TSTO

[mlorrey]

I would urge webtaz99 to actually read the page being referenced, look at the images. The shape of the two mugs certainly provides the proper shape for a ramjet.

 

[scottb50]

I used to work for a guy who had FAA approval to hang spray tanks from the wings of a single engine Cessna. That would be a wild ride with a couple of ram-jets, and a few hundred pounds of tanks and propane. <div class="Discussion_UserSignature"> </div>

 

[qso1]

Wild ride alright, especially the part where the Cessna comes apart and the pilot has to parachute back to Earth...assuming he or she brought a parachute along.<br /><br />The ramjet model looks pretty cool but can such a ramjet be scaled up and used supersonically or better yet, hypersonically? <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[mlorrey]

Ramjets without MIPCC are capable of flight to Mach 7 using hydrocarbon fuels. They have been used in missiles large enough to carry humans (if converted) at speeds up to mach 5.5. The SR-71 ran essentially as a ramjet plane from mach 2-3.2. The Nord Griffon II and Leduc 022 both flew mach 2-2.4 entirely on ramjet power (they only used their turbojet for take-off up to ~400 mph). These were all aircraft powered by ramjets, carrying people, that regularly operated supersonically. The Griffon II looked essentially like a chubby F-16.<br /><br />MiG and Tumanky asserted that the Mach 4 mothership for their Spiral/50/50 launcher was completely feasible (and the prototype was built but not tested).<br /><br />Ramjets can attain T/W essentially the same as LH2/LOX rocket engines, while attaining much higher Isp and propellant bulk densities.

 

[webtaz99]

Webtaz did load the page, read the text, and look at the pictures. Ramjets work because of physics, not aesthetics. I'm sure it will work, in the sense that it will provide a flame, but it will not be optimized in any sense. <div class="Discussion_UserSignature"> </div>

 

[spacefire]

the thrust produced is not the point here.<br />the purpose of the page is to illustrate the simplicity of the design and the extremely low cost. <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[mlorrey]

Yes, it was not being suggested for any sort of launcher, but only as a project for people interested in the technology to become familiar with it, operating requirements, etc. without having to have a lot of manufacturing equipment for sheet metal, welding torches, etc.<br /><br />As an example, on prep school kid in Maine built one for a project.<br /><br />The Maggie Muggs is certainly a design for subsonic propulsion, at best, but I don't know of many model plane builders that would attempt to produce supersonic model aircraft.

 

[scottb50]

I would think it could be tested pretty easily.<br /><br />Attach a bunch of Estes, Acme 's would be better though, rockets to the Coffee cup engine. Cardboards cheap so drop the rockets light the cup and off you go. <div class="Discussion_UserSignature"> </div>

 

[josh_simonson]

That page has nice photos, ect, but from what I gather one of those has never been tested, and frankly I have doubts about JB weld holding together when the thing is containing compressed combusting gasses. <br /><br />It is a good example though of how straightforward a ramjet is, but keep in mind a scramjet is also straightforward, just the devil is in the details of the geometry.<br /><br />Perhaps a simple solid fuel ramjet would be a better starter project. It could start under rocket power then switch to ramjet like an SA-6 does. There's quite a bit of hobbiest literature about producing solid rockets and hybrid rockets. Seems techniques from these two areas could be combined to make a solid ramjet. Perhaps when the solid fuel burns out it could ignite a pyrovalve (like used on hybrid rockets) that would allow pressure fed liquid or gas fuel to continue the burn. <br /><br />If you start kicking the butts of folks at rocketry meets, your idea would gain momentum. Should be much safer than a comparable rocket too since theres less oxidizer to make a kaboom.

 

[scottb50]

The Oxidizer doesn't go kaboom, it lets the fuel, or actually the Hydrogen in the fuel, to go kaboom. <div class="Discussion_UserSignature"> </div>

 

[josh_simonson]

Of course, otherwise I wouldn't keep a pound of KNO3 under my aquarium... Oxidizer is the explosion limiting factor in the hybrid ramjet due to an overabundance of fuel. I think the fuel grain would make a good flame inhibitor for the outer edges of the rocket grain too.

 

[scottb50]

I think it's pretty basic, provide enough oxygen to burn the Hydrogen available. How you carry and store them is the next consideration. <div class="Discussion_UserSignature"> </div>

 

[mlorrey]

"but from what I gather one of those has never been tested,"<br /><br />If you make that sort of absurd statement, you obviously didn't read the pages.<br />This specifically: http://cottrillcyclodyne.com/Maggie_Muggs/Maggie_3.html#Part_01<br /><br />Shows the one built by the kid in Maine being tested, with photos.<br />

 

[publiusr]

So you only get high with a propellant leak...

 

[josh_simonson]

I see no measurement of net thrust. Fire != functionality. Their test stand looks like it'd flip over if it produced more than 1lbf.

