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General Discussion => Advanced Concepts => Topic started by: uko on 08/19/2006 06:15 pm

Title: SSTO Thread
Post by: uko on 08/19/2006 06:15 pm
I think it's time for a real SSTO thread on this forum and it seems to me that the right place for it is in the Advanced Concepts section.

Well personally it is hard for me to understand why SSTO is not a cheaper space transportation system than a multiple stage system.

So I would appreciate if anyone could elaborate on that and also what kind of technological breakthroughs are needet to make a SSTO system affordable.
Title: Re: SSTO Thread
Post by: Jim on 08/19/2006 06:23 pm
SSTO is a holy grail.
Title: Re: SSTO Thread
Post by: yinzer on 08/19/2006 06:39 pm
Altitude compensating nozzles would be very, very useful.  Lightweight "accessories" almost as so - things like APUs and valves and such - would be useful too.  I personally think (but have no hard facts to back it up) that a big requirement is design experience.  Most conceptual design is done using statistical methods to estimate how much various things will weigh and cost, and the design database for reusable launch vehicles is practically nonexistent.

Something like X-34, where the goal wasn't so much to push the technological state of the art as it was to build and fly something and see how it worked, would have been very useful.  After X-34, one could try for a two-men-and-a-toothbrush-to-orbit, and then once the lessons had been learned from that, maybe try to build something that will carry useful payload at a reasonable cost.
Title: RE: SSTO Thread
Post by: modavis on 08/19/2006 08:21 pm

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uko - 19/8/2006  2:02 PM  ..what kind of technological breakthroughs are needed to make a SSTO system affordable[?]

Significantly more impulse from a pound of engine+propellant, and/or significantly less mass from engine+tankage+structure. That's all there is to work with.

Start from the other end: nobody built multiple stages because they liked the extra cost and complication; they did it at first because they simply couldn't get to orbit at all with a single stage, and do it today because they can't get a worthwhile payload to orbit with a single stage.

Assuming you mean a fully reusable SSTO, that makes it even harder: from that (uneconomically small) payload, you now have to subtract the mass of everything needed to get it back safely:

-thermal protection

-landing gear and/or parachute

-heavier, more complex airframe (because it will be stressed repeatedly, and because re-entry stresses are along different axes than ascent stresses)

-wings, or at least additional "shaping" for a lifting body.

At the end of the exercise, you may have no payload, or so little that the cost per pound to orbit isn't reduced at all. Bottom line: Orbital rockets are in a tough corner of engineering/economic trade space; SSTO is in a tougher corner of that; fully reusable SSTO is in an even tougher corner of that. I sympathize with the "X-program" approach of sneaking up on it incrementally, but to do that honestly you have to say at the outset "we don't know how long it will take or how much it will cost." And that's a hard sell.
 

   

Title: RE: SSTO Thread
Post by: hop on 08/19/2006 10:43 pm
One interesting approach for SSTO (or near SSTO) engines: http://www.astronautix.com/engines/rd701.htm Overall, I think the MAKS spaceplane was a pretty good concept for a re-usable near-SSTO (although the risk of columbia style TPS damage is a bit scary).  It might be interesting to try to design a DC-X style VTVL based on engines like that.

That said, I agree with modavis. Even if you want re-usability, a TSTO can be a lot simpler to build (hopefully we'll see one in the next few years from Kistler!). Yes, it is more complex than an SSTO, but it doesn't require you to push the propulsion and structure engineering nearly as hard.

While people often assume SSTO implies re-usable, expendable SSTOs are worth thinking about as well. All else being equal, and expendable SSTO should be simpler, and hence cheaper and more reliable than a multi-stage expendable... but things are decidedly un-equal. With todays technology we could build an expendable SSTO but the payload fraction would make it pointless.

Advances required to make SSTO affordable ? The most plausible one I can imagine is an improvement in structures. If CNT composites work out (a very big if), you might be able to make Atlas style balloon tanks with truly insane mass fractions, as well as making a bunch of other stuff lighter. That should make an expendable SSTO a lot easier. Depending on the details, it might be enough to make re-usable SSTOs work too.
Title: Re: SSTO Thread
Post by: mauk2 on 08/20/2006 07:40 am
The problem is energy density.

Here ya go, this should give some insight:

http://ftp.fas.org/sgp/othergov/doe/lanl/lib-www/la-pubs/00191252.pdf

Title: Re: SSTO Thread
Post by: uko on 08/20/2006 10:18 am
Well yea when I started the thread i thought about a fully reusable SSTO system.. I really cant imagine how a expendable SSTO would be any better or more affordable :)

OK as i understand, we have to develop a better source of energy (very unlikely in the near future), or better structures (more likely i suppose).

hop.. can you explain what are CNT composites?

I know that after they shut down the X-33 program, they were able to manufacture the needed composite LOX and LH2 tanks.. so I thought the tech for the composites exists already.

Also I understand a SSTO system can launch a very small payload compared to the size of the launch vehicle.. so as I see it, we have to make the launch vehicle bigger and then also the payload mass increases. If the vehicle would be completely reusable (like the VentureStar would have been), it really wouldn't be a problem i suppose.. one wold cost a lot of money in the beginning, but after that you only have to pay for gas :)
Does that make any sense?
Title: RE: SSTO Thread
Post by: lmike on 08/20/2006 12:21 pm
Numbers have been run on the Saturn S-IVB stage as an SSTO and that supposedly could lift 4mt to LEO assuming the fuel mass fraction of 91% .  Or the STS ET with 6 SSMEs.  Non-reusable, of course.  The technology is there for an SSTO as such, but not to any actual advantage...  If it's the reusability not the SSTO, well the STS is mostly reusable.  Big savings?  Nah.  Until something useful is demonstrated there'll be skepticism.  Staging actually improves performance (by improving on the final payload mass ratios).  So why bother.  Just crank out more stages with cheap labor and work on applications to increase the demand side, the only driver for cost savings.  Logically, it makes sense to me  that the lofting is a separate stage.  You get your payload to about 8km/s and that *stage* of flight is over.  So you drop that spent machinery.  Why drag all those empty tanks and other stuff with you to orbit still attached to the payload?  But if there should be a real breakthrough in propulsion (nothing short of anti-grav or magic wand) I'll change my mind.
Title: Re: SSTO Thread
Post by: uko on 08/20/2006 04:12 pm
well i wouldn't compare a fully reusable SSTO to the STS, because too many things fall off there :)

Title: Re: SSTO Thread
Post by: modavis on 08/20/2006 08:29 pm

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uko - 20/8/2006  11:59 AM  well i wouldn't compare a fully reusable SSTO to the STS, because too many things fall off there :)  

Exactly. They not only couldn't build SSTO in the 1970s, they couldn't build a fully reusable TSTO -- i.e., with the fabulous flyback first stage (FFFS) and no dropped SRBs. For starters, look at the Shuttle ET and think about the sheer size implications of having all the propellant inside two winged vehicles (let alone one). Your FFFS becomes very large indeed -- and while very large w/ empty tanks makes a nice low wing loading for the flyback, very large with mostly or partly full tanks would be unmanageable in an abort.

And as for no SRBs -- they provide, what? 85% of the total thrust at launch?  Just how many engines would the FFFS have had? (Can you say N-1?)

People who say "the Shuttle could have been a contender if it had been fully reusable" (whether SSTO or TSTO) often seem to be implying that the "things falling off" design is the way it is because of a shortage of funding or of design "nerve." I contend that it simply couldn't have been done by 1981 at any price, and very possibly can't be done today at a credible price -- at least not for an orbiter anything like the size or payload of STS.    

Title: Re: SSTO Thread
Post by: hop on 08/20/2006 10:38 pm
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uko - 20/8/2006  3:05 AM

Well yea when I started the thread i thought about a fully reusable SSTO system.. I really cant imagine how a expendable SSTO would be any better or more affordable :)
All else being equal (which as noted before it isn't) you get half the complexity, which should be a big improvement in both cost and reliability.  Such a vehicle would have a pitiful payload compared to a multi-stage vehicle of the same liftoff mass, but many people have noted that GLOW shouldn't actually be the primary factor in the cost of current LVs. The materials and fuel are (in most cases) a small fraction of launcher cost. If we get to the point where fuel and materials are the dominant factor in launch prices, optimizing GLOW makes sense again... but at that point we will have what most people define as CATS anyway.

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hop.. can you explain what are CNT composites?
Carbon Nanotubes (http://en.wikipedia.org/wiki/Carbon_Nanotubes) composites. Note that it is far from certain whether anyone will ever come up with affordable composites that come anywhere close to the theoretical maximum strength. I was just using this as an example of a plausible advance that could make SSTO a whole lot easier.

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I know that after they shut down the X-33 program, they were able to manufacture the needed composite LOX and LH2 tanks.. so I thought the tech for the composites exists already.
If I remember right, the problems with the LH2 tank were not solved at the end of the program.
Title: Re: SSTO Thread
Post by: Jim on 08/20/2006 10:46 pm
yes, they were solved.  Start out with an Al tank.
Title: Re: SSTO Thread
Post by: mauk2 on 08/21/2006 12:50 am
Yeah, as I recall, the aluminum/lithium tank for the X-33 actually wound up weighing about the same or a bit less than the target for the composite tank.  The tank itself was heavier, but other components could be made lighter/eliminated by the more better alloy.

Mass fraction was still gonna be achingly small.....

Note, small mass fraction is not always a showstopper, the old Sea Dragon concept had stunningly low mass fraction but still was one of the biggest payloads conceived.  To paraphrase a very bad man, "Quantity has a quality all it's own." :)

That said, higher energy solutions are not impossible, or even particularly difficult.  They're just scary.  :)

CNT composites are interesting as well.  Stronger materials are ALWAYS going to be useful contributors, and CNT is a pretty big step.

http://www.lanl.gov/news/releases/archive/04-076.shtml

In that article, they were growing 4cm long SWNT's back a couple of years ago.  I've seen other cites for 8cm long tubes, but I think those were multiwalled.

4 - 8 cm's in getting long enough that its not impossible to imagine "fiberglass" made of the stuff.  Sadly, epoxy is still the limiter in that case, but hey, progress is progress.  :)
Title: Re: SSTO Thread
Post by: meiza on 08/21/2006 01:04 pm
Regarding all-reusable STS, Buran had no solids, but RD-170-engined boosters which were recovered by parachute (don't know what happened to the two that flew on the only real flight). RD-170 is a kerosene engine in the F-1 thrust class, but it has higher chamber pressure and thus more thrust per area as well as better ISP. Both have been static fired for long durations and multiple times if I recall correctly.
I do not exactly know why the F-1A wasn't a basis for the shuttle boosters, but have heard that it was cheaper to develop big solids for that thrust. (?)
With the higher ISP your total mass would have gone down and the SSME:s could have taken more than 15% of the launch weight, meaning smaller boosters. (Positive feedback.) Also hazards with the solids inside VAB and moving around with crawlers could have been avoided, the whole system would have been really lightweight until fueled at the pad. Of course the complexity of more liquid engines might have given lots of new failure modes.
Title: Re: SSTO Thread
Post by: imfan on 08/22/2006 12:24 am
recovery system was not used  in both energia launches. at least as far as I know
Title: Re: SSTO Thread
Post by: Avron on 08/22/2006 04:15 am
Please help me here.. I just don't get the SSTO .. what does it give us, that we don't have now?
Title: Re: SSTO Thread
Post by: uko on 08/22/2006 06:36 am
In my view, staging is what makes launching to space complex and difficult.
If we had a fully reusable SSTO vehicle (something in "gas and go" style :) ), space access would be more or less routine by now. It would be cheap to launch and the turnaround time would be marginal.

Also SSTO is sexy, futuristic, sci-fi ;)

I think everybody would agree that SSTO is the future of launch vehicles, which means that it has to be much better than other systems.
Title: Re: SSTO Thread
Post by: modavis on 08/22/2006 09:56 am

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Avron - 22/8/2006  12:02 AM  I just don't get the SSTO ..

As Jim said, it's a Grail: a single objective that promises to solve everything. There's an irresistible appeal to "Think how expensive air travel would be if we threw away the jetliner every time." That was said to Congress a lot during the campaign for STS in 1970-1972.

Or think of the image imprinted by science fiction long before Sputnik: the rocket coming back down on a tail of fire just the way it went up, "as God and Robert Heinlein intended." (Pournelle)

Andrew Butrica handles it well in his 2003 book "Single Stage to Orbit," about SDIO and the DC-X. He begins it by quoting the opening words of Don Quixote...  :)

Title: Re: SSTO Thread
Post by: lmike on 08/22/2006 10:02 am
Quote
modavis - 22/8/2006  2:43 AM

Quote
Avron - 22/8/2006  12:02 AM  I just don't get the SSTO ..

As Jim said, it's a Grail: a single objective that promises to solve everything. ...


Good analogy, indeed.  Incidentally, no-one is looking for the actual Grail anymore.  And should you need one, there are much sturdier and cheaper Grails made in downtown Shanghai out of aluminum alloys, nowdays.
Title: Re: SSTO Thread
Post by: lmike on 08/22/2006 10:06 am
I certainly don't think SSTO is an "objective in itself" and in any way desirable as a goal until the exact need for it is about (i.e. lots and lots of frequent small payloads).  Staging improves performance via upping the final payload mass fraction.  How is staging complex?  By now it's a routine operation.  More throwaway engines, OK.  That's fine if they are cheap.  How about we just make the individual stages cheaper in mass production (now where all those payloads for the reusable SSTO are going to come from anyway?)  SSTO, especially reusable, looks just like another (bright, as always!) solution looking for a problem.
Title: Re: SSTO Thread
Post by: lmike on 08/22/2006 10:16 am
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uko - 20/8/2006  8:59 AM
well i wouldn't compare a fully reusable SSTO to the STS, because too many things fall off there :)

Never claimed it was.  It's admittedly more reusable than an ELV though.  It's also not an SSTO, of course.  Also, never claimed it was.  Mentioned that, technically, a non-reusable SSTO is considered possible since the Saturn days.  And for the reusability, we've actually had and still have a mostly reusable launch system (everything except a hydrogen tank).  However limited, these are data points, to a degree, that we have to work with.   None of the outcomes of those provide any encouragement for perusing an all-reusable SSTO.  

I don't see how combining the two flaws will result in a positive outcome.  Especially in the payload/space application demand market is as the one we have.*  

Agree that a 'stubby' SSTO could be cool looking though.  Especially with large fins on the bottom.

[edit] * And the cost of the payload development and construction is actually what's driving up mission costs nowdays!  Maybe start optimizing where it's most needed?
Title: Re: SSTO Thread
Post by: Jim on 08/22/2006 11:10 am
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uko - 22/8/2006  2:23 AM

In my view, staging is what makes launching to space complex and difficult.
If we had a fully reusable SSTO vehicle (something in "gas and go" style :) ), space access would be more or less routine by now. It would be cheap to launch and the turnaround time would be marginal.

I think everybody would agree that SSTO is the future of launch vehicles, which means that it has to be much better than other systems.

Stage is not complex.  Reusable SSTO is not the future of LV's because is unattainable.   Some other power source than chemical rocket engines is needed.
Title: RE: SSTO Thread
Post by: PurduesUSAFguy on 08/22/2006 11:13 am
As far as the dream of having a fully reusable SSTO that enables aircraft like opperation I think that is likley 50 years out, the rocket equation is a harsh mistress and as long as you are married to it it almost totally preclude a realistic SSTO RLV. I really don't think that materials science will have advanced to the point that we will be able to hit the 95% mass fraction in a rhobust vehicle before mid-century, that would require either advanced CNT composites or, idk, nano-assembled industrial diamond tanks. The only way you are going to ever make an SSTO work is with a significant air breathing componet where rockets are only used for the final boost to orbit, and even then maybe with LOX harvested from the atmosphere and tanked during flight.

I think more realistically the kind of system that you are going to get is a two stage to orbit system with a scramjet/combined cycle carrier aircraft carrying a bottom mounted semi-conformal upper stage. By using a bottom mount system you will greatly ease ground handling and integration versus piggyback carrying. I also think an interesting technology that might be applicable for such an RLV is the idea of using nano-phase aluminum in the liquid hydrogen to increase it's density and specific energy.



Title: RE: SSTO Thread
Post by: lmike on 08/22/2006 11:39 am
I suppose academically there are 2 subtopics here:

1. why should we aim for an all-reusable SSTO
2. can we do an all-reusable SSTO technically

Suppose the answer to 2. is "Yes".  The next question is -- does it provide an advantage (in the all encompassing sense, as a total) to an either non-reusable or all-reusable MSTO?  If the answer is "No" (I think), the next question is "Why bother with 1.?" ([edit]since if we can do a good SSTO stage, we can do even better with using that SSTO stage as a part of a MSTO, reusable/non-reusable doesn't matter)
Title: RE: SSTO Thread
Post by: modavis on 08/22/2006 11:44 am

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PurduesUSAFguy - 22/8/2006  7:00 AM I think more realistically the kind of system that you are going to get is a two stage to orbit system with a scramjet/combined cycle carrier aircraft carrying a bottom mounted semi-conformal upper stage.

What do we know about the aerodynamics of separation -- even bottom-mount, with gravity helping -- at hypersonic speed? I'm not saying it can't work, just that it strikes me as exceedingly hard either to test in a wind tunnel or to model on a computer. It's got to be a pretty drastic rearrangement of the shockwave pattern, which makes me nervous on general principles.

You're right that in general use SSTO is synonymous with "aircraft [or airline] like operation" -- implying not only reusability, but relatively quick turnaround, far smaller ground crews per vehicle or per launch, amortization of R&D and mfg. costs over many flights, etc. That way of thinking makes a hardware architecture carry the whole burden of the analogy. Unfortunately, it also smuggles in the implication that there's lots of unmet demand -- that the potential traffic to orbit is quantitatively comparable to, say, the inter-city train and auto and steamship traffic of the 1920s-1950s, which shifted to air travel as the price came down -- and in turn helped bring the price down more, in a virtuous circle.

I don't doubt that demand for access to space will grow with declining prices. But I don't think the shape of the curve looks nearly as favorable, because space activity has to bootstrap both its markets and its destination facilities.

"Nice plane you got there, Lindy. Now: that pile over there is the building materials for Paris..."      

 

 

Title: RE: SSTO Thread
Post by: lmike on 08/22/2006 12:00 pm
Quote
modavis - 22/8/2006  4:31 AM

... in general use SSTO is synonymous with "aircraft [or airline] like operation" -- implying not only reusability, but relatively quick turnaround, far smaller ground crews per vehicle or per launch, amortization of R&D and mfg. costs over many flights, etc. ...

It is this fundamental implication/assertion/supposedly axiom that I think we should question.  It's a myth as it stands.  For example, a single SSTO engine could be more complex in development, manufacturing, mainainance and operation than 2 stages' MSTO's engines even if they are of a different type (for 2 stage vehicles which are a known quantity and quality)

[Edit] I must add: from a purely technical standpoint; the economics are often thought of as a secondary concern for some reason, but you are right it's a function of the demand first
Title: RE: SSTO Thread
Post by: lmike on 08/22/2006 12:31 pm
Quote
PurduesUSAFguy - 22/8/2006  4:00 AM
...
I think more realistically the kind of system that you are going to get is a two stage to orbit system with a scramjet/combined cycle carrier aircraft carrying a bottom mounted semi-conformal upper stage. By using a bottom mount system you will greatly ease ground handling and integration versus piggyback carrying. I also think an interesting technology that might be applicable for such an RLV is the idea of using nano-phase aluminum in the liquid hydrogen to increase it's density and specific energy.

This is a Pegasus like horizontal launch I assume.  (don't mean to be patronizing, but...) the mg, the force of gravity is a function of altitude as in Gm/(rE + z)^2 where rE is the Earth radius and z is the altitude from the former.  You want to get out of the earth's pull as fast as you can (at given preferred G-loads, and heat loads).  Thus (sc)ramjets* are not a good idea for spaceflight.  A space bound vehicle wants to get out of the earths pull as fast as it can.

*[edit] plus they are not a new technology, and need a booster accelerator stage anyway up to 5-6M  (look at their fundamentals)
Title: RE: SSTO Thread
Post by: modavis on 08/22/2006 12:48 pm

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lmike - 22/8/2006  7:47 AM ...the economics are often thought of as a secondary concern for some reason...

That's built into the heritage of space technology. It can't be emphasized often enough: we originally got to orbit not primarily because we wanted space so bad, but virtually as a side effect of wanting to blow stuff up quickly from far away. Every spacer knows the V2 story, but many don't follow through the implications. Most of the R&D heavy lifting that went into space activity 1957-1969 had already been paid for (at a cost several times that of Apollo) at Peenemunde, then on Cold War defense budgets, as part of the race for ICBMs and spy sats: big rockets and their infrastructure, staging, avionics, global tracking systems, re-entry technologies... and a lot of expensive learning in systems engineering and management.

So these technologies started in the realm of "money's no object, it's for national security"... then in 1957-1969 shifted to "waste anything but time, it's for national prestige and global leadership"... and have been trying ever since to make the transition to the workaday world of supply/demand and return on investment. So far only commsats, remote sensing and kindred applications have gotten over that hump.

Sometimes the situtaion reminds me of a rich kid when the trust fund runs out... :(      

Title: RE: SSTO Thread
Post by: lmike on 08/22/2006 01:19 pm
I agree with the pre-conditions of the current attitudes as you outlined.  We've ridden the gravy train to its final destination.  Perhaps, we need to break out?  How?  Some argue with new technology no matter the costs.  Some argue with new economics and rationale.  There is an optimal mixture somewhere there.
Title: RE: SSTO Thread
Post by: PurduesUSAFguy on 08/22/2006 01:35 pm
Quote
modavis - 22/8/2006  6:31 AM

Quote
PurduesUSAFguy - 22/8/2006  7:00 AM I think more realistically the kind of system that you are going to get is a two stage to orbit system with a scramjet/combined cycle carrier aircraft carrying a bottom mounted semi-conformal upper stage.

What do we know about the aerodynamics of separation -- even bottom-mount, with gravity helping -- at hypersonic speed? I'm not saying it can't work, just that it strikes me as exceedingly hard either to test in a wind tunnel or to model on a computer. It's got to be a pretty drastic rearrangement of the shockwave pattern, which makes me nervous on general principles.

You're right that in general use SSTO is synonymous with "aircraft [or airline] like operation" -- implying not only reusability, but relatively quick turnaround, far smaller ground crews per vehicle or per launch, amortization of R&D and mfg. costs over many flights, etc. That way of thinking makes a hardware architecture carry the whole burden of the analogy. Unfortunately, it also smuggles in the implication that there's lots of unmet demand -- that the potential traffic to orbit is quantitatively comparable to, say, the inter-city train and auto and steamship traffic of the 1920s-1950s, which shifted to air travel as the price came down -- and in turn helped bring the price down more, in a virtuous circle.

I don't doubt that demand for access to space will grow with declining prices. But I don't think the shape of the curve looks nearly as favorable, because space activity has to bootstrap both its markets and its destination facilities.

"Nice plane you got there, Lindy. Now: that pile over there is the building materials for Paris..."      

 

 


Your right, we really don't know much about hypersonic seperation aerodynamics, and I would suspect that the current CFD models are inadequate for modeling it, so what we need is is flight data. I think the most problems would arrise when the second stage, piggy back or bottom mounted, leaves the shock cone of the carrier aircraft durring seperation, I don't think it would be a show stoper but until we have more data (or if there is data that I'm not aware of) about hypersonic carrier/parasite aerodynamics we won't know.
Title: RE: SSTO Thread
Post by: lmike on 08/22/2006 01:47 pm
Quote
PurduesUSAFguy - 22/8/2006  6:22 AM

Quote
modavis - 22/8/2006  6:31 AM

Quote
PurduesUSAFguy - 22/8/2006  7:00 AM I think more realistically the kind of system that you are going to get is a two stage to orbit system with a scramjet/combined cycle carrier aircraft carrying a bottom mounted semi-conformal upper stage.

What do we know about the aerodynamics of separation -- even bottom-mount, with gravity helping -- at hypersonic speed? I'm not saying it can't work, just that it strikes me as exceedingly hard either to test in a wind tunnel or to model on a computer. It's got to be a pretty drastic rearrangement of the shockwave pattern, which makes me nervous on general principles.

You're right that in general use SSTO is synonymous with "aircraft [or airline] like operation" -- implying not only reusability, but relatively quick turnaround, far smaller ground crews per vehicle or per launch, amortization of R&D and mfg. costs over many flights, etc. That way of thinking makes a hardware architecture carry the whole burden of the analogy. Unfortunately, it also smuggles in the implication that there's lots of unmet demand -- that the potential traffic to orbit is quantitatively comparable to, say, the inter-city train and auto and steamship traffic of the 1920s-1950s, which shifted to air travel as the price came down -- and in turn helped bring the price down more, in a virtuous circle.

I don't doubt that demand for access to space will grow with declining prices. But I don't think the shape of the curve looks nearly as favorable, because space activity has to bootstrap both its markets and its destination facilities.

"Nice plane you got there, Lindy. Now: that pile over there is the building materials for Paris..."      

 

 


Your right, we really don't know much about hypersonic seperation aerodynamics, and I would suspect that the current CFD models are inadequate for modeling it, so what we need is is flight data. I think the most problems would arrise when the second stage, piggy back or bottom mounted, leaves the shock cone of the carrier aircraft durring seperation, I don't think it would be a show stoper but until we have more data (or if there is data that I'm not aware of) about hypersonic carrier/parasite aerodynamics we won't know.
Sorry for butting in... but... Assuming we can do it, how would this be advantageous to what we have now?  Suppose we can do a scramjet TSTO with a pre-boost stage somewhere there, can we launch a GPS sat at lower cost for example?  For each technical solution I like to ask: what is its marginal utility?
Title: Re: SSTO Thread
Post by: Avron on 08/22/2006 02:50 pm
Many thanks for all the inputs... just wondering if something using mircrowave energy via pinpoint beam from orbit would provide the energy source for real SSTO?
Title: RE: SSTO Thread
Post by: modavis on 08/22/2006 02:56 pm

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lmike - 22/8/2006  9:34 AMAssuming we can do it, how would this be advantageous to what we have now?  Suppose we can do a scramjet TSTO with a pre-boost stage somewhere there, can we launch a GPS sat at lower cost for example?

All depends on the specific numbers: you might have a win if your final rocket stage can kick off at 40 km and Mach 9, but a wash, or a loser, at 30km and Mach 7. What's the scramjet fuel consumption? How much did it cost to develop the sliding titanium-columbium shingles around your variable inlet? (I'm making this $#!+ up, obviously, but you know what I mean.)

Unfortunately, less squishy numbers cost a lot to obtain. As one Dryden aerodynamics vet puts it, there's a big "desert" of both hardware experience and  modeling capability between Mach 4 and Mach 25. We explored a little way into it from one side with the X-15, and staked out a few very narrow paths across it with nose cones, ballistic capsules, and the STS orbiter, but most of it's still unknown territory.

I can see the appeal of the ever-faster, ever-higher aerodynamic approach, if only because sooner or later it might yield a viable SST.  And I can see the appeal of the steely-eyed missileman approach: what you want is orbit, so the sooner you punch up through the soup and start your serious acceleration, the better. I try to stay agnostic...  

Title: RE: SSTO Thread
Post by: lmike on 08/22/2006 03:08 pm
Quote
modavis - 22/8/2006  7:43 AM

...if only because sooner or later it might yield a viable SST.  ...

It appears still as a "goal onto itself" (Kantian philosophy, e.g. absolute morality)  Do we want it?  "A viable SST is a good thing" as a statement is given,  is it not?  At the root, isn't it what we are trying to determine?  Is this goal worthwhile?  We do have other means compliant with the laws of physics as we know them to achieve same or better results.
Title: Re: SSTO Thread
Post by: modavis on 08/22/2006 03:09 pm

Quote
Avron - 22/8/2006  10:37 AM  ...just wondering if something using mircrowave energy via pinpoint beam from orbit would provide the energy source for real SSTO?

Beamed power is always attractive, but microwaves do need a rather large antenna to give you even a dull "pinpoint"... which begs the chicken-and-egg question of what you used to get the materials for the antenna up to orbit  :(

Laser hardware is more compact -- Jordin Kare has done nice conceptual work on laser launch, and Geoff Landis on laser->electric satellite and spacecraft power. But of course as the frequency and the beam's energy density go up, you start running into "death rays from space" fears, and voila! You're in a PR minefield rather like the one mauk2 is treading over in the "More Nuclear Material" thread...  

Title: Re: SSTO Thread
Post by: lmike on 08/22/2006 03:12 pm
Quote
Avron - 22/8/2006  7:37 AM

Many thanks for all the inputs... just wondering if something using mircrowave energy via pinpoint beam from orbit would provide the energy source for real SSTO?

I'm not sure I understand the schematics, but it could via a reflector I suppose.  But why would you want it?   In the end why would you want a "future real SSTO" when we have an "actually real MSTO" with much better mass fraction for the payload?
Title: RE: SSTO Thread
Post by: modavis on 08/22/2006 03:21 pm

Quote
lmike - 22/8/2006  10:55 AM "A viable SST is a good thing" as a statement is given,  is it not?  At the root, isn't it what we are trying to determine?

That's deeper than I'm qualified to go.  All I meant was that if a viable SST looked within reach, one could hope/expect that the big budgets (much bigger than space) of military and commercial aviation would do the gruntwork of bringing it from bleeding-edge to routine. Then, once we had lots of experience with large aircraft in that flight regime, we'd be in a much better position either to build or to rule out the Fabulous Flyback First Stage for cheaper TSTO.      

Title: Re: SSTO Thread
Post by: Avron on 08/22/2006 03:25 pm
Quote
lmike - 22/8/2006  10:59 AM

Quote
Avron - 22/8/2006  7:37 AM

Many thanks for all the inputs... just wondering if something using mircrowave energy via pinpoint beam from orbit would provide the energy source for real SSTO?

I'm not sure I understand the schematics, but it could via a reflector I suppose.  But why would you want it?   In the end why would you want a "future real SSTO" when we have an "actually real MSTO" with much better mass fraction for the payload?

Just asking what options where on for alternative remote energy sources.. but make no mistake.. I see no issue with the MSTO... it works, its proven.. the only thing I would like to see is less junk and more H20 comming out the business end...
Title: Re: SSTO Thread
Post by: SonicAgamemnon on 09/08/2006 07:23 pm
Probably a stupid question, but I have to ask regardless.  Why can't we go for a "mostly" reusable design instead of something totally reusable?  I really, really, really dislike Nasa's Constellation program-- mostly throw-away design, Apollo rehashed, nearly complete retrograde IMO.  Can't we combine the X-33 design with a solid rocket booster to reach LEO and then fly back home like the shuttle?  The SRB could be integrated into the ship or attached beneath and released during ascent.  Perhaps a combination of the aerospike engine with a smaller SRB to get a decent payload into high orbit?  The x-33 has a better thermal protection design (no ceramic tiles) and doesn't have a giant external fuel tank shedding foam, etc.  Nearly everything is reusable for faster turn-arounds and lower operational cost.  COME ON!  I AM SICK AND TIRED OF MULTI-STAGE ROCKETS WITH CAPSULES ON TOP!  RETROGRADE!!!!
Title: Re: SSTO Thread
Post by: tom nackid on 09/08/2006 08:28 pm
Quote
SonicAgamemnon - 8/9/2006  2:10 PM

Probably a stupid question, but I have to ask regardless.  Why can't we go for a "mostly" reusable design instead of something totally reusable?  I really, really, really dislike Nasa's Constellation program-- mostly throw-away design, Apollo rehashed, nearly complete retrograde IMO.  Can't we combine the X-33 design with a solid rocket booster to reach LEO and then fly back home like the shuttle?  The SRB could be integrated into the ship or attached beneath and released during ascent.  Perhaps a combination of the aerospike engine with a smaller SRB to get a decent payload into high orbit?  The x-33 has a better thermal protection design (no ceramic tiles) and doesn't have a giant external fuel tank shedding foam, etc.  Nearly everything is reusable for faster turn-arounds and lower operational cost.  COME ON!  I AM SICK AND TIRED OF MULTI-STAGE ROCKETS WITH CAPSULES ON TOP!  RETROGRADE!!!!

The X-33 was never intended to go into orbit. It was a suborbital test bed. Anyway, how would an X-33 on an SRB be any better than the shuttle? It would just be a shuttle with internal tanks, lower payload and a newer (untested!) heat shield. In fact it would be going back to the Sanger, Bomi and DynSoar concepts--which predate blunt body capsules by the way!
Title: Re: SSTO Thread
Post by: SonicAgamemnon on 09/08/2006 09:46 pm
I realize X-33 was a scaled down suborbital test, but follow-on designs based on X-33 were not.  Why can't we improve upon the shuttle design instead of throwing it away entirely?  Wouldn't using newer X-33 technology with possible SRB assist deliver a better, safer, less costly new shuttle design?  Shouldn't the next, most immediate goal be to put more people and hardware in Earth orbit, not going back to the Moon or ultimately Mars?  A good long-term goal for sure, but I don't think that's what we need to be doing right now.  How would such a revised shuttle be different than the existing one?  The X-33 areospike engine is more efficient that the shuttle's engine; the huge foam-shedding external tank isn't needed, so risk to the thermal protection system drops way down and throw-away costs are reduced.  Those are two big improvments! If payload is the isseue, perhaps a more economical approach would be to put non-human cargo in orbit using a large SRB, and shuttle people (not huge/heavy cargo) to/from orbit in a new, smaller, safer and cheaper to operate, mostly reusable shuttle.

I know, it's impossible-- especially when NASA dedicates nearly its entire budget on repeating Apollo...
Title: Re: SSTO Thread
Post by: mong' on 09/08/2006 10:20 pm
one thing to realise is that exploring(and settling) the moon and mars will justify the need for cheaper access to space and not the other way around.
By going to the moon to stay and planning to settle mars we now have a destination, and that is a strong driver for reduced launch costs/higher flight rates, it will even be vital.
we can develop today an entirely reusable TSTO spaceplane to put decent payloads in orbit, the reason why we haven't is because there is no need for one, nothing we do today justifies the high flight rates needed to make an RLV affordable. a lunar/martian base can change that.
in fact going back to so called "apollo tech" (which by the way the CEV isn't) NASA actually paves the way for truly affordable space access.

and no we are not throwing the shuttle away entirely, in fact we are using it's biggest advantage: heavy lifting
the shuttle is a frustrated heavy lift. by throwing away the heaviest component (the orbiter) we can have a 100+ tons HLV, that is a smart move
Title: Re: SSTO Thread
Post by: Scotty on 09/09/2006 02:15 am
Reuseable SSTO will only be possible with a much higher isp, and the much lower take off mass fraction a high isp gives.
Get the isp up to 1100 or so, and your take off mass fraction drops to less than 50%.
Thus, a 6 million pound lift off weight vehicle (about that the shuttle weighs at liftoff) could place 2 million pounds of deployable cargo into LEO.
But, you will not get anything much over an isp of 650 with chemical propellants.
So, what are you left with?
The US Government and NASA just do not have the balls to use the "N" word on space propulsion systems.
Until they do, reusable SSTO is a dead duck.
Remember "Captain, I can not change the laws of physics".
Title: Re: SSTO Thread
Post by: mauk2 on 09/09/2006 06:41 am
Hiya Sonic!

