Minimum Cost Design Launch Vehicles

[mlorrey]

There is a pressure feed system thats been demonstrated which uses two small tanks that are alternately pressurized, draining fuel from a larger unpressurized tank. I've seen video of it pumping slurry gel quite effectively. I'd say the only real problem left with this sort of fuel is that you wind up with a thick gel residue in the tank that increases the amount of fuel mass left in the tank.

 

[qso1]

In the case of the FBMs, safety definetely played a major role in the decision to go solids. <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">"There is a pressure feed system thats been demonstrated which uses two small tanks that are alternately pressurized, draining fuel from a larger unpressurized tank."</font><br /><br />Flometrics pump<br /><br />Principle of the first mine draining steam engines turned into third millenium application, pretty neat actually. I hope they get to do flight tests soon. There's also video of actual rocket engine firing (original Atlas vernier) using that pump. And in conferences they pump Margaritas with it <img src="/images/icons/smile.gif" />

 

[mlorrey]

I think your assertion depends significantly on the shape and size of the grains, while shaking will not occur before fuel feeding to the engine starts, such shaking should only help with fuel flow, not hinder it.<br /><br />Have you ever seen what happens to sand dunes in an earthquake?

 

[webtaz99]

The NASA concept took into consideration that rockets do not always travel vertically. Especially "air-to-air missiles". <div class="Discussion_UserSignature"> </div>

 

[barrykirk]

Put the fuel tank on shock absorbers.

 

[mlorrey]

"The NASA concept took into consideration that rockets do not always travel vertically. Especially "air-to-air missiles". "<br /><br />I don't see how this applies to launchers. When a missile is under acceleration, "down" is a vector adding the gravitational acceleration vector to the thrust acceleration vector. At worst, the compound vector is at a 45 degree angle to the axis of the launcher if the launcher is parallel to the ground under 1 g thrust. The higher the rocket and the more empty the tank, the higher the thrust acceleration, which causes the compound vector to go closer to the axis. Many solid launchers reach 9 g's or more near burnout. Even if flying horizontally, a 9 g thrust acceleration would result in a compound vector of ~6.4 degrees from the vehicle axis. Thus, so long as your fuel feed line from the tank exited from the center of the bottom hemisphere, and had an inner diameter 1/9th of the diameter of the tank at that exit point, then a particlized solid fuel should drain as easily as an hourglass (some residual remains could be eliminated by shaping the bottom of the tank like an hourglass.)

 

[webtaz99]

1) This was NASA's idea, not mine. Argue with them.<br /><br />2) The solid fuel takes up less volume and is safer when in its "solid" form. <br /><br />3) To maintain proper fluidization, the particle/gas ratio must be held below a certain value, which would be exceeded by even the compaction resulting from just 1g (at rest). <br /><br /> <div class="Discussion_UserSignature"> </div>

 

[tap_sa]

<font color="yellow">"I think your assertion depends significantly on the shape and size of the grains"</font><br /><br />True, and also heavily on the composition of the grain. Fine sand flows easily in the hour glass because surfaces of particles are very hard, non-stick. Solid fuel involves rubber binder among other things.<br /><br />But suppose you get the solid propellant powder flowing from the tank, how do you shove that into the combustion chamber in an orderly fashion? Oh yeah, mixing inert carrier. Now why do we keep them separated from the beginning instead of starting with slurry? <br /><br />If we have complex machinery, tank of inert carrier, mix it and dust, blow it into the reaction chamber through some sort of injector, then what is the advantage of this contraption over ordinary liquid engine? <img src="/images/icons/smile.gif" />

 

[scottb50]

