Minimum Cost Design Launch Vehicles

[barrykirk]

Again, Hydrogen and RP-1 each have their own advantages.<br /><br />Hydrogen Advantages.<br /><br />1) Easier to use as Engine Coolant.<br />2) Higher ISP.<br /><br />RP-1 Advantages.<br /><br />1) Cheaper.<br />2) Substantially Denser.<br />3) No insulation required, for fuel, not oxidizer. (NASA is having all sorts of problems with Hydrogen insulation including loss of Columbia. )<br />4) Much higher viscosity, meaning that a crack that could cause a serious leak with hydrogen won't matter for RP-1.<br />5) Tanks are smaller and lighter and potentially present much less air drag. ( See higher density )<br />6) Turbo Pumps required are much smaller ( See higher density )<br />7) Thrust to Weight ratio is much higher ( See higher density )<br />8) More fuel and oxidizer can be carried for the same mass of rocket engine. ( See Higher Thrust to Weight ratio because of higher density. )<br />9) Smaller but heavier rocket can achieve same mass to orbit. This makes things cheaper because smaller rockets have less logistical problems.

 

[scottb50]

Kerosene would work very well and has a lot of things about it that make it attractive for a first stage. If the same basic engine and propellant tanks are used throughout a system, the system is cheaper and safer.<br /><br />Two components, Segments and Tubes, multiple Segments and longer, or shorter Tubes allow an infinite length. Then you add whatever you want to the Module, inside and out. <div class="Discussion_UserSignature"> </div>

 

[annodomini2]

Right I have a concept for a different type of Hybrid motor design, I was wondering if anyone had links to sites explaining the engineering behind the normal hybrid design (to understand how the existing works and to see if i can prove my design) and ideally links to how the ratings of ISP, thrust etc affect the performance of the vehicle?? <div class="Discussion_UserSignature"> </div>

 

[tomnackid]

"You are falling into the same trap that NASA is in, placing an unnecessary priority on environmental purity. "<br />------------------------------------------------------------------------------------------<br />Yeah its all about the environmental conspiracy. That's why NASA went with those really clean SRBs I suppose! <br /><br />The SMEs are for all practical purposes a second stage engine. History (and physics) has shown that high ISP lox/h2 engines are best for upper stages (the failure of the USSR to develop a high ISP upper stage doomed their lunar program). The SRBs are the "first" stage--dense propellant, high thrust. During shuttle development it was a toss up between lox/kerosene and solid boosters. In the end solids were chosen because it was cheaper to design a reusable solid rocket than a reusable liquid. Solids by their nature have to be robust anyway so they are easier to recover with minimal damage. The decision to ignite all of the engines on the pad was a concession to reusability. Its far easier to test the SMEs on the pad and ignite them on the pad (and abort if something goes wrong!) then to bite your knuckles waiting for an air start. Note that all of the original shuttle designs featured a lox/kerosene booster (usually a flyback design, but some early designs used a Saturn V first stage) and a lox/h2 orbiter that would air start after the separating from the booster. What we ended up with was a the compromise of parallel staging. Its not perfect from an efficiency or safety standpoint (obviously!) but it met the goals of limited reusability, high payload to/from LEO and most of all low developmental costs. There was no conspiracy of environmentalists pushing this option, in fact a lox/kerosene -- lox/h2 combination would have been far more environmentally benign then the present SRB -- lox/h2 combination!<br /><br />When engineers talk about the benefits of non/low toxic propellants they are simply being pragmatic. The more toxic a chemical the

 

[ve7rkt]

Existing hybrid motors used in high power model rocketry involve a jet spraying liquid nitrous oxide into the center of a hollow cylinder of some solid fuel WITHOUT oxidizer (paper, rubber, PVC, acrylic... I wonder if anybody's tried wood?). The bottom of the cylinder is capped off with a nozzle. The heat of the burning fuel breaks the nitrous oxide down into N2, which gets blown out the tail, and O2, which burns the fuel. That's pretty much it. Most of the spiffy engineering work beyond that seems to have been with regards to how to get the rutting thing to light properly. When I heard that Scaled Composites was going to airstart a hybrid motor... I think I've only seen one hybrid light the first try, with most of the ones I've seen requiring three or four tries. SpaceDev apparently has that sorted out though... <img src="/images/icons/smile.gif" /><br /><br />Plans for building a small hybrid motor powered by paper and the nitrous canisters for whipped cream dispensers can be found by googling for "microhybrid". The performance is much worse than commercially available solid black powder model rocket motors in the same class, because the hybrid motor is so much heavier.

 

[tomnackid]

"...I wonder if anybody's tried wood?"<br />-----------------------------------------------------------------------------------------<br /><br />"The first US tests were conducted from 1938 to 1941 by the Californian Rocket Society using coal and GOX. In 1947, the Pacific Rocket Society tested wood and LOX motors."<br /><br />From this website: http://www.hawkfeather.com/rockets/hybrids1.html<br /><br />Looks like pretty much anything that can burn has been tried in a hybrid engine, including coal and asphalt. A coal fired spaceship--that conjures up images of gangs sweaty men madly shoveling lumps of anthracite into a furnace while the rocket slowly lifts off. <img src="/images/icons/wink.gif" />

 

[tomnackid]

"Big problem is that the more mass launched at one time requires far, far more launch vehicle costs. The Saturn 5 and the Energiya could launch upwards of tens of tons of payload, but they cost in the $100 M range. "<br />-------------------------------------------------------------------------------------------<br /><br />It seems like there is some confusion here between cheap access to space and cheap launch vehicles. If I can make an analogy: Gigantic container ships make it possible to ship novelty rubber chickens from factories in China half way around the world and sell it for a profit at your local Walmart. I can't even imagine the price of these ships and the attendant maintenance costs associated with them, but its well out of the reach of most private citizens--the provence of corporations and a few tychoons. On the other hand bass boats are fairly inexpensive, within the reach of anyone with a regular income (sometimes not even that!). But if you decide to boycott your local Walmart and sail to China to buy your novelty rubber chicken directly from the factory you will find that it ends up costing you CONSIDERABLY more.

 

[webtaz99]

I remember reading a NASA Tech Notes article about a concept for a solid-fuel rocket that would pulverise the fuel in flight and transport the resulting powder by fluidizing it with an inert gas. The result was to be a solid-fuel rocket with stop and start capability and throttling between 50% and 100% power. <div class="Discussion_UserSignature"> </div>

 

[qso1]

There are all sorts of concepts within NASA, many discarded due to being impractical. How was the propellant to be pulverized? This strikes me as complicated...and impractical. <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>

 

[barrykirk]

By a chain gang of men with pickaxe's of course...

 

[scottb50]

Especially on a stage you want to work for just the initial part of the launch. A hybrid using rubber and LOX would be my choice. A bigger turbopump is all it would need. Failing that I would be more than happy staying with the Shuttle SRB design, with a few changes. Instead of shipping the metal segments to Utah, then back to the launch site, you ship segments with a rigid outer shell to the launch site and insert a number of them into fixed, single piece Housings on the launcher. After landing the aft Segment of the SRB Housing is removed, empty casings are pulled out and new ones are pushed in.<br /><br />The current SRB's are far from friendly, but they are a known asset and everybody uses them. <div class="Discussion_UserSignature"> </div>

 

[webtaz99]

The article showed a schematic diagram, with a "pulverizer" which the article said was down-sized from an existing industrial machine. They did not include details, but it seemed like a rotary device with cutting blades which slowly chewed up a cylinder of solid fuel from end to end. <div class="Discussion_UserSignature"> </div>

 

[qso1]

As I suspected, sounds complicated. Blade failure possibilities. Uneven burning of chewed up propellant chunks. I see no reason not to stick with the current design, especially since its only going to be used for a few more flights. Unless the shuttle derived vehicle options are ever put to use. <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>

 

[webtaz99]

1) The "pulverizer" was said to deliver solid fuel as "dust", not "chunks". The dust would be fine enough to be fluidized by a gas, so we're talking talcum powder here.<br /><br />2) Everything has failure modes. At least with solid fuel, if you've got it, it's gonna burn. It's still safer than liquid fuels (which was the point of the concept).<br /><br />3) I only included this as a type of engine. I did not say that it should replace anything. <div class="Discussion_UserSignature"> </div>

 

[barrykirk]

I'm not sure I buy into all this, but wouldn't it be easier to load the tank up with pre-pulverized solid. Leave the pulverizer on the ground?