I feel your frustration, dude, but Scotty is steering you right.  Barring huge breakthroughs, any sort of realistic SSTO is impossible with chemical fuels.  I'm sorry, but that's just the blunt truth.  X-33 was a huge boondoggle from the get-go, that I choose to view in a good light because some good solid engineering got done.  Not completely useless effort.

For the reason why, here's a nifty link:

http://www.pma.caltech.edu/~chirata/deltav.html

Note from the Delta-V flowchart that it requires a delta V of 9.7 kilometers per second to reach Earth orbit.  (That's a pretty good approximation of an optimized flightpath including g losses, Isp changes with altitude, body lift, drag, and a few other things I forget.)  That massive lump of Isp also requires a high specific thrust, or else g-losses and drag eat you alive and you never make it out of the soup.  That combination of factors, high delta-v and high thrust requirement, means you have to have an energetic propellant.  HAVE to.  There's no way around it, and believe me, we have TRIED.  

Now, conventional chemicals in practical terms have vacuum Isp no more than 450, and sea level Isp less than that. (Air is thick, gluey stuff, pumping rocket exhaust out into it is a miserable chore! :) )

If you are not familar with the rocket equations, you should study up on them.  They aren't THAT hard. :)  (Math is delicious!)

A nice, elegant derivation of the rocket equations is this mass fraction equation:

M = e^V/C, where:

M = mass fraction, fully loaded rocket/ weight without propellant, alway more than 1.
e = the natural logarithm "e," 2.71828....  "e" is a constant that's apparently stamped right into the guts of reality, and it's rather critical to rocketry.
V = DeltaV m/s net of  drag, g losses,  relativity, etc
C = Exhaust velocity, m/s, ignoring reactions in the exhaust stream, usually.

(Note that the graph in the link above, with that nice sweeping curve, is nothing but a graph of this equation, and that curve should be engraved on the desktop of every rocket enthusiast on the planet until it sinks in.)

Now, the exponent V/C is where all the fun happens.  If you use H2/O2 fuel, your exhaust velocity is around about 4000 meters per second, integrated over your time of flight.  Since we know you need 9700 meters of delta-V, this make V/C equal to 9700/4000 = 2.425.

So, our mass fraction equation becomes:

M = e^V/C =>

M = 2.71828 ^2.425.   Busting out the calculator, e to the power of 2.425 is: 11.3.

Okay, I have done this kind of junk long enough to look at a mass fraction of 11.3 and say "Ouch."  Why?

Well, what that 11.3 means is that your ship, full, weighs 11.3 times as much as it weighs empty.

I find it useful to invert the mass fraction:   1/11.3 = 0.088

This shows that 8.8 percent of your takeoff mass is available for structure, engines and payload.  91.2 percent has to be fuel.  Period.

That is freaking HARD. That is so hard that such frantic engineering scrambles as slush hydrogen get looked at in a desperate bid to lower tankage mass by any way possible, but honestly, a mass fraction that high is never going to give you a satisfactory machine for any practical purpose.

I'm sorry, but this is, as Scotty said, the laws of physics.  They won't bend, no matter what, and we learned that fact to our sorrow on the X-33 program.  Venturestar would have never been any use as proposed, gorgeous though it was.

Now, Scotty stated an Isp of 1100 seconds would be of use.  What mass fraction does that give us?

M = e^V/C

C is constant at 9700,  but at 1100 seconds, V shoots up to around 11,000.  That makes V/C 9700/11,000, or .88.  Hmmmm, that's WAY more reasonable!  :)

M = 2.71828^0.88 = 2.41

Now, a mass fraction of 2.4 is WAY better than 11.3.

Invert the 2.4 to get a usefull number:  1/2.41 = 0.414

So, now it only takes 59 percent of the ships mass to be propellant for an SSTO to make this performance.  This Isp is very close to what the old Timberwind program reported back in the 1980's.

Now, suppose we have an Isp of 2500 seconds.  What's your mass fraction?

V/C = 9700/25,000 = .388

M = 2.71828^.388 = 1.474

1/1.474 = .678

Now, it only takes 32 percent of your SSTO to be fuel, leading to what I think of as the SSTO "Rule of Three's".  Exhaust velocity three times delta-V means you can allocate 1/3 GLOW to fuel, 1/3 to structure, and 1/3 to cargo.

Such a vehicle is what we need to make SSTO work.  Now, how do we build it?   Because chemicals are not gonna do it.
Title: Re: SSTO Thread
Post by: lmike on 09/09/2006 08:48 am
Quote
SonicAgamemnon - 8/9/2006  12:10 PM
... COME ON!  I AM SICK AND TIRED OF MULTI-STAGE ROCKETS WITH CAPSULES ON TOP!  RETROGRADE!!!!

No one will lift a finger (or the checkbook), until there is a need for the anti-thesis of this proven and working system.  No one gives a hoot about the aesthetics of rockets.  Think economics...  (btw, thinking of spacecraft as airplanes flying higher is truly retrograde, although their economics is something to admire for us rocketeers)
Title: Re: SSTO Thread
Post by: mong' on 09/09/2006 01:24 pm
Quote
mauk2 - 9/9/2006  8:28 AM

Such a vehicle is what we need to make SSTO work.  Now, how do we build it?   Because chemicals are not gonna do it.

a gas core nuclear lightbulb would do the trick. of course you would have to get rid of all the environmentalists first.
Title: Re: SSTO Thread
Post by: lmike on 09/09/2006 01:28 pm
Quote
mong' - 9/9/2006  6:11 AM

Quote
mauk2 - 9/9/2006  8:28 AM

Such a vehicle is what we need to make SSTO work.  Now, how do we build it?   Because chemicals are not gonna do it.

a gas core nuclear lightbulb would do the trick. of course you would have to get rid of all the environmentalists first.

Chemicals can do an SSTO.  The problem is --- no one needs it.
Title: Re: SSTO Thread
Post by: modavis on 09/09/2006 02:01 pm

Quote
lmike - 9/9/2006  9:15 AM Chemicals can do an SSTO.  The problem is --- no one needs it.

Give it up, lmike. To be interested in getting humanity into space on a significant scale is one thing; to be interested in zoomy hardware for its own sake is another. Sometimes I think there's not much overlap.

 

Title: Re: SSTO Thread
Post by: lmike on 09/09/2006 02:07 pm
Just for the record, I (personally) am interested in getting as much of humanity into space as possible.  (the stress is on the word 'possible')
Title: Re: SSTO Thread
Post by: mlorrey on 09/09/2006 05:25 pm
Quote
mauk2 - 9/9/2006  1:28 AM
Now, conventional chemicals in practical terms have vacuum Isp no more than 450, and sea level Isp less than that. (Air is thick, gluey stuff, pumping rocket exhaust out into it is a miserable chore! :) )

If you are not familar with the rocket equations, you should study up on them.  They aren't THAT hard. :)  (Math is delicious!)

A nice, elegant derivation of the rocket equations is this mass fraction equation:

M = e^V/C, where:

M = mass fraction, fully loaded rocket/ weight without propellant, alway more than 1.
e = the natural logarithm "e," 2.71828....  "e" is a constant that's apparently stamped right into the guts of reality, and it's rather critical to rocketry.
V = DeltaV m/s net of  drag, g losses,  relativity, etc
C = Exhaust velocity, m/s, ignoring reactions in the exhaust stream, usually.

This is the essential misinformation of the missileer. The problem is that this is merely a derivation of the rocket equation specifically for launchers that carry all of their own propellant. This is inapplicable to any launcher that does any air breathing at any stage of the launch, for the simple reason that oxygen combusted from air can't be counted as part of the mass fraction, but does impact the Isp, which blows the logarithm out of the water.

There have been practical SSTO airbreathing engines demonstrated in flight and in the air. The Pyrojet, for instance, is a turbine based combined cycle engine capable of flight up to mach 8-10. The RBCC, or rocket based combined cycle engine, has also been tested in the wind tunnel, and was supposed to be built into a launchable scale test vehicle called GTX in 2004-2006, but was cancelled by the Bush administration. In order to account for the advantages of air breathing, one must dump the simplistic derivations such as mauk2 posts, and use the real rocket equations.
Title: Re: SSTO Thread
Post by: modavis on 09/09/2006 06:18 pm

Quote
mlorrey - 9/9/2006  1:12 PMIn order to account for the advantages of air breathing, one must dump the simplistic derivations such as mauk2 posts, and use the real rocket equations.

I'm all in favor of that -- as long as you also use the real equations for drag, shock waves, inlet temperatures, stagnation, heat flux per m^2 of skin and airframe, etc.

It is 100% true to say that the rocket equation gets less and less painful as you move its starting point higher and faster with an airbreathing first stage. But it is 100% misleading not to acknowledge that higher and faster airbreathers encounter their own set of costs and challenges, which may well outweigh their benefits as launch platforms.

As I've said before, if the global demand for faster bombers and faster airliners had paid for the development of big hypersonic airbreathers, we wouldn't still be wrangling over CATS. The fact is that it hasn't... so expecting the much smaller demand for access to space to do it is not very realistic.

I'd be happy to be proved wrong. Anybody who wants to do so can simply roll out Blackstar for a public demo flight instead of breathing hard over the pages of Aviation Leak.

 

 


 

Title: Re: SSTO Thread
Post by: kfsorensen on 09/09/2006 06:46 pm
Quote
mlorrey - 9/9/2006  12:12 PM

This is the essential misinformation of the missileer.

In order to account for the advantages of air breathing, one must dump the simplistic derivations such as mauk2 posts, and use the real rocket equations.
If you're airbreathing, then they're not the ROCKET equations anymore, are they?  Rockets, by definition, carry all their own reaction mass.
Title: Re: SSTO Thread
Post by: SonicAgamemnon on 09/09/2006 10:56 pm
Thank you for all the replies.  It's more than a bit depressing, no?  Even if an air/chemical or pure chemical SSTO is technically feasible today, there isn't a market/demand to cover the economics.  Even worse, even if enough demand could be generated worldwide, the technology may not be available.  However, couldn't this be said of the throw-away Apollo rocket/capsule approach?  I don't see a big marketplace for that service today, and I don't see XYZ Corp. making a profit sending people to Mars.  Essentially, I think both approaches cannot "economically" self-sustain.  I think it's simply mis-guided priorities, sending rockets to Mars when we cannot effectively transport many people to/from Earth orbit.  The cart is before the horse again.  We should master low and high Earth orbit first and spend the public budget there, instead of spending it on another nearly identical Apollo program!  There was a reason why the Shuttle program was funded; the need was there and it remains.  We just need a better shuttle system, and our focus should be on designing an SSTO or near-SSTO shuttle replacement first, then set our sights on Mars afterwards.  Just MHO...
Title: Re: SSTO Thread
Post by: mong' on 09/09/2006 11:30 pm
XYZ corp will make a profit sending things to mars/moon because NASA will employ them to do it, and the most affordably they can make it, the most profit they will make. contrary to today there will be a need for such services and an actual driver to reduce costs. and THIS will make space access (relatively) affordable.
we can't do much in earth orbit, there is nothing there, the real destination are the planets.

and enough with the "apollo all over again" nonsense, it isn't apollo if we plan to stay on the moon, it doesn't even remotely look like apollo. the key word is "stay". a permanent base means lots of resupplies, crew rotations, cargo delivery, and that is something NASA can't do alone if they want to concentrate on other missions. a 20 tons to LEO rocket can put rougly 3 tons of useful payload to the lunar surface, that is not bad at all and if altspace can send such rockets at their advertized price, it would make a rather affordable alternative to support a lunar base. same thing for mars

as mentionned before SSTO is a holy grail, it doesn't mean it's impossible, but a long way off. even if you could build one (which might be possible today with a real effort) it would probably not have any payload, or a ridiculous one on the order of a thousand lbs at the most, and there is not much advances we will be able to make  to substantially increase that payload. air breathing combined cycle engines look great but they have their limitations too and non negligeable weight penalty.
Title: Re: SSTO Thread
Post by: modavis on 09/10/2006 01:28 am

Quote
mong' - 9/9/2006  7:17 PM we can't do much in earth orbit, there is nothing there, the real destination are the planets.

If you can get to orbit at 10% or 20% of current $/kg, then you can get to the the planets (or the moon) that much cheaper -- or send 5x or 10x as much for the same price, take your pick.

If you can work in orbit (a lot more extensively and efficiently than we currently do), you can assemble your planetary missions out of smaller modules (fostering higher flight rates, another good thing in itself) and avoid the need for new heavy launchers. We didn't build Saturn V because it was cost-effective or sustainable; we built it because we were in a big hurry, had mastered only the rudiments of rendezvous and docking with Gemini, and wanted to keep orbital "assembly" activity to a minimum.

If you can make money in orbit, you can start the process of changing all activity there and beyond from rare, tax-funded extravaganzas to self-sustaining routine.

Sorry, mong' -- I want a permanent moon base and manned planetary exploration as much as you do. But if we do them in a way highly optimized for a specific "destination" or "mission" (and we usually do... notice how Zubrin's beloved methane got dropped from ESAS?), that does nothing towards reducing the cost to orbit. OTOH, reducing the cost to orbit -- difficult and frustrating as it is -- makes everything else easier from then on.

The chant of "all we've done for 30 years is go in circles" makes me want to tear my hair out. What we should regret is not that in itself, but that the cost of getting to those circles has stayed so flat over 30 years. For today and some time to come, the most important lesson to be drawn from "LEO is halfway to anywhere" is not "Been there, done that, let's move on"...

But "As long as it costs you thousands per pound to get halfway, you won't get 'anywhere' very often."
 

Title: Re: SSTO Thread
Post by: MKremer on 09/10/2006 06:23 am
Remember a lot of the old images about NASA's future - lots of spacesuited figures floating around, busily working to assemble stations and interplanetary vehicles out of parts. How little they knew back then.

I can comprehend 2 or 3 larger modules (plus one of more crew modules, in addition) to be mated to create an interplanetary ship, but I can't see any benefit in using lots of smaller pieces/modules to create something similar. Reason is, the more dockings/ interconnects done in orbit, the more chance for "unexplained anamolies" to crop up, IMO. That includes electrical and gas/fluid. Unless you plan for lots of extra EVAs (similar to EVAs needed for manual ISS connections after installing a module), in which case those old Bonestell paintings will come to life, the larger the integrated/tested module you can launch at once, the better the effeciency and reliability for hardware on an interplanetary journey.
Title: Re: SSTO Thread
Post by: modavis on 09/10/2006 11:08 am

Quote
MKremer - 10/9/2006  2:10 AM
...I can't see any benefit in using lots of smaller pieces/modules to create something similar. Reason is, the more dockings/ interconnects done in orbit, the more chance for "unexplained anamolies" to crop up, IMO...

Correct for now and for some time to come... but I interpret that as the way we have to work until we get good at space activity -- not as a way of working that's intrinsic to space, and which should drive architecture forever. The minimum-number-of-big-pieces approach has real costs in dollars and flexibility, and sooner or later we need to move away from it. I do understand how hard and limited EVA is, at least as well as I can without having done it (damn it.  :) ) But again, to me that means we should work toward better space suits rather than enshrine "minimum EVA" as a permanent principle.

Like all engineering, space is full of trade-offs we need to recognize and live with. But we should also keep in mind the long-term direction in which we want to shift the balance.  

Title: Re: SSTO Thread
Post by: lmike on 09/10/2006 11:17 am
Quote
MKremer - 9/9/2006  11:10 PM

Remember a lot of the old images about NASA's future - lots of spacesuited figures floating around, busily working to assemble stations and interplanetary vehicles out of parts. How little they knew back then.

I can comprehend 2 or 3 larger modules (plus one of more crew modules, in addition) to be mated to create an interplanetary ship, but I can't see any benefit in using lots of smaller pieces/modules to create something similar. Reason is, the more dockings/ interconnects done in orbit, the more chance for "unexplained anamolies" to crop up, IMO. That includes electrical and gas/fluid. Unless you plan for lots of extra EVAs (similar to EVAs needed for manual ISS connections after installing a module), in which case those old Bonestell paintings will come to life, the larger the integrated/tested module you can launch at once, the better the effeciency and reliability for hardware on an interplanetary journey.

There is always a (hard) limit to what we can launch in one piece.  On the contrary, we must create an architecture where small pieces form a larger piece that satisfies the mission.  If we succeed at that (and we can, given the current technology and physics understanding) we are home free to do whatever we please in space.  Arbitrarily.
Title: Re: SSTO Thread
Post by: mong' on 09/10/2006 11:18 am
It's a chicken and egg problem, modavis "if you can get to orbit at 10% or 20% of current $/kg", that's the problem, we won't be able to reduce the launch costs a factor of 10 unless there is a *massive* flight rate and nothing there is to do in LEO can justify that.
the assembly of very large space stations is a relic of the 50's back when large orbital facilities with hundreds of people were deemed necessary to operate and repair satellites, modern day electronics has invalidated that need.
today the science missions performed in the ISS could probably be done with individual modules individually launched, it would probably be cheaper than the ISS program (and also slightly increase flight rates by the way).

and yes I want to see reduced launch costs too, even to the point where I can buy a ticket (I would willingly sell a couple of kidneys for that) but I realize that it simply *won't* come until we have established a sustained presence somewhere in space, and the best place for that are the planets.
a base on the moon and mars will need *lots* of flights to support it (resupply, crew rotations, ...) and THIS will justify the high flight rates that bring costs down, THIS is where the private sector takes over and compete for the lowest costs, THIS is where space becomes affordable.

the harware used by NASA is irrelevent because it is only there to establish the presence at the destination, they won't be able to use it to support their bases and that is a good thing, because it means they will NEED a cheaper alternative, thus providing the badly needed flight rates to make RLV's viable and even profitable, then we will be able to talk SSTO
Title: Re: SSTO Thread
Post by: modavis on 09/10/2006 11:48 am

Quote
mong' - 10/9/2006  7:05 AM  It's a chicken and egg problem, modavis

1000% agreement. Space is full of 'em  :(

Quote
 the harware used by NASA is irrelevent because it is only there to establish the presence at the destination, they won't be able to use it to support their bases and that is a good thing, because it means they will NEED a cheaper alternative...

I wish I could share your optimism that the response to that situation would be "OK, the base is there so we have to find a way to support it"... rather than "Whoa, we just noticed how expensive supporting the base will be. Bad idea, shut it down."

Title: Re: SSTO Thread
Post by: meiza on 09/10/2006 12:07 pm
One thing that is interesting now are new startups like XCor and Armadillo Aerospace among numerous others (some even in Asia and Europe) that are trying to develop reusable, reliable, easily and cheaply operated liquid rocket engines and vehicles. Maybe something useful will come out of that and it will lower the cost of access to space tenfold or even more. Of course, they are demonstrating very small steps, but building and operating hardware nevertheless. They're not megaprograms using billions of dollars, or stunts using throwaway motors, but multiple approaches to really operable stuff. Maybe some of them will succeed. I follow the spacetransportnews.com website with interest. The mentality there is often to sacrifice some performance for other factors, like safety, price or ease of operation.
Title: Re: SSTO Thread
Post by: lmike on 09/10/2006 12:18 pm
Quote
meiza - 10/9/2006  4:54 AM

One thing that is interesting now are new startups like XCor and Armadillo Aerospace among numerous others (some even in Asia and Europe) that are trying to develop reusable, reliable, easily and cheaply operated liquid rocket engines and vehicles. Maybe something useful will come out of that and it will lower the cost of access to space tenfold or even more. Of course, they are demonstrating very small steps, but building and operating hardware nevertheless. They're not megaprograms using billions of dollars, or stunts using throwaway motors, but multiple approaches to really operable stuff. Maybe some of them will succeed. I follow the spacetransportnews.com website with interest. The mentality there is often to sacrifice some performance for other factors, like safety, price or ease of operation.

This is a good point.  However, "reusable SSTO" is not what they aim for.  "Cheaper access to LEO" is what they aim for.  Implementation and goal.  My whole contention was that the "reusable SSTO" as a savior is incorrect a question as posed.  It's possible it could "save us", but not a requirement.
Title: Re: SSTO Thread
Post by: meiza on 09/10/2006 05:47 pm
I agree exactly, lmike.
Title: Re: SSTO Thread
Post by: MartianBase on 09/11/2006 01:00 am
Quote
Jim - 22/8/2006  5:57 AM

 Reusable SSTO is not the future of LV's because is unattainable.  

Frankly I find the idea of Single Stage to Orbit as being ridiculous
or a case pushed forward by many people who watch too much BuckRogers cartoons or george lucas movies.

The X-33 venture-star and  X-34 might have made some fancy and expensive graphics presentations but that's all they would ever be, SSTO is beyond our current technology

Forget about Sticking a Nuke-Engine on the rear because not only does it break a heap of international laws and break that Nuke treaty - perhaps more importantly the US media and American public don't want to see a Chernobyl come crashing down on their heads,
 it was difficult enough for NASA to get Cassini's RTG unit into space without the enviromentalists jumping up and down.
Title: RE: SSTO Thread
Post by: vt_hokie on 09/11/2006 05:10 am
What about fully reuseable TSTO?
Title: Re: SSTO Thread
Post by: soldeed on 09/11/2006 06:33 am
Everyone wants to see the 2001 space odessy space clipper, and It'll be here someday, but we need a few breakthroughs in propulsion technology before we get there. And thats the only application a reusable winged orbiter is good for; ferrying people, or medium pressurised cargo to and from LEO. Bulk cargo like habitats, and moon or mars ships will continue to rely on big dumb boosters for many years to come. What we got now; conventional chemical rockets, are good enough to get the exploration and colinization ball rolling.
Title: RE: SSTO Thread
Post by: modavis on 09/11/2006 05:26 pm

Quote
vt_hokie - 11/9/2006 12:57 AM What about fully reuseable TSTO?

Probably technically do-able, just possibly economically do-able. But it might well have to be done privately, along the lines of The Rocket Company:

http://www.amazon.com/Rocket-Company-General-Publication-S/dp/1563476967/sr=8-1/qid=1157992298/ref=pd_bbs_1/102-4289117-6520904?ie=UTF8&s=books

Why? Because to be technically do-able it's got to be a lot more modest in size and payload than the shuttle -- and for NASA to do that would seem a step backward and an admission that the shuttle (and NASP, and X-33) were "a bridge too far." They were, of course. But remember the flak that Griffin caught when he said -- quite accurately -- that STS had been "extremely ambitious and just barely possible"? Many space critics jumped straight from that to "NASA admits its blunder," while many shuttle fans were offended that he'd implied their beloved hangar queen was a mistake. Likewise, his reasonably accurate description of VSE/ESAS as "Apollo on steroids" has been turned into ammunition against it. One side says "been there, done that, why bother?" and the other says "been there, done that, gotta go to Mars."

One of the core lessons of STS is that ever since the fast pace of the moon race, it's hard for NASA to take the modest, incremental steps that are needed: if something isn't positioned as a breakthrough or order-of-magnitude improvement in X,Y,Z, it rarely gets off the ground. IMHO that's as much a failing of the public -- of Apollo-level expectations without Apollo-level funding -- as of the agency. If private enterprise makes progress on a fully reuseable TSTO, I'd say it will be less because private enterprise is inherently lean & smart than because they can do it in less of a spotlight, and work the tough trade space of engineering x economics rather than the even tougher trade space of engineering x politics.  

Title: Re: SSTO Thread
Post by: mauk2 on 09/11/2006 06:27 pm
modavis touches on an interesting point:

Apollo was a stunt.   A colossal and successful stunt, but still, just a stunt.  

It served its short-term purpose, but at a dire cost in public expectations.

We need to change our entire approach to space, and bluntly, I really don't think NASA has the wherewithal to do that.  Even more sadly, due to superstitious and outdated laws, innovation in this field is artificially squashed.

Until we change those laws, we are going to see little to no appeciable progress, barring some truly fundamantal breakthroughs.

And yes, such breakthroughs may happen, but they also may not.   How long are we willing to wait?
Title: Re: SSTO Thread
Post by: mauk2 on 09/11/2006 07:00 pm
Hiya, mlorrey! :)


Quote
This is the essential misinformation of the missileer. The problem is that this is merely a derivation of the rocket equation specifically for launchers that carry all of their own propellant.

LOL!  Erm, okay.  :)  I rather thought that that's what we were discussing.  


Quote
This is inapplicable to any launcher that does any air breathing at any stage of the launch, for the simple reason that oxygen combusted from air can't be counted as part of the mass fraction, but does impact the Isp, which blows the logarithm out of the water.

This is absolutely correct!  However, such air-breathing designs, as rightly pointed out, have their own huge issues, namely, drag, weight penalties due to complexity, and of course, complexity.

In a nutshell, the performance gains possible in excess of drag losses are, to date, so small as to be useless.  Worse, there are other consequences caused by operating at high speeds inside a working fluid, such as airframe loading and skin heating, to name a couple of doozies.  (If you have any links to sources of recent breakthroughs, I would certainly appreciate looking over that info.)   Now, is it possible that such issues could be overcome with enough furious engineering effort?

Perhaps.  I am not aware of any fundamental physical laws that bar air-breathing SSTO's from working, but such a design would be massively specialized and very narrowly focused.  (Supersonic combustion is non-trivial.)  More importantly, we need high Isp systems outside the atmosphere just as badly as we need them inside the atmosphere.  Why expend all this effort on such a narrowly useful design?  We're not looking at a perpetual jobs program for rocket scientists, we want a usable method to get out of the cradle.  :)

We don't need a massively engineered and narrowly focused design.  We need a robust, flexible, non-stressed system.  We need the SSTO analog of the WW2 Liberty Ships.

Just because it might be possible, with extraordinary effort, to avoid the "N" word doesn't make it smart.  That same amount of engineering effort expended on high energy propellants will gain us far more results that are applicable in a far wider range of scenarios.  :)
Title: Re: SSTO Thread
Post by: SonicAgamemnon on 09/20/2006 05:59 pm
Hey, I'm not alone!  This is from another public forum discussing the need for SSTO, a better shuttle:

"Frankly, Bush's new strategy for space, like virtually all of his other strategies, is completely wrong.  Look, serious exploration of space requires complete systems of expoloration vehicles.  Bush's 'Apollo' concept, going directly from Earth to the moon is a big step backwards.  The previous NASA strategy of using the shuttle for earth-to-orbit, the ISS for orbital research and space-based construction of interplanetary vehicles is correct.  But like any system, it's as strong as it's weakest link.  We need to fill out the existing systembased on the ISS by creating a reusable earth-moon transport vehicle that can be reprovisioned in orbit at the ISS.  It would move components for a lunar orbital platform (probably usually unmanned), lunar landers, and lunar base to lunar orbit.  Etc.

It seems clear that YES, the shuttle needs to be redesigned.  I think we would be better served taking everything we learned in the shuttle program and applying it to a redesigned Shuttle 2.  This would fill the gap until a space plane of some sort is eventually developed.  YES, we also need a heavy-lift vehicle, something that can get the components of a lunar base into orbit.  Transportation is based on SYSTEMS.  The new NASA apollo approach is laughable.  When is the last time you took an airplane from your house to your vacation hotel and back, just to throw it away?  No, you use your car to drive to the airport, plane to another airport, then a bus or car to the hotel.  In space the car is the shuttle, the airport is the ISS, the plane is a reusable point-to-point space vehicle, etc etc etc.

If we cannot see this we will give our advantage to other nations.  We have invested so much, and only needs another 25% to complete the system to a point where we can leverage it's strengths...  Other nations will see this and simply lift everything we learned and graft it onto their space program but with a proper strategy and will win in space.

What a shame.  Bush and NASA are ruining america in every way possible."

I agree with him 100 percent...
Title: Re: SSTO Thread
Post by: Jim on 09/20/2006 06:05 pm
wrong.   SSTO doesn't work.  RLV are more expensive for low flight rates
Title: Re: SSTO Thread
Post by: mong' on 09/20/2006 06:43 pm
how original, another piece of NASA/Bush hating.
this guy, whoever he is clearly does not understand the complexity of spacecraft design/operation and the budget constraints of NASA. "let's just build an entirely reusable lunar architecture instead of an expendable one !" that's some genius thinking....

"We have invested so much, and only needs another 25% to complete the system to a point where we can leverage it's strengths..."
 right.....

"We need to fill out the existing systembased on the ISS by creating a reusable earth-moon transport vehicle that can be reprovisioned in orbit at the ISS"
except it's not in the right orbit, It will soon reach its maximum design life, and is not a refueling station.
Title: Re: SSTO Thread
Post by: Seattle Dave on 09/20/2006 08:29 pm
Quote
mong' - 20/9/2006  1:26 PM

how original, another piece of NASA/Bush hating

Liberals are scratched records.
Title: RE: SSTO Thread
Post by: vt_hokie on 09/20/2006 08:44 pm
This exchange has the potential to get ugly in a hurry.  Let's not go down that road.
Title: Re: SSTO Thread
Post by: josh_simonson on 09/20/2006 09:46 pm

Educated folks tune out when they see a logical fallacy such as the ad hominem above used in an argument...  

 

The way I see it is that Aries V IS shuttle 2.  STS is a couple times over the  least cost effective launch system in existance ($13,300/lb @6/yr).   80% of the orbited mass of the STS is useless junk if it's job is simply to deliver something into orbit.  Aries V replaces that junk with useful payload and - miracle of miracles - suddenly it is 5 times more cost effective.  What other 'shuttle 2' plan can provide a 5x price performance increase over STS?  If you go to an orbiter that has a 50% payload, that requires the unit launch costs to fall 10X to compete with Aries V.  I just can't see that happening.

STS only costs $2600/lb to orbit if you count the entire spacecraft, the problem is that most of it is useless in space.  It's far easier to cut that junk out entirely than cut it's price by an order of magnitude.

Title: RE: SSTO Thread
Post by: vt_hokie on 09/20/2006 10:41 pm
I think Ares V is a good idea, but I'd love to see a small reusable space plane for crew transport.  Let's say for the sake of argument that Blackstar does exist.  Could such an air launched system possibly cost as much to operate as the Ares 1/Orion vehicle?  Maybe it would - I don't know.  I would guess not, however, and it would provide more of a launch on demand capability than a vehicle that relies on lengthy conventional launch vehicle preparations.
Title: Re: SSTO Thread
Post by: mong' on 09/20/2006 10:54 pm
an RLV will always cost more (in fixed costs) than an EELV of the same payload class, the RLV compensate for the higher fixed costs with higher flight rates
Title: Re: SSTO Thread
Post by: vt_hokie on 09/20/2006 11:07 pm
Quote
mong' - 20/9/2006  6:37 PM

an RLV will always cost more (in fixed costs) than an EELV of the same payload class, the RLV compensate for the higher fixed costs with higher flight rates

Why is that?  How could throwing away 5 expensive SSME's or RS-68's with every Ares V flight, not to mention all of the avionics and other complex hardware, possibly be cheaper than developing reusable launch vehicle technology?  

When it comes to fixed costs, a lot of that seems to be related to launch vehicle preparation and launch pad support.  A runway based vehicle would cut a lot of that, no?  (Granted, you won't get heavy lift capability with present technology from a "space plane" but for crew transport functions, well, a small reusable space plane seems logical.)
Title: Re: SSTO Thread
Post by: mong' on 09/20/2006 11:30 pm
yes it could but It would be extremely difficult. we can in principle build an entirely reusable TSTO to carry small payloads to LEO, but not much than a few tons, taking off horizontally would increase the deltaV needed. not to mention the need to reinforce the landing gear to be able to stand the 500 to 600 tons gross mass (at least), the landing gear is already quite a heavy part.
and you still need most of the infrastrucure to service your LV at the runway anyway.

an RLV has high fixed costs because of the servicing it requires after and before each flights; a lot of man hours, specialized infrastructure, even spare parts built on demand. all of this is horrendously expensive, to compensate for that the RLV needs to fly a lot, and there is not currently the need for such flight rates.

and yes you can probably operate a TSTO spaceplane RLV for the price of Ares V (maybe even for slightly less), but it won't give you anywhere near the heavy lift capability of the Ares. it's all about what we need first. for now we need heavy lifting, Ares does that. after that an RLV might be judged useful to support our activities beyond LEO
Title: Re: SSTO Thread
Post by: vt_hokie on 09/20/2006 11:50 pm
Quote
mong' - 20/9/2006  7:13 PM

and yes you can probably operate a TSTO spaceplane RLV for the price of Ares V (maybe even for slightly less), but it won't give you anywhere near the heavy lift capability of the Ares.

Well yeah, I realize that.  I will concede that for heavy lift, RLV technology just isn't there yet.  But would you say that a TSTO reusable space plane could be operated for less than Ares I and the Orion capsule?

Title: Re: SSTO Thread
Post by: Jim on 09/21/2006 12:02 am
Quote
vt_hokie - 20/9/2006  7:33 PM

Quote
mong' - 20/9/2006  7:13 PM

and yes you can probably operate a TSTO spaceplane RLV for the price of Ares V (maybe even for slightly less), but it won't give you anywhere near the heavy lift capability of the Ares.

Well yeah, I realize that.  I will concede that for heavy lift, RLV technology just isn't there yet.  But would you say that a TSTO reusable space plane could be operated for less than Ares I and the Orion capsule?


Not for 4 flights a year.  As stated in other threads, it takes 40-60 flights a year
Title: Re: SSTO Thread
Post by: vt_hokie on 09/21/2006 12:10 am
Quote
Jim - 20/9/2006  7:45 PM

Not for 4 flights a year.  As stated in other threads, it takes 40-60 flights a year

I'm skeptical of that number.  Orion will be mighty expensive to operate with those 4 flights per year.  You don't think RLV technology could enable, say, 12 flights per year for the same cost?  We're not talking profitability here - just the amount of flights we can get out of NASA's fixed operating budget.  Taking the alleged Blackstar again, how much refurbishment could there be between flights to equal the cost of an entirely new Ares I launch vehicle and Orion capsule?
Title: Re: SSTO Thread
Post by: Jim on 09/21/2006 12:21 am
It has appeared and reappeared in every study.  The DDTE costs of an RLV are enormous.   Also most of the cost in launch ops is labor and RLV uses more
Title: Re: SSTO Thread
Post by: HailColumbia on 09/21/2006 01:03 am
Quote
vt_hokie - 20/9/2006  7:53 PM


I'm skeptical of that number.  Orion will be mighty expensive to operate with those 4 flights per year.  You don't think RLV technology could enable, say, 12 flights per year for the same cost?  We're not talking profitability here - just the amount of flights we can get out of NASA's fixed operating budget.  Taking the alleged Blackstar again, how much refurbishment could there be between flights to equal the cost of an entirely new Ares I launch vehicle and Orion capsule?

gaaaaa. you always do this. its not apples to apples. Differant missions. Orion goes to the moon, your imaginary SSTO spaceplane that runs on magic beans does not.  