Very little. That's why the best choice is the SS1 engine with LOX. A LOX/LH2 igniter motor would be a good idea too.<br /><br />The main advantage over liquids is you can build a solid rocket the same way, just bigger or smaller and they provide a lot of thrust for a short time, as long as you can reload them quickly. With the hybrid design you could stop an engine if needed. Might or might not work, but at least it's an option.<br /><br />I like the idea of multiple solid segments cast in an ablative coated outer housing and shipped to the launch site. Pull out used Segments and insert new ones into a single piece, fixed tube, attach the nozzle and your ready for flight. <div class="Discussion_UserSignature"> </div>

 

[tap_sa]

I don't like solids anywhere except LAS and small separation motors, where reliable ingition and instant thrust is nice.<br /><br />Hybrids have complexity of liquid engines, Isp of solids, failure modes of both. Crew of SS1/SS2 is as good as dead if chunk of solid fuel comes loose inside reaction chamber and plugs the throat.

 

[webtaz99]

The inert carrier is a gas, chosen for low density. A very small tnak at very high pressure would work. <br /><br />Not all solid propellants would work with a liquid carrier, and any "slurry" would be heavier than the solid propellant and gas carrier. <div class="Discussion_UserSignature"> </div>

 

[publiusr]

Good points.

 

[publiusr]

Bump.

 

[mdodson]

"It is a total waste of resources to deorbit the big upper stage tanks from orbit. They should be produced intended to be recycled, as livable habitat, rather than returned and reused on earth."<br /><br />No energy is used to deorbit the ET's - energy is saved by not hoisting them TO orbit. They aren't returned and recycled, they drop into the Indian Ocean.<br /><br />The SRB's and SSME's get the orbiter out of the atmosphere, but in an orbit that would re-enter the air roughly 90 minutes later. The circularization burn 45 minutes after launch with the OMS engines raises that perigee out of the atmosphere.<br /><br />Do you recall the glee in 1984 or so, when NASA and Martin decided that they could save 400 pounds by not painting the tanks? That makes me skeptical about mods. <br />

 

[qso1]

MDodson:<br />Do you recall the glee in 1984 or so, when NASA and Martin decided that they could save 400 pounds by not painting the tanks? That makes me skeptical about mods.<br /><br />Me:<br />The first of the unpainted ETs was actually flown on STS-3 in March 1982. Leaving the paint off didn't seem to cause a problem. I would be more concerned about the structural mods which have reduced ET weight over the years but even this has so far not been a problem. <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>

 

[josh_simonson]

That has to make one wonder if the paint was helping maintain the structural integrity of the foam...

 

[docm]

Especially if it was a latex paint, which can stretch & flex. <div class="Discussion_UserSignature"> </div>

 

[bpfeifer]

“That has to make one wonder if the paint was helping maintain the structural integrity of the foam...”<br /><br />And<br /><br />“Especially if it was a latex paint, which can stretch & flex.”<br /><br />I remember watching the return to flight news conferences on NASATV and this was one of the topics that appeared repeatedly. The short answer is that the engineers determined that the paint used didn’t improve the integrity of the foam. One of the return to flight modifications they were researching were paints or similar materials that could be applied to the existing design to help hold the foam on. <br /><br />I think they ended up pursuing the best tactic, which is a two-pronged approach. First they are removing any foam they can possibly get rid of, and secondly researching why cracks form in the first place. Some cracks are caused by the foam application method while other cracks are caused by thermal stress. It’s not perfect, but it is much better.<br /> <div class="Discussion_UserSignature"> Brian J. Pfeifer http://sabletower.wordpress.com<br /> The Dogsoldier Codex http://www.lulu.com/sabletower<br /> </div>

 

[docm]

It'll be perfect when the tanks and their insulation are used at the bottom of an Ares V stack where they can't screw anything else up <img src="/images/icons/tongue.gif" /> <div class="Discussion_UserSignature"> </div>

 

[mdodson]

"That has to make one wonder if the paint was helping maintain the structural integrity of the foam..."<br /><br />I thought that the problem was inside of the foam next to the tank.<br /><br />Part of the process used to be to smooth the outside of the freshly-applied coating. So there really is an "ET foam hone". (grin)

