Airbreathing SSTO

If polywell fusion is developed, in what ways will the world change for better or worse? Discuss.

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TallDave
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Postby TallDave » Wed Mar 19, 2008 3:20 am

This might interest you if you haven't seen it before.

IEC and CBFR drives are both mentioned.

http://www.k-meyl.de/go/65_Sekundaerlit ... s_Vol2.pdf

djolds1
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Postby djolds1 » Wed Mar 19, 2008 4:47 am

93143 wrote:I'm working on my PhD in aerospace engineering right now.


LOL!

(glyph of whip cracking). :D

Good to know we have someone with high skill in the matter.

93143 wrote:Actually most of my knowledge is quite new; I've been looking stuff up as fast as I can think of it, and there will be gaps in my knowledge. But my handle on basic engineering principles is much better (MSc in Mec E), and I do know something of the history of the Shuttle. Besides, you're the one who said (on nasaspaceflight) that it was for budgetary reasons that we got a shuttle that was cheap to develop and expensive to run, rather than the reverse.

The original Shuttle design was for a fully-reusable TSTO with flyback first stage (much easier to deal with than the SRBs). The orbiter would have been much fluffier due to integral tanks, possibly leading to a more robust TPS, and there would have been no foam shedding problem. Von Braun felt he had to push the current shuttle design because if he had held out for the original there would simply have been no shuttle at all.

Interestingly, there was a paper at the 2008 AIAA conference in Reno that detailed some design studies for a quick-response, quick-turnaround low-cost TSTO launch system with a fully reusable flyback first stage...


Politics forced the segmented Thiokol SRB. There was a superior unitary body design in contention. Would've meant no Challenger.

Assuming we're stuck with conventional chem rockets, I do like the paraffin hybrids.

93143 wrote:I didn't change the subject. My engine concept is basically an extension of stuff that HAS been tested - some of it flight-tested - with the addition that heating/enthalpy addition is electric rather than by combustion. QED is just a 'most-probable' placeholder for the electric portion. I'm not rigidly attached to the REB idea, but I do think Bussard (who has actually designed nuclear thermal rockets that worked) probably knew what he was talking about. If the 6 GW space Polywell proves workable, there WILL be engine tests.


Agreed about Bussard knowing his business. And you're right about tests, unless there's a quantum jump leapfrog concept that works out (such as Martin Tajmar's 2006 work at ESA).

Duane
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djolds1
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Postby djolds1 » Wed Mar 19, 2008 7:42 am

TallDave wrote:This might interest you if you haven't seen it before.

IEC and CBFR drives are both mentioned.

http://www.k-meyl.de/go/65_Sekundaerlit ... s_Vol2.pdf


Interesting. Here is the full document:

http://tinyurl.com/34xrve

Section 2.4 is especially interesting. A CBFR fusion driven turbojet that only heats the air for thrust, no additional fuel used.

Duane
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MSimon
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Postby MSimon » Wed Mar 19, 2008 9:37 am

djolds1 wrote:Agreed about Bussard knowing his business. And you're right about tests, unless there's a quantum jump leapfrog concept that works out (such as Martin Tajmar's 2006 work at ESA).

Duane

I have been doing some thinking about a 6 GW unit. I think it would require a significant jump in super conductor technology and heat transfer. LH as reaction mass may be a requirement.

We will get there. Eventually. It may take as long as 10 or 15 years from the successful WB-100 demo operation.

We are probably stuck with chem jobs for the next 20 years.
Engineering is the art of making what you want from what you can get at a profit.

djolds1
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Postby djolds1 » Wed Mar 19, 2008 10:46 am

MSimon wrote:I have been doing some thinking about a 6 GW unit. I think it would require a significant jump in super conductor technology and heat transfer. LH as reaction mass may be a requirement.


May depend on the intended use. A planetary-only civilian suborb transport might be able to use a far smaller reactor.

MSimon wrote:We will get there. Eventually. It may take as long as 10 or 15 years from the successful WB-100 demo operation.

We are probably stuck with chem jobs for the next 20 years.


As long as Richard Hull is wrong and the polywell plays out. I am hopeful about the polywell's prospects, but will retain a healthy skepticism for the time being.