Let's assume blackstar is real, it dosent meet any of NASA's goals.  Maybe we would save some money, but we would be no closer to the moon.
Title: RE: SSTO Thread
Post by: vt_hokie on 09/21/2006 01:06 am
mmmmm....magic beans....

Well, let's forget about the lunar flights and just stick with ISS missions for now.  I'm just trying to wrap my head around the idea that manufacturing an entirely new launch vehicle and a new Orion capsule for each flight will be cheaper than refurbishing and turning around a small reusable space plane.  Intuitively, that just seems hard to believe.
Title: Re: SSTO Thread
Post by: Jim on 09/21/2006 01:07 am
The capsule may be reusable
Title: RE: SSTO Thread
Post by: Jim on 09/21/2006 01:08 am
Quote
vt_hokie - 20/9/2006  8:49 PM

mmmmm....magic beans....

Well, let's forget about the lunar flights and just stick with ISS missions for now.  I'm just trying to wrap my head around the idea that manufacturing an entirely new launch vehicle and a new Orion capsule for each flight will be cheaper than refurbishing and turning around a small reusable space plane.  Intuitively, that just seems hard to believe.

Problem is there is nothing small about a vehicle that can carry 4-6 crew
Title: RE: SSTO Thread
Post by: HailColumbia on 09/21/2006 01:11 am
Quote
vt_hokie - 20/9/2006  8:49 PM

mmmmm....magic beans....

Well, let's forget about the lunar flights and just stick with ISS missions for now.  I'm just trying to wrap my head around the idea that manufacturing an entirely new launch vehicle and a new Orion capsule for each flight will be cheaper than refurbishing and turning around a small reusable space plane.  Intuitively, that just seems hard to believe.

Maybe it's not, but Orion will be making very few trips to ISS. DEVELOPING your RLV will cost more then all of the orion ISS flights. It will be cheap because the spacecraft will already exist and jsut happens to have the capability. we dont need to develop an RLV for what? 10 total flights?
Title: Re: SSTO Thread
Post by: modavis on 09/21/2006 01:12 am

Quote
Jim - 20/9/2006  8:04 PM  It has appeared and reappeared in every study.  The DDTE costs of an RLV are enormous.   Also most of the cost in launch ops is labor and RLV uses more

Agreed on the DDTE costs -- I have no trouble believing some black-budget billions may have gone toward a Blackstar, but I have a very hard time believing there was enough to make it work.

But the Shuttle, X-15, DC-X and Spaceship One all together don't give nearly enough data points to speak with confidence about orbital RLV ops costs either way. Me, I think the longed-for "aircraft-like operations" are more a product of experience (= lot$ of flights over lot$ of time) than of technology and design, but I'd give a Scots verdict of "not proven" for now.      

Title: RE: SSTO Thread
Post by: vt_hokie on 09/21/2006 01:25 am
Quote
HailColumbia - 20/9/2006  8:54 PM

Maybe it's not, but Orion will be making very few trips to ISS. DEVELOPING your RLV will cost more then all of the orion ISS flights. It will be cheap because the spacecraft will already exist and jsut happens to have the capability. we dont need to develop an RLV for what? 10 total flights?

So, are we done with research in LEO forever after 2016?  Our manned space program will consist solely of low frequency excursions to the moon?  It would seem odd to abandon LEO ops altogether, but I guess that's what this Apollo-rehash calls for.
Title: RE: SSTO Thread
Post by: vt_hokie on 09/21/2006 01:28 am
Quote
Jim - 20/9/2006  8:51 PM

Problem is there is nothing small about a vehicle that can carry 4-6 crew

How about a 2-3 person crew?  A modern Soyuz class vehicle, I suppose you could say.
Title: RE: SSTO Thread
Post by: HailColumbia on 09/21/2006 01:46 am
Quote
vt_hokie - 20/9/2006  9:08 PM

Quote
HailColumbia - 20/9/2006  8:54 PM

Maybe it's not, but Orion will be making very few trips to ISS. DEVELOPING your RLV will cost more then all of the orion ISS flights. It will be cheap because the spacecraft will already exist and jsut happens to have the capability. we dont need to develop an RLV for what? 10 total flights?

So, are we done with research in LEO forever after 2016?  Our manned space program will consist solely of low frequency excursions to the moon?  It would seem odd to abandon LEO ops altogether, but I guess that's what this Apollo-rehash calls for.

Nah, not rehash, we are finishing the job. Imagine if apollo never ended. Instead of sending the shuttle up on thrilling missions to study the effects of zero gravity on tiny screws, we would have been building bases on the moon. Imagine if we never lost the capability of the saturn V, I would bet that the first mission to mars would be a distant memory.
Title: RE: SSTO Thread
Post by: vt_hokie on 09/21/2006 01:55 am
Quote
HailColumbia - 20/9/2006  9:29 PM

Nah, not rehash, we are finishing the job. Imagine if apollo never ended. Instead of sending the shuttle up on thrilling missions to study the effects of zero gravity on tiny screws, we would have been building bases on the moon. Imagine if we never lost the capability of the saturn V, I would bet that the first mission to mars would be a distant memory.

We haven't even begun to tackle the radiation problem, or developed the capability of a self sustained spacecraft with no re-supply supporting humans for over a year.  I doubt we'd have made it to Mars by now.  

This nation should be able to afford a reusable LEO transportation system, and LEO space station, and lunar exploration.  Why must it always be either/or with NASA?
Title: Re: SSTO Thread
Post by: Jim on 09/21/2006 01:59 am
I worked all of the Spacehab missions.  The same experiments flew over and over and over.  Similar ones are on the ISS.  I have yet to hear of break thru.  LEO is just an rest stop
Title: RE: SSTO Thread
Post by: dbhyslop on 09/21/2006 02:00 am
Quote
vt_hokie - 20/9/2006  9:08 PM
So, are we done with research in LEO forever after 2016?  Our manned space program will consist solely of low frequency excursions to the moon?  It would seem odd to abandon LEO ops altogether, but I guess that's what this Apollo-rehash calls for.

A couple weeks ago on NASA TV I saw Jeffrey Williams tapping an acrylic cylinder repeatedly to see how bubbles move through gelatin in space.  Are we willing to give up this cutting edge research to explore another world?  The NAS thinks so and I agree.  The Apollo landings had a tremendous impact in earth and planetary sciences and quite literally only scratched the surface.  There's also an experiment on the ISS to see how long it takes allergens to accumulate in the station.  Did we decide to spend a hundred billion dollars to find out about the bubbles and the ragweed, or did we devise the bubbles and the ragweed to rationalize the cost?

LEO isn't being abandoned.  A private company is flying a prototype of a low-cost commercial space station module and two other companies have been given contracts to develop manned launchers.  Our wildest dream for NASA has been that it might be the trailblazer letting commercial interests get a foothold in every step out into space before itself moving further outward.  Now that's actually happening and we're complaining about it?

If the type of experiments being done on the ISS are that important, I'm sure they will continue after 2016 on private spacecraft.  I'm sure NASA will be able to rent a Bigelow module for a lot less than the ISS costs.

Dan
Title: RE: SSTO Thread
Post by: Jim on 09/21/2006 02:04 am
Quote
vt_hokie - 20/9/2006  9:38 PM
This nation should be able to afford a reusable LEO transportation system, and LEO space station, and lunar exploration.  Why must it always be either/or with NASA?

Just because we can "afford" it doesn't mean we need it.    It needs to cheap and it isn't yet
Title: RE: SSTO Thread
Post by: HailColumbia on 09/21/2006 02:06 am
Quote
vt_hokie - 20/9/2006  9:38 PM


We haven't even begun to tackle the radiation problem, or developed the capability of a self sustained spacecraft with no re-supply supporting humans for over a year.  I doubt we'd have made it to Mars by now.  
Of course we havent, the centerpiece of the space program has been the shuttle for 25 years, why develop these technologies if you are stranded in LEO? If we dident abandon the moon, we would have done it.

Quote
vt_hokie - 20/9/2006  9:38 PM
This nation should be able to afford a reusable LEO transportation system, and LEO space station, and lunar exploration.  Why must it always be either/or with NASA?

I totally agree with that statement, but for some reason, I do not dictate national policy, and NASA only gets 15 billion or so a year. The solution is simple I suggest you all elect me president. Under the HailColumbia administration,  NASA will get 250 billion a year, a fleet of RLVs, Lunar and Mars colonies, Space Station Freedom (with co-orbiting platforms of course), and a battlestar.

But until that happens, I suggest we stick with returning to the moon
Title: RE: SSTO Thread
Post by: modavis on 09/21/2006 02:38 am

Quote
Imagine if apollo never ended...  Imagine if we never lost the capability of the saturn V...

Imagine if everyone who posts here were actually 500,000 space-loving American voters forty years ago (or now, for that matter). What a wonderful world it would be.

Now, in the world we actually live in -- where grown-ups could see by 1967 that Apollo was going to wrap up, and whatever followed was going to be considerably less ambitious -- your point is..?

Title: Re: SSTO Thread
Post by: HailColumbia on 09/21/2006 03:06 am
I was just trying to point out that heavy lift is going to open the solar system back up, and hookie's RLV will not.
Title: RE: SSTO Thread
Post by: vt_hokie on 09/21/2006 03:10 am
I hope you're right.  We shall see.  I still hope to see a reusable space plane before I die, though!
Title: RE: SSTO Thread
Post by: Avron on 09/21/2006 04:05 am
Quote
vt_hokie - 20/9/2006  10:53 PM

I hope you're right.  We shall see.  I still hope to see a reusable space plane before I die, though!


There is one landing at KSC tomorrow...
Title: RE: SSTO Thread
Post by: vt_hokie on 09/21/2006 04:14 am
Quote
Avron - 20/9/2006  11:48 PM

There is one landing at KSC tomorrow...

Indeed!  I should've said another reusable space plane after the shuttle's retirement.  Hopefully RLV's won't be my generation's Apollo - something we tell our kids about which they may never see themselves.
Title: Re: SSTO Thread
Post by: mong' on 09/21/2006 11:43 am
RLV's are inevitable. we will see them at some point. my bet is right after we have setup lunar and martian permanent bases.
as I said in another post it's all about what comes first, well in this case it's HLV, but RLV's will be essential to settle the inner solar system
Title: Re: SSTO Thread
Post by: kraisee on 09/21/2006 03:17 pm
Yeah, I see RLV's as being a key component for crew launch.   Recovering all of the flight hardware after each mission will provide the very best environment to learn about the system's behaviour.

I don't think it's quite so necessary with Cargo-only flights, and given the vast costs involved in combining heavy lift and reusablility together, I'd prefer to spend the money on making a massive disposable booster system.   Something really simple, just vast - Nova-class - 500 tons to LEO ballpark.   Robust, simple, uncomplicated, not very high-tech, but powerful.   The ultimate 'big dumb booster' :)

But for the crew, I'd like a relatively small "space-plane" TSTO, able to launch about 10 people at a time, with travelling luggage.   I'd love to see something really "elegant" like the 2001 Pan Am Clipper or the X-24B.   I wouldn't like a butt-ugly concept like the X-24A though, unless it was considerably safer for some reason or other.

But an Apollo-style capsule is fine with me too.   I rather like the shape.

Ross.
Title: Re: SSTO Thread
Post by: mong' on 09/21/2006 04:09 pm
yes, crew transport is probably a good place to start using RLV's, we just need to have a place to send them at least 30 times a year.
and it might not be that complicated to think about reusability for heavy lifters. partial reusability at first like flyback boosters attached to the rocket's core, then the entire first stage, and eventually the rest. it makes a lot of sense to want to reuse the massive first stage an HLV requires, rather than the more simple upperstage which is basically a tank with a couple of engines.

for a fully Reusable HLV whose first stage is a lox/rp1 powered spaceplane with 5 RS84's. the second stage is a DC X like spacecraft powered by a LOX/LH2 reusable engine like the integrated powerhead demonstrator tested recently.
the stack's liftoff mass is approximately 2000 mT and with good mass ratios on the order of 1/8 for the first stage and 1/10 for the second stage (achievable with a DC X design) it should be able to deliver 70-75 mT to LEO. not bad for an RLV !

P.S: happy birthday Ross !
Title: Re: SSTO Thread
Post by: vt_hokie on 09/21/2006 04:16 pm
Quote
mong' - 21/9/2006  11:52 AM

yes, crew transport is probably a good place to start using RLV's, we just need to have a place to send them at least 30 times a year.

I thought that was the idea behind ISS.
Title: Re: SSTO Thread
Post by: josh_simonson on 09/21/2006 08:13 pm
I don't think LH2 is a good fuel for re-useable upper stages.  The surface area/fuel weight of the fuel tanks is too high to cover with a TPS.  X-33 didn't come close to 90% FF using state of the art design, a 90% FF upper stage would have to be bigger than X-33 to pull that off.  

Single stage to tether seems like the best bet for a cheap launch system to me.  It uses an easy version of SSTO and an easy version of the space elevator, and combines them.
Title: Re: SSTO Thread
Post by: meiza on 09/21/2006 08:45 pm
Quote
josh_simonson - 21/9/2006  8:56 PM
Single stage to tether seems like the best bet for a cheap launch system to me.  It uses an easy version of SSTO and an easy version of the space elevator, and combines them.

...and requires equatorial launch.
Title: Re: SSTO Thread
Post by: josh_simonson on 09/22/2006 11:46 pm
Actually it doesn't, the tether can be in any orbit since it doesn't have to be stationary relative to the ground.
Title: Re: SSTO Thread
Post by: meiza on 09/23/2006 12:56 am
Hmm, I'm not so familiar with tethers...  How do you electromagnetically accelerate it then? Seems to me the acceleration is always perpendicular to the north-south magnetic field lines and thus is in the equatorial direction or up or down from the planet's surface.
Title: Re: SSTO Thread
Post by: Dan Moser on 09/25/2006 11:45 pm
Hi, folks.  First-time poster here.

For nearly two decades I have been looking into the technical specifics of low-cost launch vehicles and space transportation systems, both as a student and professional:  multi-stage vs. SSTOs, RLVs vs. ELVs, hydrogen vs. hydrocarbon, turbopumps vs. pressure-fed, solids vs. liquids vs. hybrids, air-breathing vs. all rocket.  Here's a few general conclusions I have reached in this area:

1. Expendable vehicles are much cheaper than reusables for low to moderate flight rates.. It's hard to justifiy the development expense of RLVs unless you have need to fly a space mission on nearly a daily basis.  For the foreseeable future, you're better off with an expendable vehicle with a reusable factory.

2. Expendable SSTOs are possible today, but are only practical with the following technologies: altitude compensating nozzles, composite structures, LOX/hydrogen or tripropellant (LOX with hydrogen and hydrocarbon fuels).  A pressure-fed SSTO cannot be achieved without high-performance composite tanks.

3. A reusable all-rocket SSTO could probably be made at great expense, but with nearly zero payload... so it's not worthwhile.  RLVs should have two or more stages.

5. Although lower-performing than multi-stage, SSTOs may be preferable for cost, reliability and range safety reasons because there are no staging events, and nothing is jettisoned into areas where it might endanger those on the surface.

6. Turbopump systems are very complicated and expensive.  A vehicle that is simple, cheap and reliable should be pressure-fed.  Composite tanks allow pressure-fed rockets to become practical, including expendable SSTOs.

7. An air-breathing engine is very heavy, and should not be hauled all the way to orbit.  However, using a jet aircraft as a reusable first stage is very practical and efficient.

8. Solids rockets are simple and work well, but are rather low performing.  Liquid rockets can have high performance, but can sometimes be troublesome.  Hybrids combine the troubles of liquids with the low performance of solids.

Visit my webpage if you'd like.... Happy landings

http://home.comcast.net/~compositex
Title: Re: SSTO Thread
Post by: David AF on 09/26/2006 12:32 am
Welcome to the site. You'll be right at home here.
Title: Re: SSTO Thread
Post by: mauk2 on 09/26/2006 01:16 am
Hiya Dan!  

Welcome to the site, I like the cut of your jib, you seem to have a solid foundation on ya. :D

Your comments on pressure fed designs resonates with many of my own feelings.  The turbopumps we have developed for our rocketry are marvels of engineering, but are just way, WAY too expensive, complex, and highly stressed to make me comfortable.

But, pressure fed tanks are HEAVY.  Even high specific strength materials only gain us so much.

Luckily, some very smart guys have recently puzzled out a "third way" which compromises between the performance of the turbopumps and the simplicity of the pressure tanks:

http://www.flometrics.com/rockets/rocket_pump/rocketpump.htm

I recommend a a quick looksee at the concepts at that site.  Inspired simplicity, if I may say so myself. :)

Combine such "pistonless pumps" with extreme low-cost relaxed designs like TRW's ablative pintle engine and we may knock some of the ridiculous costs out of rocketry.

http://www.st.northropgrumman.com/media/SiteFiles/_docs/propulsion/092500_low_cost_engine.pdf

http://spaceflightnow.com/news/n0009/26trwpintle/


Sadly, we are still left with the low Isp of chemicals, but ehn, my feelings on that topic are likely well-known. :D

Title: Re: SSTO Thread
Post by: mlorrey on 09/26/2006 06:18 am
One minor quibble on point 7: An air breathing RBCC hydrocarbon engine has a T/W of at least that of an LH2 rocket engine, with much higher average Isp, and less complexity. Air breathing hydrogen engines are a waste of time no matter where you are flying.

On point 1: break even for SSTO RLV is a sortie rate of weekly, not daily, though if you are only going to build one of them, don't waste your money on a one off. For twice the money you can have ten, for ten times the money you can have a hundred vehicles in operation.

Also, I'd add point 9: if you are going to build an SSTO or TSTO RLV, do it right the first time: build hot structures with integral TPS. Don't build a brickyard over an aluminum airframe.
Title: Re: SSTO Thread
Post by: Dan Moser on 09/26/2006 07:25 am
Thanks for the welcome.  

I am very familiar the pintle injector and the flometrics pump concept.   I'm actually not anti-pump, but doing pump designs properly, that is, cheap, lightweight, efficient, and reliable... is a very tall order.  I have not seen all of the necessary data to assess if flometric pumps make sense... and I'm not about to slam them or praise them without that data.  As with any rocket component, you have to run pump design options through validated cost-perfromance models and conduct a thorough build-test-rebuild-retest effort before you know if it's a good idea or not.  I assume flometrics has that effort well underway, and I wish them well.

On mauk2's comment that "pressure fed tanks are HEAVY. Even high specific strength materials only gain us so much." Note that high-performance filament-wound composite tanks are typically one-fifth of the weight of the very lightest metal tanks of equivalent pressure and volume... ONE-FIFTH!...  20%...  five times lighter...  however you say that, I say that's very signficant and it would be understating it to say it "only gains us so much."  In general, making the gross weight of a booster stage lighter by 1% is equivalent to gaining approximately 7 seconds of Isp.

On mlorrey's point on T/W of hydrocarbon RBCC vs. LH2 engines.. I don't disagree with that, though I do not which specific engines you are comparing.  Engine thrust/weight is one of those intermediate parameters, like propellant density, that does not mean much by itself.. .  Nobody will say that higher T/W and denser propellants are not better, but what is the real value of "better"?  To answer that, you have to roll up all of those intermediate parameters and components into a vehicle system which gets a certain payload up to a certain orbit for a certain dollar amount.  Pressure-fed rocket engines are often misjudged in Thrust/Weight because the tank and pressurization systems are sort-of part of the engine system, not just the injector-chamber, plus there is a scaling effect.  

All too often, I've seen critical launch vehicle design decisions made on the basis of beliefs and emotions.  Unprovable beliefs are rampant, such as: "higher Isp is always the answer", "RBCCs are the engines of the future", and "reusability is the only way to lower costs."  Believers do not feel a sense of having to prove their assertions to anyone.  They cherish their shiney visions of the ultimate rocketship, and all who disagree with them are considered enemies and rivals.  That's too bad because doing rockets successfully is hard enough as it is without vervent beliefs and emotions getting in the way of important facts.

Anyway, enough rambling.. be good!

Title: Re: SSTO Thread
Post by: vt_hokie on 09/27/2006 01:24 am
Quote
mlorrey - 26/9/2006  2:01 AM

Also, I'd add point 9: if you are going to build an SSTO or TSTO RLV, do it right the first time: build hot structures with integral TPS. Don't build a brickyard over an aluminum airframe.

Of all the technologies that were to be evaluated on the ill-fated X-33, the metallic TPS is one that I would think is worthy of continued development.
Title: Re: SSTO Thread
Post by: vt_hokie on 09/27/2006 01:30 am
Quote
Dan Moser - 26/9/2006  3:08 AM

All too often, I've seen critical launch vehicle design decisions made on the basis of beliefs and emotions.  Unprovable beliefs are rampant, such as: "higher Isp is always the answer", "RBCCs are the engines of the future", and "reusability is the only way to lower costs."  Believers do not feel a sense of having to prove their assertions to anyone.  They cherish their shiney visions of the ultimate rocketship, and all who disagree with them are considered enemies and rivals.  That's too bad because doing rockets successfully is hard enough as it is without vervent beliefs and emotions getting in the way of important facts.

You forgot the most important one!  Space planes look cool and sexy!   ;)

In all seriousness, what are your thoughts on the alleged "Blackstar" TSTO system?
Title: Re: SSTO Thread
Post by: mlorrey on 09/28/2006 12:48 am
Quote
Dan Moser - 26/9/2006  2:08 AM

  In general, making the gross weight of a booster stage lighter by 1% is equivalent to gaining approximately 7 seconds of Isp.

On mlorrey's point on T/W of hydrocarbon RBCC vs. LH2 engines.. I don't disagree with that, though I do not which specific engines you are comparing.  Engine thrust/weight is one of those intermediate parameters, like propellant density, that does not mean much by itself.. .  Nobody will say that higher T/W and denser propellants are not better, but what is the real value of "better"?  To answer that, you have to roll up all of those intermediate parameters and components into a vehicle system which gets a certain payload up to a certain orbit for a certain dollar amount.  Pressure-fed rocket engines are often misjudged in Thrust/Weight because the tank and pressurization systems are sort-of part of the engine system, not just the injector-chamber, plus there is a scaling effect.  

All too often, I've seen critical launch vehicle design decisions made on the basis of beliefs and emotions.  Unprovable beliefs are rampant, such as: "higher Isp is always the answer", "RBCCs are the engines of the future", and "reusability is the only way to lower costs."  Believers do not feel a sense of having to prove their assertions to anyone.  They cherish their shiney visions of the ultimate rocketship, and all who disagree with them are considered enemies and rivals.  That's too bad because doing rockets successfully is hard enough as it is without vervent beliefs and emotions getting in the way of important facts.

I was specifically talking about the hydrocarbon RBCC engines that were supposed to be built into the GTX test vehicle before the vehicle project was cancelled (not the LH2 model). The engines were fully tested in wind tunnels, fully simmed and verified through Navier Stokes analysis.

I completely agree that high Isp is not the be all/end all. I think an excessive focus on Isp is the hobgoblin of the LH2 fuel proponents, to the exclusion of things like fuel density and resulting structural size and mass. However, with hydrocarbon RBCC that isn't an issue: you've got the same T/W of LH2 engines, more than 3 times the average Isp of LH2 engines, with the small pump size, lower thermal regime, and small tankage size advantages of hydrocarbon fuelling, with the additional advantages of not needing anywhere near the same amount of LOX tankage as for a hydrocarbon rocket engine. Hydrocarbon RBCC should be a no-brainer as the evolutionary path to go.

I agree with you about composite tanks: its a fantastic improvement in technology.

But your dismissal of belief I think is excessively cynical, though it has its place (such as getting rid of the idea that environmentalism should override fuel decisions). Without a belief in what *could be*, one lacks the vision to see what will be, if only we have the courage of our convictions. A shining example is the growth of private space development and space tourism, a market that NASA dismissed and obstructed actively until recently.

Quote
As with any rocket component, you have to run pump design options through validated cost-perfromance models and conduct a thorough build-test-rebuild-retest effort before you know if it's a good idea or not.

I agree heartily. I think a major gripe some of us have is that our ideas about various RLV technologies are poo-pooed, dismissed, and diregarded based on certain embedded interests without allowing a test process of validating cost-performance models AND conducting THOROUGH build-test-rebuild-retest efforts of technologies like RBCC, SHARP, etc., and even when they are done, the results are disregarded in favor of embedded interests, whether they be certain contractors, or the self interest of maintaining the standing army of NASA people in the shuttle program that is the real financial 800 lb gorilla in the room that nobody wants to deal with, and even NASA administrators brag will not lose a single job over the VSE transition.
Title: Re: SSTO Thread
Post by: Dan Moser on 09/28/2006 06:59 am
mlorrey's comments on the RBCC engine were, I think, accurate.  My original point was essentially that an airbreathing engine shouldn't be hauled all the way to orbit as part of a space launch architecture, not that such an engine has no value. I think RBCCs as a general class of engines, show great promise in a reusable first stage application, but it will happen only if there is financial justification for development cost of that stage.  

Perhaps I was excessively cynical about beliefs, but it has been discouraging for me to see stuborn beliefs and idealistic visions get in the way of good engineering and financial decisions on launch vehicles.  In particular, people in powerful management positions with strong egos will often bully through their own stupid fantasy spaceship ideas at the expense of funding more financially sensible and technically viable approaches. Nobody has all the necessary facts to make easy no-brainer decision on launch vehicle options, so it does sometimes become necessary to rely on beliefs to some degree.  

mlorrey's point about NASA's decisions being overly swayed by job preservation is right on.  The unimaginative Aries I and Aries V vehicles are being politically sold as a jobs preservation tools in the post-shuttle world... and that's distasteful.  It smells like those needless government jobs in socialist countries, and it is painful to see that going on in our (supposedly) free market economy.  Still, I give credit to Griffin for coming up with a reasonable compromise to obtain better manned exploration systems within the imposed constraints of schedules and budgets.  The new vehicles are far from ideal, but ... you gotta admit... they are a helluva lot less stupid than the shuttle.  

On the Darkstar TSTO, I'm not that familiar with its details, but I do know of some similar proposed systems, such as launching a single stage to orbit from a supersonic aircraft platform, like a B-1 bomber.  That's doable, and it makes some financial sense in the near term to use an existing aircraft that can be easily adapted to a launch platform role, rather than starting with a clean sheet.   AirLaunch LLC, one of my customers, is planning to use an essentially unmodified  C-17 as a launch platform.  Aside from the small performance gains from the aircraft speed and altitude "head start", the main advantage is getting away from launch range headaches & expenses, which are at least $1.5M regardless of the launch vehicle size.

Title: Re: SSTO Thread
Post by: mauk2 on 09/28/2006 10:12 am

Hrrrrm.

Allow me to clarify my stance.  :)

The issue with SSTO (and all rocketry, for that matter) is energy available.  Isp is a handy shortcut to address this, but Isp is NOT the end-all, be-all of the design goal, energy is.

For example, switching from H2 to H2O CRUSHES your Isp at a given energy level.  But, if we have access to enough energy on the vehicle, you can regain that loss through sheer brute force.  Chemical fuels do not have that power.  Not today, and probably not ever.  A potential system that I happen to like is a positron (antimatter) fueled design using plain old water as reaction mass.  With our current materials tech, such a design would be a real nice performer.

I have said it before, and I will say it again: We need high energy propellants to make an SSTO work in the real world.  Period, end of discussion.  Sorry if that irritates people, but facts is facts.  If you want to avoid the "N" word, work on beamed energy solutions, because classic rocketry on chemical fuels are never gonna work.

So, the accurate fact that 1 percent of Gross Weight is the equal of around 7 seconds is barely relevant, because 7 seconds is such a tiny increase compared to what we need to make such vessels workable.   If we switch from low energy propellants to an easily constructable higher energy alternative that gains us 500 seconds or 1000 seconds or ideally, 2000+ seconds, NOW we approach a workable system.

All the hangups about airbreathing, and fear over the "N" word, and all the rest of the sacred cows out there, are impeding us.  There is no feasible way to make a real-world-useful SSTO when it takes 90+ percent of your GLOW in nothing but props.  Until we accept this, we are not going to make any significant progress toward workable "spaceships."  The Space Shuttle and the X-33 program were painful lessons on this.

This is an issue in the fundamental physics of the problem.  No amount of engineering effort will make that better.  

Sorry.

That said, Dan Moser's comments about NASA make me cringe.    

What we need to do is open access to high energy systems to the private sector, and allow the rush and boil of the market take care of this.  Until we do so, we're not getting anywhere.
Title: Re: SSTO Thread
Post by: mlorrey on 09/28/2006 05:38 pm
Well, Mauk, you've got a paradox: any time you are talking nuclear, that means DOE or military control, particularly given the present geopolitical situation. Getting costs down is dependent on getting it OUT of government control.

I'm glad Dan brought up Airlaunch. I was just rereading their trade study the other day. They've got a 2,000 lb payload capability for a $5 million launch price tag. Thats enough payload for a one man capsule, for instance, at a price 1/4th that charged by the rock-bottom Soyuz.

As for Isp: actually, getting average trip Isp above 500 seconds is all that is really needed to make a viable SSTO. Look at this chart of Isp:mass fraction. At 500 seconds, you only need a mass fraction of 0.78. Entirely possible without extreme airframe engineering. Various RBCC designs have average trip Isp of 1000-1500 seconds, which brings mass fraction requirements down into the range of normal aircraft.

The simple fact is that absolutely nobody but a Stalinist government is going to get away with forcing through a nuclear powered launch system. I don't like it, but you see how much the moonbats protest over sending troops overseas, they will froth with terroristic rage if anybody tries to build a nuke launcher. Your security costs alone will outweigh everything else.
Title: Re: SSTO Thread
Post by: Jim on 09/28/2006 05:51 pm
Quote
mlorrey - 28/9/2006  1:21 PM
I'm glad Dan brought up Airlaunch. I was just rereading their trade study the other day. They've got a 2,000 lb payload capability for a $5 million launch price tag. Thats enough payload for a one man capsule, for instance, at a price 1/4th that charged by the rock-bottom Soyuz.

You only get the rocket for $5m.  No adapter, no electrical umbilicals, no integration services.  Just the hardware, which is useless without the others
Title: Re: SSTO Thread
Post by: josh_simonson on 09/28/2006 06:33 pm
You also need a spacecraft to ride in and a destination to go to.  Neither of those are free.

That $5m comes out to $2500/lb - exactly the cost of soyuz launches.
Title: Re: SSTO Thread
Post by: Dan Moser on 09/28/2006 07:54 pm
Questions for mauk2:

Specifically, which "high energy materials" are you referring to? Antimatter? And who is denying access to the private sector?  

I gather from your comments that a 90% propellant mass fraction for a LOX/LH2 SSTO seems to be a disgustingly bad number to you, but if your propulsion dry mass fraction is only 5% (definitely doable), then that leaves 5% of the mass for payload.  That may not sound like much, but it's better than just about all currently operational launch systems.

Anyway, the most important number you need to optimize is cost per unit mass of payload, and all the other numbers.. propellant mass fraction, Isp, tank volume,  drag coefficient, engine thrust-to-weight, propellant cost, energy density, specific strength, range costs, etc..  don't mean squat if they do not lead to a system that has lower cost per unit mass of payload.   High energy materials sound good, but maybe they will fall short far short of becoming an automatic, no brainer solution to high launch costs anytime soon.   If you have a system to achieve lower launch costs using high energy materials... GREAT!  Let's hear about it!  

happy landings

Dan
Title: Re: SSTO Thread
Post by: SteveMick on 09/28/2006 08:08 pm
Ad one of the "moonbats" who is opposed to our sending troops into a situation which the recent N.I.E. says is making us less safe, I would like to point out that proposing a nuclear thermal rocket to LOWER launch costs is consistent with a detachment from reality consistent with your support of random wars for corporate enrichment. BTW they are still looking for recruits so I urge you to join up if you beleive or just admit your hypocrisy and begin to deal with the real world.
Steve
"Reality has such a liberal bias" Stephen Colbert
Title: Re: SSTO Thread
Post by: Dobbins on 09/28/2006 09:00 pm
Can we leave the off topic political rants out?
Title: Re: SSTO Thread
Post by: SteveMick on 09/29/2006 03:35 pm
I assume you are responding to the mlorrey post and that it is just coincidence that your response came after mine since the "moonbats" reference came from there and I was merely responding to that.
 My scepticism over NTR being used to LOWER launch costs is of course non-political and based on the real world. Since you neither aknowledge this or respond to it in your post, you MUST have been responding to mlorrey. Well either that or its my veiwpoint that you find problemmatic.
Since that would indicate that you are uncomfortable with viewpoints that might oppose your own, but quite comfortable with those compatable with your own being expressed; and that in turn would make your post hypocritical; you must be responding to mlorrey belatedly. I think though you can understand why your post might be misinterpreted as itself political.
 Now do you have a reply to my on-point assertion that using nuclear tech to lower launch costs is questionable to say the least?
Steve
Title: Re: SSTO Thread
Post by: Dobbins on 09/29/2006 04:00 pm
I object to ANY non space related political views on a space forum, be they from the left or the right. I want as broad a base of public support for NASA as possible and you aren't going to get that if support for the agency becomes associated with the left or the right.

The only way I can see the war being topical is a discussion of war spending impacting NASA funding, as happened during the Viet Nam War.
Title: Re: SSTO Thread
Post by: Dan Moser on 10/01/2006 03:28 am
So, anyway.. backing away from devisive political stuff and back to the topic of SSTOs.  

An SSTO using "present day" all-rocket chemical propellant technology demands very high performance, which pretty much confines us to LOX/LH2 or LOX with a combination of LH2 and a hydrocarbon fuel..  AKA: tripropellant.  The higher density hydrocarbon fuels are useful in reducing tank volume (and therefore weight and aerodynamic drag), but in order to beneficially affect performance, they must be burned early in the ascent.  In other words, LOX/hydrocarbon is most effectively used for the initial boost, and LOX/hydrogen is most effective to finish the job of accelerating the craft to LEO velocity.  

An old professor of mine mentioned of the possibility of using powdered aluminum as a fuel to substitute for hydrocarbon in the tripropellant scheme.  In this case, the aluminum powder is stored at the bottom of the hydrogen tank, so it is burned early in the ascent along with some liquid hydrogen, then the hydrogen takes over as the sole fuel for the remainder of the ascent.  Has anyone else heard of such an arrangement?  I would imagine there are lots of practical problems with this... the injector holes clogging up with aluminum particles comes to mind...  but the concept may have some merit.

I'm about to do a trade study with ascent simulations using various tripropellant combinations.. so if anyone out there has done some similar work.. please let me know of your findings.  

Happy Landings!

Dan
Title: Re: SSTO Thread
Post by: lmike on 10/01/2006 10:42 am
re: tricomponents. What about the RD-701/704? An attempt at high ISP, hight thrust at sea level, large throttling capability, multi-altitude regimes. Kerosene, LH, and LOX. Not intended for an SSTO per say, but http://www.buran.ru/htm/rd-701.htm was suposed to be used for the air-launched MAKS TSTO scheme. The nozzles had dual expansion mode (via a movable nozzle extension). Fairly high ISP in the second mode (there were serveral variants on the nozzle and combustion cycle schemes, the double chamber is depicted in the photo) (this is from the MAKS air-launched TSTO) Pretty deep throttling capability (down to ~40%) A dozen of firings on a test stand had been done at some point before it went 'nowhere'. This has more on the engines: http://www.buran.ru/htm/40-3.htm (will need to use an online translator though) with some (interesting) analysis of the results (which do indicate improvement in mass fraction for 2-stage schemes at least) Pair that with an aerospike?

