Cheapest rocket possible

[mrmorris]

<font color="yellow">"I am not back tracking on myself, but will admit that I have a rather hard time explaining some concepts"</font><br /><br />So you're not backtracking at all from this statement then:<br /><br /><i>"To assert that a rocket can go faster then the escape velocity of its exhaust, which is where the engine¡¦s thrust is released, violates Newton¡¦s third law of motion. "</i><br /><br />Interesting. This is all just a misunderstanding. We all failed to understand what you meant by that. Yep.<br /><br />Well enough on that topic then. Everybody move along. Back to your homes. Nothing to see here. Just a slight misunderstanding. MBA_UIU did <b>not</b> make a stupid statement and then spend several days defending it. He just had a hard time explaining his perfectly correct statement to people as dense as your average SDCer.

 

[tap_sa]

<font color="yellow">"Without doing any math I believe comes out to something like 40 times its mass to reach 3 times its exhaust velocity and so on. "</font><br /><br />Solve the rocket equation for massratio and you get m_initial/m_empty = e^{(dV/Vexhaust)}. So the result in your case is e³ = 20.086, which is quite doable.

 

[annodomini2]

Shouldn't the other questions be:<br /><br />1. What are you actually launching?<br />2. How much does it weigh (approximately!)?<br />3. Is life support required? (I.e. humans etc (affects acceleration capability not to mention extra weight etc.)<br />4. How many launches are intended for the vehicle?<br />5. in support of 4 does it need to be reusable?<br />6. does it have re-entry into the atmosphere requirements? <div class="Discussion_UserSignature"> </div>

 

[tomnackid]

I think the cheapest possible chemical rocket would be something like Sea Dragon. Big as an ocean liner, made of steel plate welded together like a submarine, one huge low pressure engine. No thermal protection system, just let the whole thing plop into the ocean and salvage what you can. The whole thing would be towed out to sea for launch. A nuclear powered ship or a huge bank of solar cells would electrolysise then liquify seawater into LOX and H2.<br /><br />The physics of chemical rockets mean that the way to reduce per pound launch costs is to build really big rockets. Build it big enough and SSTO becomes feasible even with low performance, low tech materials and engines.<br /><br />Unfortunately its a catch 22. No one wants to build big rockets because they say there is not a big enough market. No one wants to do big space operations because launch costs are too high. <br /><br />Here is a link: <br /><br />http://fpmail.friends-partners.org/~mwade/lvs/searagon.htm

 

[ortemus74]

Shouldn't the other questions be: <br /><br />1. What are you actually launching? <br />2. How much does it weigh (approximately!)? <br />3. Is life support required? (I.e. humans etc (affects acceleration capability not to mention extra weight etc.) <br />4. How many launches are intended for the vehicle? <br />5. in support of 4 does it need to be reusable? <br />6. does it have re-entry into the atmosphere requirements? <br /><br />1. a boeing 717 - LOX/kerosene spaceplane<br />2. 20,000lbs. with a 4,000lbs. payload. Cost $30,000 fuel<br />3. YES<br />4. Over 100<br />5. It should be...<br />6. Yes - Tungsten carbide underbelly

 

[ortemus74]

FORGET THE SHUTTLE...<br /><br />Check out this kerosene/LOX rocket engine.<br /><br />http://www.xcor.com/rotary2.jpg<br /><br />Add it to a scramjet and THAT'LL BE THE CHEAPEST ROCKET POSSIBLE!!!

 

[vogon13]

Orion!<br /><br />(you all never get tired of me pushing Orion do you?)<br /><br /><img src="/images/icons/wink.gif" /> <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>

 

[tap_sa]

<font color="yellow">"Add it to a scramjet and THAT'LL BE THE CHEAPEST ROCKET POSSIBLE!!!"</font><br /><br />Forget the scramjet and it'll be even cheaper <img src="/images/icons/smile.gif" /><br /><br />Btw that link of your is XCOR 5000lb thrust, are you building an N-1 clone or a very small rocket? For good and cheap kerosene/RP-1 engines go shopping to Russia, they have best know-how in that area.