Given the Polywell working, I can wait 20 years.

Duane
Last edited by djolds1 on Wed Mar 19, 2008 2:20 pm, edited 1 time in total.
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drmike
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Postby drmike » Wed Mar 19, 2008 1:31 pm

djolds1 wrote:
TallDave wrote:This might interest you if you haven't seen it before.

IEC and CBFR drives are both mentioned.

http://www.k-meyl.de/go/65_Sekundaerlit ... s_Vol2.pdf


Interesting. Here is the full document:

http://tinyurl.com/34xrve

Section 2.4 is especially interesting. A CBFR fusion driven turbojet that only heats the air for thrust, no additional fuel used.

Duane


Thanks guys - that is quite an interesting report.

Keegan
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Postby Keegan » Thu Mar 20, 2008 8:57 am

^Yep Interesting read, although i havent got to the scalar waves bit yet ....hmmm.

I need to say one thing here though....

REDUNDANCY

If you have ever worked in aerospace very soon you will find everything has at least a twin redundant system. Engines, Pilots, Hydraulics, Avionics, Wheels. Some of it is pure over engineering, Most of it keeps our planes in the air and off the ground.

At the present stage, a Direct Conversion BFR with a 3MEV electric field the minimum radius is 6m. Thats a big ugly sphere from an aerodynamics/hypersonic perspective. Whats to say that a Safety Authority demands we have 2 reactors for redundancy ?

You have to understand that a BFR spaceplane not only needs an engine to accelerate but also to slow down. If things go wrong you simply wont be left stranded out in space, but stranded out in space it full velocity. You will not be able re enter the atmosphere.

So if a SSTO BFR spaceplane seems like a delicate proposition, it may be simply unachievable if you include any serious redundancy.
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drmike
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Postby drmike » Thu Mar 20, 2008 1:45 pm

Nukes are trained to put in 3 backups for non-critical systems, and 5 levels of backup for critical ones, at least in the US and Europe. Nuclear powered rockets won't be any different.

The shuttle has 3 engines but only 1 set of fuel tanks. If a tank fails, there's no stopping and no continuing. You die. So it's not like everything built is always safe with a backup.

Commercial flying machines will have to be built with multiple engines, but the first ships to Mars can be far more risky. I certainly wouldn't mind being lost on the way to Mars and not have the ability to come back.

Mumbles
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Lost in Space...

Postby Mumbles » Thu Mar 20, 2008 7:18 pm

drmike wrote:...the first ships to Mars can be far more risky. I certainly wouldn't mind being lost on the way to Mars and not have the ability to come back.

Perhaps it would be better to say I certainly wouldn't mind accepting the risk that there was a single-point failure that could leave me lost on the way to Mars and not have the ability to come back...

Eventually, "commercial" exo-atmospheric/interplanetary shipping will have to have some safety features built into the system. But those safety features might be sufficient consumables to wait out a broken BFR propulsion system while waiting for a rescue rendezvous ship to arrive...? (And, of course, said rescue ship on stand-by...)

But I would agree that IF the whole BFR space propulsion can be proven, there will be plenty of people willing to accept the known risk of a single-point failure as an acceptible cost of getting to the Moon/Mars (or Ceres, Pallas, Juno, Vesta,... wherever...)

A known risk, analyzed and accepted, is often much less hazardous than an unknown risk that becomes a problem without any forethought or planned response...

Be Safe
Mumbles

93143
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Postby 93143 » Thu Mar 20, 2008 8:21 pm

TallDave & djolds1: Thanks for the reference. Looks interesting - it seems NASA doesn't rule anything out until it's been given a good solid try...

Food for thought:

20 6 GW BFRs would put out the same amount of power as five F-1s and (if my estimates are reasonable) weigh less than a Saturn V.

Not enough less that it would be a good idea to try a pure-rocket all-QED/ARC VTVL SSTO, but coupled with chemical assist and ram air...? Maybe wings? (Heh... I can see it now...)

Yeah. Anyway...

More food for thought:

Most of the scaling in Polywell is with magnetic field. Assuming magic coils that can generate the maximum safe (ie: not ion-trapping) field at any size, and assuming the maximum safe field doesn't change with size, and ignoring thermal concerns, the gain scales linearly with size. Add POPS and you now have an inverse scaling cancelling the size advantage.

