EELV+ a balloon

[chriscdc]

I remember seeing an X-prize propsal that used a balloon to get above the thickest part of the atmosphere. Would there be much performance increase of an EELV if it was taken around 20miles up before launch?<br />Could it therefore be used to lift bayloads that only the shuttle could have lifted before?

 

[spacefire]

what about if the balloon were filled with hydrogen and the rocket would use that hydrogen as fuel? <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[gunsandrockets]

I remember once upon a time a proposal for a giant semi-derigible winged airship based on the C-5A Galaxy jet transport. As I recall it would have had a cargo capacity of one million pounds. Something like that would work great for airlaunching a rocket from an altitude of around 30,000 feet.

 

[mikejz]

Actually, before the X-Prize there was a prize for the first amature group to launch a rocket into space. Many of the groups that tried did the exact same thing, however most ran into technical problems.<br /><br />I believe that JP aerospae was on of the groups that was involved in that effort with a balloon based launch platform. For large launcher it will in all odds not be all the worthwhile. For suborbital it really is a gem (afterall your 24 miles up when you launch!) Maybe it would work for a small orbital launcher....

 

[vogon13]

Gaseous hydrogen in a balloon is quite dangerous, and AFAIK, all hydrogen burning rocket engines require liquid H at the inlet to the turbo pump mechanism.<br /><br /> <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>

 

[mikejz]

I wound not say that a hydrogen balloon is really that much of a danger--just careful precausions and you should be okay.

 

[vogon13]

A large group of thoroughly trained anal retentive Germans couldn't keep the Hindenberg from blowing up, probably best to look at a different technology.<br /><br />IIRC, gaseous hydrogen is flammable (and explosive) in a wider range of concentrations in air than any other substance. Helium has (IIRC) 92% of the lifting power of hydrogen, so just make the balloon 8% bigger.<br /><br />(yeah, I know the math ain't right, sue me, it's close enough)<br /><br /> <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>

 

[spacefire]

Sorry, I should have made myself more clear:the gaseous hydrogen from the ballon would be injected directly in the nozzle. <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[vogon13]

SSME engine runs at a chamber pressure of 3000+ PSI, balloons right at 0 PSI. Suspect catastrophe is brewing!<br /><br /> <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>

 

[mikejz]

The key is keeping oxygen out of the balloon itself. Filling and realse could also be done by remote control to reduce further any risks. Also while the balloon is airborn, what (outside of maybe lightning) stands to serve as a source of ignition? Seeing that the balloon is going to around 100,000 feet up, even if the hydrogen is relased, there is not enough oxygen to support a big explosion.

 

[nexium]

I agree: Negligible fire hazard for a hydrogen ballon at 50,000 feet or more. I also agree, getting one psi hydrogen up to 3000 + psi will require heavy and bulky equipment. The rocket flame for the 2nd stage needs io be hundreds of feet from the balloon. Neil

 

[spacefire]

I said nozzle, not combustion chamber! <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[nyarlathotep]

<blockquote><font class="small">In reply to:</font><hr /><p>I remember seeing an X-prize propsal that used a balloon to get above the thickest part of the atmosphere. Would there be much performance increase of an EELV if it was taken around 20miles up before launch? <p><hr /></p></p></blockquote><br /><br />Yes, you'll probably see a trivial increase in isp and dV, but it's going to cost. To lift a 300-700 ton EELV to 20 miles you're going to need a blimp the size of Canada.

 

[vogon13]

How does that increase thrust? What is the point in doing it? Exhaust stream from engine throat will have to accelerate the material you are adding and it will decrease the reaction force of the rocket. Lowering the Isp of the system is ungood.<br /><br /> <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>

 

[spacefire]

Mr Rocket Scientist, say we have an overexpanded nozzle because your rocket is designed to achieve optimum efficiency (pe=pa) at a higher altitude. Wouldn't you say that increasing the the pe (by dumping gas at the exit of the nozzle) would help your rocket by not allowing those nasty shocks to enter the nozzle? Those shocks can separate your boundary layer inside the nozzle and deteriorate performance further. <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[vogon13]

Mass flow through nozzle will have to accelerate the material you inject into the nozzle. This lowers the Isp of the system. You do not want to do this.<br /><br />Low Isp = bad <img src="/images/icons/frown.gif" /><br /><br />High Isp = good <img src="/images/icons/smile.gif" /><br /><br /><br /> <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>

 

[spacefire]

the burning hydrogen will expand and accelerate it on its own, <b>hopefully</b> matching the speed of the exhaust gases. <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[tap_sa]

<font color="yellow">"I said nozzle, not combustion chamber!"</font><br /><br />No combustion chamber, no throat. No throat no transition to supersonic flow. No supersonic flow and the nozzle is useless. Your Isp would rival that of flatulence.<br /><br />Abysmal injection pressure means abysmal mass flow. That combined with abysmal Isp means abysmal² thrust.<br /><br />What I'm trying to say is that balloon fed rocket engine is not good <img src="/images/icons/wink.gif" />

 

[spacefire]

the rocket will not depend entirely on the balloon for hydrogen supply.<br />for a short while, that gas could improve the effciency of the engine. <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[tap_sa]

How?

 

[spacefire]

obvioulsy you didn't read all my posts. <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[tap_sa]

I did but didn't get it. Could you please try to elaborate more?

 

[le3119]

I'm about ready to build myself a huge 100 story multistage inline launch system. It would deliver over 10,000 metric tons to orbit, eliviating the need for any more rocket launches ever again!

 

[spacefire]

here's what I posted:<br />"Mr Rocket Scientist, say we have an overexpanded nozzle because your rocket is designed to achieve optimum efficiency (pe=pa) at a higher altitude. Wouldn't you say that increasing the the pe (by dumping gas at the exit of the nozzle) would help your rocket by not allowing those nasty shocks to enter the nozzle? Those shocks can separate your boundary layer inside the nozzle and deteriorate performance further."<br />most rockets get lower ISPs at low altitudes because they are designed for higher altitudes.<br />This EELV will be carried bya balloon to say 100,000ft, but you can design it for space (vacuum). <br />Use the above mentioned system and you'll get a bit better ISP after ignition, when you are still at low altitudes.<br />If only I could think of a way to transfer the H2 from the balloon to the EELV....<br /><br /> <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[tap_sa]

Hoisting the rocket up to 100k ft will naturally help the engines to take advantage of lower initial ambient airpressure. What you plan to do with the gas in the balloon is still unclear. There's ordinary rocket engine but in addition you inject gas from balloon into the nozzle? At what point? Using what as a pump? Why?