 

[mlorrey]

Given they only tested it with a low powered leaf blower, I doubt they were able to simulate more than 50 mph winds, so your nit picking is simply sour grapes at being proven wrong due to your own lack of due diligence. Given it only weighs 15 ounces, 1 lbf = T/W > 1, so it is functional, even if it only produces that much thrust....<br /><br />If you were smart, you'd build a Maggie Muggs and try your darndest to make it as high performance as possible and test it at as wide a velocity range as possible. The design is really no different from other subsonic designs, such as those installed by the Defense Department after WWII on wingtips of P-51s and other piston driven aircraft. <br /><br />There are crucial design parameters with ramjets, essentially that exhaust cross sectional area is 1.4 times the intake cross sectional area. Exhaust:Intake ratio is the crucial parameter for design to a specific speed range, and combustion cross section needs to be larger than both for sub-hypersonic speeds, and larger than the intake for all speeds. Outside of these, the only crucial parameter is the F/O ratio.<br /><br />Ramjets are not complex, do not need to be complex, to get useful functionality out of them. Getting max possible thrust out of them does require some work and some science, but doing so is not necessary for useful work.

 

[scottb50]

So the idea is a larger leaf blower?<br /><br /> <div class="Discussion_UserSignature"> </div>

 

[webtaz99]

LOL!<br /><br />I got one that goes to 11. <div class="Discussion_UserSignature"> </div>

 

[mlorrey]

yes, and multiple leaf blowers, feeding into a de laval nozzle to accelerate the flow even more. Make a backyard wind tunnel.

 

[scottb50]

Gee that sounds just about like a jet engine to me. Exhaust it into a ramjet adding additional fuel, just like an after burner. As speed increases air is ducted directly to the afterburner and fuel is added, the jet engine is then shut down. Reaching mach 10-12 the inlets are sealed and fuel and LOX convert the afterburner to a rocket engine. <br /><br />Piece of cake, I think I even have some JB Weld around somewhere.<br /><br />Sounds a lot more complicated than straight rockets and jet engines though. <div class="Discussion_UserSignature"> </div>

 

[mlorrey]

Its a wind tunnel. Don't be foolish.

 

[scottb50]

He's not dead. He's juat pining. <div class="Discussion_UserSignature"> </div>

 

[tap_sa]

<font color="yellow">"multiple leaf blowers, feeding into a de laval nozzle to accelerate the flow even more."</font><br /><br />If you want supersonic windspeeds, as using de laval nozzle indicates, you need more initial gas pressure than leaf blowers can provide. IIRC you need at least a few bars at the de laval nozzle inlet in order to have Mach 1 condition at the throat. No Mach 1, no supersonic expansion at the divergent part of the nozzle.

 

[qso1]

mlorrey:<br />Ramjets without MIPCC are capable of flight to Mach 7 using hydrocarbon fuels. They have been used in missiles large enough to carry humans (if converted) at speeds up to mach 5.5. The SR-71 ran essentially as a ramjet plane from mach 2-3.2. The Nord Griffon II and Leduc 022 both flew mach 2-2.4 entirely on ramjet power (they only used their turbojet for take-off up to ~400 mph). These were all aircraft powered by ramjets, carrying people, that regularly operated supersonically. The Griffon II looked essentially like a chubby F-16. <br /><br />MiG and Tumanky asserted that the Mach 4 mothership for their Spiral/50/50 launcher was completely feasible (and the prototype was built but not tested). <br /><br />Ramjets can attain T/W essentially the same as LH2/LOX rocket engines, while attaining much higher Isp and propellant bulk densities.<br /><br />Me:<br />My question is "Can the ramjet device proposed here be scaled up to carry humans"...and to add to it, carry humans economically?<br /><br />The ones you mention I'm already aware of although the SR-71 takes off from the ground under its on power implying it is using turboramjets. Guess what I'm getting at, the ramjet proposed here is proposed on its simplicity, while military test vehicles involve much expense in development even thought their ramjets are relatively simple. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[mlorrey]

The Maggie Muggs ramjet is proposed not for any purpose of actual propulsion of manned vehicles, but simple as a science experiment. It is not intended to scale, though something similar was tested with US and british versions of the V-1 buzzbomb.<br />Military test vehicles involve much expense primarily because they have a much more complex mission requirements list than a simple launcher demands. They demand things like: must launch from short runways, carrying x thousand pounds of ordnance/missiles, fly x nautical miles at b speed and/or y miles at z speed, fly high g combat maneuvers at c speed for d minutes, carry e thousand lbs of heavy radar and avionics equipment to detect the enemy, deploy weapons, and block the enemy's ability to detect and attack you, and then fly back to base of origin, with f radar cross section, g noise profile, h peak velocity, i landing speed, etc etc etc.<br /><br />When dealing with naval combat aircraft, it is even worse due to the unique problems of carrier takeoff and landing operations.<br /><br />With a launcher, I really don't have those problems. The flight profile has many of the same elements, but in many ways, the requirements on the airframe are much lower and simpler than with a military test vehicle. Launchers usually have mostly compressive stresses along their primary axis, with few lateral stresses. Even with winged launchers (like my X-106) the stresses are much lower since we don't have to worry about dogfighting capability. As an example, the F-106 was designed to handle 9 g's, while the Shuttle Orbiter never sees much more than 1.5 g's on reentry. The X-106 could handle up to 4 g's on a high AOA reentry profile (similar to the FIRST system) of 60-70 degrees to drop as much velocity as possible at altitudes where the Orbiter barely notices the atmosphere.<br /><br />We don't have to worry about carrying a propulsion system to get us up to ramjet speed. There are plenty of alternatives to carrying an installed turbojet: