TSTO

[webtaz99]

Call me stupid, but if you dropped a ramjet prototype from a balloon or small aircraft, couldn't it get the first 100-200 mph for free? Of course, it would have to pull out of a dive at high speed when it lit.... <div class="Discussion_UserSignature"> </div>

 

[webtaz99]

Even though a "mass driver" can't hurl realistic payloads into orbit, it should be able to get a ramjet going fast enough without applying too many G's. It would be good to get them lit before leaving the ground. <div class="Discussion_UserSignature"> </div>

 

[ldyaidan]

Another possibility for frequent launches is waste management. Our landfills are overflowing, and we generate tons of trash every day. If we can find cheap access to space, we could launch this trash into the sun, where it would be incinerated. Now, I'm not sure what kind of long term effects it would have on the sun, so we would have to do some research there, but it seems like it would be a reasonable solution, and might even get the environementalists on our side.<br /><br /><br />Rae

 

[mlorrey]

Disposal of nuclear wastes and highly toxic chemicals may make this worthwhile, but not ordinary trash. This suggestion is not worthwhile.

 

[mlorrey]

Yes, a mass driver would work, but would it be economical? Going with the most gee-whiz idea is often not the one that is most economical (one reason I advocate ramjets vs scramjets and hydrocarbons vs LH2). Why use electromagnets and not just a steam catapult? Why not a tow launch?<br /><br />My ideal:<br />Take a tunnel boring machine, and bore a tunnel, 30' in diameter, from near the peak of a mountain at a 45 degree initial angle, down and curved to a base under the floor of the valley on the opposite side. Tunnel is lined with concrete and plate steel welded to the rebar in the reinforced concrete.<br /><br />The propellant is water, driven to steam in massive quantities very fast by the combustion of rocket-like combustors in boiler vessels.<br /><br />This would allow construction of a ramjet/rocket launch stage using an STS ET for fuel tanks, backed by a sabot, which would exit the launch tube at around mach 1 (a 500 foot tall tower around the exit would be constructed as a big silencer).<br /><br />Sounds great, but it is, once again, an example of gee-whiz technology.<br /><br />A realistic alternative: iron rails, two sets in parallel, with big wide train cars powered by massive air transport-type turbofan engines, driving the launcher up to 400+ mph. This would likely be the most economical, as rail is cheap to lay today (they have robots that do it now), and there are so many surplus rail cars you can pick them up for scrap to build your launch platform out of.<br /><br />I've been envisioning this sort of launch system for years now, and of building it in the Nazca plains, ending up the side of a small mountain. The locals would get lots of jobs, and the government would love its tourist attraction and tie-in with the legend/mythology of 'ancient astronauts' having a "spaceport" there (despite the scientific facts to the contrary).

 

[j05h]

>Even though a "mass driver" can't hurl realistic payloads into orbit, it should be able to get a ramjet going fast enough without applying too many G's. It would be good to get them lit before leaving the ground. <br /><br />Foster-Miller was working on a maglev train that could do this. They were going to build a train to run on a DoE (?) circular track in the desert. With a ten-mile track, a launcher could even select a rough direction to launch in. They talked about flying X33 off the maglev. I'm pretty sure the maglev achieved the same level of success as X33. Other options would include a rocket sled (many are capable of multiple Mach) and ekranoplane (see Caspian Sea Monster) for getting your ramjet up to speed. These are all much more complex than hobbyist level. I like the balloon-drop idea - it'd take a large cluster of weather balloons to lift but is possible. Pull-out of the dive is a challenge. <br /><br />My favorite "multimode" launcher proposal is still Marshall Savage's "Bifrost" in The Millenium Project. Maglev sled up Mt. Kilimanjaro to laser-ignited ice for fuel. The additional lasers are installed across Indian Ocean facilities, powered by OTECs. <br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[n_kitson]

<blockquote><font class="small">In reply to:</font><hr /><p>Close the inlet, start pumping in oxidizer too -> scramjet turns into rocket engine. <p><hr /></p></p></blockquote><br />At which point it is by definition no longer airbreathing and no longer scramjet <img src="/images/icons/smile.gif" />

 

[webtaz99]

>>Yes, a mass driver would work, but would it be economical? Going with the most gee-whiz idea is often not the one that is most economical (one reason I advocate ramjets vs scramjets and hydrocarbons vs LH2). Why use electromagnets and not just a steam catapult?<<<br /><br />The US Navy is moving from steam catapults to "electromagnetic systems". More force-per-length and better control are two reasons. <div class="Discussion_UserSignature"> </div>

 

[mlorrey]

Which says absolutely nothing about the economics of it. How about dollars per length? The Navy spends whatever they need to get the performance they want, witness the A-12 "$100 billion = no planes" fiasco.

 

[mikeemmert]

The problem with launching any kind of supersonic craft from the ground is that the vehicle needs to be too strongly built to withstand aerodynamic forces. It's pretty easy to get to the stratosphere with all kinds of existing turbojet technology.<blockquote><font class="small">In reply to:</font><hr /><p>(mlorrey) ...and hydrocarbons vs LH2...<p><hr /></p></p></blockquote>Psychlopropane? <img src="/images/icons/crazy.gif" /><br /><br />...Sorry, I just couldn't resist...<br /><br />Well, let me try a more positive suggestion, then. In the 1960's somebody sold cylinderheads for two-stroke motorpsychles called "The Fan-Dancer". It was an aluminum extrusion with radial cooling fins. What made it neat was that the cooling fins had cooling fins!<br /><br />If you're going to use that stuff (and it certainly has powerful advantages) you might consider the piping to transfer it being extruded metal with fins on the inside. And the fins would have to have fins if you expect to make the psychlopropane (<img src="/images/icons/crazy.gif" />) safe to use.<br /><br />I can't figure out how to pump psychlopropane (<img src="/images/icons/crazy.gif" />) without making it explode. Cavitation, you know...<br /><br />To test this, use plenty of sandbags. Observe the tests with mylar mirrors (don't use glass, 7 years bad luck).

 

[rocketman5000]

One way to reduce cavitation is to have smaller pressure ratios across the pump. To get the required pressures for operaton you could have a series of pumps

 

[propforce]

<blockquote><font class="small">In reply to:</font><hr /><p>Psychlopropane? <br /><br />...Sorry, I just couldn't resist... <p><hr /></p></p></blockquote><br /><br />What's so 'Psycho' about it? <img src="/images/icons/laugh.gif" /><br /><br /><br /> <div class="Discussion_UserSignature"> </div>

 

[nacnud]

The way it reacts?

 

[mlorrey]

I think Mikeemmert was being hyperbolic. Cyclopropane isn't going to explode in a turbopump: there is no oxidizer to allow combustion, and a compression turbine isn't going to allow cavitation anyways, given the pressures.

 

[mikeemmert]

<blockquote><font class="small">In reply to:</font><hr /><p>What's so 'Psycho' about it?<p><hr /></p></p></blockquote><br /><br />Psychlopropane...:<br /><br /><blockquote><font class="small">In reply to:</font><hr /><p>"Cyclopropane is a cycloalkane molecule with the molecular formula C3H6 consisting of three carbon atoms linked to each other to form a ring, with each carbon atom bearing two hydrogen atoms. The bonds between the carbon atoms are a great deal weaker than in a typical carbon-carbon bond. This is the result of the 60° angle between the carbon atoms, which is far less than the normal angle of 109.5°. This ring strain has to be subtracted from the normal C-C bond energy, making the resultant compound more reactive than acyclic alkanes and other cycloalkanes such as cyclohexane and cyclopentane...<br /><br />Because of the strain in the carbon-carbon bonds of cyclopropane, the molecule has an enormous amount of potential energy. In pure form, it will break down to form linear alkanes and alkenes, including "normal", non-cyclic propane. This decomposition is potentially explosive, especially if the cyclopropane is liquified, pressurized, or contained within tanks...<br /><br />At room temperature, sufficent volumes of <font color="yellow"><i><b>liquified cyclopropane will self-detonate</b></i><font color="white">(repeat: <font color="red"><b>SELF DETONATE</b><font color="white">). To guard against this, the liquid is shipped in cylinders filled with tungsten wool, which prevents high-speed collisions between molecules and vastly improves stability.<p><hr /></p></font></font></font></font></p></blockquote><br /><br />NOTE: This might not kill the idea. Now, tungsten wool is kind of heavy and stuffing pipes with it will restrict their flow. That's why the Fan-Dancer idea of extruded pipes with fins that have fins.<br /><br />I'm not trying to be a pessimist or pooh-pooh the idea entirely. But there are problems. If these are solved, then you have a high-

 

[mikeemmert]

Thank you for your positive suggestion to try to solve this problem. mlorrey say the pressures needed are low, but that's in the overall context of whatever design he's using.<br /><br />I have noticed that psychlopropane freezes at a higher temperature than methane boils. I can't find anything about solubility.

 

[mlorrey]

Firstly, I dispute your sources on the "self detonation" claim. Here is an MSDS for cyclopropane which states no such thing, only that it has an autoignition temperature of 498 C, and can form explosive mixtures with air (which still require a source of ignition).<br /><br />http://www.scottecatalog.com/msds.nsf/d118573c489f39cc852569af00702e6f/df5f3042cb2e1bc585256a0a004e30b9?OpenDocument<br /><br />http://www.mathesontrigas.com/pdfs/msds/MAT06080.pdf<br /><br />I see nothing here which states that cyclopropane will detonate independently of any oxidizer... in fact it says "stable at normal temperatures and pressure".<br /><br />As its boiling point is -27 F and its freezing point is -198 F, it is clear that cyclopropane is a mild cryogenic that is no more hazardous than LOX. It doesn't even polymerize. <br /><br />Mikeemmert's comments are over the top.

 

[mikeemmert]

Hello, mlorrey;<br /><br />We have a dispute over sources. I'm sticking by mine. Here is the disclaimer from Scott Specialty Gases:<br /><br />"<font color="yellow"> Information included in this document is given to the best of our knowledge, however, no warranty is made that the information is accurate or complete. We do not accept any responsibility for damages by the use of the document.<font color="white">"<br /><br />Matheson Trigas has a similar disclaimer.<br /><br />Here's some interesting things from the Matheson Trigas MSDS:<br /><br />"<font color="yellow">10. STABILITY AND REACTIVITY<br />REACTIVITY: Stable at normal temperatures and pressure.<br />CONDITIONS TO AVOID: Avoid heat, flames, sparks and other sources of ignition. Minimize contact<br />with material. <b>Containers may rupture or explode if exposed to heat.</b><br />INCOMPATIBILITIES: oxidizing materials<br /><b>HAZARDOUS DECOMPOSITION:</b><br />Thermal decomposition products: oxides of carbon<br />POLYMERIZATION: Will not polymerize...<br /><br /> 7. HANDLING AND STORAGE<br />STORAGE: Store and handle in accordance with all current regulations and standards. Subject to storage<br />regulations: U.S. OSHA 29 CFR 1910.101. Grounding and bonding required. Keep separated from<br />incompatible substances...<br /><br /> FIRE AND EXPLOSION HAZARDS: Severe fire hazard. Severe explosion hazard. The vapor is heavier<br />than air. Vapors or gases may ignite at distant ignition sources and flash back. Dust/air mixtures may ignite<br />or explode. Electrostatic discharges may be generated by flow or agitation resulting in ignition or explosion...<br /><br /> FIRE FIGHTING: Move container from fire area if it can be done without risk. Cool containers with water<br />spray until well after the fire is out. Stay away from the ends of tanks. For fires in cargo or storage area: Cool<br />containers with water from unmanned hose holder or monitor nozzles until well after fire is out. If this is<br />impossible then take the following precautio</font></font></font>

 

[webtaz99]

They are using linear motors on roller coasters too. It's not <b>that</b> expensive. A turbofan-, tubojet- or rocket-powered sled could do the same job, and maybe do it cheaper (cheaper to build, maybe, but not cheaper to opertate). However, the "mass driver" version would offer better acceleration and control, poses no explosive threat, and would be shorter in length. <div class="Discussion_UserSignature"> </div>

 

[mlorrey]

Nowhere do you quote anything that says that the fuel will detonate under normal temperatures and pressures. Its autodetonation temperature is 498 degrees C, significantly above its -27 F boiling point. Explosion of liquid cyclopropane containers would be from boiling pressurization, which is no different than the hazard of the same from boiling LOX or LH2. You are being hyperbolic.

 

[mlorrey]

Roller coasters don't need to go that fast, and are generally built by companies that have a lot of their own capital, so they don't have to pay interest to banks.<br /><br />Capital intensive projects incur significant interest costs over time, particularly if maintenance costs decrease sortie rates at all. A doubling of manhours of maintenance results in 1/4 the projected sortie rate, so while maintenance cost doubles, revenue drops by 75%. <br /><br />With a turbofan system, engines can be swapped out for each other without having to shut down the launch system, just use other sleds. With a magnet system, swapping out magnets shuts down the launch rail for all sleds. Thus, while the jet engine system sortie rate may be reduced slightly, the magnetic launch system sortie rate drops to zero.<br /><br />It is not more economical.

 

[vulture2]

Cyclopropane used to be used rather commonly as an inhalation anesthetic. It has very low toxicity and was reasonably safe to use, even around oxygen sources, until electric spark discharge devices became popular for cauterizing during surgery.

 

[vulture2]

Re cyclopropane and "self detonation" <br /><br />Cyclopropane used to be used rather commonly as an inhalation anesthetic. It has very low toxicity and was reasonably safe to use even around oxygen sources. It dropped out of favor only because electric spark discharge devices became popular for cauterizing blood vessels during surgery. However I am not sure the energy content is all that much higher than normal propane.

 

[mlorrey]

"However I am not sure the energy content is all that much higher than normal propane. "<br /><br />Good question. Dr Bruce Dunn says that cyclopropane/LOX can put 122% of the payload in orbit that RP-1/LOX can put, given equal tankage volume. Plain old propane only puts 91%. LH2/LOX puts up 50%. The only real downside of cyclopropane is that it is expensive, but fuel cost is rarely more than a few percent of the cost of launch.<br /><br />The only fuels Dunn has examined that compare to cyclopropane are UDMH, methyacetylene, and propargyl alcohol.<br /><br />Combusted with H2O2, cyclopropane orbits 140% of the payload that RP-1/H2O2 can launch for equal tankage volume, which is only matched by propargyl alcohol. The next best are 1,3 cyclopentadiene at 123% and 1,2 butadiene at 129%. Propane combusted with H2O2 orbits 88% of the payload.<br /><br />So, yes, cyclopropane is markedly superior to propane. The real choices are to look at the other high performance high density fuels, their prices, as well as the relative cost of handling, storing, and building a launch vehicle around it.<br /><br />Other data: <br />cyclopropane/LOX vacuum Isp: 388.8 sec<br />with H2O2: 351.5 sec<br /><br />propane/LOX vacuum Isp: 382.2 <br />H2O2: 345.6 sec<br /><br />Bulk Densities: <br />cyclopropane/LOX: 969 kg/m^3<br />H2O2: 1273 kg/m^3<br /><br />Propane/LOX: 924 kg/m^3 <br />H2O2: 1231 kg/m^3

 

[webtaz99]

I would urge you to get together with a college physics professor. There is no way a pair of coffee mugs has a worthwhile shape for ramjet. <div class="Discussion_UserSignature"> </div>