 

[ve7rkt]

That's... a shockingly good point. If what you need is solid fuel sand, fill the tank with solid fuel sand.

 

[qso1]

It could be adapted on another solid rocket design and understand, I'm not saying it wouldn't work, just sounds a little more complicated than solid boosters are right now. As for solid/liquid propellant safety. Liquids were considered safer by NASA all through the 1960s, 70s. It wasn't until the shuttle began flying that NASA decided it could "Manrate" as it was once known, solid propellant rockets. The reason is that liquid rockets can be shut off once fired where solid rockets will burn till the propellant is depleted. <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>

 

[tap_sa]

<font color="yellow">"wouldn't it be easier to load the tank up with pre-pulverized solid. Leave the pulverizer on the ground?"</font><br /><br />Given the acceleration and shaking any powder in tanks would compact and stick together into chunks, being powder no more. Besides powder does not flow from the tank like liquid, you need something to dig it and shove toward combustion chamber.

 

[webtaz99]

Exactly. <br /><br />Also, this concept was aimed at smaller rockets, like longer range air-to-air and surface-to-air missiles, ICBMs, and sounding rockets. For such uses, liquid fuels have posed dangers for decades, and for that reason military rockets (aside from orbital boosters and some ICBMs) are solid fueled. But solid fuel rockets cannot stop and start, or throttle. <div class="Discussion_UserSignature"> </div>

 

[tomnackid]

There have been designs for "slurry" fuels--powdered solid fuel mixed with some liqiud (kerosene, alcohol, lh2) then combined with an oxidizer in the combustion chamber like a normal liquid fuel rocket. Powdered aluminum, magnesium and boron have been investigated. They all present practical problems that limit their usefulness although aluminum slurries have been studied for use in lunar launch vehicles since aluminum is so prevalent in the moon's crust. The Air Forces' "blackstar" (assuming it really exists) is rumored to use boron spiked fuel for an extra performance boost. <br /><br />I believe at least one aerospace company tried to develop a molten aluminum / lox engine for use on the moon! Talk about pushing the envelope.

 

[tap_sa]

Slurries are viscous and abrasive, difficult to pump and make sure the particles don't clog injector etc. Pressure feeding might work but that's unfashionable at the moment.<br /><br />One company has demonstrated magnesium/CO2 engine! Yes, it burns carbon dioxide, magnesium is such a bully that it rips out the oxygen from CO2 molecule. Aimed at Martian application.<br /><br />Heard of talk about LOX/Al slurry 'monopropellant'. At first it sounds crazy but then you remember that when aluminium oxidizes it forms a protective layer. So particles in the LOX are first protected well, until the stuff is fed to combustion chamber where heat melts the particles breaking the layer and allowing combustion. Would be great for lunar application if they get it to work.<br /><br />Seen also molten sulphur/LOX proposed for Moon. Yucky exhaust but who cares since there is no atmosphere to ruin.

 

[j05h]

>I believe at least one aerospace company tried to develop a molten aluminum / lox engine for use on the moon! Talk about pushing the envelope.<br /><br />I guess you could place hardware components on the launch pad to get aluminum plating. It might look cool, like those "crystal growing" kits, in metal.<br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[qso1]

The military went to solids in ICBMs for example, primarily because of shorter reaction times for solids rather than liquid/solid safety. <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>

 

[qso1]

One day some of the more exotic solutions may emerge. But that won't happen until it can be shown that they have a large enough advantage over present day techniques to justify the expense of developing them. <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>

 

[webtaz99]

The military went to solids on sub-launched missiles due to safety reasons (ask the Russian Navy for details). <div class="Discussion_UserSignature"> </div>