rocket engine with solid fuel pellets

[spacefire]

I think Goddard was experimenting with something like this before he switched to liquids.<br />For suborbital private flights, where you don't need that much performance, but you want to keep the costs down, would this system be preferred over a classic liquid rocket engine or even a hybrid?<br />Safety wise, since the pellets are 'fed' to the combustion chamber, wouldn't that minimze the risk of an explosion?<br />Now comes the question whether the mechanism to deliver pellets is within technological grasp, and cheaper to make than the alernatives.<br />If the pellets were to have metallic compounds in them, would it be possible to move them with magnetic fields?<br />This is wild supposition...input is most welcome <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[mlorrey]

What size pellets are you talking about? if they are small, you need them to combust before they leave the combustion chamber. if they are large and are supposed to stay in the chamber, you have to worry about them plugging the throat (or pieces falling off and doing so) and causing an explosion. What is supposed to be the advantage of pellets? Seems to me you are looking to build with the worst aspects of solid fuels and the worst aspects of liquid fuels. <br /><br />The way to overcome it would be to make it a solid fuel PDE system, which would essentially function like a machine gun firing blanks. Build in a high speed feed system to fire 1000 rds/minute or more, and a cartridge that fires in reverse: the brass cartridge is a projectile ejected out the rear by the explosion of the propellant. So long as your propellant is a detonating explosive and not a deflagrating one, you should be able to attain a significant Isp that would make up for the bulk of the system.

 

[tomnackid]

For some of the early Orion tests they used what was essentially a machine gun to fire shells that exploded (conventional explosives that is!) at a predetermine point behind the Orion model's pusher plate. I think they might have even progressed to the point of doing some short free flights to test the stability of the whole concept. Of course explosive shells end up being a lot more expensive than conventional rocket fuels and would probably have much poorer ISP although I recall that Pournelle used the concept of a "non-nuclear Orion" to build a quick an dirty launch vehicle in "King David's Spaceship".

 

[spacefire]

is it possible to move the pellets around without using any mechanical systems? i.e. with electromangentic fields? I don't care if the iron particles would damage the nozzle, that can be replaced after every flight. <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[mlorrey]

Mmmm, how are you going to generate the power for your magnetic fields? Permanent magnets are very heavy. Power generation equipment is heavy. Once again, you are detracting from the performance.<br /><br />There is this principle in engineering called KISS: Keep It Simple and Stupid: the less complicated your design, the more likely it will work.

 

[vogon13]

For instance, the pressure inside the combustion chamber of the SSME is around 3000 PSI. <br /><br />How do you open up the chamber and put a 'chunk' of something in it?<br /><br />How fast does the 'chunk' burn? If it hangs up going into the combustion chamber (and it is burning) you now have a huge problem with a conflagration outside of your combustion chamber.<br /><br />How does the pellet ignite at launch? Can we turn the engine off, and relight it in flight?<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[spacefire]

each pellet would provide some thrust during the burn, then the next pellet would arrive and so on. the pressure in the combustion chamber would equalize with the atmospheric soon after the burn is done.<br />keep in mind this is a short burn, for a suborbital craft, so the electrical energy to be stored onboard doesn't have to be that huge. <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[annodomini2]

<blockquote><font class="small">In reply to:</font><hr /><p>Mmmm, how are you going to generate the power for your magnetic fields? Permanent magnets are very heavy. Power generation equipment is heavy. Once again, you are detracting from the performance. <br /><br />There is this principle in engineering called KISS: Keep It Simple and Stupid: the less complicated your design, the more likely it will work. <p><hr /></p></p></blockquote><br /><br />Also know as 'Keep It Simple and Safe' <div class="Discussion_UserSignature"> </div>