[edit] but in keeping with the theme, the *costs* vs. bipropellant engines are anybody's guess
Title: Re: SSTO Thread
Post by: TyMoore on 10/01/2006 04:08 pm
Well, I've looked at some tripropellant schemes before using powdered aluminum--but never powdered aluminum with liquid hydrogen as the carrier. The combination I briefly looked at was a suspension of aluminum dust in melted parafin. The slurry would have to be continuously 'stirred' to prevent the aluminum from settling out. This can be done by diverting some of the high pressure flow from a turbopump and directing it upward at the bottom of the tank--turbulance will stir the tank pretty well. But turbulance is what you want to avoid if the rocket is flying--big probelm there..

The other problem is pumping 'sludge'--it get's really difficult because viscosity of the resultant fluid isn't entirely understood: a proper suspension of ultrafine solids in a liquid will approximate a gel--but injecting this stuff into a combustion chamber?? I would imagine that you would have to use a pintile injector. I don't think you could use a traditional axial flow turbopump for pumping this stuff--it would almost have to be a centrifugal pump I'd think.

It's interesting to think of aluminum dust as a way to increase the bulk density of the fuels, but it requires completely different ways to pump, plumb, and inject these gel suspensions...I know that there has been some interesting research done on organometallic gel fuels before:

http://www.ingentaconnect.com/content/tandf/gcst/2006/00000178/00000006/art00008#search=%22aluminum%20gel%20fuels%22

Another interesting paper is available at:

http://aerodyne.technion.ac.il/~rocketw3/benny5.pdf#search=%22Thixotropic%20Effect%20of%20Inorganic%20Gel%20Fuels%20%22

Doing a general search for "gelled fuels" at the AIAA website returned dozens of papers on the subject which leads me to think that many people consider metallic suspension fuels to be promissing.

I hope this helps!
Title: Re: SSTO Thread
Post by: mauk2 on 10/01/2006 10:27 pm
Hello, mlorrey! :)

You state:  "Well, Mauk, you've got a paradox: any time you are talking nuclear, that means DOE or military control, particularly given the present geopolitical situation. Getting costs down is dependent on getting it OUT of government control."

While I completely agree with the "out of government control" part of this, I have to disagree with the "DOE or military control" part.  Indeed, there is a very strong precedent for a government agency which can give strong and effective REGULATION of nuclear materials without direct CONTROL of said materials, namely the NRC, the agency currently tasked with regulating (not running) the nations huge fleet of power reactors. (Among other things.)

http://www.nrc.gov/who-we-are.html

I can certainly see the NRC or a related agency overseeing such usage.   Indeed, a near-ideal situation in my opinion would be a NASA/NRC hybrid.  

As a note, you are presenting a false dilemma with such declarations.  Sadly, you are in very good company in such discussions, because discussions about the effective exploitation of space resources are rife with such false dilemmas.  False dilemma is a particularly insidious logical fallacy, and can be extremely difficult to detect or counter.  That said, the first step to overcoming these fallacies is to recognize that they exist, which is why I bring up the point.

http://www.cuyamaca.edu/bruce.thompson/Fallacies/dilemma.asp

I strive to avoid logical and factual errors when posting, but I have been known to succumb to such.    We're all human! :)


As for your posted chart, I have only one question: What is the DeltaV those mass fractions represent?  I am partial to 9700 m/sec for LEO, as that gets you a "real orbit" with a useful height and inclination, a real lifespan before reboosting, and a hefty allowance for real-world launch losses.  I strongly suspect that chart is using a "softer" number, that will technically allow for LEO operations, but is a trifle misleading.  

As for the ancillary issues of air-breathing combined cycle powerplants, I and others have already noted the problems therein.  :(

Further, I personally do not consider a vehicle with a fuel mass fraction of 78 percent to be highly viable.   I base this contention on reality, in that I am aware of no system that has ever been used in real-world conditions has had a fuel mass fraction nearly so miserable.  For example, what is the fuel mass fraction of a modern container ship?   More directly applicable, what is the fuel mass fraction of a large airliner, like the A-380?

Until we can achieve fuel mass fractions comparable to those numbers, space access will remain problematic.  Luckily, such fuel mass fractions are far from impossible, unlike what many of us have been often told.  There are simply challenges to be met. :)  I choose to remain optimistic.
Title: Re: SSTO Thread
Post by: meiza on 10/01/2006 10:46 pm
Use lox-kerosene monopropellant. Kerosene solidifies into white blobs at lox temps and the mix can be injected to a combustion chamber without the flame propagating back to the tank. John Wickman has studied it, material here: http://www.space-rockets.com/Loxmono.html

:-)
Title: Re: SSTO Thread
Post by: mauk2 on 10/02/2006 12:18 am
Hello, Dan! :)

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 Questions for mauk2:  

Oooh, I love quesrtions! :)


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Specifically, which "high energy materials" are you referring to?

I care not.  Anything which will grant us LARGE increases in specific energy.  Zip fuels, while fun, are not gonna make enough difference to make any real difference.  Neither are any "standard" chemical fuels, not even such highly speculative mixtures like nano-fine lithium and liquid hydrogen.  Metastable chemicals like various cubane mixtures, nitrogen fullerenes, ozone oxidizers, and the holy grails, monatomic metallic hydrogen or spin-stabilized triplet helium, all could give advances, but honestly, anything less than the metallic mono-hydrogen is not going to do much  in real-world situations.  Even worse, all of those except the cubane is speculative as of now, and in the case of the "good stuff" metallic hydrogen is so speculative we have no idea even where to start.

It is possible to get effective high energy into the propellant using beamed energy, effectively leaving your engines on the ground, but such laser boosted designs have a large and serious set of problems of their own, not least being firing a potent laser out of the soup we breathe.

Aside from those two classes of solutions, we're really left with only nuclear solutions.  If anyone out there has a viable alternative that doesn't involve the "N" word, I'm all ears.

I tend to favor good old uranium, in either the cheap U235 or high-octane U233 variants, but plutonium is also a strong contender.


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Antimatter?

Antimatter is a relative newcomer, due to recent advances in production of positrons.  

A quick note:  As a rule of thumb, antimatter is looked at in two "flavors."   Namely, anti-protons and anti-electrons, or positrons.   Anti-protons are useful for triggering fission reactions, at the expense of high-energy gamma rays.  Positrons are useful for primary energy production only, as they cannot interact with nuclei, and the gammas they produce too soft to interact with nuclei either.

So, an antimatter powered SSTO would be most likely a positron-powered design, which would require a stunningly huge amount of positrons, likely in the gram range at least.  Such a design scares the poo outta me, because a containment failure on that much antimatter would be...bad.  The gamma flash is likely to melt a good chunk of your spaceship, and anybody alive anywhere near it would be killed instantly.  On the good side, once the gamma flash is finished, there's no aftertaste!

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And who is denying access to the private sector?

The US government, in our case, andin the larger case, anybody who's a signatory to the NPT (Non Proliferation Treaty) along with several other documents.  As a first step, we need to get those old, outdated treaties corrected, or we need to withdraw from such.

Another alternative, and one that I suspect is more likely, is to simply use a non-signatory state as the place where we finally get serious about this process.  I personally am looking hopefully toward India.

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I gather from your comments that a 90% propellant mass fraction for a LOX/LH2 SSTO seems to be a disgustingly bad number to you...

Correct!

See my prior post for more detail.

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....5% of the mass for payload. That may not sound like much, but it's better than just about all currently operational launch systems.  

True, 5 percent payload is way better than our current launchers.  But sadly, that is such a remarkably low benchmark I can't find any way to get excited about it.  Sorry.  :(

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If you have a system to achieve lower launch costs using high energy materials... GREAT! Let's hear about it!  

As a matter of fact, I'm doing exactly that in a seperate thread on this very board!  :)
Title: Re: SSTO Thread
Post by: Jim on 10/02/2006 01:02 am
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mauk2 - 1/10/2006  8:01 PM
The US government, in our case, andin the larger case, anybody who's a signatory to the NPT (Non Proliferation Treaty) along with several other documents.  As a first step, we need to get those old, outdated treaties corrected, or we need to withdraw from such.

Another alternative, and one that I suspect is more likely, is to simply use a non-signatory state as the place where we finally get serious about this process.  I personally am looking hopefully toward India.

Not going to happen.  And the US is not going to use another country to do illegal or dirty work wrt nuclear material
Title: Re: SSTO Thread
Post by: Dan Moser on 10/02/2006 01:45 am
meiza,

Yes, I spoke with John Wickman about this LOX monopropellant work back in '93 or so.  He seems to have done little with it since then.   All tests were conducted at EXTREMELY low pressures, almost ambient pressure as I recall, probably for safety reasons.  Confine that stuff in a pressurized tank, and you've got a great bomb! There is little advantage in going this route... the kerosene is a little denser, but harder to vaporize, mix, and burn in the combustion chamber.  You save yourself a separate tank, but buy yourself a HUGE safety problem.  Any fuel thoroughly mixed with an oxidizer, especially if one or both are in liquid form, creates a shock-sensitive high explosive.  As with any monopropellant, the higher the Isp, the lower the stability.  Pure nitromethane is a high performing monopropropellant... and an incredibly dangerous high explosive.  Even widely-used hydrazine is mildly shock sensitive.  Mix a few percent of alcohol into H2O2 and you start to loose safe storability.. Some friends of mine created and tested MOx, a mixture of methane and oxygen, and it was INCREDIBLY dangerous.  Intended for use as a mining explosive, it proved to be even too unstable for that...  their test hardware was blown to bits when a nitrogen purge valve opening caused enough of a shock to set it off!  Even so, some people were out there saying MOx would be a great high-performance rocket monopropellant... TOTAL INSANITY!   If you wish to avoid killing people, you'd better keep your oxidizer and fuel in separate tanks and avoid so called high-performance monopropellants.

As to the LOX/hydrogen-aluminum tripropellant idea, I'm pretty sure that's not going to work all that well.  It's not too hard to make aluminum nanospheres with smooth sufaces so as to not to increase viscosity of the slurry to a great extent, so that's not really the problem.  Overall propellant density does indeed go up when you add aluminum, but with high-performance composite tanks, low density propellants is much less of a performance penalty.  The problem is, it just doesn't seem to enhance performance all that much for all the technical risks it imposes.  It may be hard to warm up and ignite all those tiny aluminum balls in the necessary time frame.. plus you've got slagging problems with molten aluminum oxide droplets condensing onto nozzle surfaces... lots of practical problems.  I'll probably stick with LOX/hydrogen-hydrocarbon tripropellant for further analysis, but the expendable pressure-fed SSTO concept works just fine on paper with LOX/hydrogen bipropellant alone.

Happy Landings,

Dan
Title: Re: SSTO Thread
Post by: mauk2 on 10/03/2006 01:09 am
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Jim - 1/10/2006  7:45 PM

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mauk2 - 1/10/2006  8:01 PM
The US government, in our case, andin the larger case, anybody who's a signatory to the NPT (Non Proliferation Treaty) along with several other documents.  As a first step, we need to get those old, outdated treaties corrected, or we need to withdraw from such.

Another alternative, and one that I suspect is more likely, is to simply use a non-signatory state as the place where we finally get serious about this process.  I personally am looking hopefully toward India.

Not going to happen.  And the US is not going to use another country to do illegal or dirty work wrt nuclear material


Really?

I will point out that there is strong precedent for exactly this sort of action.  In 2001, the US withdrew from the ABM treaty, to loud and nigh-unanimous criticism from practically all spectators, and in the intervening five years the world has not ended and the sky has not fallen.


http://archives.cnn.com/2001/ALLPOLITICS/12/13/rec.bush.abm/


Indeed, the NPT includes a similar withdrawal clause as the ABM did.

While I do NOT advocate we withdraw from the NPT, it is unwise indeed to state categorically, "Not going to happen."   It darn well could.  I would prefer we expand the "peaceful uses" clause to allow EPP's and other nuclear powered space drives.  Until we do, we're anchored here at the bottom of the well.


As for my hopes for India, (a non-signer of the NPT and thus completely free to develop a nuclear powered SSTO) I will point out that India has also been the recent recipient of strong nuclear overtures from the US:

http://www.cfr.org/publication/9663/usindia_nuclear_deal.html?breadcrumb=default

http://en.wikipedia.org/wiki/Nuclear_Non-proliferation_Treaty

So, there is a great deal of light at the end of the tunnel, folks.  :)  Who knows, I might just live long enough to see us get over this irrational terror after all!  :)
Title: Re: SSTO Thread
Post by: yinzer on 10/03/2006 03:31 am
Withdrawing from the ABM treaty meant that Russia could, if it wished, start developing ABMs.  Big whup.  Withdrawing from the ABM treaty could have much more severe negative effects.  Not going to happen.
Title: Re: SSTO Thread
Post by: Dan Moser on 10/04/2006 06:14 pm
mauk,

I am puzzled why you think that a 90% propellant mass fraction is so horribly bad for a you-can-build-it-today chemical propellant SSTO, yet you think it's reasonable to ride your hopes for low cost space transportation on India's nuclear program and/or another country pulling out of the NPT, which you believe will lead to private firms being granted access to the NTR technology.  

Anyway, Uncle Sam could authorize the development of a NTR SSTO anytime, if it made sense... ah, there's the rub... it does NOT make sense.  Not for Russia, France, or China neither.  India will no doubt come to the same conclusion, if it has not already.  Yes, a nuclear SSTO could be built, but it will not be built simply because its development and operations costs are far too high. As if that weren't enough, public opinion would not be open to the idea, at least not for many decades to come.  Waiting for nuclear and antimatter technology to be accessable to private enterprise will be a very long wait indeed.  Not in your lifetime or mine.  Deny it and dream on if you wish, but you will eventually have to accept it as truth.  

90% today, or some lower percent never.  You decide.
Title: Re: SSTO Thread
Post by: mauk2 on 10/04/2006 08:37 pm
Hello Dan! :)

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I am puzzled why you think that a 90% propellant mass fraction is so horribly bad for a you-can-build-it-today chemical propellant SSTO....

Because such a device does not exist.  There is not a "build it today" system that will do that once you move off paper and start cutting metal, and I would be astonished if any reputable mechanic would even begin to sign off on such lunacy.

Even if it DID exist, trying to squeeze the entire dry mass of a viable design down to 5 percent of GLOW is, frankly, laughable.  Maybe in a few more decades we will have access to macro-scale nano materials or structural diamond or similar amazing materials.  But, as I have pointed out, such ultra-materials give even LARGER gains when combined with high energy propellants.

Nothing we have today, even in the labs, will get us a robust, viable vehicle with a mass fraction that high.  I have sincere doubts it is even possible in the lifespan of anyone on this board.  How long are YOU willing to wait?

For an example of a real-world system, the Airbus A-380 is a wonderful new bit of tech.

http://www.airbus.com/en/aircraftfamilies/a380/a380/specifications.html

Even with EXTENSIVE use of the best materials technology available, the minimum empty weight of that plane is 608,000 pounds, with a maximum takeoff weight of 1,235,000 pounds. 608/1235 = .49

THOSE are REAL mass fraction numbers for a device built to operate in real world conditions.  Granted, an SSTO is a considerably simpler device than an airliner (no wings, no flaps, no landing gear, just for starters) so we can likely do considerably better than that 50 percent mass fraction, but I can see NO WAY, with either current tech or even reasonably expected future advances, we are going to see a robust, reuseable, inexpensive device at a mass fraction of a feathery 5 percent.

If that's the option we choose to follow, then we'll be lucky if our childrens grandchildren are getting off the planet, because I suspect that's how long it will take for materials tech to advance that far, if ever.

I suspect people fail to recognize the magnitude of difficulty this problem presents.

The problem is energy density.  We can recognize that and act rationally to address it, or we can act irrationally and fail.  Period.  

I'm sorry this is so disturbing to people, but the facts are the facts.

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Anyway, Uncle Sam could authorize the development of a NTR SSTO anytime, if it made sense... ah, there's the rub... it does NOT make sense.

Of course not, no reasonable NTR is able to reach 2500+ Isp without risking leakage into the atmosphere.  While such leakage is no big deal, the irrational fear of radiation we have been brainwashed into leaves little recourse.  Luckily, we have much better ways than using an NTR.  :)

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90% today, or some lower percent never. You decide.  

Then it's never, dude.  Because doing it with chemicals is impossible.

Physics don't bend.  Period.

We can get over our irrational fears, or stay home.  It's just that simple.

Sorry.
Title: Re: SSTO Thread
Post by: Dan Moser on 10/04/2006 10:46 pm
Hey, "Dude"

Expendable SSTO technology does indeed exist in present day.
You can say it doesn't all you want, but it DOES exist.  Here's a simple example:

The shuttle ET weighs 59,500 pounds empty, and holds 1,589,000 pounds of LOX/hydrogen.
3 RS-68 engines would generate 663,000 pounds SL thrust each, for a total of 1,989,000, with an Isp 359 sec. SL and 409 sec. vacuum.
Each engine weighs 14,876 pounds, for a total weight of 44,628 pounds for 3 engines.
Throw in 10,000 pounds extra for added plumbing, structures & avionics, and an extended nozzle for the one of the engines bringing its Isp to 450 sec vacuum. (conservative)
Now put a 60,000 pound payload on top.
Total GLOW = 59,500 + 1,589,000 +  44,628 + 10,000 + 60,000 = 1,763,128 pounds
Propellant fraction = 1,589,000 / 1,763,128 = 90.1%
Payload fraction = 60,000 / 1,763,128 = 3.4%

Now these are EXISTING launch vehicle building blocks in current production.  Now what were you saying about nobody ever signing off on such lunacy?

The ET is old technology, and few reasonable people in the industry would doubt that it could be made much lighter and cheaper today.   Dry weight savings trades pound-for-pound to payload mass increase.

No irrational fears here!  Facts is facts.  Like you said: Physics don't bend (I should know, I have a degree in Physics).

Oh yeah, here's another fact : Operational NTR-based launch vehicles do NOT exist today!  

The 3 issues that NTR proponents like to ignore are COST, COST, and COST.  They like to accuse everyone else of stupidity and nuclear-phobia to justisfy the lack of acceptance of their "dream ship".. never mind the realities of the price tag....  No, Mr Mauk, I do not have a phobia about Uranium (except that some madman will get his evil hands on some).  I have an opinion about NTRs based on facts, not a phobia.  Now, if you're really courageous, how about addressing the COST issue for NTRs, unless you have "COST-phobia", that is.

Quoting mass fractions of airliners is not at all relevant to a launch vehicle argument.  River barges have propellant fractions less than 1%. Hang gliders have no propellant mass at all.  Airliners, barges, and hang gliders all have this in common, though:  they cannot reach orbit.  And by the way.. nuclear-powered airplanes are very possible and they would also have zero propellant mass fraction, yet you see exactly zero of them today.  How do you explain that? .. oh, right... I forgot... stupid people with irrational nuclear-phobia, huh?

You can stay home and pout about mass fractions and stupid hippie-types with nuclear-phobia all you want, meanwhile others will be blazing the trail to space with chemical propellants.  This is a fact, and you will eventually have to learn to live with it.
Title: Re: SSTO Thread
Post by: mauk2 on 10/04/2006 11:35 pm

Howdy Dan! :)

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Expendable SSTO technology does indeed exist in present day.

I will note that in your (interesting) example vehicle, you included one extra word:

"Expendable."  Methinks we're arguing apples and oranges here.

I do not dispute that if we are willing to dispose of our vehicle on every flight, it is barely feasible to use chemicals to reach orbit on a 90-odd percent mass fraction.   But a disposable vehicle is hardly robust OR viable in the same way a fully reusable airliner is.

In short, that is NOT the vehicle that will open space access for us in any real-world application.  No businessman is going to tolerate such a level of costs.   The only way it could be even slightly viable is if there were some resource of enormous value in LEO.  But, there isn't such a resource in LEO.  There are such resources in space, but much further out than LEO.

So not viable.  Sorry.

The difference between the possible and the practical is a vast gulf.

We need practical vessels.  Period.  No disposable solution is a practical transportation system, unless there are truly vast returns to be made.

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Oh yeah, here's a REAL fact : Operational NTR-based launch vehicles do NOT exist today!

Yes, and as I stated before, NTR is a dead end.  

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The 3 issues that NTR proponents like to ignore are COST, COST, and COST.

I am not a proponent of NTR's, so I have no idea why you're continuing to beat that dead horse.

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Quoting mass fractions of airliners is not at all relevant.

On the contrary, mass fractions of airliners are the most relevant economic model we currently have.  Airlines make money.  Indeed, they make so much money there is brutal competition in that marketspace.  Airliners are high-Isp, self-contained transport devices.  I argue, and will continue to argue, that this is the most compelling case for high energy solutions for our space access needs.  Is the analogy perfect?  Nah.  But it's close enough to give us an idea, and the differences can be readily modeled.

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Coal barges have propellant fractions around 1%.

Correct!  Indeed, using relatively simple nuclear-based systems it is possible to achieve quite similar mass fractions for spacecraft used for Solar System exploitation.   Sadly, I know of no feasible system that will achieve LEO with a mass fraction that good, which is why I don't use ocean liners and container ships for the economic model, I use airlines.  

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And by the way.. nuclear-powered airplanes are very possible and they would also have zero mass fraction, yet you see exactly zero of them today. How do you explain that?

It's simple.  A hydrocarbon-powered high-bypass jet engine can achieve an Isp of over 10,000, because it has access to an external working fluid.  If such a device is possible that achieves such high efficiencies so easily, why bother developing anything else?  Especially since radiation concerns at such close proximities to reactors are FAR from trivial. :)  Sadly, for space applications, that working fluid is no longer your friend, and different solutions are required.  Not desireable.   REQUIRED.  

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You can stay home and pout about mass fractions and stupid hippie-types with nuclear-phobia all you want, meanwhile others will be blazing the trail to space with chemical propellants.

Well, honestly, I wish you good luck on that!  Who knows, maybe I'm wrong! :)
Title: Re: SSTO Thread
Post by: Dan Moser on 10/05/2006 02:01 am
An expendable SSTO is what I have been proposing all along.  From my very first post on this thread, I have been stating that an expendable is the only viable SSTO option.  The added mass required to enable reusability makes the RLV SSTO's payload all but disappear, making it a very tough sale indeed.  

As for the comment...  "a disposable vehicle is hardly robust OR viable in the same way a fully reusable airliner is"
... based on what frame of reference?
Is an automobile tire not robust enough just because it has to be replaced after only 40,000 miles, barely one and a half times around the world?

The point I have been trying to make is that a expendable launch vehicle CAN be made very inexpensively and still be economical to operate.  An RLV has a lot of performance penalties and refurbishment expenses that occur on every flight, and that makes it less valuable..  very expensive, but less valuable... it all comes back to life cycle cost.  Make the expendable launch vehicle very inexpensive, and it has the potential to become much less expensive to operate per flight than an RLV.  RLV proponents like to say "you wouldn't  throw a car away after one tank of gas,"  but that's a total faulty argument, though it does make sense to a layman (or a congressman).  What if the gas tank was 400 times larger, then would it make sense? What if the car cost you  $50 new, but cost you $30 everytime you drove it?  Wouldn't a $25 car you threw away after each use make sense then?.. disregarding the environmental impact for now.

Think about common, everyday things that are expendable, that is.. thrown away after one use... aerosol cans, soft drink bottles, waste can liners, rubber gloves, baby diapers, cigarette lighters... all of these things have reusable versions, but in most cases it takes more time (and time IS money) to refurbish them for reuse than it's worth, so most everyone decides that a buying the cheap, lightweight throwaway version makes more sense.

In the case of launch vehicles, the value of mass at various times during flight is far different from a car or plane.  A pound of payload to orbit costs, let's say $1,000 per pound (actually much more than that today), so by adding to the vehicle's mass to make it reusable, and therefore haul less payload, you loose $1,000 per pound, or you have to make the vehicle bigger, which increases costs another way.  

Now consider this... an expendable upper stage attached to the payload has made it all the way to orbit... that expended stage is also worth $1,000 per pound in orbit IF it is constructed of materials that can be RECYCLED into other useful products... radiation sheilding, structural building materials, habitat shelters, even food and water (an "organic" rocket that can be burned and recycled by orbiting greenhouses).   So, the expendable SSTO can be worth several times more after the end of its useful life than it cost to build it (initially <$100/pound).

Let's say the RLV upper stage costs $200 per pound to build (cheap by all accounts)... it flies to orbit, delivers its payload... reenters, and lands... now it has to be inspected, refurbished, maintained, etc. so it is worth considerably less than $200 per pound after it lands.

How's this for a throw-away-car-after-one-use analogy:  You buy a new car for $10,000, then drive it to a place where you can sell it for $30,000 in scrap metal... I contend that anyone who says "no thanks, I'm going to reuse this perfectly good car" is a bloody fool!  Why not take the profit and buy two new cars, rather than have one slightly used car?

and Mauk... I still have no idea what kind of nuclear/antimatter/warpdrive thing you are proposing or what it might cost.  It's antimatter.. wait, no it's not... it's NTR.. wait, no it's not.  I only know that you think high propellant mass fractions and expendable rockets are somehow bad based on some kind of astandard.. maybe from an airliner comparison.  Could you be more specific on what you are proposing?  I'm not trying to be rude, and I always try to be open-minded about new ideas... if only I knew specifically what those ideas were.

Happy Landings,

Dan
Title: Re: SSTO Thread
Post by: meiza on 10/05/2006 11:13 am
One of the main reasons for reusability is reliability, ie that you can test expanding the flight envelope slowly and also can do aborts without destroying the vehicle (since the vehicle is designed to land), and when you fly operational flights, your every flight isn't the first flight, but the vehicle has many succesful tests and flights behind it, unlike with expendable hardware.
Title: Re: SSTO Thread
Post by: lmike on 10/05/2006 11:41 am
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meiza - 5/10/2006  3:56 AM

One of the main reasons for reusability is reliability, ie that you can test expanding the flight envelope slowly and also can do aborts without destroying the vehicle (since the vehicle is designed to land), and when you fly operational flights, your every flight isn't the first flight, but the vehicle has many successful tests and flights behind it, unlike with expendable hardware.

I'd like to understand this argument better.  We have 2 scenarios:
 
1.  expendable
Article A can achieve 2 km/s
... tweak the design ...
Article B can achieve 5 km/s
... tweak the design ...
Article C can achieve LEO
fix the design, crank out the launchers

2.  reusable
Article A version 1 can achieve 2 km/s
... tweak the vehicle ...
Article A version 1.1 can achieve 5 km/s
... tweak the vehicle ...
Article A version 1.2 can achieve LEO
fix the design, crank out the vehicles

At which step does the second variant start to provide higher reliability than the first?  To me they seem to say essentially the same thing.  In fact reusable Article A version 1.2 is the same as the expendable design C.  "Test, tweak, repeat" is relevant here and there.  Replace "vehicle" with "design" and we have the same thing.  Once one fixes a successful re-usable design, one still has to manufacture the units.  

Once one factors in the needed mainainance for the reusable (non-existent for expendable launchers)  the reliability is still controlled at the factory, not at the concept level.

[edit] come to think of it, there seems to be little envelope for collecting useful information (regardless of reusability), you are either sub-orbial or orbital.  Incremental steps don't really give any advantage.  And expendables passed that in one leap.
Title: Re: SSTO Thread
Post by: Jim on 10/05/2006 11:56 am
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meiza - 5/10/2006  6:56 AM

One of the main reasons for reusability is reliability, ie that you can test expanding the flight envelope slowly and also can do aborts without destroying the vehicle (since the vehicle is designed to land), and when you fly operational flights, your every flight isn't the first flight, but the vehicle has many succesful tests and flights behind it, unlike with expendable hardware.

That is a false relation between reusability and reliability.  A reusable LV has more parts and therefore lower reliability.

It boils down to what level of redundacy is employed.   For the same levels, a expendable is more reliable.

Not every RLV has recoverable aborts.

ELV's can have test flights to verify the flight envelope.
Title: Re: SSTO Thread
Post by: meiza on 10/05/2006 02:35 pm
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lmike - 5/10/2006  12:24 PM

I'd like to understand this argument better.  We have 2 scenarios:
 
1.  expendable
Article A can achieve 2 km/s
... tweak the design ...
Article B can achieve 5 km/s
... tweak the design ...
Article C can achieve LEO
fix the design, crank out the launchers

2.  reusable
Article A version 1 can achieve 2 km/s
... tweak the vehicle ...
Article A version 1.1 can achieve 5 km/s
... tweak the vehicle ...
Article A version 1.2 can achieve LEO
fix the design, crank out the vehicles

At which step does the second variant start to provide higher reliability than the first?  To me they seem to say essentially the same thing.  In fact reusable Article A version 1.2 is the same as the expendable design C.  "Test, tweak, repeat" is relevant here and there.  Replace "vehicle" with "design" and we have the same thing.  Once one fixes a successful re-usable design, one still has to manufacture the units.  

Once one factors in the needed mainainance for the reusable (non-existent for expendable launchers)  the reliability is still controlled at the factory, not at the concept level.

[edit] come to think of it, there seems to be little envelope for collecting useful information (regardless of reusability), you are either sub-orbial or orbital.  Incremental steps don't really give any advantage.  And expendables passed that in one leap.

You're thinking in expendables, just about "fixing a design" and then "cranking out them". You don't separate design and operations.

Once you have a reusable vehicle (a concrete material vehicle, not just a design) you can do multiple flights with it and gain confidence in its abilities. Multiple flights with one physical vehicle. First do flights that you can do easy aborts on.
New airplanes do taxi tests and then short flights etc etc.

If you have an expendable vehicle, every flight is a first flight. It sounds like yet another soundbite but there's an idea backing it.  You can test at component level but I don't know how much is done on the complete interacting level. Apollo did a huge amount of testing of the components and subsystems, it was very expensive and spent a big portion of the budget. It worked and the hardware produced was reliable. Many people proposing liquid rocket engines over "The Stick" say that liquids can be test fired before the launch, which is a big advantage. And a liquid rocket launch can be aborted if good thrust is not obtained in the first seconds before liftoff. These both stem from the fact that the liquid rocket engine is to a certain extent reusable.

It's a quite clear question really.

I don't myself believe that an SSTO reusable vehicle will be done, but I do believe that some stages in a multistage vehicle can be reusable and work well in the long run.
Title: Re: SSTO Thread
Post by: meiza on 10/05/2006 02:56 pm
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Jim - 5/10/2006  12:39 PM
That is a false relation between reusability and reliability.  A reusable LV has more parts and therefore lower reliability.

Your relation is false too. If you have a nine part expendable design that has been just manufactured but not tested (others
have been tested some tens of times) or then a ten part reusable design that has been tested a hundred times, which one is more reliable?

Really, it's a compromise. How much more complexity and how much more reusability.
And how much more complex does a reasonable performance RLV really have to be? You can always reduce
requirements and complexity at the cost of performance.
Everybody probably thinks SSME vs RS-68. Well, SSME is clearly much more complex but how much is that because
of tougher performance requirements and how much because of reusability?
If an RS-68R was done with a regenerating nozzle, how far would it be from reusability...
And SSME has demonstrated reasonable reliability. It's a chore to maintain of course, but it isn't said that
a simpler engine couldn't be done as reusable.

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It boils down to what level of redundacy is employed.   For the same levels, a expendable is more reliable.

Not every RLV has recoverable aborts.

I'm not claiming that all RLV:s are more reliable than all ELV:s. That would be idiocy.

Do you claim that testing doesn't need to be done, since all reliability is achieved by designing in redundancies?
Of course not, maybe for the most basic of products with very little parts and lots of margin, or stuff with extremely
rigorous and expensive quality control during manufacturing.

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ELV's can have test flights to verify the flight envelope.

The ELV models yes but not the actual rockets you buy services from. It's always a new one.
And how many test flights do you have money to do with an expendable vehicle design?

Again on the soundbite department, when the Falcon I had an engine problem on a test flight,
it miserably crashed and is still standing down. While when the XCOR Ez-Rocket had a problem,
the pilot just landed without power, the problem was fixed and they flew again shortly.
That of course depends on the design of an RLV. A vertical landing rocket would have crashed. But
with that you would have down perhaps lots of tethered flights, like Armadillo Aerospace is doing.

But on the whole, it's a completely different mindset and approach and it's not evidently clear for me
how reusables are so damn bad?!
Clearly, they add complexity and clearly they reduce performance and clearly they increase testability.
Title: Re: SSTO Thread
Post by: Jim on 10/05/2006 03:17 pm
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meiza - 5/10/2006  10:39 AM
Again on the soundbite department, when the Falcon I had an engine problem on a test flight,
it miserably crashed and is still standing down. While when the XCOR Ez-Rocket had a problem,
the pilot just landed without power, the problem was fixed and they flew again shortly.
That of course depends on the design of an RLV. A vertical landing rocket would have crashed. But
with that you would have down perhaps lots of tethered flights, like Armadillo Aerospace is doing.


you can't make that comparsion. They are apples and oranges.   Also, It wasn't the first flight of the EZ

The EZ is an airplane not an LV.  Totally different regimes and environments.

Spacex is fixing other issues.
Title: Re: SSTO Thread
Post by: Dobbins on 10/05/2006 03:35 pm
A Reusable launch vehicle isn't reusable if it isn't serviced between flights. This means you have to have a service center to service the RLV between flights. That means you incur fixed costs for a building, staff, etc. Fixed costs are exactly what the name implies, fixed, they don't change regardless of how many RLV service jobs you do. The more jobs you do, the lower the average service job is because the fixed costs are spread over more flights. This means RLVs are not economically viable without a high enough flight rate to support a service center, otherwise the overhead of the service center will drive the costs per flight above the cost of an ELV.

If an airline only flew a jet a few times a year it would not be able to justify the costs of maintaining a service center capable of working on jets. An airline's high flight rate is what makes the service center possible and what makes a jet airliner economically viable.
Title: Re: SSTO Thread
Post by: meiza on 10/05/2006 03:40 pm
falcon and ezrocket...

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Jim - 5/10/2006  4:00 PM

you can't make that comparsion. They are apples and oranges.   Also, It wasn't the first flight of the EZ

The EZ is an airplane not an LV.  Totally different regimes and environments.

Spacex is fixing other issues.

True, one has to work with that since so little work has been done on reusable first stages. Anyway it shows what it means if you can do aborts.

