38
Location
Washington DC
You guys crack me up LOL!!!

I'll be waiting to see your test results, and report Can't wait to be enlightened.

As for being allowed, another mis-interpretation of the safety code on your part. There is nothing anywhere expressed by any manufacturer or entity that does not allow the use of a delayed motor in a lower stage. Your assuming things that are not there. That's like saying we can't use delay train containing motors in clusters because they would also be defined "boosters". I'm sure it would also make you uneasy to know many a competitior has used red labled booster motors in very small upper stage models to deploy a recovery system or streamer. Manufacturers have purposely been quite broad in their scope as to what is and is not allowable with there products.

Mark:
Have to disagree with the flash pan analogy as they are notorious for NOT lighting all motors in the clusters while toasting the bottom of the model with a ball of fire. Spider igniters on the other hand are specially made to very closely fit a small tube directly in line with the throat of each clustered motor nozzle seperated by a very thin tiny gap. Observing these in Night operation shows clearly it's not flaming bits but actual Flame shooting directly into each nozzle and yet on larger clusters more often then not some motor or motors still do not light.
Neither of these examples really fit whats going on within the confines of a booster body with a sustainer motor up to 10-12" away. It does sort of fit with taped together booster/sustainer motors but then again we have to remember Tape butted motors have a higher failure rate then gap staged motors???
One thing I forgot to mention in the earlier post was the possible added effect of "Afterburn" as the propellant breaks through creating a pretty hefty length flame as well. I don't claim to know exactly how it works, but accept that it's some combination of these things that come together making the process very helpful for staging motors with some pretty impressive distances between motors.
 
Last edited:

tbzep

Well-Known Member
Joined
Jan 18, 2009
Messages
1,714
Reaction score
1
You guys crack me up LOL!!!

I'll be waiting to see your test results, and report Can't wait to be enlightened.
No problem. Stand at 50 yards with a circle drawn on your shirt and grab some safety glasses and I'll hit you with some 8 shot. We can count the whelps whenever the stinging stops. :p (for the humorless folks, I'm kidding)

As for the safety code and manufacturers' intentions, catalogs stated "Single stage" for decades and listed motors in the category. I believe motors at one time or other have been stamped "single stage" also, though I don't have any here at work to look at right now. Literature from Estes has emphasized to only use xx-0 motors as boosters, etc.
 

tbzep

Well-Known Member
Joined
Jan 18, 2009
Messages
1,714
Reaction score
1
I'm sure it would also make you uneasy to know many a competitior has used red labled booster motors in very small upper stage models to deploy a recovery system or streamer. Manufacturers have purposely been quite broad in their scope as to what is and is not allowable with there products.
LOL! Your memory is very short. In TRF 1.0, I posted about using a booster motor as a zero delay single stage motor and you threw a fit that it was against the safety code and I should never suggest such a thing. Now you are using that very thing to defend yourself. I only posted about the safety code thing because you slammed me in that thread.

BTW, they outlawed it after Bob Kaplow used it in Superroc.

All these are your quotes:

Booster motors are intended to be used for just that, Boosting lower stages or in clusters along with delay and ejection charge fitted motors. It's not a hard concept, almost common sense one would think. The motor has a RED lable marked "Booster" motor, Let's use them as the manufacturer intended.
Now let's get back to the subject of clustering Estes SR-71.
All that considered, What I'd like everyone reading this thread to understand is This:
"Booster motors ARE NOT INTENDED by the Manufacturer, to be used to deploy a recovery system...PERIOD".