Summary: The gain of a POPS Polywell (with magic magnets and first-wall protection system) is independent of the size of the device.

What's more, the power out now scales with area, so you're actually better off with a bunch of small reactors than with one big one...

REDUNDANCY


Make the spaceship bigger. Use two reactors (or four for an SSTO). That should give you enough margin for 'reactor-out' capability.

...I have just run some numbers on ARC. (I really should take a closer look at those papers, when I get time...) Apparently waste heat from a 6 GWe reactor consumes ~120 kg/s of H2 if the temperature rise is 800K. That's enough hydrogen to generate 17 GW if burned with an appropriate amount of air or LOX. Of course, if you actually do burn it you're ahead of the game, but that's hard to do in air at high speed, and LOX is heavy. (Actually, even if you don't burn it, you might still be ahead of the game in terms of pure rockets, because you don't have to carry LOX).

Triple the temperature rise and you might need exotic refrigeration technology, but the hydrogen mass flow rate can be cut to the point where your engine power is greater (even if no hydrogen actually burns) than it would have been if you had used a scramjet. If you really want, you can still try to burn the stuff, doubling your power (and probably your thrust, at scramjet speeds).

EDIT: I really should learn not to spout off on this stuff without doing the math. 1000 kg/s of air at Mach 10 (quite a reasonable amount) is 4.5 GW of kinetic power. Adding 13 GW to this is not really amenable to small-epsilon square root approximations... /EDIT

I wonder how much an aerodynamically survivable ultra-high-temperature radiator system would actually weigh? Heck, you could probably enhance lift AND thrust with judicious placement of a radiator like that...
Last edited by 93143 on Wed Mar 26, 2008 7:35 pm, edited 1 time in total.

drmike
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Postby drmike » Fri Mar 21, 2008 12:50 pm

Mumbles: I 100% agree - like one astronaut told a reporter "If you don't have butterflys in your stomach sitting on the pad, you don't understand the problem."

Keegan
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Postby Keegan » Sat Mar 22, 2008 11:19 am

Oh i found another version of "Advanced energetics for aeronautical applications"

Bussard and IEC gets mentioned a few times.

Cant seem to find a full version of the report anywhere. Hmmm

The links posted before just talk about scalar waves. darn interesting stuff, though. Im reading Maxwell's A treatise on electricity and magnetism, its amazing to think that his equations describe both scalar and EM waves but were re written shorthand just to emphasize EM waves. Wow
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drmike
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Postby drmike » Sat Mar 22, 2008 1:42 pm

In Jackson "Classical Electrodynamics" he splits out the longitudinal from transverse waves in the chapter on "time varying fields, maxwell's equations, conservation laws". He uses the shorthand notation for longitudinal waves as

grad ( d phi / dt ) = 4pi J_l

where phi is the potential and J_l is the longitudinal current. This is derived from the Coulomb gauge, where the potential is integrated over all space. The problem with this gauge is that it is not causal - the potential from a charge distribution affects all space in zero time.

Rearranging the order of derivatives you get d E / dt = - 4pi J_l which is a scalar electric field not tied to a wave. It should be highly directional - if J_l is along a specific axis there will be no fields perpendicular to that axis. If you stand on top of a radio antenna I'd think you'd get a huge scalar wave since J_l is big. Maybe that's what we should be looking for with SETI?

wizz33
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file location

Postby wizz33 » Sun Mar 23, 2008 1:47 am

i already seached for the pdf
From: http://ntrs.nasa.gov/archive/nasa/casi. ... 172301.pdf

those longitudinal electical waves sure are intersting for ftl comm.
and that you only need 40 Mw to power a plane.

djolds1
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Re: file location

Postby djolds1 » Wed Apr 16, 2008 1:19 am

wizz33 wrote:i already seached for the pdf
From: http://ntrs.nasa.gov/archive/nasa/casi. ... 172301.pdf

those longitudinal electical waves sure are intersting for ftl comm.
and that you only need 40 Mw to power a plane.


Interesting.

The longitudinal/scalar waves function exactly as tachyons are hypothesized to. The higher the energy, the slower they propagate.
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