SpaceX can't test flying without having to completely succeed, sure they spend a lot of extra time and money before even trying again. If their rocket was able to expand envelope on multiple succeeding lower risk and low cost (lower cost than having to rebuild) flights, perhaps they had been flying those already and discovered many other problems that would not have destroyed the vehicle but had caused an abort.
Elon has himself stated that he can take what, three failures?
Title: Re: SSTO Thread
Post by: Dan Moser on 10/05/2006 04:14 pm
Reliability comes from good launch vehicle engineering.  Period. This engineering has to be done whether the vehicle is expendable or reusable.  The better the engineering, the more reliable the vehicle is.  RLV proponents are often under the illusion that you automatically get reliability by reusing the vehicle, which means the systems are "well proven".  Well.. look at the reliability of airplanes and automobiles... older vehicles with lots of miles/hours do indeed breakdown.  New vehicles can breakdown too.  Note that if an RLV fails on the first flight, there ain't no reusing it.

Almost all RLV designs I've seen proposed cannot do an engine out abort at any time during the ascent and land intact.  The EZ rocket example cited does not change that, since the EZ rocket.. very cool though it is... is not even close to being a launch vehicle.  It's a beautiful looking, yet very loud airplane with lousy gas mileage.

Now I'm not really anti-reusability.  In certain launch systems, reusability can be economically implemented.  A resuable first stage with an expendable upper stage appears to be the best of both worlds.... if it's done properly.
Title: Re: SSTO Thread
Post by: meiza on 10/05/2006 06:53 pm
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Dan Moser - 5/10/2006  4:57 PM
Reliability comes from good launch vehicle engineering.  Period.

Heh, that is a gross oversimplification and omission. Testing is very important too.

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This engineering has to be done whether the vehicle is expendable or reusable.  The better the engineering, the more reliable the vehicle is.  RLV proponents are often under the illusion that you automatically get reliability by reusing the vehicle, which means the systems are "well proven".  Well.. look at the reliability of airplanes and automobiles... older vehicles with lots of miles/hours do indeed breakdown.  

Reusable things malfunctioning often follows a bathtub curve. There are early failures because of manufacturing defects and then late failures because things wear out. Grossly simplified of course.

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New vehicles can breakdown too.  Note that if an RLV fails on the first flight, there ain't no reusing it.

If the failure results in loss of vehicle, it definitely is a bad thing, probably even worse than with expendables since more
money was invested in it and all that. If the failure is such that you can recover, it necessarily isn't that bad.

Quote
Almost all RLV designs I've seen proposed cannot do an engine out abort at any time during the ascent and land intact.  The EZ rocket example cited does not change that, since the EZ rocket.. very cool though it is... is not even close to being a launch vehicle.  It's a beautiful looking, yet very loud airplane with lousy gas mileage.

Now I'm not really anti-reusability.  In certain launch systems, reusability can be economically implemented.  A resuable first stage with an expendable upper stage appears to be the best of both worlds.... if it's done properly.

Yeah, ez-rocket is not a launcher. But it's a company that is slowly working itself toward something that one day could be useful for space launches becoming routine. (Being mostly that rocket engine operations become routine, safe, easy, reliable.)
I agree that it's probably safest to start with a reusable first stage. That's the most expensive part of the rocket anyway (except the payload of course, but they stay up until they break anyway). Also margins would have to be so big that the parts do not wear much during use and inspections don't have to be so thorough.

But I find it really weird, even disturbing that many people here find no value in testing stuff.
Surely if you bolt a new or just overhauled jet engine on a plane, you do some test runs and diagnostics before it's cleared for flight. Especially if it's the only engine in the plane.
It works on practically every thing. In software too. It's a problem with expendable hardware that you can not test it. You have to rely more on other methods used for ensuring reliability. Testing is not the end-all be-all but it surely is damn helpful in the real world. Even SpaceX test runs its engines on static firings. Are they wasting money?
Title: Re: SSTO Thread
Post by: Jim on 10/05/2006 07:06 pm
Quote
meiza - 5/10/2006  2:36 PM
It's a problem with expendable hardware that you can not test it. You have to rely more on other methods used for ensuring reliability. Testing is not the end-all be-all but it surely is damn helpful in the real world. Even SpaceX test runs its engines on static firings. Are they wasting money?

ELV hardware and systems get tested.  Just not flight tested.
Title: Re: SSTO Thread
Post by: Dan Moser on 10/05/2006 11:04 pm
Quote
meiza - 5/10/2006  1:36 PM

Quote
Dan Moser - 5/10/2006  4:57 PM
Reliability comes from good launch vehicle engineering.  Period.

Heh, that is a gross oversimplification and omission. Testing is very important too.

No, good engineering INCLUDES testing.  Several redesign-retest are typically necessary.
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This engineering has to be done whether the vehicle is expendable or reusable.  The better the engineering, the more reliable the vehicle is.  RLV proponents are often under the illusion that you automatically get reliability by reusing the vehicle, which means the systems are "well proven".  Well.. look at the reliability of airplanes and automobiles... older vehicles with lots of miles/hours do indeed breakdown.  

Reusable things malfunctioning often follows a bathtub curve. There are early failures because of manufacturing defects and then late failures because things wear out. Grossly simplified of course.


Expendable things also follow the bathtub curve, at least the first part of it anyway.  In this case the horizontal axis is serial number of units produced, rather than number of uses.  The cause of failures becomes known when you produce and acceptance test many of the same article.  Expendable hardware should also be subjected to acclerated life cycle testing for qualification, just like reusable hardware.
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New vehicles can breakdown too.  Note that if an RLV fails on the first flight, there ain't no reusing it.

If the failure results in loss of vehicle, it definitely is a bad thing, probably even worse than with expendables since more
money was invested in it and all that. If the failure is such that you can recover, it necessarily isn't that bad.


Probably worse with expandables?  NO WAY!! I stroingly disagree.  RLVs inherently cost more, both in recurring cost (per vehicle) and non-recurring (up-front development) cost.  You think the Shuttle failures were noit as expensive as Delta failures, then I take it?  No sir, loosing an RLV will be a MUCH bigger deal than loosing an ELV, regardless of whether or not lives are lost!

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Quote
Almost all RLV designs I've seen proposed cannot do an engine out abort at any time during the ascent and land intact.  The EZ rocket example cited does not change that, since the EZ rocket.. very cool though it is... is not even close to being a launch vehicle.  It's a beautiful looking, yet very loud airplane with lousy gas mileage.

Now I'm not really anti-reusability.  In certain launch systems, reusability can be economically implemented.  A resuable first stage with an expendable upper stage appears to be the best of both worlds.... if it's done properly.

Yeah, ez-rocket is not a launcher. But it's a company that is slowly working itself toward something that one day could be useful for space launches becoming routine. (Being mostly that rocket engine operations become routine, safe, easy, reliable.)
I agree that it's probably safest to start with a reusable first stage. That's the most expensive part of the rocket anyway (except the payload of course, but they stay up until they break anyway). Also margins would have to be so big that the parts do not wear much during use and inspections don't have to be so thorough.

But I find it really weird, even disturbing that many people here find no value in testing stuff.




There is tremendous value in testing.  Who is saying there isn't?  It's an absolute neccessity!

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Surely if you bolt a new or just overhauled jet engine on a plane, you do some test runs and diagnostics before it's cleared for flight. Especially if it's the only engine in the plane.
It works on practically every thing. In software too. It's a problem with expendable hardware that you can not test it.

Where did you ever get that idea that you cannot test expendable hardware?.  Every ELV component must go through qualification testing and acceptance testing.

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You have to rely more on other methods used for ensuring reliability. Testing is not the end-all be-all but it surely is damn helpful in the real world. Even SpaceX test runs its engines on static firings. Are they wasting money?
 

[/QUOTE]

I doubt that SpaceX is wasting money on testing.  Every Delta engine is also static fired before use, and I expect most if not all liquid engines for ELVs are.  Solid rockets are obviously a different matter.  By the way, the reusable shuttle SRMs are man-rated, yet they cannot be test fired before every mission.
Title: Re: SSTO Thread
Post by: mauk2 on 10/06/2006 06:19 am
hello Dan!

Quote
I still have no idea what kind of nuclear/antimatter/warpdrive thing you are proposing or what it might cost.

Ah, such a deceptively simple question.  :)

http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=3615&posts=107&start=1

I am attempting to lay out our best, current-tech or near tech options for high energy systems in that thread.  I encourage you to read it, along with the linked sources.

If that's a bit too daunting, here is a nutshell:

First, we must have high Isp and high thrust systems to achieve LEO.

Second we must have high Isp systems for solar system exploration.  High thrust is desireable here, but less important.

Third, we need high power electrical generators.

After extensive review, there's only three propulsion schemes I can find that make any sense.  One system is only good for earth surface to cis-lunar, one system is adaptable for surface launch and can get us out to Jupiter or so without too much work, and the third system is a good long-range system that also provides large amounts of electricity, making feasible exploitation of the outer planets at least and maybe into the Kuiper belts.  This is important, as access to the helium-3 reserves in the gas giants is a "big deal."  :)

The first system is the ultra-clean but white-knuckle dangerous positron powered SSTO.

The second system is an External Pulsed Plasma drive, with a chemical lofter stage if we want to use it for ground launch from Earth.

The third system is a self-heating plasma fission fragment drive using magnetic mirrors, that is also a dandy source of electricity in almost any amount we dare design it for.

Of the three, the EPP is by far the best developed.  I favor an antimatter-catalysed variant, but that's optional.  Since the EPP is also the most flexible (has the largest performance envelope) that's the design I advocate most.

NTR's are interesting, but just are not all that good performers.  The three designs I advocate can do everything an NTR can, better, so why waste the effort on NTR's?
Title: Re: SSTO Thread
Post by: meiza on 10/06/2006 05:12 pm
Quote
Jim - 5/10/2006  7:49 PM

Quote
meiza - 5/10/2006  2:36 PM
It's a problem with expendable hardware that you can not test it. You have to rely more on other methods used for ensuring reliability. Testing is not the end-all be-all but it surely is damn helpful in the real world. Even SpaceX test runs its engines on static firings. Are they wasting money?

ELV hardware and systems get tested.  Just not flight tested.

Yes, because they can't, they would be destroyed. But if they could be, they would.
Title: Re: SSTO Thread
Post by: meiza on 10/06/2006 05:56 pm
Quote
Dan Moser - 5/10/2006  11:47 PM

Quote
meiza - 5/10/2006  1:36 PM

Quote
Dan Moser - 5/10/2006  4:57 PM
Reliability comes from good launch vehicle engineering.  Period.

Heh, that is a gross oversimplification and omission. Testing is very important too.

No, good engineering INCLUDES testing.  Several redesign-retest are typically necessary.

I'm not talking about testing prototypes during development and then doing changes, I'm talking testing the actual hardware you will fly on. Testing when the design is finalized. Testing after production, testing between overhauls, you name it.
Your TV (the physical unit) was tested that it works correctly before it left the factory, that kind of testing.

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Quote

Reusable things malfunctioning often follows a bathtub curve. There are early failures because of manufacturing defects and then late failures because things wear out. Grossly simplified of course.


Expendable things also follow the bathtub curve, at least the first part of it anyway.  In this case the horizontal axis is serial number of units produced, rather than number of uses.  The cause of failures becomes known when you produce and acceptance test many of the same article.  Expendable hardware should also be subjected to acclerated life cycle testing for qualification, just like reusable hardware.

Stuff like toasters, which is a mass-produced product which has that kind of "with more units produced, the process will be refined and defects will be weeded out" effect still has, for an individual toaster, a bathtub failure probability curve. If toasters were expendable, they'd all be on the first high point of the bathtub curve. A reusable (not too old and worn) previously tested toaster very probably has a somewhat higher reliability rate than a brand new toaster that has not been tested and is thrown away after use.

I'm not saying it's the only way to achieve reliability, but it can be helpful.

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Quote
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New vehicles can breakdown too.  Note that if an RLV fails on the first flight, there ain't no reusing it.

If the failure results in loss of vehicle, it definitely is a bad thing, probably even worse than with expendables since more
money was invested in it and all that. If the failure is such that you can recover, it necessarily isn't that bad.


Probably worse with expandables?  


I didn't say that, I said destruction of a reusable is a worse thing than destruction of an expendable, because the reusable is more expensive. If the reusable vehicle can do an abort (jettison fuel and land with spare engine etc) and land intact, then it's clearly not as bad.

Quote

NO WAY!! I stroingly disagree.  RLVs inherently cost more, both in recurring cost (per vehicle) and non-recurring (up-front development) cost.  You think the Shuttle failures were noit as expensive as Delta failures, then I take it?  No sir, loosing an RLV will be a MUCH bigger deal than loosing an ELV, regardless of whether or not lives are lost!

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But I find it really weird, even disturbing that many people here find no value in testing stuff.

There is tremendous value in testing.  Who is saying there isn't?  It's an absolute neccessity!

You argue that testing copies is as good as testing the actual article. I argue that testing the actual article can give additional reliability.

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Quote
Surely if you bolt a new or just overhauled jet engine on a plane, you do some test runs and diagnostics before it's cleared for flight. Especially if it's the only engine in the plane.
It works on practically every thing. In software too. It's a problem with expendable hardware that you can not test it.

Where did you ever get that idea that you cannot test expendable hardware?.  Every ELV component must go through qualification testing and acceptance testing.


The one-use hardware items on the expendables can't be tested (some other, similar items can be tested but not the physical items), since they are one-use only. The system as a whole can not be tested. The items are mainly one-use because the whole rocket is one-use.

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You have to rely more on other methods used for ensuring reliability. Testing is not the end-all be-all but it surely is damn helpful in the real world. Even SpaceX test runs its engines on static firings. Are they wasting money?
 

I doubt that SpaceX is wasting money on testing.  Every Delta engine is also static fired before use, and I expect most if not all liquid engines for ELVs are.  

Yes, because testing the items can bring out problems you didn't see in component testing or in testing other copies of the same design.

Quote
Solid rockets are obviously a different matter.  By the way, the reusable shuttle SRMs are man-rated, yet they cannot be test fired before every mission.

NASA's man-rating is a very nebulous concept.
Title: Re: SSTO Thread
Post by: Jim on 10/06/2006 07:55 pm
There is no advantage wrt tested hardware that an RLV has over an ELV.  Shuttle proves it.  The Delta II is just as reliable, same as Atlas II
Title: Re: SSTO Thread
Post by: meiza on 10/06/2006 08:17 pm
How can you prove it with one example? And I wouldn't count the SRB:s as a real reusable since the segments have to be recast and restacked. The SSME is an extremely complicated high-performance high-pressure staged combustion cycle engine, I already mentioned that there are many other factors that are different with it compared to RS-68 than reusability.
I don't know about the RD-180 complexity numbers.
Title: Re: SSTO Thread
Post by: Dan Moser on 10/07/2006 05:48 am
ON the contrary, you can definitely test an ELV as a system on the ground before flight.  Static fire hold-down on the stand.  In addition, each component or subsystem is tested before being given a "GO":  the propellant tanks are proof pressure tested, plumbing assemblies are leak checked, injector is cold-flowed, valves are cycled,  sensors are calibrated, avionics evaluated through built-in-test circuits, TVC system is powered up and checked out, the igniter is pulsed, etc.  And just because an RLV has been flown successfully does NOT mean it will automatic work perfectly on all subsequent flights.  Things wear out and break.  The truth is, there is absolutely NO evidence that RLVs are inherently more reliable than ELVs, yet this is a widely held belief and selling point amoung RLV proponents.  I'm not saying ELVs are more inherently reliable either...  I'm saying that good engineering, manufacturing, and maintenance make reliability happen... not which letter you choose to put in front of LV.
Title: Re: SSTO Thread
Post by: meiza on 10/07/2006 12:37 pm
So, if you test-run engines, you already are gaining component reliability because of component reusability. You probably have tested the small parts the engine is made of, but still want to test it as a whole working unit.

It's uneconomical to design ELV engines for a thousand firings to test them a lot, if they're anyway ditched after the one and only flight. You fire 'em maybe once (dunno?) and hope you're far enough at the bathtub curve. I don't know how many test firings actually generally do find problems. With such short lives the current expendable rocket engines have, testing gives also potential problems and when the design and manufacturing process of expendable engines is seen to be mature, test firings can perhaps be left out, I think I've read about this happening at least in Russia.

In flight there are still more variables in play, you just can't test it all in a hold down test. As mentioned in the other thread by Jim that the Delta IV heavy test flight was just for discovering problems like that cavitation one. Expendable launch vehicle design testing, that one, that discovered a small correctable problem in the design.
Reusable light vehicle testing can discover problems in the actual hardware.

If you have a robust reusable vehicle, it isn't working at the brink of destruction all the time, but is designed to handle the aspects of space launch with easiness. Test firings and test flights are not something that might "break it" or wear it significantly, instead, it likes test firings and test flights!
Title: Re: SSTO Thread
Post by: Jim on 10/07/2006 01:35 pm
Quote
meiza - 7/10/2006  8:20 AM
In flight there are still more variables in play, you just can't test it all in a hold down test. As mentioned in the other thread by Jim that the Delta IV heavy test flight was just for discovering problems like that cavitation one. Expendable launch vehicle design testing, that one, that discovered a small correctable problem in the design.
Reusable light vehicle testing can discover problems in the actual hardware.

So what is the difference?!  On either, the problem is fixed before the next flight
Title: Re: SSTO Thread
Post by: meiza on 10/07/2006 01:56 pm
In this case, not much, but this case was a clear design flaw. With manufacturing flaws however...
Title: Re: SSTO Thread
Post by: Jim on 10/07/2006 01:59 pm
Quote
meiza - 7/10/2006  9:39 AM

In this case, not much, but this case was a clear design flaw. With manufacturing flaws however...

The RLV would have parts that wear out or fail from reflight
Title: Re: SSTO Thread
Post by: meiza on 10/07/2006 02:10 pm
That's a design problem.
Title: Re: SSTO Thread
Post by: meiza on 10/07/2006 02:18 pm
Look, I'm not saying RLV is automatically an end-all be-all of reliability and safety, but being able to reuse (and design for reuse) "the whole shebang" can be very helpful in increasing reliability and safety. A significant advantage in RLV vs ELV approach.

There are of course many other factors that affect reliability and safety too.
Title: Re: SSTO Thread
Post by: Jim on 10/07/2006 02:31 pm
Quote
meiza - 7/10/2006  10:01 AM

Look, I'm not saying RLV is automatically an end-all be-all of reliability and safety, but being able to reuse (and design for reuse) "the whole shebang" can be very helpful in increasing reliability and safety. A significant advantage in RLV vs ELV approach.

That isn't an advantage.  More complexity decreases reliability
Title: Re: SSTO Thread
Post by: meiza on 10/07/2006 02:46 pm
Not always. And where do you gather that reusables have to be so much more complex? Shuttle is, but that's got very different requirements and design decisions from EELV:s in many other regards too.
Title: Re: SSTO Thread
Post by: Jim on 10/07/2006 02:53 pm
Quote
meiza - 7/10/2006  10:29 AM

Not always. And where do you gather that reusables have to be so much more complex? Shuttle is, but that's got very different requirements and design decisions from EELV:s in many other regards too.

Because RLV's have systems that are not required by ELV's.  Recovery, landing, deorbit, etc
Title: Re: SSTO Thread
Post by: meiza on 10/07/2006 03:37 pm
Those systems still don't necessarily retract from mission success probability (payload delivery to right place and speed), and one can factor redundancies in them.
Title: Re: SSTO Thread
Post by: Dobbins on 10/07/2006 03:51 pm
Quote
meiza - 7/10/2006  11:20 AM

one can factor redundancies in them.

That will make the RLV even more complex.
Title: Re: SSTO Thread
Post by: meiza on 10/07/2006 11:23 pm
It's a tradeoff.
Title: RE: SSTO Thread
Post by: lmike on 10/07/2006 11:25 pm
Interesting.  I still don't think this argument is very persuasive.  Some repeating of what has been said...

There is little distinction between a design's reusability and a hardware’s reusability.  In fact, the former is far more important for reliability than the latter.  Then it's down to manufacturing control which is a valid concern in both schemes.  

But still, interestingly, as far as reliability is concerned, ELVs have both design reusability (combustion cycles, tankage architectures, ignition schemes, guidance electronics, firmware for it, etc...), AND hardware reusability (tankage tooling, pads, ...)  as a *launch system*   It's just for some of them the metal is bent anew.  The metal would still be bent anew for a reusable launcher to replace the fatigued components.

No one will fly a reusable vehicle just to test a piece of telemetry processing circuitry (subsystem xyz version 1.2.a) for example, the circuit will still be tested on the ground as a 'black box' (if the engineering practices are good) just like for ELVs.

Well, if the reusable test-bed system is only tested as a complete system with many various modifications inside that may or may not work, then where is the advantage?  (btw, the reusable STS Shuttle had *no* test flights, went straight to orbit, still it worked fairly well in the 'ELV like' testing mode)

[edit] I'm not an anti-reusability 'zealot', but there do seem to be too many 'faith' or equally bad car-analogies based arguments for it, which is not healthy from engineering standpoint.  I think partial reusability *may* bring better mission outcomes in terms of *costs* per mission at much higher launch rates of smaller payoloads than we have now, in a multi-launch architecture, but that's a different arguement.  But of course as soon as we have a fully reusable scheme that beats ELVs for costs (including insurance which reflects reliability) of launching a GSO sat , I'll be convinced.  Perhaps that leap does require 'faith' based engineering.
Title: Re: SSTO Thread
Post by: meiza on 10/07/2006 11:49 pm
You can fly less risky test missions with less tankage, so you have good engine out margin etc..

I think one could do more formal analysis on this than what has been talked about in this thread, for example look at historical records of launch failures in new and old rockets and classify them into various classes (design error, manufacturing error and whatnot human process error) and look if reusability would have somehow helped with them, if the rocket could have been tested as a whole before the flight. It's of course impossible to say, but some background could help.

It is also worth noting that many high-reliability designs are in fact quite reusable, like the RD-180 or RL-10. Having big margins and making components not wear significantly during use sure sounds like a good way to get reliability for me. (There are other ways too of course.)

It's an interesting thing to extend the reusability argument to tankage tooling... I don't think it applies too well. I mean, that's true for everything that is manufactured. Do you then extend to the tools that made the tools etc? Maybe you could say reusable about the pad tech and automation though. This is more of a random mumble by me, I don't really have an opinion.

There's some philosophical greater point behind here which I can't yet spell out right, I have to ponder it for a while. (About repeatable processes.)

Lmike I think you're arguing still about design testing when I'm talking about physical hardware testing. And yes, I actually think you can have fairly rigorous control that you have to re-testfly to test even not very significant changes. Besides, test flying (no revenue) doesn't probably cost as much as with expendables.
Title: Re: SSTO Thread
Post by: lmike on 10/08/2006 12:33 am
Quote
meiza - 7/10/2006  4:32 PM

You can fly less risky test missions with less tankage, so you have good engine out margin etc..
You mean with less propellants loaded?  So you can with ELV designs (has been done).  Don't see the necessity for this mode of testing now though.

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meiza - 7/10/2006  4:32 PM
I think one could do more formal analysis on this than what has been talked about in this thread, for example look at historical records of launch failures in new and old rockets and classify them into various classes (design error, manufacturing error and whatnot human process error) and look if reusability would have somehow helped with them, if the rocket could have been tested as a whole before the flight. It's of course impossible to say, but some background could help.
It would be great to look at this sort of analysis.

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meiza - 7/10/2006  4:32 PM
It is also worth noting that many high-reliability designs are in fact quite reusable, like the RD-180 or RL-10. Having big margins and making components not wear significantly during use sure sounds like a good way to get reliability for me. (There are other ways too of course.)
Of course!  One F-1 was fired for over 2000 seconds on a test stand.  [edit] With many restarts!  In this context I took 'reusable' to mean 'ground to LEO reusable vehicle' (or a 'spaceplane') as is often contemplated by many people.  That's what I'm "arguing" (actually trying to understand the proponents) "against".  The context matters.  There is reusable and there is reusable.  I think we have found a point of agreement(?)

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meiza - 7/10/2006  4:32 PM
It's an interesting thing to extend the reusability argument to tankage tooling... I don't think it applies too well. I mean, that's true for everything that is manufactured. Do you then extend to the tools that made the tools etc? Maybe you could say reusable about the pad tech and automation though. This is more of a random mumble by me, I don't really have an opinion.
Yes, I do.  A *reusable design can be duplicated affordably and consistently on reusable tooling.  (just one way to look at the modern ELVs)  Which produces reliable items of the said design.  
Yours is not a "mumble" by any means, it's a valid question about the terminology.  One can't have a discussion without agreed on terminology.  But like I said the context matters.  (and originally the context of the discussion was not limited to the vehicle itself)

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meiza - 7/10/2006  4:32 PM
There's some philosophical greater point behind here which I can't yet spell out right, I have to ponder it for a while. (About repeatable processes.)
Great.  Philosophy is not obsolete (I don't mean to be patronizing, but some folks in discussions for some reason feel squeamish about expressing philosophy.  The ancient Greeks did most for us, but we can expand on it).  It shows our general approach to things.  Especially in this sort of musings about the future.


[edit] *in the context of this sub-discussion I mean "reliable" as equivalent to "reusable"
Title: Re: SSTO Thread
Post by: Dan Moser on 10/08/2006 01:33 am
Well, reliability of RLVs vs. ELVs is obvously a source of disagreement.  There's no settling that argument with real world examples, since true RLVs are only on the drawing board right now (Shuttle is the closest thing, and it's only partially reusable, as well as insanely over-complicated and expensive).  While RLV reliability is undeniably unproven (because they're only on paper), ELV reliability is pretty well established, and it CAN be very good.. but is occasionally very bad.  What typically happens with a new ELV design is that failures are frequent during the first dozen flights or so, then it gets much better as the design flaws and manufacturing processes are discovered and resolved.  This is suspiciously like the first part of that famous bathtub curve.  The only differece is, you never get to the other peak on the farside of the curve because you are never flying old, worn-out hardware.

Anyway, this thread is on SSTOs, and nobody is seriously proposing a reusable SSTO nowadays.  The dreamey days of the DC-X / Clipper seem to be over.  Even the old reusable SSTO guys are now moving on to proposing something more viable, like two stage fully reusables or reusable first stages teamed with an expendable upper stages.

My main assertion relative to the topic of this thread has been that the only SSTOs that are feasible are expendable. I do not see how we get the performance out of a reusable SSTO that uses chemical propellants (antimatter/nuclear/warpdrive proponents are on another thread) to make it worthwhile because of the added dry mass required to enable reentry and safe return. Nobody has really debated that point.  Now there is nothing wrong with multi-stage rockets, but being forced into the expendable corner on Single-Stage-To-Orbit launch vehicles turns the design into some interesting directions, such as the Recyclable ELV idea I proposed a few pages back.  
Title: Re: SSTO Thread
Post by: lmike on 10/08/2006 01:53 am
Quote
Dan Moser - 7/10/2006  6:16 PM
...
My main assertion relative to the topic of this thread has been that the only SSTOs that are feasible are expendable. I do not see how we get the performance out of a reusable SSTO that uses chemical propellants (antimatter/nuclear/warpdrive proponents are on another thread) to make it worthwhile because of the added dry mass required to enable reentry and safe return. Nobody has really debated that point.  Now there is nothing wrong with multi-stage rockets, but being forced into the expanable corner on Single-Stage-To-Orbit launch vehicles turns the design into some interesting directions, such as the Recyclable ELV idea I proposed a few pages back.  

I agree with the assertion.  But if there is nothing wrong with multi-stage rockets (there is nothing wrong with them), why bother with SSTO at all?  I think that the opposite of this question was originally posed.  No one is forcing us into SSTO.  No one knows what the advantages are (well, besides that they are "cool").  But somehow "it's supposed to be good for you".  "Why don't we all just accept it?"
Title: Re: SSTO Thread
Post by: Dan Moser on 10/08/2006 02:25 am
lmike asks:  "But if there is nothing wrong with multi-stage rockets (there is nothing wrong with them), why bother with SSTO at all?"
 
One reason to use SSTOs is to avoid launch delays caused by the potential of dropping booster hardware on someone downrange.  The Air Force requirements for "responsive space lift" specified no long holds on the pad due to range problems like a fishing boat or whatever wandering into the potential impact zone of spent stages and debris.  This is not as much of an issue with flyback reusable boosters or when aircraft are used as lauch platforms, such as with Pegasus and AirLaunch.

Another impetus for SSTOs is the elimination of staging events, which are historically problematic events during ascent..  something doesn't separate cleanly, or separates too early, or too late.

Lastly, the SSTO delivers the maximum amount of spent propulsion mass to orbit.  This is of no value if the spent stage goes unused until its orbit decays. On the other hand, if you can recycle the spent stage materials into useful things in orbit (radation shielding, astronaut habitat, etc.) , then your expendable rocket could become part of the valuable payload.

Having said that, multi-stage vehicles are more versatile and robust than SSTOs... They have fewer performance sensitivities and their shortcomings can be managed without too much difficulty.
Title: Re: SSTO Thread
Post by: lmike on 10/08/2006 02:48 am
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Dan Moser - 7/10/2006  7:08 PM
...
One reason to use SSTOs is to avoid launch delays caused by the potential of dropping booster hardware on someone downrange.  The Air Force requirements for "responsive space lift" specified no long holds on the pad due to range problems like a fishing boat or whatever wandering into the potential impact zone of spent stages and debris.  This is not as much of an issue with flyback reusable boosters or when aircraft are used as lauch platforms, such as with Pegasus and AirLaunch.
Yes this makes sense, but this disposing of used stages seems minor of a head-ache in the currently provided multi-stage launches.  It can even be exactly predicted where the stages fall.  I don't even think it figures into the insurance calculations.

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Dan Moser - 7/10/2006  7:08 PM
Another impetus for SSTOs is the elimination of staging events, which are historically problematic events during ascent..  something doesn't separate cleanly, or separates too early, or too late.
Separation mechanics has been studied and implemented throughout the years exhaustively.  Failure to separate is not frequent recently.  Still if it were, is it as big of a deal to provide redundant separation charges, stage event synchronization, compared to building a single stage vehicle?  Air-launch relies on the biggest separation mechanic head-ache of them all!  (I consider air-launch to be a stage)

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Dan Moser - 7/10/2006  7:08 PM
Lastly, the SSTO delivers the maximum amount of spent propulsion mass to orbit.  This is of no value if the spent stage goes unused until its orbit decays. On the other hand, if you can recycle the spent stage materials into useful things in orbit (radiation shielding, astronaut habitat, etc.) , then your expendable rocket could become part of the valuable payload.
I've always assumed (perhaps wrongly) that the SSTO launcher is thought of as a part (attached to) of the SSTO payload (otherwise it's 2 stage)  So there is no talk of stages.   It's a Single Stage.  Suppose it's not.  The upper stage of an ELV is also most often delivered to orbit and is subject to decay and perhaps could be used for "something" (like the multitude of proposals for the spent STS ET tanks)  Similarly, a Centaur still attached to the payload upon the final trajectory injection...

(personally, I think the separation between the payload and the launch stage(s) is more robust)
Title: Re: SSTO Thread
Post by: Launch Fan on 10/08/2006 05:39 pm
I agree that if there's nothing wrong with staging, then why worry about moving to SSTO. By the time there's a viable SSTO, staging vehicles will have reduced costs yet further.
Title: Re: SSTO Thread
Post by: Dan Moser on 10/08/2006 06:29 pm
Quote
lmike - 7/10/2006  9:31 PM

Quote
Dan Moser - 7/10/2006  7:08 PM
...
One reason to use SSTOs is to avoid launch delays caused by the potential of dropping booster hardware on someone downrange.  The Air Force requirements for "responsive space lift" specified no long holds on the pad due to range problems like a fishing boat or whatever wandering into the potential impact zone of spent stages and debris.  This is not as much of an issue with flyback reusable boosters or when aircraft are used as lauch platforms, such as with Pegasus and AirLaunch.
Yes this makes sense, but this disposing of used stages seems minor of a head-ache in the currently provided multi-stage launches.  It can even be exactly predicted where the stages fall.  I don't even think it figures into the insurance calculations.

Insurance is irrelevant because the range safety guys will not allow you to launch if there is any traffic in the stage impact zone.. The added expense of multiple launch delays can be very high indeed.

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lmike - 7/10/2006  9:31 PM  
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Dan Moser - 7/10/2006  7:08 PM
Another impetus for SSTOs is the elimination of staging events, which are historically problematic events during ascent..  something doesn't separate cleanly, or separates too early, or too late.
Separation mechanics has been studied and implemented throughout the years exhaustively.  Failure to separate is not frequent recently.  Still if it were, is it as big of a deal to provide redundant separation charges, stage event synchronization, compared to building a single stage vehicle?  Air-launch relies on the biggest separation mechanic head-ache of them all!  (I consider air-launch to be a stage)

Nevertheless, stage separation system failures do occasionally occur.  Also, there is a considerable expense associated with stage separation systems.  More parts, more complexity, more weight...  these inevitably lead to lower reliabilty and higher cost.  As for air-launching being a big headache, that may be... but keep in mind it is replacing all the ground launching headaches and expenses too.  BTW, the Orbital Pegasus has never had a failure associated with air launching, but they have had a stage separation failure.

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lmike - 7/10/2006  9:31 PM  
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Dan Moser - 7/10/2006  7:08 PM
Lastly, the SSTO delivers the maximum amount of spent propulsion mass to orbit.  This is of no value if the spent stage goes unused until its orbit decays. On the other hand, if you can recycle the spent stage materials into useful things in orbit (radiation shielding, astronaut habitat, etc.) , then your expendable rocket could become part of the valuable payload.
I've always assumed (perhaps wrongly) that the SSTO launcher is thought of as a part (attached to) of the SSTO payload (otherwise it's 2 stage)  So there is no talk of stages.   It's a Single Stage.  Suppose it's not.  The upper stage of an ELV is also most often delivered to orbit and is subject to decay and perhaps could be used for "something" (like the multitude of proposals for the spent STS ET tanks)  Similarly, a Centaur still attached to the payload upon the final trajectory injection...
Perhaps you misunderstood me about this point.  The spent stage I am referring to is the single stage, the SSTO launch vehicle. The upper stage of a multistage launch vehicle, such as a Centaur stage, is also delivered to orbit along with the payload, so its materials could also be recycled in a similar way to what I described.  My point was that the SSTO delivers several times more of this potentially recyclable material mass and larger tank volumes to orbit than an upper stage would, and this another potential advantage of SSTOs.

 
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lmike - 7/10/2006  9:31 PM
(personally, I think the separation between the payload and the launch stage(s) is more robust)

More robust than what?  I don't understand this comment.  Please clarify.

Now, I'm not saying that SSTOs are better than all multi-stage options overall, but SSTOs do have some advantages over multi-stage launch vehicles for Earth-to-LEO missions, as I have tried to list here.  Obviously, upper stages or high deltaV spacecraft propulsion will be necessary for higher energy orbits, such as geostationary or interplanetary.  If you want to avoid liquid hydrogen, low structural mass fractions, and/or wish to recover & reuse your launch vehicle, then SSTOs are not the way to go.
Title: Re: SSTO Thread
Post by: Dobbins on 10/08/2006 06:41 pm
Quote
Launch Fan - 8/10/2006  1:22 PM

I agree that if there's nothing wrong with staging, then why worry about moving to SSTO. By the time there's a viable SSTO, staging vehicles will have reduced costs yet further.