 

[qso1]

Guess you'd have to look at footage of the STS-1 and 2 missions to see if any foam came off. If paint did help keep foam on, that would be one of the few things I would think NASA could do without extensive redesign for the last shuttle missions to ensure they fly safely. <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>

 

[nspace]

An interesting debate to be sure but so far I have read many ill informed views over why Big Dumb booster projects have failed or why they won’t succeed etc. First off the only recent project of note based on this concept has been Beal Aerospace's BA-1 launcher. I want to state whole heartily that this was a 100% feasible launch system that would have yielded a far lower operational cost than any other LV in its weight class. It did not fail based on its technological merits, or systems failures or even the company business model. It was cut down by the unfair advantage won by large aero firms using their political might in congress to close out private enterprise. First by locking NASA and DARPA into anti-competitive LV procurement plans, and secondly by stirring up regulatory issues against Beal's proposed launch site.<br /><br />This is not the first time above has happened, one only need to look into the failure of OTRAG to see the same agendas played out.<br /><br />Current launch vehicle manufacturers rely on huge manufacturing infrastructure that employs 1000s of Americans right across the nation, and thus senators lobby to keep jobs in their states. A large low cost LV's developed in house by a small firm is a major threat to the future sustainability of these industries. Yet at the same time the current model inflates the cost of the technology they produce beyond reason, that is why current LV's cant realise drastic cost reductions. It is not because they need to strap an SSME to a Saturn 5 core, and strap on 2 Titan SRM's.<br /><br />To argue that one should use a SSME to develop a low cost LV is a misguided argument as it is one of the most complex LRM's ever produced and is backed by a team of 1000s to bring to operation. Also the technologies required to store liquid hydrogen in a flight weight vehicle again raise technical complexity and cost, just look at the long sad and protracted effort of Japan to realise a reliable cryogenic engine. It is not worth

 

[barrykirk]

Well the BDB argument does have a lot of merit. One of the important things about the rocket equation is the ratio of the dry mass of the rocket to the fuel mass.<br /><br />Neglecting the engines most of the dry mass is the fuel tank.<br /><br />A large thickwalled tank with a small SA to volume ratio can have the same dry mass to fuel mass ratio as a much higher tech thin walled tank that is smaller.<br /><br />Ergo, the best way to improve the tank mass to fuel mass ratio is to use a bigger tank.

 

[scottb50]

I agree with a lot of your comments, especially that it would be politically difficult to butt heads with the established big players. Beyond that I see your point about cryogenic propellants and the complexity involved, but I also am looking at them for the long term, not simply for a launch vehicle. As far as using existing engines, SSME and the RL10 particularly, is the majority of the expense has been paid for and there has been a lot of proven flights for both engines. I would thing the advantage of not having to design, build and test new engines would tend to outway the reduced costs less energenic porpellants offer.<br /><br />As an example one area I am looking at is using a core concept. Instead of one huge tank feeding three SSME's each engine is attached to it's own smaller tank assembly and the complete assembly is attached to other identical assemblies. The scale allows much simpler construction and the ability to use various numbers of cores for different capability launchers further reduces costs.<br /><br />Further if you use the same Modules that you use for the core for a second stage, with two smaller engines attached, then use those same Modules as components for Stations and Space Vehicles you essentially build an entire infrastructure with a single component that can be cheaply and rapidly built. The Module I envision uses two identical Segments that attach to each other encasing a single piece Tube. That seems pretty simple and cheap.<br /><br />Further if you build everything around Hydrogen and Oxygen it becomes even simpler. Thrusters could use compressed gasses and just the amount needed could be produced in Space rather than tankering huge amounts of cryogenics by using water.<br /><br />I think the long view is more important than simply getting to LEO, if you limit your goal to that then it is up to others to figure out what to do with what you put there. What I see is a comprehensive solution: A fleet of various capability launchers, Assembly <div class="Discussion_UserSignature"> </div>