Please discuss an approach for cheaper SSTO - going big

[spacefire]

<p>I'm talking about building a SSTO the size of the Empire State building. Big engines, thick walls, stronger than a battleship. Outside of Earth's atmosphere, wouldn't it be more efficient because everything would scale up, including the velocities. Like, say you have something like SS1, but a hundred times bigger. Drag notwithstanding, shoouldn't it be able to attain speeds a hundred times larger than the regular SS1?</p><p>&nbsp;</p><p>Just something I'm throwing around, please feel free to refute my argument!&nbsp;</p> <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[Boris_Badenov]

<font size="2">A Gas Core Nuclear Rocket Engine or a Polywell Fusion Rocket Engine will be the best bet for an SSTO. IMO the best start would be a smaller demonstration ship that would be used to test out either technology, or better yet both. The&nbsp;only way we're going to&nbsp;colonize the Solar System is to embrace Nuclear Power for propulsion & the generation of electricity.</font>&nbsp; <div class="Discussion_UserSignature"> <font color="#993300"><span class="body"><font size="2" color="#3366ff"><div align="center">. </div><div align="center">Never roll in the mud with a pig. You'll both get dirty & the pig likes it.</div></font></span></font> </div>

 

[kelvinzero]

<p>A hundred times bigger does not mean a hundred times faster.&nbsp;Simplistically, two rockets using the same type and fraction of fuel would end up going the same speed.</p><p>Read this:</p><p>http://en.wikipedia.org/wiki/Specific_impulse</p><p>(the details are not too important. The important bit is that the exhaust velocity is determined by the type of fuel, not how much of that fuel you burn)</p><p>&nbsp;</p><p>&nbsp;</p><p>&nbsp;</p>

 

[spacefire]

<p>but we're not talking only about engine efficiency. though the exhaust velocity is the same, the thrust will be higher since it is scaled up by the weight of the propellant. </p><p>However, is it possible that the vehicle can have a higher t/w ratio if the entire thing is scaled up? possibly that it becomes more structurally efficient, weighing less forthe same strength, or highercombustion chamber temperatures are achievable, etc....</p> <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[kelvinzero]

<p>&nbsp;At some point making a rocket bigger is going to make things harder&nbsp;rather than more efficient.&nbsp;</p><p>Regardless of the size, it has to expend about the same proportion of its mass per second. Because volume is proportional to the width cubed, and surface area is proportional to the width squared, this means the super hot propellent passing through a given&nbsp;surface cross section per second&nbsp;has to increase and at some point these would exceed any plausible material strength.</p><p>(disclaimer: Im not a rocket scientist but Im still pretty sure this logic holds)</p>

 

[webtaz99]

Physics is a harsh mistress. <img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-wink.gif" border="0" alt="Wink" title="Wink" /> <div class="Discussion_UserSignature"> </div>

 

[nimbus]

Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>A Gas Core Nuclear Rocket Engine or a Polywell Fusion Rocket Engine will be the best bet for an SSTO. IMO the best start would be a smaller demonstration ship that would be used to test out either technology, or better yet both. The&nbsp;only way we're going to&nbsp;colonize the Solar System is to embrace Nuclear Power for propulsion & the generation of electricity.&nbsp; <br /> Posted by boris1961</DIV>What would the propulsion type be?&nbsp; Something like VASIMR?<br /> <div class="Discussion_UserSignature"> </div>

 

[Boris_Badenov]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>What would the propulsion type be?&nbsp; Something like VASIMR? <br />Posted by nimbus</DIV></p><p><font size="2">For the Polywell System, yes. I think VASIMR would be perfect. The GCNR is the engine for the other.<br /><br /></font></p> <div class="Discussion_UserSignature"> <font color="#993300"><span class="body"><font size="2" color="#3366ff"><div align="center">. </div><div align="center">Never roll in the mud with a pig. You'll both get dirty & the pig likes it.</div></font></span></font> </div>