Because some people fall in love with a concept and continue to pursue it regardless of anything else. SSTO is one of these concepts, RLVs and spaceplanes are a couple of others.
Title: Re: SSTO Thread
Post by: Seattle Dave on 10/09/2006 03:21 am
Quote
Dobbins - 8/10/2006  1:24 PM

Quote
Launch Fan - 8/10/2006  1:22 PM

I agree that if there's nothing wrong with staging, then why worry about moving to SSTO. By the time there's a viable SSTO, staging vehicles will have reduced costs yet further.

Because some people fall in love with a concept and continue to pursue it regardless of anything else. SSTO is one of these concepts, RLVs and spaceplanes are a couple of others.

It's the "looks cool" element that saw the VSE gain some bad press.
Title: Re: SSTO Thread
Post by: Dobbins on 10/09/2006 04:29 pm
Quote
Seattle Dave - 8/10/2006  11:04 PM

It's the "looks cool" element that saw the VSE gain some bad press.


These people have let a spaceplane become an end in itself rather than a means to an end. They want their spaceplane even it it isn't the best solution to the problem of traveling to the Moon and Mars.

The same is true of many SSTO buffs, they don't care if a SSTO is or isn't the best solution to the challenge at hand, they try to fit a SSTO in even if it means trying to change mission goals to fit their "cool" pet project.
Title: Re: SSTO Thread
Post by: mauk2 on 10/09/2006 08:41 pm

Hmmmm.

Quote
They want their spaceplane even it it isn't the best solution to the problem of traveling to the Moon and Mars.

This raises an interesting question.

What IS the "challenge at hand?"  What do people think it is?

Many (FAR to many in my opinion) people view the challenge as getting robotic probes up, or placing token flags.

Looking back over history, the human urge to go and see has never flagged.  Given that even now with our pitiful capabilities, people are already willing to expend huge sums to go and see, do people really believe that this current model will remain in place for the forseeable future?

Yes, it may be irrational to want to go "out there."  Welcome to being human.  Eventually, somebody WILL go.  Heck, how many years ago did we climb Everest for the first time?  Now it's a tourist destination. (An extremely dangerous one, but nonetheless....)

So, what mission do we plan for?  Narrow science missions in the current .gov straitjacket, or the missions that thousands of years of history tell us are as inevitable as dawn?  I mean, Columbus did not start his voyage in a canoe strapped to the tip of a mast.  :)

As technology improves, it is getting easier and easier to "do rockets."   The last massive hurdle is the energy density of available propellants, and we already know ways around that.  How much longer are artificial taboos around using those technologies going to last?
Title: Re: SSTO Thread
Post by: Jim on 10/09/2006 08:46 pm
Forever.   No nukes for launch
Title: Re: SSTO Thread
Post by: Dobbins on 10/09/2006 09:41 pm
Quote
mauk2 - 9/10/2006  4:24 PM

What IS the "challenge at hand?"  

NASA's job is to develop space technology and do science research. In this context that means doing science on the Moon and Mars and developing the basic technology and procedures for living off world.

It is no more NASA's responsibility to provide transportation and accommodations for tourists in LEO or on the Lunar surface than it's their job to provide transportation to the cape and hotel rooms for tourists who wish to watch a shuttle launch.

If you want private transportation to a lunar hotel I would suggest that you invest your money in a private company who's purpose is catering to space tourists.
Title: Re: SSTO Thread
Post by: Dobbins on 10/09/2006 09:43 pm
Quote
Jim - 9/10/2006  4:29 PM

Forever.   No nukes for launch

Amen. Ignoring political realities is as foolish as ignoring the physics of spaceflight.
Title: Re: SSTO Thread
Post by: Dan Moser on 10/09/2006 10:02 pm
Forever is a pretty long time, but I agree with Jim in principle.  Mauk seems to want everyone to stay on the ground until he & his fantasy Physics buddies invent some kind of dreamey antimatter/dusty pulsed plasma propulsion before we venture outward... No doubt advancements will continue to be made, but Orville & Wilbur did not wait until the technology was ready to build a 747, they used today's technology and flew today.  So, Mr. Mauk, what do you say to today's space explorer?.. wait a lifetime for technology that may not even exist at all, and don't worry about the price tag?

Sorry, Mauk, but the world simply will not wait for that sort of dreamey nonsense!  Chemical propellants work and work well.  For some reason, you think 90% propellant mass fraction is a scarey deal, yet you think a pocketful of positrons is the ultimate answer.  Oh well, it's good for a laugh!
Title: Re: SSTO Thread
Post by: lmike on 10/10/2006 03:43 am
Dan, first of all thanks for expanded answers to my questions. Yes, range safety is an expense (not the case in East European launches as there is almost none - stages fall onto a desert/ocean -- there is really not much "range safety" for the Protons, they still deliver sats). By "more robust" I meant that a scheme where the launcher is a distinct stage to the payload is more robust than a scheme where the launcher and the payload are one whole system (an SSTO). And we can argue these points ad infinuum.

Yes, there are areas where an SSTO can be better in than an MSTO. My question was basically "Is it worth it?" As a sum total. I.e. if the multi-stage rockets can be improved in those areas (and they can be, *if* they need to be), is the expense of the process of improving lesser or greater than the process of producing an operational SSTO (leaving reusable / non-reusable aside)? If multi-stage can be improved to address these, then why an SSTO? (Is there something basic in the multi-stage scheme that makes it inferiour? And yes, you've listed the points and I appreciate that -- this is what I wanted to see, but I don't think they are a problem.)
Title: Re: SSTO Thread
Post by: Dan Moser on 10/10/2006 05:51 am
Quote
lmike - 9/10/2006  10:26 PM

My question was basically "Is it worth it?" As a sum total. I.e. if the multi-stage rockets can be improved in those areas (and they can be, *if* they need to be), is the expense of the process of improving lesser or greater than the process of producing an operational SSTO (leaving reusable / non-reusable aside)? If multi-stage can be improved to address these, then why an SSTO? (Is there something basic in the multi-stage scheme that makes it inferiour? And yes, you've listed the points and I appreciate that -- this is what I wanted to see, but I don't think they are a problem.)

I would not call multi-stage launch vehicles inherently inferior at all.  They are all we have today.. and they work.. and they will continue to be the backbone of the launch industry... and improvements will continue to be made.  The expense of developing a new SSTO could be relatively low and could very well be justified with the right design, a good development team and favorable launch market conditions.  On the downside, SSTOs require the performance only found with liquid hydrogen fuel, which is kind of a bitch to deal with.   I only started posting on this SSTO topic thread because I wanted to outline the prospects and limitations of near term SSTOs, but multi-stage rockets are clearly here to stay, and that's just fine by me....  I'm a big fan.
Title: Re: SSTO Thread
Post by: mauk2 on 10/10/2006 10:33 pm
Quote
Dan Moser - 9/10/2006  4:45 PM

Forever is a pretty long time, but I agree with Jim in principle.  

Why?  :)

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Mauk seems to want everyone to stay on the ground until he & his fantasy Physics buddies invent some kind of dreamey antimatter/dusty pulsed plasma propulsion before we venture outward...

I have not once stated such.  Chemically lofted EPP's are the best, and most viable near term high energy propulsion solution we have available.

Have you read the thread I linked?  This is not "dreamey" in the slightest, and I have provided links to upwards of a hundred factual resources to prevent exactly this sort of mis-characterization.   "Fantasy physics."  LOL!

Shame on you for your closed-mindednes.


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No doubt advancements will continue to be made,

No doubt. :)

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but Orville & Wilbur did not wait until the technology was ready to build a 747, they used today's technology and flew today.  

High energy designs were developed in the 1960's capable of Isp's of 10,000+, given modern materials.  And the modern materials in questions are not laboratory wonders, it's plain old high strength steels and CAD/CAM design methods.  There was no technical or engineering reason not to develop this technology further.

Do you disagree?  Because I have the links to source documents to demonstrate it.

There is nothing "dreamey" about this technology, it is actually quite simple and robust, and uses no new principals.  Developing it, absent the suffocating mantle of .gov red tape, would be a simple task.

It is, however, "scarey."  All applications of high energy engineering are scarey.  But fertilizer and airliners are both far more common and deadly than any system I propose, and I don't see anyone working to illegalize those.  

No, we chose to deliberately turn away from high energy solutions due to a short-term political climate, and thus we are struggling to "make do" with the low specific energies of chemical fuels.  The NPT(Non-Proliferation Treaty) which bars advancements in this field has done little to nothing to stop outlaw states, as recent events in North Korea highlight once again.   If the NPT is doing more harm than good (and I postulate exactly that) then we should alter it or withdraw.

These are the facts as I see them, I'm sorry if that bothers you.   Do you see different facts than I do?  


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So, Mr. Mauk, what do you say to today's space explorer?.. wait a lifetime for technology that may not even exist at all, and don't worry about the price tag?

The technology is 40+ years old and well developed.  Remove outmoded laws that artificially suppress this technology, while emplacing strong and effective regulation, and let private industry do what it does.  The gold rush for space resources would make your head spin.

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Sorry, Mauk, but the world simply will not wait for that sort of dreamey nonsense!

I strongly object to this characterization, which is simply wrong.  The first Orion project produced working designs for high energy propulsion designs, and with modern technology, we could do much better.

But honestly, we could use the EXACT same technology and get real, robust space access.

Institutionalized fear of all things "nuclear' is the obstacle, and a baseless fear at that.  Antimatter solutions are workarounds to address that fear, but are not required to make the principals work.  Also, antimatter in the form of anti-protons (not positrons, which scare the poo outta me) are a very elegant way to address many concerns of EPP's.  Not required, but elegant.  I like elegant. :)


Quote
Chemical propellants work and work well.  For some reason, you think 90% propellant mass fraction is a scarey deal, yet you think a pocketful of positrons is the ultimate answer.  Oh well, it's good for a laugh!



Well, I wish you the best of luck with that.  At least I've amused someone.  :)  

As an aside, does anyone have an example of any transportation system in human history which succeeded at such low mass fractions as chemical SSTO's?  (Reference to coal barges got me to thinking about this.)  If so, please relate what it is, because I have pondered this at length, and have not found one even close.  

If no such system exists, then what is different about access to space versus historical uses of transportation systems that makes chemical rocketry different and viable?
Title: Re: SSTO Thread
Post by: Jim on 10/10/2006 11:05 pm
Have fun in your fantasy land.
Title: Re: SSTO Thread
Post by: Dobbins on 10/10/2006 11:28 pm
mauk2, as long as you are wishing for some Star Trek Technology, why not toss a transporter into your fantasy? Then we could beam people right up and eliminate the need for anything as primitive as a launcher!

Title: Re: SSTO Thread
Post by: meiza on 10/11/2006 12:48 am
I don't wish this messageboard to turn into such cheap insults.
Title: Re: SSTO Thread
Post by: Dan Moser on 10/11/2006 01:00 am
What is NEVER addressed by Mauk2 is the issue of the COST of these "fantasy Physics" propulsion systems.    Now there's a serious case of costphobia!
It's so easy to assert that  Uncle Sam is suppressing advanced technology, and you can never prove that because... how convenient is this?... Uncle Sam is also supppressing the proof.  Well, I say.... PROOVE IT!  Show us the test data for an engine test with Isp = 10,000 sec. !!
Oh.. right... that evil Uncle Sam is (conveniently) suppressing that too!
(Reminds me of Michael Palin the surf in Monty Python & the Holy Grail... "Help, help, I'm being repressed !! ")

Now, I am not trying to be confrontational or overly critical, and I certainly encourage research into new technologies, but wild assertions that these high energy density systems are ready for use and well-proven since the '60s... and stating (or at least implying) that chemical propulsion is obsolete and futile... and that the main obstacle to implementing these "proven" systems is governmental obstructionism.... These assertions lack credibility without hard evidence.  

Few would argue against the paramount importance of reducing the COST of space access to open the final frontier of space...  Propellant mass fraction is merely an intermediate number, though an important one, but COST and RELIABILITY numbers override all others.  Ultra-high energy densities sound like a good thing, but would a launch system using these ultra-high energy densities reduce the COST and raise the RELIABILITY of space access?   Convincingly answer THAT, Mauk2, and I'll be on your side.

Title: Re: SSTO Thread
Post by: selden on 10/12/2006 10:45 pm
While I doubt that a nuclear powered SSTO actually would be built, calling it fantasy is inappropriate. As Mauk has pointed out, design studies were made in the early '60s that indicated that the technology would be feasable. Of course, they were far from being blueprints at that point, although preliminary plans for the necessary testing were described.

Some of the then-classified documents describing Project Orion are now readily available by way of NASA's Technical Reports server at http://ntrs.nasa.gov/ Not all of the documents are available, however. Whether it's because they're still classified or simply not cataloged is hard to determine.

I was interested to discover that the wording of the new Space Policy document does not preclude such a development, although they may not intentionally have written the "Space Nuclear Power" section with it in mind.  http://www.ostp.gov/html/US%20National%20Space%20Policy.pdf
Title: Re: SSTO Thread
Post by: Dan Moser on 10/13/2006 01:35 am
Quote
selden - 12/10/2006  5:28 PM

While I doubt that a nuclear powered SSTO actually would be built, calling it fantasy is inappropriate.

If it will never be built, that means it is a fantasy by definition, right?  Whether it will never be built because of political realities or technical issues.. doesn't really matter.  The result is the same.

Quote
selden - 12/10/2006  5:28 PM
As Mauk has pointed out, design studies were made in the early '60s that indicated that the technology would be feasable. Of course, they were far from being blueprints at that point, although preliminary plans for the necessary testing were described.

The most desirable result of any research project is "feasible, but needs more funding."  The "Yes, no problem" result means it's ready for commercialization, so no more R&D funds.  Likewise, the "No, not a chance" result leads to a termination of R&D funds.  Any R&D project manager knows that the "Well.. maybe" result is what you always shoot for.  Just because you did a design study and have a crude concept on paper doesn't mean you are ready to start building a spaceship.  
 
Quote
selden - 12/10/2006  5:28 PM
Some of the then-classified documents describing Project Orion are now readily available by way of NASA's Technical Reports server at http://ntrs.nasa.gov/ Not all of the documents are available, however. Whether it's because they're still classified or simply not cataloged is hard to determine.

Project Orion's funding was terminated for a reason.  You can blame irrational nuclear-phobia if you want, but this was undeniably an extremely high risk - high cost program.  If you have to spend something like a trillion dollars before you even know if it's going to work, maybe it's not such a great idea.   Nuclear detonation research, I would hope, would still be classified

Quote
selden - 12/10/2006  5:28 PM
I was interested to discover that the wording of the new Space Policy document does not preclude such a development, although they may not intentionally have written the "Space Nuclear Power" section with it in mind.  http://www.ostp.gov/html/US%20National%20Space%20Policy.pdf

I think you missed a key word in the first sentence:  "Where space nuclear power systems safely enable or significantly enhance space exploration or operational capabilities, the United States shall develop and use these systems."  The key word is "safely."  No way does this document keep the door open for nuclear SSTOs.

Selden, my point was that without a credible arguement for reducing the cost of safe, reliable Earth-to-LEO transportation, nuclear and other futuristic high-energy systems will be limited to low thrust space-based propulsion beyond LEO...  but only if they can show higher cost effectiveness than other options (solar-themal, solar-electric, etc.)  The cost issue is consistently avoided by futuristic propulsion system proponents.

Title: Re: SSTO Thread
Post by: Pete at Edwards on 10/13/2006 03:46 am
What major differences do we think would be around today if VentureStar had worked out?
Title: Re: SSTO Thread
Post by: Dobbins on 10/13/2006 04:41 am
Quote
Pete at Edwards - 12/10/2006  11:29 PM

What major differences do we think would be around today if VentureStar had worked out?

We would be stuck in LEO for at least another 25 years.
Title: Re: SSTO Thread
Post by: pip on 10/13/2006 05:53 am
Naw, we wouldn't be stuck in LEO for another 25 years.  If they did everything right flights would have become super-routine and the economics would have improved.  Private VentureStars and government operators could have assembled moon traveling vehicles in orbit at minimum expense at an early date.  Economics of scale would have rocked it all the way out.  They could have had twenty of them flying and they'd be building all sorts of crazy stuff up there.
Title: Re: SSTO Thread
Post by: Dan Moser on 10/13/2006 06:19 am
Quote
Pete at Edwards - 12/10/2006  10:29 PM

What major differences do we think would be around today if VentureStar had worked out?

hmmm... IF it had worked out?  Ways to make the Venture Star "work out" might be to add strap-on boosters and/or an upper stage.. in other words, the Venture Star is not a viable SSTO design..  neither technically nor financially.  Just shy of $ 1 Billion was spent on X-33 development, Lockheed-Martin could have commercialized the technology but chose not to.. apparently the Atlas 5 EELV family is far more viable and profitable.

As I understand it, the main problem was shrinking payload capacity.  The reusability requirement demanded extra mass for TPS, landing gear, etc.  Too far aft CG was a big technical problem.  The linear aerospike engine on the tail was was heavy, which made the empty vehicle highly unstable upon atmosperic re-entry.  A nose weight was required to stabilize it enough to acheive gliding flight.  All of those added heavy components that kept popping up effectively shrunk the payload mass to near zero. No payload, no customers.

Title: Re: SSTO Thread
Post by: Dobbins on 10/13/2006 07:01 am
Quote
pip - 13/10/2006  1:36 AM

Naw, we wouldn't be stuck in LEO for another 25 years.  If they did everything right flights would have become super-routine and the economics would have improved.  Private VentureStars and government operators could have assembled moon traveling vehicles in orbit at minimum expense at an early date.  Economics of scale would have rocked it all the way out.  They could have had twenty of them flying and they'd be building all sorts of crazy stuff up there.

Just because you want something to happen doesn't mean it will. The commercial market wouldn't automatically recover just to serve the whims of spaceplane buffs. The competing foreign launchers would still be subsidized and going after the limited number of launches available. The spaceplane would still only have a tiny payload if built as an SSTO and be incapable of carrying most loads into orbit. If strap on boosters are added you lose some reusability, raise costs, and still have a payload below that of EELVs. The economics of the market would still require a higher flight rate than the spaceplane had customers for so it would be like the shuttle, gobbling money even when it wasn't flying.

NASA would be stuck with a new spaceplane that didn't even have the shuttle's payload capacity and even more expensive per pound to orbit than the shuttle. As happened with the Shuttle NASA would spend all it's money on overhead and looking for missions to justify the existence of the spaceplane. The difference is NASA would be stuck with the new spaceplane for a longer timespan than the soon to be retired shuttle.
Title: Re: SSTO Thread
Post by: vt_hokie on 10/13/2006 07:56 am
Quote
Dobbins - 13/10/2006  12:24 AM

We would be stuck in LEO for at least another 25 years.

I disagree.  If it had worked out, we'd have a safer, less expensive, higher flight rate shuttle already, meaning we could probably start building a heavy lifter like Ares V and mount beyond-LEO missions in the same timeframe we're looking at now, and we'd have a superior LEO transportation system in the meantime.
Title: Re: SSTO Thread
Post by: vt_hokie on 10/13/2006 08:08 am
Quote
Dobbins - 13/10/2006  2:44 AM

The spaceplane would still only have a tiny payload if built as an SSTO and be incapable of carrying most loads into orbit.

Fully reusable TSTO seems like a more realistic goal.

Quote
If strap on boosters are added you lose some reusability, raise costs, and still have a payload below that of EELVs.

You may not have to lose reusability, if something like the proposed shuttle LFBB is used.  But sure, it would increase cost and complexity.

Quote
The economics of the market would still require a higher flight rate than the spaceplane had customers for so it would be like the shuttle, gobbling money even when it wasn't flying.

The shuttle gobbles money while it's not flying, and we're lucky to get 4 flights per year.  For the same amount of money NASA puts toward shuttle ops, could we not get maybe a dozen or two dozen flights per year?  I'm not expecting it to be profitable, but I think we can get more flights for our money with a shuttle 2.0 than we do with the existing shuttle.

Quote
NASA would be stuck with a new spaceplane that didn't even have the shuttle's payload capacity and even more expensive per pound to orbit than the shuttle.

This I don't understand.  Why could we not match the shuttle's payload capacity with at least an incremental improvement in costs?

Quote
As happened with the Shuttle NASA would spend all it's money on overhead and looking for missions to justify the existence of the spaceplane.

If we had a VentureStar right now, one mission would be completing ISS.  Wouldn't it be nice to lift the remaining components within, say, a year vs over the next 4 or 5 years?
Title: Re: SSTO Thread
Post by: Jim on 10/13/2006 12:00 pm
There is no proof the Venturestar's turnaround capability.  It could be worse than the shuttles.
Title: Re: SSTO Thread
Post by: Jim on 10/13/2006 12:04 pm
Common fallacy.  Let's have a vehicle that flies 20-40 times a year.  Oops, forgot a few things

1.  there aren't 20-40 payloads to be flown a year
2.  there isn't $ for 20-40 payloads a year
3.  there isn't infrastructure (launch site, range, tracking systems, factories, etc) for 20-40 payloads a year
Title: Re: SSTO Thread
Post by: Dobbins on 10/13/2006 01:37 pm
Quote
vt_hokie - 13/10/2006  3:51 AM

If we had a VentureStar right now, one mission would be completing ISS.  Wouldn't it be nice to lift the remaining components within, say, a year vs over the next 4 or 5 years?

ISS componants were designed for the Shuttle payload bay, which is why we can't send them up on cheaper EELVs now. So even in the unlikely event that Venturestar had the ability to lift that  much mass it still wouldn't be capable of doing ISS construction.

As for the Rose colored glasses tales about quick turnarounds and dirt cheap launch costs, I heard that song and dance in the 70s about the Shuttle.
Title: Re: SSTO Thread
Post by: Dan Moser on 10/13/2006 06:51 pm
If you want a reusable spaceplane, forget about SSTO.

I'm amused by how often people want to put wings on a rocket design, thinking lower costs and quicker turnaround times must surely be the result.  Applying the same logic, perhaps air freight would be cheaper if airplanes more closely resembled ocean freighters, which haul much larger loads at much lower cost than airplanes. Or maybe airplanes should land on railroad tracks so they will become as cheap as trains.

To get a pound of payload to LEO requires over 1,200 times as much energy than getting a pound of cargo up to cruising altitude on a jet plane. This leads to some pretty fundamental design differences.  Maybe a big tube filled with propellant standing with pointey end up isn't "cool" enough for some people, but that's what makes sense if you want to get to space.
Title: Re: SSTO Thread
Post by: vt_hokie on 10/13/2006 09:22 pm
Quote
Dobbins - 13/10/2006  9:20 AM

ISS componants were designed for the Shuttle payload bay, which is why we can't send them up on cheaper EELVs now. So even in the unlikely event that Venturestar had the ability to lift that  much mass it still wouldn't be capable of doing ISS construction.

Unless it had a shuttle-like payload bay.

Let me ask this question:  If we started today with a clean sheet and designed STS version 2.0 using the best available technology, don't you think that we would end up with something significantly better than the space shuttle?  Certainly we could improve at least somewhat on safety, reliability, and operational cost.  

If I may be allowed to veer off topic briefly, this letter to The Economist was posted recently on a rail discussion board:

WHEEL OF FORTUNE
>
> SIR - If German and Japanese taxpayers wish to support the
> development of high-speed magnetic levitation (maglev) trains it is
> up to them ("Still aloft, just", September 30th). However, maglev
> railway has for years been a discredited solution seeking a problem.
> In Britain such a project would be a folly and a bigger waste of
> money (and political capital) than Concorde or the Millennium Dome.
>
> On railways the wheel is not the problem and it should not be
> replaced with more complex and energy-consuming maglev systems that
> require vast additional investments. The wheel is a remarkable piece
> of technology, simple in principle and effective at speeds adequate
> for high-speed trains. The real challenge is in the track: high
> speeds need relatively straight tracks and lots of land. Therefore
> our focus should be on making a high-speed train that is as
> environmentally benign and economic as possible.
>
> Trains are designed for transport, not to provide electrical and
> mechanical engineers with futile intellectual challenges. Is there
> any point in imposing a huge extra burden on taxpayers and pension
> funds to save a few minutes (perhaps) for a few travellers?
>
> John Emanuel
> Chairman
> UTEK Europe
> Berkhamsted, Hertfordshire



It reminds me somewhat of the space plane vs capsule debate.  Seems you old technology guys (and gals) win for now, but I still think maybe someday people will be riding a high speed maglev train to the local airport to catch a hypersonic scramjet powered aircraft!   ;)

This reply from the same discussion basically sums up my feelings:

I personally don't think that the Concorde was a waste.....it was an achievement. However, for all intents and purposes, it was an experimental airliner, and thus the reason for its fuel inefficiency and pollution problems. The real waste was not continuing the development of the SST.

As for Maglev, the technology is still raw - approximately at the stage that the railways were in the 1830s - however, as the Shanghai Airport Line shows, it's maturing. It's not yet a replacement for conventional rail by all means, but also it's by no means a "failed" technology either.
Title: Re: SSTO Thread
Post by: hop on 10/13/2006 11:38 pm
Quote
vt_hokie - 13/10/2006  2:05 PM
Let me ask this question: If we started today with a clean sheet and designed STS version 2.0 using the best available technology, don't you think that we would end up with something significantly better than the space shuttle? Certainly we could improve at least somewhat on safety, reliability, and operational cost.
That is almost certainly true, but how long would it take for the reduced operational cost to pay off the development  and construction costs ?

I agree that if STS could have been a starting point for an evolutionary development, it could have turned into something that was ultimately much better. There was a similar argument a while back on one of the sci.space groups that the first iteration of STS should have been an X-plane, i.e a techonology demonstrator / test bed for the production vehicle. But in reality, the cost of the first iteration was so high it ended up trading development cost for long term operating cost and reliability, never mind building flying prototypes or follow-ons.
Quote
As for Maglev, the technology is still raw - approximately at the stage that the railways were in the 1830s - however, as the Shanghai Airport Line shows, it's maturing. It's not yet a replacement for conventional rail by all means, but also it's by no means a "failed" technology either.
Or perhaps it shows that politicians are still willing to spend other peoples cash on expensive showpieces, regardless of whether they are justifiable by any objective technical or economic criteria. Something you might say about a few aerospace projects, for that matter.

Which interpretation is closer to the truth may not be clear for a few decades, history is littered with examples of both :)
Title: Re: SSTO Thread
Post by: Dobbins on 10/14/2006 02:17 am
Quote
vt_hokie - 13/10/2006  5:05 PM

Quote
Dobbins - 13/10/2006  9:20 AM

ISS componants were designed for the Shuttle payload bay, which is why we can't send them up on cheaper EELVs now. So even in the unlikely event that Venturestar had the ability to lift that  much mass it still wouldn't be capable of doing ISS construction.

Unless it had a shuttle-like payload bay.

The huge payload bay is one of the things that drive Shuttle costs up.

Quote
Let me ask this question:  If we started today with a clean sheet and designed STS version 2.0 using the best available technology, don't you think that we would end up with something significantly better than the space shuttle?  Certainly we could improve at least somewhat on safety, reliability, and operational cost.  


It would still have the high costs you incur when you build  RLV and don't have the flight rate to pay for the overhead of a center to service the RLV. How much more expensive is open to question. For example what kind of TPS are you going to use? Starting the project without knowing what kind of TPS it will have is foolhardy. You can hope that some new breakthrough like a metalic TPS can be developed in the course of the project, but if you run into problems you wind up with major delays, a canceled program or having to settle for a fragile SST type TPS, something that will drive safety margins down and costs up.

It simply isn't the right time to build spaceplane 2.0. Baring a major unforseen breakthrough it will not be incapable of flying the Moon and Mars missions that are planned. It won't have the flight rate needed to offset he costs of maintaining a RLV service center. The technology is rather dicey because of past mistakes of trying to develop overly ambitious spaceplanes instead of first developing the basic technology needed to build sucessful spaceplanes.
Title: RE: SSTO Thread
Post by: lmike on 10/14/2006 09:49 am
SSTO RLVs are cool.  I don't think there is anything useful about them though.  If you persue them, have a day job, please.
Title: Re: SSTO Thread
Post by: Jim on 10/14/2006 01:06 pm
I am going to post this on both threads (STS 2.0)

What orbit and payload mass is the SSTO or TSTO RLV suppose to be optimized for?

28.5 degrees 160 nmi?  What happens if you want polar?  PL mass drops by almost 50%
GTO/GSO?  Now another stage or two is needed?  look at the kludged systems and upperstages the shuttle required
Title: Re: SSTO Thread
Post by: modavis on 10/14/2006 03:57 pm

Quote
Jim - 13/10/2006  7:47 AM  Common fallacy.  Let's have a vehicle that flies 20-40 times a year.  Oops, forgot a few things  1.  there aren't 20-40 payloads to be flown a year 2.  there isn't $ for 20-40 payloads a year 3.  there isn't infrastructure (launch site, range, tracking systems, factories, etc) for 20-40 payloads a year

This is the central flaw of the technology-centric "build it and they will come" approach. The temptingly low $/lb figures are an average to be attained over a long period of high flight rate and fast turnaround... but the spending required to enable that HFR and FT comes up front. So if you don't have very deep and very patient pockets, you're going to have to start with much higher $/lb... which could well lead to "build it and they'll cheer, sit on their hands, and wait for prices to come down."               

Title: Re: SSTO Thread
Post by: mauk2 on 10/15/2006 02:19 am
Hmmm.  Fanmail!  :D

Quote
Have fun in your fantasy land.

How remarkably constructive.  Why are you posting in the "advanced concepts" forum again?  Do you have anything concrete to add?  Is perhaps the physical foundation of my argumentation incorrect?  Have I made some error?

I'm just human, maybe I simply don't understand the physics at hand.  


Quote
mauk2, as long as you are wishing for some Star Trek Technology, why not toss a transporter into your fantasy?

Okay, this is simply tiresome.  This sort of post-and-run is against the rules of this forum.  Please, post constructively!


Quote
I don't wish this messageboard to turn into such cheap insults.

Thank you for your fair consideration.  :)  I don't expect people to agree with me, I am aware of the deep prejudices against my views, as I used to hold those prejudices myself.  

What I DO expect is rational discussion, not one liners.


 
Quote
What is NEVER addressed by Mauk2 is the issue of the COST of these "fantasy Physics" propulsion systems.


The reason for that is that people who rely upon economics arguments expect there to be some profit motive for early exploitation.  There may be some thin pretense for such in history (Columbus, Indian spices, and Isabella's jewels are a classic historical example) but people will go and look for themselves, no matter what.  I happen to think that there is a huge profit motive once we start prospecting in space, but we are nowhere near that stage yet.  

The issue facing us is deeper than that.  Before Columbus could start his expedition, a ship had to be developed that could undertake the long, open-ocean sail, such as the nao and caravel:

http://www.evgschool.org/Columbus's%20Sailing%20Ships.htm

Over time, such vessels (and the all-important rigging) were developed for exploration and exploitation of the African coast.  There was a constant, incremental drive to "try a little harder" with each succesive design, but it was a gradual process.

Sadly, the current situation is not nearly so easy.  There IS no analog to the "coast of Africa" upon which we can develop the ships to use for exploration.  

Our current chemical-fueled space vessels are roughly analogous to bark canoes.  They will get a few people and perhaps a smidgeon of supplies where we want to go, but they are a far cry from the sturdy and capable Nina, Pinta, and Santa Maria which Columbus sailed, or the fleet of SEVENTEEN ships he used for his second expedition.  Seventeen!

However, there IS no economic incentive to develop those sturdier vessels (which I will argue demand high energy propellant, you may choose to disagree) because there is nothing of real worth in LEO.  If we had high energy comsats which demanded heavy lift that might be an incentive, but the advent of long distance fiber optics removed that as a driver.

This is by far the largest exploratory hurdle we have faced in our history.  Getting out of the Earth's gravity well is vastly more difficult than crossing an ocean, and even worse, there is no obvious gleaming new continent on the other side.

Compared to past exploratory/exploitative leaps, we as a species are going to HAVE to do this one as a "blind leap."  There are no slaves or spices or fabulous cities full of gold above our heads.  We will have to grit our teeth and make the leap and develop all those resources from scratch.

Now, fortunately, we have the wisdom to see the vast resources there, IF we can get there in a real way FIRST.  (Helium-3, fissiles, platinum group and rare earth metals, constant solar power, etc.)

This is the false dilemma people so love to bring up when this discussion is being made.  If we want to go, we will have to pay whatever it costs to go there, and all that money will have to be completely "on spec" far more than Queen Isabella selling her jewels.  

If we are unable to pony up that initial cost, we won't go.  

Period.

Now, there is a complication in this story.  The Apollo program was a huge point of national pride, but it falsely set a massive expectation, namely, that chemical rockets are great performers, and can get us to the Moon.  But sadly, there isn't all that much on the Moon when the best we can do is the equivalent of a bark canoe.  I have argued (convincingly, as evidenced by the ridicule I receive instead of real counter arguments) that we have to move to stronger medicine than chemical fuels.  But we have such a fear of high energy technology these days, we are very reluctant to make that switch.

Can we go to the Moon on Chemicals?  You bet.  But we're not going to establish those cities full of gold using them and that is the hurdle we must overcome. So, that "on spec" money that must be used to cross that first huge hurdle is being squandered in main on systems that are wholly inadequate to the task at hand.  To extend our analogy, we have the best darn bark canoes in history.  But they're still just canoes, while we need a caravel.

Does that clarify things any for you? :)

Quote
Maybe a big tube filled with propellant standing with pointey end up isn't "cool" enough for some people, but that's what makes sense if you want to get to space.

Makes perfect sense to me!  As long as the Isp is somewhere north of 3000 or so, that is.  

Fortunately, reaching such Isp is not at all difficult.  :)
Title: Re: SSTO Thread
Post by: kevin-rf on 10/15/2006 03:40 am
mauk2,

I would like to do a thought exercise with you comparing Lox/H2 rockets with nuclear thermal LH engines.

Lets start with the basics 2 H2 + O2 = 2 H2O
     1. It gives us an ISP of about 420-450.
     2. The reaction has a molecular weight of (4x1 + 2x16) 36.
     3. The storage ration is roughly 3 units (1 Lox unit, 2 LH2 unit)

To get an ISP of ~450 from LH you need to do the following...
     1. Have the equivalent mass of LH2.
     2. The equivalent volume of LH2 to a Lox/LH system is 2 units + 16x1 units = 18 units or 6 times the enclosed volume of a Lox/LH system.

In simple terms to lift the equvalent of a single core Delta IV you need six common core boosters.

Not very good but it does get better, most of the nuclear engines that where tested had ISP's of ~900-1000 or twice the ISP. This doubling of the ISP will result in half the equivalent storage units, so you go from 18 storage units to 9. This would take your single core Delta IV to a three common core vehicle for the same payload. Flying a Delta IV payload on a Delta IV heavy.

Now your dream of a 3000 ISP engine will help bring you volume back down to the same as a normal Lox/LH system (18 / 6 = 3).

The problem is I have only been able to find one reference ( http://www.astronautix.com/props/nucarlh2.htm ) to a nuclear thermal at an ISP greater than 1000. And that was a paper design ( http://www.astronautix.com/engines/rd600.htm ) that was never tested.