The motor manufacturers make this FACT very clear. We as responsible modelers should NOT be promoting a process or proceedure that is a direct contridiction to the manufacturers intended and expressed insturctions. Can this be expressed any more clearly? Booster motors are NOT to be used in place of single or upper stage motors at have a delay train.


http://www.rocketryforumarchive.com/showthread.php?t=41729&highlight=bob+kaplow+booster+superroc
 

Micromeister

Micro Craftman/ClusterNut
TRF Lifetime Supporter
TRF Supporter
Joined
Jan 19, 2009
Messages
15,074
Reaction score
38
Location
Washington DC
They stopped putting that suff on motor lables in the mid 90's along with most of the different motor type color coding. Used to be Upper stage motors were had purple lettering, lower stage or single stage green, and boosters Red. Currently all but boosters are green or green&blk lettering with boosters remaining red.
But none of this has a thing to do with a delayed/ejection charged motor being used as a booster. There is just no bases for such a suggestion.


Not a short memory; Just wanted to see if someone was still carry the same gurdge...as suspected, you are.

Really no defense necessary but since you obviously wanted to try again to make some sort of statement, I'll be happy to rebut it.

The Difference my friend, is I wasn't suggesting such a use by inexperienced modelers in your average run of the mill mod-roc. Rather speaking about a semi-common practice used in spacific tiny competition models where the modeler HAS the knowledge to do and has done the research to make such a system work Safely. It's all about WHO we are suggesting a specific technique to and in what context.
I'd still have to "slam" as you put it, such a discussion in this forum (LPR) if proposed to be done by JohnQ rocketeer. The quote is still just a revelant as it was in TRF 1.0. "Booster motors ARE NOT INTENDED to be used to deploy recovery systems, PEROID."
Am I supposed to say I'm sorry I dared address a potentially harmful suggestion to inexperinced folks reading? Nope! it ain't a gonna happen bunkey, we have to Think before we Act or Type;)
Now lets put this pointless past bickering aside and get back to the subject of gap staging.
 

luke strawwalker

Well-Known Member
Joined
Jan 18, 2009
Messages
9,139
Reaction score
14
Pretty sure he meant that the concept of gap staging will work for 1/2A through D engines, not a 1/2A lifting a D...

Still, an interesting concept. If I could get my hands on a few A10-0 or A8-0, it could make for a seriously awesome flight with a D on top. Lifting up 10-20 feet, dropping the booster, and then shooting off for the stars.


On a similar note, is the ejection charge from a motor with a standard delay sufficient to ignite a second stage, or the ejection charge different in motors intended to be used as boosters?
I would of course make sure that the rocket would still be traveling at a high enough velocity when the second stage lights, but it could make for an awesome effect, looking like an air-start.
Hehehehe... sounds like a 'cold launch' to me... :)

"Cold launch" was a method that the Soviet Union developed to extend the range of their nuclear missiles during the cold war. It involved a large 'gas generator' that essentially blew the missle out of the silo like a person puffing a spitball from a straw... the missle usually had a plug-like adapter on the bottom of it like a piston, which took the force of the gas generator and lifted the missle on top of it out of the silo, then seperated. The piston usually had small sideways mounted rocket engines on it that ignited once it seperated and pushed it off to one side out of the way, and the missile's rocket engines immediately fired up and continued the missile on it's way. The piston was fired off to the side to prevent the missile's rocket engines from blasting it back down into the top of the silo, potentially damaging the silo and preventing it from being reloaded easily. Not firing the rocket engines inside the silo made it MUCH easier to reload the silo as there was far less damage done than a "fire in the hole" liftoff which US missiles use. The system is very similar to that used aboard submarines, which eject their ballistic missiles from the submarine using compressed air, and once the missile breaks the surface the rocket engine is ignited.

I've seen footage of an SS-18 Satan being cold-launched from a Soviet silo... including slo-mo footage of the piston seperating from the missle bottom and it's side-rockets firing, and the main rocket engines of the missle firing up. They may have it on Youtube...

Later!
 

Lentamental

Well-Known Member
Joined
Jul 27, 2009
Messages
359
Reaction score
1
I actually saw this one launcher someone made, that was effectively an air cannon that the rocket slid down, with an electric trigger, that ignited the rocket at the same time as releasing the air. The leads to the igniter were long enough, and the motor took long enough to ignite, that it usually lit 10-15 feet in the air. Wish I still had that link. It was AWESOME!
 
Top