 

[tap_sa]

<font color="yellow">"you all never get tired of me pushing Orion do you?)"</font><br /><br />We'd get worried if you stopped doing that <img src="/images/icons/laugh.gif" />

 

[tempel1]

Dear friends <br />Go here please:<br />http://saturn.jpl.nasa.gov/news/press-release-details.cfm?newsID=117 <br />” The spacecraft's VELOCITY RELATIVE TO THE SUN is at about 26 kilometers per second (about 59,250 miles per hour). Cassini is now more than 9 million kilometers (almost 6 million miles) from Earth”. <br /><br />Since our probe is launched from the earth, it has already a velocity of 65,000 miles per hour (earth's velocity). <br /><br />Why have NASA engineers steered Cassini on this trajectory? <br /> http://www.space.com/php/multimedia/imagedisplay/img_display.php?pic=h_cassini_trajectory_02.gif&cap=The <br /><br />Instead of increasing Cassini's velocity they have slowed down it at 59,250 miles per hour. <br /><br />NASA engineers think the earth is the center of our solar system and don't consider earth's velocity. <br /><br />In this wrong way Cassini has travelled for 2 200 000 000 miles to meet Saturn. <br /><br />Cassini would have been able to fly along a straight line travelling for less than 1 000 000 000 miles. <br /><br />65,000 miles per hour (earth velocity) + 36,000 miles per hour (spacecraft's velocity) = 101,000 miles per hour <br /><br />1 000 000 000 miles : 365 days : 24 hours : 101,000 miles per hour = 1.13 years <br /><br />If NASA engineers considered the earth's velocity, Cassini could meet Saturn in one year! <br />

 

[darkenfast]

Well, I have trouble adding up my age, so there won't be any 'rithmetic in my post, just an observation or two. There was a lot of design work and some prototype testing a while back on various SSTO vehicles. I'm pretty sure that the velocity change that would have been attained by the vehicle on reaching orbit would be quite a bit more than the exhaust velocity of the LOX/LH engines, and without multiple stages, or even dropping off some engines, like the old Atlas did. Is that not correct? I think this falls into the category of a "sailing faster than the wind" claim (same type of claim, but a different example in terms of the physics). When people hear the claim that some catamarans and iceboats can attain velocities higher than the wind, some of them will not accept that, believing that it is physically impossible. It isn't, and no laws of physics are broken, as is also the case with the SSTO.

 

[rogers_buck]

I'm going to weigh in here with a rollup of several ideas that I think are tought to beat for the cheap.<br /><br />The first is to use a payload over engines configuration. To visualize, picture the Space Shuttle underneath the ET. Of course the to orbit module wouldn't have wings and the engines would be in their own returnable module. The advantages are that the structural strength of the fuel tank need only support its own weight and that of the fuel.<br /><br />The second idea is coaxial staging. In this scheme, the first stage totally surrounds the second stage like a hotdog bun surrounds a hot dog. By doing this, the first stage doesnt need to support the weight of the second stage and the second stage can do away with thermal insulation for cryogenics entrely. The second stage won't even need to be painted for cosmetics. The overall stack is a short squat form with engines arrayed around the outter perimeter. To maximize cheapness an N-1 style steering by thrust scheme could be used. When an outter stage burns out, it simply slips off the stack and falls away before the inner stage lights. You could have many layers of rings like a christmas tree with this concept.<br /><br />The third idea is to use coiled construction for the outter coaxial first stage. Picture two long skinny tankes (oxidizer/fuel) coiled up around the second stage like two interleaved garden hoses. This construction technique would be simple and strong.<br /><br />An extremely powerfull rocket constructed using these techniques would be as light weight and simple to build. The draw backs relate to the second stage payload being surrounded on 3 sides by explosive cryogenics and on the fourth side rocket engines. This all makes manned versions kind tough..

 

[barrykirk]

Actually most rockets do end up travelling faster than their exhaust.<br /><br />SSME I believe has an exhaust velocity of less than <br />10, 000 MPH but orbital velocity is 17,000 MPH