Why am I skeptical? The exhaust temperature of the ISP of 900-1000 engines was 1500 degrees. To increase the ISP to 3000 you need to increase that temperature to ~4500 degrees. They had enough trouble keeping those nuclear reactors together at 1500 degrees, good luck wth 4500 degrees. I don't want to think how much fissile material will fly out the tail pipe at that temperature.

Seems to me a complicated way to develop a vehicle of similar size an existing chemical rocket.

Sorry,
Title: Re: SSTO Thread
Post by: Dobbins on 10/15/2006 04:40 am
Quote
mauk2 - 14/10/2006  10:02 PM


Quote
mauk2, as long as you are wishing for some Star Trek Technology, why not toss a transporter into your fantasy?

Okay, this is simply tiresome.  This sort of post-and-run is against the rules of this forum.  Please, post constructively!


Constructively?

A week ago some random crackpot showed up on this forum, a chap with a web page full of junk science who was demanding that his views be accorded an unearned respect on a par with real science. Would it be constructive to deal with junk scientists, UFO buffs, and conspiracy theorists as if their views were on a par with those of real science?

No it would not, it just encourages junk science and drags the forum down to their low level. Even worse pretending that junk science is worthy of the same respect as real science is treason towards the very concepts that science is built on.

The same is true of people who want to ignore other aspects of reality in pursuit of some whim or another. Ignoring economic and political reality is just as bad as ignoring physical laws in favor of junk science.

You are demanding that your whims be accorded a position of respect equal to those based on sound economics and political realities, even though your concepts haven't earned that honor any more than a perpetual motion based system of space transportation. That unearned respect is something I'm no more willing to grant you than I'm willing to grant the same to the UFO buffs or Nigerian spammers.
Title: Re: SSTO Thread
Post by: modavis on 10/16/2006 03:43 am

Quote
mauk2 - 14/10/2006  10:02 PM  What I DO expect is rational discussion, not one liners.    

When are YOU going to offer anything but "one liner" characterizations ("irrational," "superstitious," and so forth) of the reasons why your talk will remain just that? If you have constructive ideas for changing the broad context of opinion on nuclear power, I for one am all ears, but here's a clue: "We need it for SPAAAACE" hasn't been enough, isn't enough, and won't be enough.

If you don't have constructive ideas for doing that, be prepared to grow old moaning "why isn't anyone listening?" The deafness is closer to home than you think.
 

 

Title: Re: SSTO Thread
Post by: Dan Moser on 10/16/2006 05:56 am
Quote
mauk2 - 14/10/2006  9:02 PM

As long as the Isp is somewhere north of 3000 or so, that is.  

Fortunately, reaching such Isp is not at all difficult.  

Your bluff is CALLED on this one!  Prove this outrageous assertion .. with facts, this time... not more BS weblinks that have little more than theoretical conjecture.   Also, your response to my challenge for cost data, was again.. quite predictably.. avoided.  The truth is... there is no working high thrust engine with Isp of 3,000 sec. or even close to that... at any cost.  Just because a scientist makes a plasma flash in a vacuum chamber doesn't mean you have a working rocket engine design... let alone a space transportation system.. Answer these questions specifically for the benefit of us primitive, neanderthal chemical propulsion guys:

1. How must thrust does your Isp > 3,000 sec. engine make?
2. How much does it weigh?  
3. How much power and propellant does it require?
4. What does the power supply weigh?
5. How much will it cost.. non-recurring and recurring?

My prediction:  Mauk2 can't answer ANY of these questions with numbers supported by data. We're probably in for more jibberish about Queen Isabella or some such nonsense.
Title: Re: SSTO Thread
Post by: rfoshaug on 10/16/2006 08:27 am
Sorry to interrupt such a lovely and constructive debate, but I've got a question about the aerospike engines planned for the VentureStar project. :)

According to http://www.boeing.com/defense-space/space/propul/RS2200.html the RS-2200 aerospike engine was to have an Isp of 347 seconds at sea level, and 455 seconds in vacuum.

This isn't too impressive, is it? I thought aerospikes were supposed to have way better specific impulse at low altitudes than conventional bell nozzles? The space shuttle's SSMEs have a sea level Isp of 363 seconds, and 453 seconds in vacuum.

Of course the aerospikes would have been throttleable down to about 20%, which would be vital to avoid exessive G loads as the vehicle gets lighter, but as it used 7 (?) of these engines, this could be solved using SSME's and shutting them down symmetrically as the flight progresses.

I don't know the mass of the aerospikes, but are they considerably lighter weight than the SSMEs (3,200 kg / 7,000 lb)? If not it would seem that the SSME would be a better choice to power the VentureStar? Why develop new engines when existing ones do a better job? Or am I missing something here?
Title: Re: SSTO Thread
Post by: Jim on 10/16/2006 11:27 am
They were heavier.
Title: Re: SSTO Thread
Post by: rfoshaug on 10/16/2006 11:31 am
So why did they want to use heavier, less efficient engines? Especially for SSTO, this sounds like a bad idea?

Only one word comes to mind....

Politics?

Because the ones deciding things invested too much pride in aerospikes?
Title: Re: SSTO Thread
Post by: Jim on 10/16/2006 12:06 pm
The whole design of the X-33 was around the aerospike.
Title: Re: SSTO Thread
Post by: rfoshaug on 10/16/2006 12:41 pm
Yes, but why design the X-33 around the aerospike if it in fact was a disadvantage compared to SSME?

Or did the relatively "poor" performance of the engines only become known later in the design when it was too late to switch to another engine?

If so, is the entire aerospike concept flawed, or could new more efficient aerospikes be developed?

Aerospikes have been hailed as the new more efficient rocket engine - especially at lower altitudes. But if a good ol' SSME has better Isp AND is lighter for more or less the same thrust, why would anyone use aerospike engines for SSTO?



On the other hand, I found this at Astronautix:
http://www.astronautix.com/engines/l1loster.htm

Sea level Isp of 455 seconds for a kerosene-fuelled engine? Surely this must be impossible? I can't seem to find any other info on the web about this engine. If true, this would be a very good choice for SSTO - with smaller tanks than a LH2-fuelled engine. But it seems like fiction to me. :)
Title: Re: SSTO Thread
Post by: Jim on 10/16/2006 01:08 pm
The X-33 was NOT an SSTO.  It was a technology demonstration vehicle.  It was never intended for orbit, only to Mach 13 or so.   Venturestar was the full scale version
Title: Re: SSTO Thread
Post by: rfoshaug on 10/16/2006 01:39 pm
Sorry, my bad - I was talking about the Venturestar, not the X-33.

The X-33 used XRS-2200 engines while the Venturestar (which was to be a SSTO) used RS-2200.

But the questions still remain:

- Was the sea-level Isp of the RS-2200 known at the early stages of VentureStar development - and if so, why did they spend millions to develop engines that were heavier and less efficient than SSME?

- Do all aerospike concepts have Isp equivalent to this - and if so, what's the point in having them? Is the concept of aerospikes in general flawed?

- Is this engine: http://www.astronautix.com/engines/l1loster.htm real or at least theoretically possible? Would an Isp of 455 sec at sea level using kerosene be possible? What would the vacuum Isp of such an engine be?

- Could a VentureStar-like SSTO be developed using conventional or uprated SSME engines (especially considering that the heavy engines were part of the reason why they had to slim down the fuel tanks which finally failed during a test)?
Title: Re: SSTO Thread
Post by: Jim on 10/16/2006 01:53 pm
RS-2200 and  VentureStar development  was not started.  Just powerpoint designs
Title: Re: SSTO Thread
Post by: rfoshaug on 10/16/2006 02:35 pm
Okay, but there's no doubt that aerospikes were planned to be used on VentureStar. All the "powerpoint designs" showed the VentureStar with aerospikes at its rear end. They even used the designation RS-2200 for the engine, and the general specifications were there. The XRS-2200 is also listed with similar Isp, and several test firings of these engines were done.

The X-33 was a technology demonstrator to test key technologies for VentureStar, such as aerospike engines, the general aerodynamic layout, TPS etc. So it was pretty clear that they would design the VentureStar with aerospikes.

So the questions in my previous posts still stand unanswered.

:)
Title: Re: SSTO Thread
Post by: Jim on 10/16/2006 02:53 pm
google x-33, venturestar and aerospike and find out and tell us

RS- 2200 would have been lighter
Title: Re: SSTO Thread
Post by: Dan Moser on 10/16/2006 08:40 pm
I think there is an erroneous perception among many that VentureStar was killed by politics.  NASA threw over $900 Million at the idea through the X-33 program, hoping this would kick start a commercial venture and/or be the start of the new, improved Shuttle.  It was a technical disaster and promtly abandoned by both NASA and Lock-Mart.  Replacing the disappointing aerospike engine with SSMEs, J-2s, RL-10s or whatever engine would not have helped the technical viability of the concept.  The vehicle's empty weight projections grew to such an extent that payload capacity shrunk to zero.  No payload.. no paying customers.
Title: Re: SSTO Thread
Post by: mauk2 on 10/16/2006 11:28 pm
hello, Kevi-rf! :)

Quote
I would like to do a thought exercise with you comparing Lox/H2 rockets with nuclear thermal LH engines.

While that is certainly possible, I don't think it is productive.  After much analysis, I have concluded that NTR's are a technological dead end, barring major breakthroughs in materials technology or plasma control, and more importantly, other systems such as External Pulsed Plasma give much higher performance for much less effort.   EPP is plagued with radioactive leakage, but so are the high-Isp NTR designs.  If you have to have a leaky drive for a given performance level, why build the complicated, difficult one?

If ANY radioactive leakage is abrogated by superstitious fears, then antimatter is the only remaining choice with today's technology, sadly.

(Note, all seen in the perspective of the SSTO performance envelope.  Once you're in space, the EPP advantage becomes overwhelming.)

As for the rest of your post, there are some okay points there, but you're starting from an imperfect assumption.  I, for one, think NTR should be ruled out, and don't think I've ever advocated it seriously.


Hello, Dobbins! :)

Quote
Constructively?

Yes, constructively.  As in, in a positive way, leading to a fact-based conclusion.

Quote
You are demanding that your whims be accorded a position of respect equal to those based on sound economics and political realities, even though your concepts haven't earned that honor any more than a perpetual motion based system of space transportation.

Ah, now, that is a constructive point, one that I can address.  

First, my "whims" are firmly based in physics and history.  I have asked this before and received no answer, so I will do so again:  Does anyone know of any transportation system ever in history that succeeded in real-life conditions with a fuel fraction of 90 percent?  Or even close there-to?  If the answer to that question is "no,"  as I strongly suspect it will be, then what is different about space access?  If you can argue convincingly that space access has a viable, market-based future at that miserable fuel fraction, then I'll be happy to concede your points.  But the current government-dominated solution is not long-term viable by any stretch of the imagination.  "Those who do not know history are doomed to repeat it", etc, etc.

For the economics portion of space access we have two paths forward: Create an economically viable transport system which can tolerate a mass fraction so high, or embrace high energy propellants and return to historical mass fractions.  Now, we have been attempting, in various ways, to create an economy based upon high mass fractions for 50+ years, and aside from very narrow niches, I don't see much success.  Price per pound has not budged, as far as I can tell.  This state of affairs has persisted for so long that people have forgotten and even actively oppose the other path, which is perfectly viable, just "scarey."

I fully realize that to people unfamiliar with the high energy propellants field, many claims sound "wacky."    I post many, many source documents to the underlying work in the field to fend off exactly these sorts of accusations.   This is far from "junk science."   :)   Stanislaw Ulam was many things, but he was no mumbling crackpot.  :)

Title: Re: SSTO Thread
Post by: mauk2 on 10/17/2006 12:00 am
hello Dan! :)

Quote
Your bluff is CALLED on this one!

LOL!  You got me! :)  

Quote
Answer these questions specifically for the benefit of us primitive, neanderthal chemical propulsion guys:


Now, there you go, mischaracterizing me again.  There is nothing primitive whatsoever about modern chemical rocket engines.  They are miracles of design and engineering.  Turbopumps are astonishing devices.  I mean, 70,000 horsepower out of a machine that is the same size as my car's engine?  Holy crap! :)

Modern rocket engines are like swiss watches cubed and powered by nitroglycerine. (How cool would that be!)  But, to stretch the analogy, while a million dollar diamond and graphite nitroglycerine-powered watch might be VERY COOL, a dollar store quartz crystal watch will keep time just as good.  Different operating principals, you see.

While modern rocket engines are incredibly good tech, that does not mean they are good solutions to move us forward.  Not through any fault of the engineers.  It's not their fault that chemical fuels are low energy, and fearful politicians forbade the high energy alternative years ago, for reasons that seem increasingly irrelevant.



Quote
1. How must thrust does your Isp > 3,000 sec. engine make?

The ten meter engine module designed for the Apollo followon had a maximum design acceleration of two g's at a total ship weight of 100,000 kilograms.  But honestly, an EPP can be built for almost any level of thrust you care to engineer it for up into the hundreds of million of pounds force.  Ground-launch of EPP's is extremely problematic in my opinion, but  simple lofter stage can readily correct that, and a cheap chemical lofter can be built in truly sick sizes.   As a note, 3000 seconds is at the lower range of EPP performance envelopes even using plain old steel and gas-filled shocks.  Not complicated stuff.


Quote
2. How much does it weigh?

It varied depending upon design constraints, but around twenty thousand kilos is a nice conservative figure.


Quote
3. How much power and propellant does it require?

Surprisingly little!  The most energy-intensive portion of an EPP's operation is injecting the pulse units into space behind the momentum conditioning system.  Fortunately, using bleed-off gas from the shock absorbers was more than sufficient to provide this energy, and had the side effect of helping to keep the shocks cool.  Other power requirements are also modest, a simple feed system to handle the pulse units would be electrically powered and could be served by fuel cells or a nuclear power source such as the SP-100 or a variant without too much trouble.

The "propellant" gets complicated.  I'd point you at the "More nuclear material" thread for more details of pulse units.  The propellant mass fraction is proportional to the Isp and Delta V, of course.

Quote
4. What does the power supply weigh?

A few hundred kilograms is sufficient.  Fuel cells or a reactor could readily handle this chore.  

Quote
5. How much will it cost.. non-recurring and recurring?

Who knows? :)  Let's build a prototype and find out!

My suspicion is, it would be quite economical.  For an example, basing upon airline economics models (similar Isp and fuel fractions) and given the likely expense of pulse units, I'd say fuel costs (unlike chemical designs) would be the largest component of flight cost.    It's the classic "chicken and egg" issue yet again:  There's no "there" there, so we have to build it on spec or stay home.  Costs per pound are likely to drop dramatically, as EPP concepts scale upward remarkably well.

For links and further discussion, may I refer you to the "More Nuclear Material" thread, yet again.  I don't want to drag this too far off course. :)
Title: Re: SSTO Thread
Post by: mauk2 on 10/17/2006 12:14 am
hello, rfoshaug! :)

Let me see if I can't toss a little more concrete info to you than the monosyllabic grunts you've been getting so far. :D

Yes, the engineers of X-33 and Venturestar were very aware of the thrust and Isp profiles of the aerospike.  While very few have flown, the concept is very well studied.  They knew that Isp off the ground would be rather awful, but felt there were other reasons for using them.

1) Isp increases with altitude.  Integrated over the projected flightpath, the Isp was a bit better versus a DeLaval nozzle, as the gains at altitude compensated and you spend more time at altitude.  Using a "pole vault" style flight path with a high thrust-to-weight off the pad can help with this.

2) Form factor.  Bell nozzles seriously messed with the aerodynamics of the lifting body, while the aerospikes tucked neatly along the back of the vessel.  The Space Shuttle requires a little "tab" along the back of the ship to make re-entry happy.  With much bigger nozzles and a MUCH wider body, the added weight of such a tab, in a razor-thin design already, would kill it.

3) Steering by differential throttling.  The SSME has to gimbal to steer, and uses hydraulics to do so.  The Venturestar was expected to HAVE no hydraulics, and the engines were bolted firmly in place, immovable.  Steering would be done by throttling various thrust chambers.  Elegant, if the throttling could be made reliable.

I hope this clears it up.  There were a lot of reasons that the aerospike was considered the best solution.  Sadly, the goal was quite a bit too ambitious.  
Title: Re: SSTO Thread
Post by: Jim on 10/17/2006 12:45 am
Quote
mauk2 - 16/10/2006  7:43 PM
 
Quote
5. How much will it cost.. non-recurring and recurring?

Who knows? :)  Let's build a prototype and find out!

)

Not a good enough reason
Title: Re: SSTO Thread
Post by: Dobbins on 10/17/2006 02:43 am
Quote
mauk2 - 16/10/2006  7:11 PM

If ANY radioactive leakage is abrogated by superstitious fears, then antimatter is the only remaining choice with today's technology, sadly.


Antimatter???? With Today's technology?????

With today's technology we can only produce trace amounts of anti-hydrogen barely enough to conduct physics experiments. It wound take centuries to create an ounce of anti-hydrogen with today's technologies and that is centuries of running particle accelerators which gobble large amounts of electricity. The last time I checked electricity wasn't free so we are looking at a very expensive ounce of anti-hydrogen. Today's technology is nowhere near solving the containment problem which is just as hard, if not harder, than the containment problem with nuclear fusion. The  fusion containment problem has kept fusion power 20 years in the future for the past 40 or 50 years.

The reaction of anti-matter with matter results in high energy gamma rays and daughter particle anti-particle pairs which are radioactive and which have energy levels similar to cosmic rays. Like the containment problem with storing the anti-matter fuel today's technology is no where near being able to contain the byproducts of matter anti-matter reactions occurring at a level consistent with it's use as a fuel.

Use of anti-matter with today's technology is pie in the sky of the worst sort.
Title: Re: SSTO Thread
Post by: Dobbins on 10/17/2006 02:46 am
Quote
mauk2 - 16/10/2006  7:11 PM

First, my "whims" are firmly based in physics and history.  I have asked this before and received no answer, so I will do so again:  Does anyone know of any transportation system ever in history that succeeded in real-life conditions with a fuel fraction of 90 percent?  Or even close there-to?  If the answer to that question is "no,"  as I strongly suspect it will be, then what is different about space access?  If you can argue convincingly that space access has a viable, market-based future at that miserable fuel fraction, then I'll be happy to concede your points.  But the current government-dominated solution is not long-term viable by any stretch of the imagination.  "Those who do not know history are doomed to repeat it", etc, etc.

For the economics portion of space access we have two paths forward: Create an economically viable transport system which can tolerate a mass fraction so high, or embrace high energy propellants and return to historical mass fractions.  Now, we have been attempting, in various ways, to create an economy based upon high mass fractions for 50+ years, and aside from very narrow niches, I don't see much success.  Price per pound has not budged, as far as I can tell.  This state of affairs has persisted for so long that people have forgotten and even actively oppose the other path, which is perfectly viable, just "scarey."

I fully realize that to people unfamiliar with the high energy propellants field, many claims sound "wacky."    I post many, many source documents to the underlying work in the field to fend off exactly these sorts of accusations.   This is far from "junk science."   :)   Stanislaw Ulam was many things, but he was no mumbling crackpot.  :)


Could you translate that from Sloganese to English?
Title: Re: SSTO Thread
Post by: rfoshaug on 10/17/2006 10:47 am
Thanks Dan and Mauk2 for that info on VentureStar and X-33.

So - am I correct if I assume that the only advantages with aerospikes are their shape, which is easier to integrate into an aerodynamic airframe, as well as the simplicity of not having to gimbal the engines? And that there are no real performance advantages at low altitude (actually a slight disadvantage both in Isp and weight)?

:)
Title: Re: SSTO Thread
Post by: Jim on 10/17/2006 11:00 am
There is an advantages at low altitudes.  Regular engines have nozzles optimized for a specific altitude.  The aerospike compensates for altitude.
Title: Re: SSTO Thread
Post by: Dan Moser on 10/18/2006 05:49 am
Quote
rfoshaug - 17/10/2006  5:30 AM

So - am I correct if I assume that the only advantages with aerospikes are their shape, which is easier to integrate into an aerodynamic airframe, as well as the simplicity of not having to gimbal the engines? And that there are no real performance advantages at low altitude (actually a slight disadvantage both in Isp and weight)?

:)

Well, actually, a linear aerospike may be a bit easier to integrate into a linear aft body of the the X-33/VentureStar "slice-of-pie" shape, but that rather silly shape was never demonstrated to be advantageous.  The linear aerospike was a very heavy engine because of high cooling requirements and high complexity.  I also recall that gimballing in the pitch direction was required, which introduced even more cost, weight, and complexity.  In terms of Isp performance in the "real world", plug nozzles and aerospikes (even the circular varieties) are not too bad at liftoff, but they suffer from complex slipstream losses and vacuum loss mechanisms that erase most, if not all of their theoretical altitude compensation benefits.  Raising the Pc on more conventional engines usually has the same benefit, and is easier and more straightforward to implement. A few other variable expansion ratio nozzle types may hold promise:  modified Expansion-Deflection, slotted nozzles, dual bell, dual expanders, etc.
Title: Re: SSTO Thread
Post by: rfoshaug on 10/18/2006 09:01 am
Thanks for the info, Dan! :)

I guess it was more a case of X-33/VentureStar being shaped to fit the aerospikes, than the aerospikes being chosen because they would fit the fuselage then.

If they had made an SSTO with more conventional lightweight engines, a less flattened fuselage (which would have made the tanks rounder and lighter and easier to make), and worried more about making the thing fly than employing new and exciting technologies, it might actually have worked, it seems.
Title: Re: SSTO Thread
Post by: Dan Moser on 10/18/2006 03:53 pm
Quote
rfoshaug - 18/10/2006  3:44 AM

If they had made an SSTO with more conventional lightweight engines, a less flattened fuselage (which would have made the tanks rounder and lighter and easier to make), and worried more about making the thing fly than employing new and exciting technologies, it might actually have worked, it seems.

It would be more accurate to say that it might have worked less poorly.  VentureStar probably would not have made it to LEO at all, even with zero payload, and a lighter reusable SSTO design has a much better chance of making it to LEO, albeit with virtually zero payload.  Either way... the bad result is.. zero payload mass.  The inherent extra dry mass needed to enable reusability is the primary obstacle.  Without a breakthough in materials and/or propulsion technology, a viable payload mass dictates that a successful SSTO design must be expendable.  Put another way, a successful reusable vehicle must have more than one stage.
Title: Re: SSTO Thread
Post by: mauk2 on 10/20/2006 07:12 pm
Hmmmmm.

Quote
Not a good enough reason


Actually, this is correct.  Here IS the good enough reason:


M = e^V/C, V=9700m/sec, C=4000m/sec

All the gas burner advocates out there who scorn high energy solutions have had 50+ years to make a viable way off Earth while satisfying that statement.

They have all failed.

Either show a viable market based transportation model at a 90 percent fuel fraction, work to change the paradigm that a 90 percent fuel fraction is required, or accept that we aren't going.

I mean, it is not at all a given that we WILL go, folks.

I have already stated that those who do not know history are doomed to repeat it:

http://www.ripon.edu/academics/global/Levathes.html

IF we do not shake off this superstitious fear of high energy solutions, it is not at all a given that we will make it anyway.  In the early 1400's the Chinese had the greatest ocean-going fleet in the world, by a huge margin.  Foolish, short-sighted politics burned the entire fleet and ended the entire thing.  China stayed home for 500 years, while the West claimed the huge prize of the North American continent, and only in the last few decades has China finally shaken off its malaise. The Chinese could have beaten Columbus by 50+ years, and could have had a colonial empire worldwide a century before any other European power did.  

We could ALL be speaking Chinese right now, except for foolish political decisions.

I posit that we are very close to making exactly the same mistake, on a much larger scale.   The wealth to be had in the Solar System is much, much greater than that of a single continent.

You may agree or disagree with my assessment, but the physics and the history is on my side of the argument.  Seems pretty darned compelling to me.  Even if I am speaking "Sloganese."  

Is that like a Chinese dialect? :D

Title: Re: SSTO Thread
Post by: Jim on 10/20/2006 07:56 pm
History is against you and economics, which are stronger than physics.
Title: Re: SSTO Thread
Post by: meiza on 10/20/2006 10:23 pm
I'm open to nuclear propulsion in space, but not on launch from Earth...

And actually aren't you proposing at least a first stage with a chemical rocket since those high exhaust speed particles tend to stop in air.

Probably a realistic alternative is a compromise, use high energy propulsion after some deltavee treshold (ie to Mars and beyond) and other constraints (it's not useful to build such for a small probe). It also gets rid of the contamination of innocent bystanders and nature.
Title: Re: SSTO Thread
Post by: mauk2 on 10/20/2006 10:36 pm
Quote
History is against you and economics, which are stronger than physics.

History is against me?   Do you care to prove this contention?  I have made my points and provided supporting links to historical fact.

We have your word that I am wrong.

So far, I think the weight of the evidence is against you, unless you claim to speak with deific authority. :)

Or do you contend that the Chinese did NOT destroy their ocean going capacity in the 1400's for solely political reasons?  

A situation that I will point out is remarkably similar to where we are right now in regards access to space?

Alas, I must respectfully disagree.  We will correct this situation, or someone else will go instead of us.
Title: Re: SSTO Thread
Post by: Jim on 10/20/2006 10:48 pm
economics is against everyone.  Look at the NK situation.  No one is going to do it
Title: Re: SSTO Thread
Post by: Dobbins on 10/20/2006 10:59 pm
Quote
mauk2 - 20/10/2006  6:19 PM

History is against me?   Do you care to prove this contention?  I have made my points and provided supporting links to historical fact.


No, All you have done is chant the same stale slogans ad nauseum. They didn't work the first time you said them and they still aren't working after repeating them over and over.

Your anti-matter powered rockets aren't viable. You are asking us to accept on blind faith that some how, some where, some body will come up with an economical source of anti-matter, with a means of reliably containing the anti-matter, and with some means of using it without showering the launch path with gamma rays and highly radioactive daughter particles. Your slogans and misapplied history lessons aren't a mantra that can magically make all these problems vanish in a puff of smoke.
Title: Re: SSTO Thread
Post by: Dan Moser on 10/22/2006 04:25 am
Quote
mauk2 - 20/10/2006  1:55 PM

All the gas burner advocates out there who scorn high energy solutions have had 50+ years to make a viable way off Earth while satisfying that statement.

They have all failed.

Either show a viable market based transportation model at a 90 percent fuel fraction, work to change the paradigm that a 90 percent fuel fraction is required, or accept that we aren't going.


Nope, you got it totally backwards, again!  It is the foolish idea of setting off a string of nuclear bombs behind a huge steel plate with shock absorbers that failed 50 years ago.  It miserably failed technically, economically, environmentally, and politically.  It does not make sense on ANY front.  Not a single engine like this was ever tested.  You can blame superstitions all you want.  You can provide links to moldy old theoretical studies until the cows come home, but the facts won't change.  

Fixating on the propellant mass fraction number is borderline insanity behavior.   For the umpteenth time, it's the cost number that matters, and you continue to avoid the cost issue like it was the plague!  Tubes filled with 90% chemical propellant ARE what is required to get people and stuff transported to space successfully. You can deny it until your ears bleed, but it is happening today and will continue happening more and more frequently with each passing year.  The real space pioneers are blazing the trail to the final frontier right now, and they're not setting off nuclear bombs to do it.  You can watch & learn, or piss & moan.  The choice is yours.
Title: Re: SSTO Thread
Post by: Dan Moser on 10/22/2006 09:20 pm
A travel agent’s recent phone conversation:

TA:  “Thanks for calling Pacific Travel.  How may I help you?”

mauk2: “I would like to fly to Hong Kong ASAP!”

TA:  “Certainly, sir. Tickets are $1,000.  When would you like to depart?”

mauk2: “Wait a minute!  Do you guys still burn lots of jet fuel in those airplanes?”

TA:  “Yes sir.. a 747 needs about 50,000 gallons of Jet-A to fly across the Pacific.”

mauk2: “That’s ridiculous!  Don’t you dim-witted gas burners know that a few grams of plutonium or uranium have as much energy potential as 50,000 gallons of fuel?”

TA:  “Yes sir, but I didn’t know nuclear engines were available for 747s.”

mauk2: “Well, there aren’t any yet... but it’s only because of government interference! That mean old Uncle Sam won’t allow public access to nuclear weapons technology!”

TA:  “That’s reassuring, sir, but has anyone ever designed, built, or tested these engines?”

mauk2: “No, no, and no, but some 40 year old theoretical studies say it’s possible.”

TA:  “Yes sir, perhaps it is possible, but how much would these engines cost to build and operate, and when would they become flightworthy?”

mauk2: “I have no idea about cost or schedule… but let’s start building one! Just send me a blank check, then I’ll buy some U235 from India or North Korea, but maybe we could instead use antimatter, or...”

TA:  “Sir, what about that plane ticket to Hong Kong?  I can guarantee the cost and schedule of the flight.”

mauk2: “I’m not going until you get your airplane fuel mass fractions down to some arbitrarily lower number of my choosing using really impressive ultra-high energy density materials. In the 14th century, the Chinese fleet was...”

TA:  “..(click)..”

mauk2: “Hello.. hello?  Why doesn’t anybody ever listen to me?”
Title: Re: SSTO Thread
Post by: meiza on 10/22/2006 10:07 pm
This thread has taken a direction to bs analogies instead of technical or economical insights. :(

Title: Re: SSTO Thread
Post by: Dobbins on 10/23/2006 03:08 pm
Quote
meiza - 20/10/2006  6:06 PM

I'm open to nuclear propulsion in space, but not on launch from Earth...

And actually aren't you proposing at least a first stage with a chemical rocket since those high exhaust speed particles tend to stop in air.


No he's dragging out the old project Orion yet again. It includes launch from Earth by setting off a whole series of nuclear bombs to blast the spaceship off from Earth. He's adding to the madness by wanting private ownership of the nukes that blast his spaceship into orbit and tossing in a bit of Sci-Fi by substituting Anti-matter bombs for H-bombs.

He ignores that this scheme will scatter fallout over wide areas of Earth every time his rocket bomb blasts off.

These things aren't just a hazard when launched from Earth's surface. Use one to exit from LEO and you leave fallout in an orbit that will decay and fall back to Earth. The EMP from the Nuke blasts will also kill any satellite that happens to be within a few hundred miles of launch. You can't use them for a launch from a higher orbit that is within Earth's magnetic field because the field will trap the radioactive particles increasing the radiation of the Van Allen Belts making that region far more dangerous. They can't be used for launch from the Moon, or Mars, or any place else that has a gravitational field because the fallout will contaminate that world.

The whole plot shows a lack of connection with reality.
Title: Re: SSTO Thread
Post by: meiza on 10/23/2006 03:32 pm
That is valid critique on actual points.
Title: Re: SSTO Thread
Post by: hyper_snyper on 10/23/2006 05:31 pm
I've never understood what people saw in the nuclear pulse concept.  It's borderline cartoony...like something the coyote would use to catch the road runner.
Title: Re: SSTO Thread
Post by: Dobbins on 10/23/2006 07:51 pm
Quote
hyper_snyper - 23/10/2006  1:14 PM

I've never understood what people saw in the nuclear pulse concept.  It's borderline cartoony...like something the coyote would use to catch the road runner.

The part that stuns me is the attitude that often goes with this and other fringe concepts. An almost religious cult like devotion where the concept becomes the "one true faith" and the devotee refuses to admit even a possibility that something may be wrong with his idea. Sometimes this attitude goes as far as open hostility towards the "sinners" who refuse to accept the fringe concept.

Frankly it's a waste of time attempting to have an honest debate with these apostles of fringe concepts, but it is important to expose the concept so that some people on the forum won't taken in.
Title: Re: SSTO Thread
Post by: mauk2 on 10/23/2006 08:48 pm
Ah, more fanmail. :)

Quote
economics is against everyone.

This is correct, as I think I pointed out. :)

Unlike any point in the past, we HAVE to make the huge leap off Earth completely "on spec" as it were.  In such a situation, squandering our resources on inadequate solutions is foolish.  Unless you just want a jobs program for rocketeers.  Which may be what we decide we do want.


Quote
Look at the NK situation.

Correct!  Our foolish political efforts to avert proliferation in the form of the NPT are proved to be ineffectual.  The NPT (an ineffectual document whose original purpose seems abrogated) is the primary instrument that prevents work on high energy propellants.  I mean, the world is full of smart folks, if we'd simply open this field of endeavor to study, I have little doubt that advances would happen quickly.  

Quote
No one is going to do it

Quite possibly no one in the US is going to do it.  I have no doubt that SOMEBODY will.  Let's just hope it isn't the Chinese.  But they have an insular history way deeper than ours, even. :)

Title: Re: SSTO Thread
Post by: mauk2 on 10/23/2006 09:23 pm
Quote
No, All you have done is chant the same stale slogans ad nauseum. They didn't work the first time you said them and they still aren't working after repeating them over and over.

That is your opinion, and you are welcome to it.  As is likely obvious, I disagree.  

Answer me this:  In the absence of high energy propellants, we are left with creating a workable, economically viable in a free market, transportation system at a fuel fraction of at LEAST 90 percent, and likely far higher (due to their being little of real value in LEO).  What is it?  

Please describe what such a transport system would look like.  Even a rough, first degree approximation would be fine.

Quote
Your anti-matter powered rockets aren't viable.

It's quite possible.  Luckily, antimatter isn't the only, or even best, high energy propellant avaliable to us.   It just helps.

That being said, NASA is certainly poking at antimatter with some small interest, likely driven by their pathological fear of the "N" word:

http://www.spaceref.com/news/viewsr.html?pid=12510

The way to disprove the viability is to build one, don't you agree?  :)  Worked for the X-33!

Quote
You are asking us to accept on blind faith that some how, some where, some body will come up with an economical source of anti-matter, with a means of reliably containing the anti-matter...

"Blind faith?"  

Please see prior link.  Antimatter production on the miniscule scales needed is not particularly challenging, assuming antiprotons.  Storage seems viable as well.  At this point in time, there doesn't seem to be any fundamental physics in the way of the method working, which means that it's just a matter of engineering.  That could change, of course, but hey, there's always the non-antimatter solutions. :)

Indeed, there have been studies done of mining antimatter out of the solar wind and various planetary magnetospheres.  While at first blush it seems feasible, even I do not advocate quite that yet.  But it is an interesting possibility. (As a note, a link to that antimatter mining comcept has been on this very board for months.)

Quote
and with some means of using it without showering the launch path with gamma rays and highly radioactive daughter particles.

Radiation is highly over-rated. :)

First, an antimatter SSTO powred by positrons is far more benign than you give it credit for.  The only reason to look at such an expensive and dangerous beast is the extreme cleanliness of the design.  Positrons emit only "soft" gamma rays at 511 Kev. While certainly not good for you, such gamma rays are quite short-ranged in air, and are far to low in energy to have significant nuclear interactions.  Instead, they interact only with electron shells, meaning they are no more "radioactive" in their leavings than good old chemicals.  So, in the case of the positron powered SSTO, your rad fears are completely incorrect.

Second, an EPP is very, very difficult to run in an atmosphere, due to the "external" part of the name.  So, it is far more reasonable to use a chemical lofter stage to get it above the turbopause before you begin pulsing.  (Vacuum is good.)  Above the turbopause means there is no more turbulent mixing witht he rest of the atmosphere.  The radioactive debris from the pulse units can be kept aloft via this method and diluted until its impact is no different than the constant shower of cosmic background we endure every second of our lives.

In both cases, there is no direct gamma exposure to anyone along the flightpath.

Your concerns about radiation,  while understandable, are baseless, when examined with an eye to how things could easily be done, rather in the "straw man" anti-"N"-word arguments you see so often.

I mean, I gotta live here, I wouldn't be advocating anything apocalyptically dirty. :)

Quote
Your slogans and misapplied history lessons aren't a mantra that can magically make all these problems vanish in a puff of smoke.

No, all that is required to "puff smoke vanish" these concerns is a dose of facts and common sense.  As for the "misapplied" part of those history lessons?  Time will tell.
Title: Re: SSTO Thread
Post by: Dobbins on 10/23/2006 09:27 pm
Quote
mauk2 - 23/10/2006  4:31 PM

 The NPT (an ineffectual document whose original purpose seems abrogated) is the primary instrument that prevents work on high energy propellants.


mauk2, when are you going to drop this rampant dishonesty and quit mislabeling the nuclear explosive devices used in this scheme as "high energy propellants"?
Title: Re: SSTO Thread
Post by: mauk2 on 10/23/2006 10:00 pm
Quote
Nope, you got it totally backwards, again!

Heh.  Well, you can certainly claim that, but so far, the citations in this thread are all mine, and all seem to support my side of the argument.  :)

Quote
You can provide links to moldy old theoretical studies until the cows come home, but the facts won't change.

You are correct.   Physics has not changed at all in the last 50 years.  

Please, explain exactly what engineering or technical burdle exists to invalidate the External Pulsed Plasma concept.   Yes, it was originated by the old mad, bad bombers, whose engineering credentials are not in the slightest doubt.

Put that aside.

Explain exactly why it would not work.  Be detailed.  Oh, and no puffing about economics:  The economics at this stage means diddly.  I see no economical model to LEO the markets will be interested in.  Maybe in a century space tourism, but even that is iffy at best.

Similarly, no puffing about politics.  As I posted, if we allow ourselves to be stopped by our own politicians, we deserve whatever fate befalls us.  I like to think we are wise enough to learn from history, although many days I wonder.

So, have at it.  Why won't it work?

Quote
For the umpteenth time, it's the cost number that matters, and you continue to avoid the cost issue like it was the plague!

Okay, let's turn this around.

What is the costing model for coal mining?  How does it compare to space access?

What is the costing model for commercial airlines?   How does it compare to space access?

What is your proposed costing model for future space access at 90+ percent fuel fractions?  How does it compare to any historical model?

I will freely admit, it MIGHT be possible to create an economical model that is viable at that fuel fraction.  I don't see how, but it IS possible, I suppose.  

You obviously deeply disagree with my proposals, so let's hear yours!   How do YOU say we should proceed?  I mean, you COULD be spot on!

Title: Re: SSTO Thread
Post by: mauk2 on 10/23/2006 10:43 pm
Quote
That is valid critique on actual points.

It certainly is, except that what he is critiquing bears only modest resemblance to what I propose.  This is called "straw man" argumentation, and is a classic logical fallacy.  For shame.  I'm right here, try arguing against what I actually say, rather than what you wish I'd said.

Quote
I've never understood what people saw in the nuclear pulse concept.

Oh, such a deceptively simple statement.  :)

In the "More Nuclear Material" thread, I have posted extensively on this.  In a nutshell, to access the energy levels needed to reach Isp in the high thousands regime, we surpass the material strangth of any conceiveable material at anything approaching state of the art.  Now, there IS a way to perform engineering above this point, using high energy engineering techniques.  The power of such mechanisms is impossible to resist, so the only way to utilize these principals is to do it outside of your vessel.  

It is possible to access much higher energy levels with an extenal process than an internal process.  Higher energy = higher Isp.  Higher Isp = better mass fractions.  Better mass fractions = better viability.

Thus, the appeal of the External Pulsed Plasma designs.

I steer clear of the nuclear pulse name these days, because it is perjorative and increasingly innacurate, due to positron propellant concepts.

Quote
It's borderline cartoony...like something the coyote would use to catch the road runner.

LOL!

Man, that'd be one FAST road runner, if it took an EPP to catch him. :D

But, despite the initial incredulity ("Zis is not nuts, zis is SUPER nuts," was an infamous early reaction) there is a tremendous amount of real physics and engineering behind the concept.

And for certain, it almost has to work better than chemicals do.  :)

I have been asking for folks to show how chemicals will work, if we fail to switch to high energy propellants.  I deeply suspect no one will do any better than the famous 52-54 Von Braun plan:

http://home.flash.net/~aajiv/bd/colliers.html

But, I could be wrong.  :)
Title: Re: SSTO Thread
Post by: Jim on 10/23/2006 10:48 pm
Quote
mauk2 - 23/10/2006  6:26 PM
 there is a tremendous amount of real physics and engineering behind the concept.

There is no engineering behind this.  Just crack pots
Title: Re: SSTO Thread
Post by: mauk2 on 10/23/2006 11:07 pm
Quote
mauk2, when are you going to drop this rampant dishonesty and quit mislabeling the nuclear explosive devices used in this scheme as "high energy propellants"?

There is nothing dishonest about it.  "High Energy Propellants" is accurate.  The category includes inertially confined fission devices, inertially confined fission/fusion devices, antimatter catalyzed fission/fusion devices, and direct utilization of antimatter in the form of positrons.  If we get lucky and have some huge advance and metastable chemicals become feasible, it could also include monatomic hydrogen and similar materials, although I'm not holding my breath for that one.  I do not care WHAT we use for the high energy propellant, I care only that we give them an honest, fair try at the problem.

Yes, there are a number of high energy devices which would do the job that are similar in function to old-fashioned nuclear bombs.  But there are others that would not.  

High energy propellants are tools.

Is it possible to misuse a tool?  As the events of 911 showed us, yes, absolutely.  But I don't see anyone moving to outlaw all airliners because they were misused as weapons.

If that is the test we wish to apply to all future advances, we might as well stop technology and get off, because the ride is making us dizzy. :)

Oh, wait, we already did that for rocketry, didn't we? :(
Title: Re: SSTO Thread
Post by: Dobbins on 10/24/2006 12:36 am
Quote
mauk2 - 23/10/2006  6:50 PM

Quote
mauk2, when are you going to drop this rampant dishonesty and quit mislabeling the nuclear explosive devices used in this scheme as "high energy propellants"?

There is nothing dishonest about it.

Horse feathers.

An honest man doesn't feel a need to hide the truth behind the kind of verbal trickery that is employed by shady politicians and flim-flam artists. The fact that you have chosen to use an obfuscative term for nuclear weapons doesn't say much for the overall honesty of your presentation.
Title: Re: SSTO Thread
Post by: josh_simonson on 10/24/2006 01:17 am
Last I checked nuclear submarines costed more to build and maintain than diesel ones, what makes you think rockets would be different?

>Actually, this is correct. Here IS the good enough reason:

>M = e^V/C, V=9700m/sec, C=4000m/sec

>All the gas burner advocates out there who scorn high energy solutions have had 50+ years to make a viable way off Earth while satisfying that statement.

How about M= e^V/C, V=8200m/s, C=4000m/s.   That's the equation for a tether interceptor using a spectra tether with a 1.5km/s tip velocity.  That's equivalent to an SSTO with an ISP of 531s!  While the bottom number isn't rising, the top number will continue to fall as material science produces stronger tethers.  There's more than one way to skin a cat and closed minded obsession with one aspect of the process is unlikely to be optimal.  I'd expect that for the cost of a nuclear rocket we could develop a tether that cuts the V by a greater percentage than the nuclear rocket increases C.
Title: Re: SSTO Thread
Post by: Dan Moser on 10/24/2006 08:33 pm
Here is what I've been working on:  a pressure-fed expendable SSTO.  The mass budget breakdown as follows for two selected sizes, with working names Bluebird and Eagle.. Bluebird is simply the proof of concept subscale model of the Eagle, kind of like the SpaceX Falcon 1 is to the Falcon 9.

   Bluebird   Eagle
Payload   1,000    12,505
Propellant   18,000   180,000
Tank/Insulation   438    4,075
Chamber   229    1,507
Injector   95    447
Avionics   30    30
TVC   40    188
plumbing   30    141
Misc. Dry   50    235
Total Structural   913    6,623
Total Gross   19,913   199,128
Payload/Gross Fraction   0.0502   0.0628
Propellant/Gross Fraction   0.904   0.904
Structural/Gross Fraction   0.0458   0.0333
Propellant/Stage Fraction   0.952   0.965

Features include a filament wound composite tank/airframe, ablative chamber, variable expansion ratio nozzle, variable area injector.  The propulsion system called is ECPS (http://home.comcast.net/~compositex/compositex.htm#ecps) which burns LOX/Hydrogen propellant.  Note that as the launch vehicle gets larger, the payload fraction gets better.  This favorable scaling effect is mostly due to the fact that larger ablative chambers tend to have much better thrust-to-weight ratios.  The designs are still works in progress, but I am estimating the cost to orbit of this series of vehicles will be well under $500 per pound, perhaps as low as $200 per pound.   The vehicle is so cheap to manufacture that a significant fraction of the total launch cost is range cost (range safety, weather, tracking, security, etc.).  I have some hope that situation will change with the opening of new private/foreign space ports and/or a shift in government range management practices, especially given the fact that an SSTO does not shed any hardware downrange.  Right now, it costs at least $1.5 Million to fly your rocket on a government range, regardless of how small or inexpensive it is.
Title: Re: SSTO Thread
Post by: meiza on 10/24/2006 10:38 pm
438 kg tank holding 18 tons of propellants!
Let's see. Assuming mixture ratio of 6:1, one seventh or 2600 kg is hydrogen. Since it weighs 0.071 kg per liter or 71 kg per cubic meter, the tank volume must be about 37 cubic meters. With a 3 meter diameter the hydrogen tank would be about 5 meters in length. Having surface area about 61 square meters.

We disregard the lox tank since it's tiny. :)

Simplifying, given the weight and surface area of the tank, about 77 percent or 50 square meters of the surface is on the cylindrical portion, giving about 337 kg or 6.7 kg per square meter. Carbon fiber's density is about 1.75 g/cc or 1750 kg/m^3. That would give a thickness h of about 3.8 millimeters.

Tensile strength of carbon fiber is about 3.5 GPa.

The tension on a differential width dL ring of the tank would be dL times tank pressure P times the perpendicular surface component (sin losses, ie the component contributing to the "pull-apart" force) of 2r. The strength would be tensile strength times dL times the thickness, 0.0038 meters.
So the pressure P = h * G / 2r = 0.0038 m * 3.5e9 N/m^2 / 3 m = 4.4e6 N/m^2 ~= 4 megapascals or 40 bar or 640 psi.

Huh, I hope I dunno if calculated it right quickly here.

Did I hit any close of the proposed tank and chamber pressure?

If it's 40 bars, that's quite low. In sea level engines, the V2 or A4 had 15 bars in the chamber, the Saturn V F-1 had 70 bars and Delta IV RS-68 has about 100 bars (1400 psi). And the latter only has Isp of 365 at sea level.

What's the planned Isp at sea level?


(Carbon fiber info from Vince Kelly's page, RS-68 from Boeing, others from Astronautix)
Title: Re: SSTO Thread
Post by: Dan Moser on 10/25/2006 12:04 am

Tank max. operating pressure is 230 psia.
Tank burst pressure is 460 psia (i.e. safety factor is 2.0, which is conservative. 1.5 is the recommended minimum).
Tank performance factor(PV/W) is ~1.9 Mega inches.  PV/W, that's burst pressure times internal volume divided by empty weight.
Initial Pc is 180 psia, in other words, dP at injector is 50 psi, or 27.8% of Pc, which is also conservative for first order combustion stability.
Initial Isp at sea level is 282 sec., rapidly increasing as higher altitudes are achieved.
Maximum Isp in vacuum is >450 sec.

I have run some ascent simulations on this design, though I can't figure out how to paste the plot and pictures into this message board.  The plots will be available at (http://home.comcast.net/~compositex/compositex.htm) in the next day or two.  

Title: Re: SSTO Thread
Post by: Dan Moser on 10/25/2006 01:23 am
Quote
meiza - 24/10/2006  5:21 PM

438 kg tank holding 18 tons of propellants!

Actually, no.  We have a units disconnect. That's 18,000 pounds of propellant in a 438 pound tank for the Bluebird.
180,000 pounds of propellant in a 4,075 pound tank for the Eagle.
Title: Re: SSTO Thread
Post by: meiza on 10/25/2006 11:24 am
Well, I used metric units throughout so my example was just about twice as big.

How would the thing look with aluminium or thin steel tanks? What would the payload be?

I guess doing analysis isn't completely straightforward as the Isp varies so much during the flight.
Title: Re: SSTO Thread
Post by: vt_hokie on 10/25/2006 12:04 pm
Quote
hop - 13/10/2006  7:21 PM

Or perhaps it shows that politicians are still willing to spend other peoples cash on expensive showpieces, regardless of whether they are justifiable by any objective technical or economic criteria.

Hmm, you mean like these gas turbine powered high speed trains (http://forums.railfan.net/image.cgi?Amtrak/Amtrak_Turboliners_Stored_at_Bear_Del._6-05b_Medium.jpg) that New York spent $70 million to refurbish, only to send the trains into long term storage after barely any use?  :(   After traveling aboard high speed trains in Europe, it really frustrates me to see the poor state of passenger rail in this country.  

Title: Re: SSTO Thread
Post by: Dan Moser on 10/25/2006 03:52 pm
Quote
meiza - 25/10/2006  6:07 AM

How would the thing look with aluminium or thin steel tanks? What would the payload be?

High specific strength metal tanks, such as lithium-aluminum or maraging steel, would be approximately 4-5 times heavier in a pressure-fed design.  This would wipe out the payload mass entirely, resulting in a non-viable SSTO.  If you are using a pump-fed engine, things change because metal tanks could be made much thinner, and therefore light enough to do the job, but the costs will climb.

Quote
meiza - 25/10/2006  6:07 AM
I guess doing analysis isn't completely straightforward as the Isp varies so much during the flight.

Definitely true.  This is not a job for a simple calculator.  It's best to use time-stepping ascent simulation program with changing parameters, and run that simulation hundreds of times to find the best design specifications.
Title: Re: SSTO Thread
Post by: mauk2 on 10/26/2006 06:40 pm

Well, let's see what we've got in here, lately....

Quote
Horse feathers.

LOL!  I've always been fond of "HORSE HOCKEY!" but that's a good one too.

Quote
An honest man doesn't feel a need to hide the truth behind the kind of verbal trickery that is employed by shady politicians and flim-flam artists.

What exactly is untruthful about the term "high energy propellants"?   Of course, there is nothing untruthful about it, it just doesn't carry the shock-value punch that you would like it to have.  Sorry, but I refuse to play that silly game.  

Calling a pulse unit a nuclear weapon is exactly the same sort of sleazy shock trick as calling a commercial airliner a guided missile.  

Would you feel better if I used the term "flaming radioactive baby-killing ogre guts"? :)

Quote
The fact that you have chosen to use an obfuscative term for nuclear weapons doesn't say much for the overall honesty of your presentation.

I choose to use terms that are more accurate and less emotionally charged.  I rather thought that was wise.  The fact that you want to keep dragging this topic up for discussion is much more indicative of your prejudices than mine.

Characterizing a pulse unit as a nuclear weapon is, as I stated, exactly like characterizing airliners as weapons.   They are different things, in intent and design.  This is the sort of foolish reasoning that leads to efforts at coating ammonia nitrate so that it cannot be made explosive, or the idiocy that has practically gutted home chemistry sets.

The world is not safe, and efforts to make it that way are foolish and insular.  EPP is not hard.  As technology marches on, the barriers to entry to that technology steadily fall.  Eventually, somebody is going to do it, and whoever it is will be the next power to dominate history for the next few centuries.  

But you don't have to take my word on it.  Ted Taylor, arguably the greatest advocate of minimal fissile mass devices (bombs as he quaintly called them after the habit of a lifetime) stated that the pulse unit designs possible with the old Orion design were completely different than military weapons.

http://makezine.com/images/07/strangelove.pdf

Indeed, the miniscule amounts of fissile material needed were so small that to this day, the results are classified.  The reason is obvious, if you have read Carey Sublettes Nuclear Weapons FAQ, as insertion times for low critical designs are by necessity very short, meaning that practically any fissile material can be used.  That is a very scary fact, but a fact it remains.  (Perversely, the lower you drive the critical mass, the safer the device becomes, and via the use of antimatter it is possible to even use only fertile material, with no fissiles at all!)

However, the world is full of bright people, somebody else will figure this fact out eventually.  Our future is a high energy one, unless we do as the Chinese did, which means only that someone else will do it, eventually.  We can run around in fear trying to stuff that genie back into the bottle, or we can accept the truth and work with it moving forward.

I choose to move forward.  You may choose differently.  :)
Title: Re: SSTO Thread
Post by: Jim on 10/26/2006 06:54 pm
Quote
mauk2 - 26/10/2006  2:23 PM

What exactly is untruthful about the term "high energy propellants"?   Of course, there is nothing untruthful about it, it just doesn't carry the shock-value punch that you would like it to have.  Sorry, but I refuse to play that silly game.  

It is a lie.  Plain and simple.  The intent to decieve is a lie.  You are using political terms and what are they for?  Lying.  

No, you chose to play another silly game.   "Physics packages" is another BS name.

 Just as the contents of bomb are called chemical explosives,  the proper term is nuclear explosives or devices.  The contents of bomb are not called "propellants".
Title: Re: SSTO Thread
Post by: mauk2 on 10/26/2006 07:16 pm
Okay, some more good stuff here....

Quote
Last I checked nuclear submarines costed more to build and maintain than diesel ones, what makes you think rockets would be different?

Heh.  Well, the smartass response is: "Because there's no water in space.  Duh."

The more reasonable answer is: This is exactly the same analogy as to why there are no nuclear airplanes.  Since such craft have access to an external working fluid, existing low-energy solutions (diesel fuel) can achieve extremely high Isp's.  Since Isp is such a massively important metric, that overwhelms many lesser issues.

Submarines are a trifle more complex than airplanes, due to the very long loiter times demanded by the military.

But to directly answer your question, nuclear rockets are the ONLY way to cross this hurdle with todays technology.  Antimatter is very close, and depending on what projects exist that we don't know about, may be far more developed than we realize.  Aside from those two concepts, there is no viable technology out there to serve as the "diesel" subs, to compete against the "nuclear" subs.

Quote
How about M= e^V/C, V=8200m/s, C=4000m/s.

LOL!  When I first read this, I thought you were planning to shrink the planet.  A great trick, if you can pull it off!  :D

Quote
That's the equation for a tether interceptor using a spectra tether with a 1.5km/s tip velocity.

Very true!  Tether plans, though, beg the question on how you are going to get the tether mass up there in the first place, as well as how are you going to power and drive the tether systm.   Most papers I've seen on near-term tethers have mass ratios of at LEAST 100 to 1.

Bootstrapping is a process that is so complex that I just can't envision it ever happening in the real world.

More importantly, even if you got the tether up, there really isn't too much to do in LEO.  Sure, you can in theory use a momentum transfer system to move about the Solar System, but how do you build it in the first place?

As an aside, while tethers get a lot of attention, I happen to think that IF we decide to move in this direction, Dr. Birch's dynamic compression members are a far stronger concept, given recent advances in sensor and computing.  Sadly, he only posts them to the Web as compressed .gif's....

Maybe I'll unpack a few of those and pop them onto rapidshare or something, his ideas are at least as strong as Forward's and should get a better audience.

Quote
There's more than one way to skin a cat and closed minded obsession with one aspect of the process is unlikely to be optimal.

I think I'm offended by this characterization.  :D

I am far from "closed minded."  I'm just further along in this process than most of the people in this forum.  I am intimately familiar with tethers, space elevators, and compression members.  I have examined beamed power designs in stupidly deep detail. (Nuclear pumped free-electron lasers are a truly scary concept!)  I have read reams of papers on metallic hydrogen and monatomic hydrogen.  I have looked at mass drivers of magnetic and electrical designs.  I spent a long time examining light-gas cannons bored into the Antarctic ice caps.  I have sought out and examined every scheme that has even a whiff of real weight to it, and I continue to do so. (Notice I utterly ignored the current thread about the mass driver in this very forum.  Such schemes won't work, and we knew this in the 60's.)

None of that stuff works.  Very little of it even has a ghost of a prayer of ever working.

The problem is energy density.  The solution is high energy propellants.  Fortunately for us, it isn't difficult.  It's just very scary.

Please note, the high energy propellants I advocate are the least frightening versions that I can find.  Such concepts as Zubrins Nuclear Salt Water Rocket are quite viable, but TRULY SCARY.
Title: Re: SSTO Thread
Post by: Jim on 10/26/2006 07:21 pm
"The solution is high energy propellants. "

So you are proposing H2 and Florine then.   If not, you are lying again

"I'm just further along in this process than most of the people in this forum. I am intimately familiar with tethers, space elevators, and compression members. I have examined beamed power designs in stupidly deep detail. (Nuclear pumped free-electron lasers are a truly scary concept!) I have read reams of papers on metallic hydrogen and monatomic hydrogen. I have looked at mass drivers of magnetic and electrical designs. I spent a long time examining light-gas cannons bored into the Antarctic ice caps. I have sought out and examined every scheme that has even a whiff of real weight to it, and I continue to do so. "

Further along.   Do you have any practical experience.  So tell what you do in the real world?  You haven't provided any data on your "expertise", just your broken record ofbacking of a fringe concept and distain of anyone that disagrees with you
Title: Re: SSTO Thread
Post by: mauk2 on 10/26/2006 07:30 pm

Quote
It is a lie. Plain and simple. The intent to decieve is a lie. You are using political terms and what are they for? Lying.

Are you calling me a liar? :)

Ok, Mr. Monosyllable, please answer me these two yes/no questions:  Is an electron-positron annihilation a nuclear process?   Is it a high energy process?  

This should be amusing. :D   Anybody care to take bets on those questions being answered?


Quote
No, you chose to play another silly game. "Physics packages" is another BS name.

I also don't happen to like the phrase "physics package", and try not to use it, although I sometimes slip up.  It smacks to uncomfortably of ICBM design for my tastes.


Quote
The contents of bomb are not called "propellants".

This is correct!  You have also placed your finger on a large difference between a military weapon and a pulse unit, congratulations!  

Do you have any concept how pulse units work?   They do indeed have propellants, usually beryllium oxide or tungsten placed inside the radiation channel of the holhraum.  Honestly, about anything can be used as propellant, depending upon the Z you need.

Maybe you should be more careful of what you post.   I also went over this in careful detail in the "More Nuclear Material" thread, may I humbly direct you there for much more information.
Title: Re: SSTO Thread
Post by: Jim on 10/26/2006 07:35 pm
Yes, you are a liar.  You intend to deceive.
Title: Re: SSTO Thread
Post by: josh_simonson on 10/27/2006 01:05 am
Tethers aren't all that attractive at the moment because the tip velocity is still on the slow side for the concept to be compelling, but higher strength fibers (though doubtfully space elevator worthy) are on the relatively near horizon.  As I said, for the net capital, political, social and environmental costs of a nuclear booster we could probably carry out a fiber 'manhattan project' that would realize a comparable or better means of orbital transportation.


If Elon wanted to build a nuclear rocket, do you think the government would let him?  Hell no.  A nuclear scheme would by definition be a government scheme, and a government scheme in practice costs twice as much as a non-governmental one.  That's a big strike against it right there.
Title: Re: SSTO Thread
Post by: Dobbins on 10/27/2006 03:02 am
Quote
josh_simonson - 26/10/2006  8:48 PM

If Elon wanted to build a nuclear rocket, do you think the government would let him?  Hell no.  A nuclear scheme would by definition be a government scheme, and a government scheme in practice costs twice as much as a non-governmental one.  That's a big strike against it right there.

The US government does not operate in a vacuum. The American people, operating through their government, would stop Elon, NASA, or any one else wanting to operate a nuclear reactor powered rocket from Earth's surface. There would be far stronger opposition to this than to nuclear power plants. A nuclear reactor powered launcher is not politically viable in the United States.

Other nations which don't have to take the will of the people into consideration haven't attempted to build nuclear reactor powered launchers. That alone is a strong clue that they are not economically viable compared to chemical launchers.

No one, other than a hand full of crackpots, is going to fall for the hair brained scheme of using rockets that are powered by spitting nuclear explosives out the arse of the launcher all the way to orbit.
Title: Re: SSTO Thread
Post by: Dan Moser on 10/27/2006 06:30 am
The website has been updated with more current information and a recent ascent simulation plot on the Eagle expendable SSTO design effort.

http://home.comcast.net/~compositex/compositex.htm#ecps

P.S  This is a Uranium-free design.  Chemical propellants rule!
Title: Re: SSTO Thread
Post by: meiza on 10/27/2006 11:03 am
Dan, what IS the ECPS system? The page has paragraph after paragraph of praise but no description whatsoever... Heating propellant and oxidizer to pressurize tanks?
And you can attach pictures by clicking the "attach file after posting" - checkbox.
Title: Re: SSTO Thread
Post by: Dan Moser on 10/27/2006 04:18 pm
Quote
meiza - 27/10/2006  5:46 AM

Dan, what IS the ECPS system? The page has paragraph after paragraph of praise but no description whatsoever...

Praise?  There is ample general description there, if you are interested.  Specific system details are proprietary.  Do you have a more substantive criticism of it?
 
Quote
meiza - 27/10/2006  5:46 AM

Heating propellant and oxidizer to pressurize tanks?

No, not necessarily.  Self-pressurization can take place with adiabatic tank conditions, as with the nitrous hybrid rocket in SpaceShipOne and the AirLaunch LOX/propane "Vapak" type system.  Heat transfer can also be used to evaporate propellants to sustain tank pressure during liquid withdrawl.
Title: Re: SSTO Thread
Post by: hop on 10/27/2006 11:15 pm
Quote
Dan Moser - 27/10/2006  9:01 AM
Do you have a more substantive criticism of it?
Not exactly criticism, but a question: Do you believe you have solved the problems of composite tanks at LH2 temps ? Have you tested them under flight conditions ?
Title: Re: SSTO Thread
Post by: Dan Moser on 10/28/2006 01:26 am
Quote
hop - 27/10/2006  5:58 PM

Do you believe you have solved the problems of composite tanks at LH2 temps ? Have you tested them under flight conditions ?

Yes, we believe we have a workable solution, though the proof is in the testing.  Composite material strength is not the issue, it is providing a leak-proof liner that is the real challenge.  Linerless tanks are generally not nearly as light as lined tanks.  

No, we have not yet flight tested with LH2, but pressure testing has occurred with LN2 and LOX.  This is a good indication it will also work with LH2, since there is little thermal contraction between LN2 and LH2 temps.
Title: Re: SSTO Thread
Post by: meiza on 10/28/2006 09:52 am
Do you need a huge oven for curing?
Title: Re: SSTO Thread
Post by: mauk2 on 10/28/2006 04:05 pm
Okay, back to this fun thread. :)

A while back, I asked for people to describe a viable, market-based transportation system based upon a fuel fraction of at least 90 percent.  I think folks misunderstood.

By "transportation system" I meant the WHOLE system, including supporting infrastructure, sources of revenue, supplies of raw materials, etc.  If anyone still wants to take a stab at that, I'd be interested in seeing it, but as I have stated, I wager it'll look a lot like what Von Braun came up with in the early 50's.

As an aside, I also asked people to explain the non-economic, non-political reasons why high energy propellant systems won't work, and as expected, have received nothing in response.  There's a reason for that.

Aside from emotional "IT'S EVIL NUKES!", "THAT'S SO CARTOONY SOUNDING",  and "YOU ARE A DIRTY LIAR" type responses, no one has put up any particularly compelling arguments against high energy propellants.  For that matter, nobody has put up any compelling argument for high-fuel fraction designs, either.  Sounds like we're, as usual, paralyzed by our superstitious fears of the "N" word and drifting sideways in the status-quo.



Now, that said, Dan has some interesting stuff going on.  Let's take a look at it. :)


Quote
Features include a filament wound composite tank/airframe,

Nifty!  If you've gotten the composite/cryogenic problem licked, that's actually really good.  Do you have a timeframe for flying one?


Quote
ablative chamber,

I knew I liked the way you thought. :) I'm a bit of a fan of ablative chambers, following the KISS principal.


Quote
variable expansion ratio nozzle,

Is that a simple one-piece dropping skirt, or are you trying something fancy?  I'm not a big fan of the additional complexity of variable nozzles, but if you're bold enough to strive for SSTO on chemicals, you kinda have little choice.

Quote
variable area injector.

Interesting.  Can you elaborate on this?

quote] The propulsion system called is ECPS (http://home.comcast.net/~compositex/compositex.htm#ecps)[/quote]

Neato!  Have you run any numbers on the pistonless pump concept versus this one?  If your tanks are as strong and light as you claim, you don't really need those, but those are some pretty bold tank claims you're making, and it might be wise to have a workaround in the wings.


Quote
which burns LOX/Hydrogen propellant.

Really, the only even slightly viable option.

Quote
Note that as the launch vehicle gets larger, the payload fraction gets better.

Ah, yes, the wonderful square/cube law, love it or hate it. :D


Quote
This favorable scaling effect is mostly due to the fact that larger ablative chambers tend to have much better thrust-to-weight ratios.


Out of curiosity, how big do you think this concept would scale?  IF you can drive the component cost low enough, you might be able to out-do the old Sea Dragon concept by quite a good margin.


Quote
The designs are still works in progress,

Uh, oh.  Well, good luck!  Break a leg, etc.  


Quote
but I am estimating the cost to orbit of this series of vehicles will be well under $500 per pound, perhaps as low as $200 per pound.

Well, that's excellent!  

Quote
The vehicle is so cheap to manufacture

You hope. :)  Keep your fingers crossed.


Lots of good solid ideas there!  While the viability is far from proven, this is definately a lot of good ideas, and I hope you do well with it.  

Title: RE: SSTO Thread
Post by: vt_hokie on 10/28/2006 04:09 pm
I do not believe that fear of radioactive nuclear reaction byproducts should be classified as "superstitious".
Title: Re: SSTO Thread
Post by: Jim on 10/28/2006 04:11 pm
You have yet to qualify yourselve and your background.  Copying and pasting text hardly qualifies you as an expert.  And your refusal to acknowledge that you are promoting nuclear devices, better yet NUCLEAR BOMBS, and deceitfully calling them "high energy propellants" is another
Title: Re: SSTO Thread
Post by: Dan Moser on 10/28/2006 05:38 pm
A few answers:  

No, we do not need a large oven for the baseline resin system.  However, if another high-curing temp. resin system pops up that would be superior, a big oven is not hard to do. We plan to stay away from autoclave curing processes.

The baseline variable expansion ratio nozzle features a variable throat area translating plug, similar to how they throttle some solid motors.  BTW, solids throttle "backwards" in that smaller throat areas increase thrust.

The variable area injector is sort of like a hybrid of two other proven injectors:  (1) the Apollo LEM descent engine, which was a variable area pintle injector with a 10:1 throttling ratio, and (2) the Lance missile which had a translating sleeve, which could do 40:1 throttling.  We need about 4:1 throttling to limit acceleration to about 4G or less.  Only a few moving parts.

Upper scaling limit?  Who knows...  Sea Dragon was perhaps a bit too ambitious, but technically sound.  BTW, I did some composite tank design work for Bob Truax in the past.  He has got a lot of great ideas!

On the nuclear booster issue and the heated dialogue it has lead to:  Commercial space transportation is becoming very similar to other forms of transportation in that when someone want to move somebody or something somewhere, the two most important issues are--- a.) how much it will cost, and b.) how soon it will get there.  The issue of how much propulsive mass it requires doesn't enter into it.  To get high-thrust, high-Isp nuclear propulsion implemented into an Earth-to-LEO launch system, the following things have to happen:

1. Government has to allow nuclear materials and technology to be used in propulsion development... probability of this is near zero, especially given the fact that nefarious jihadis want the proliferation of that technology worse than hardcore space cadets do.
2. Government has to allow nuclear materials to be used in a launch operations... probability of this is near zero, since the environmental impact is so grave..
3. Public opinion has to be supportive of nuclear launch vehicle operation... probability of this is near zero, maybe lower.  You can call it superstition or paranoia, but it's real, and it won't go away by trying to talk people out of it.
4. The cost has to be significantly lower than existing launch systems... probability of this is near zero..  the actual probability is irrelevant because reasons 1, 2, and 3 are sufficiently insurmountable hurtles to preclude this from EVER happening.

Until there is a genuine breakthough in propulsion physics that doesn't litter the Earth with radiation and nuke-wielding jihad bastards, chemical propellants will remain the sole road from Earth to LEO.

 
 

Title: RE: SSTO Thread
Post by: mauk2 on 10/28/2006 08:42 pm

Hrrrrrrm.

More responses! :)

Quote
I do not believe that fear of radioactive nuclear reaction byproducts should be classified as "superstitious".


Why not?

I have been waiting for a while for a relevant question to be asked about this very topic.  The fact that I get superstition-driven, purely emotional responses WITHOUT that question is powerfully indicative of the atavistic fear that drives this issue.

What is that relevant question?  

Well, the layman's version is, "How much radiation would this release?"  

The slightly more informed version is, "How much would this add to our annual background radiation dose?"  

The version I'd really love to see is, 'How many becquerels are we talking about here, and of what nuclides?"  The "old school" version of that would ask about curies, but ehn, whatever. :D

Until someone asks something like that, all of the objections are merely uninformed, fear-driven knee-jerk response, that I can dismiss as superstition.  How can you object to something without even knowing what it is?  That is not a rational, thinking, response, now is it?  That's like I hold out a closed box and say, "Would you like this?"  What would YOU ask?  Or would you simply refuse instantly?  

Hopefully that clarifies things.  

Anybody care to ask?  :)
Title: Re: SSTO Thread
Post by: Jim on 10/28/2006 08:52 pm
Actually, you are living in a closed box in your own reality and refuse to knowledge that despite the physics involve, it is not a viable concept.  It doesn't matter what it in the box.  It is Pandora's and not worth opening.
Title: RE: SSTO Thread
Post by: vt_hokie on 10/28/2006 08:54 pm
Another question is how much would this add to our radiation dose when things go catastrophically wrong, as inevitably happens sooner or later with imperfect human technology.
Title: Re: SSTO Thread
Post by: mauk2 on 10/28/2006 09:06 pm

Hmmmm.

Quote
You have yet to qualify yourselve and your background.

And I won't, either.  There's several reasons for this.

First, I like for my arguments to stand on their own merits.  Always have.  The alphabet soup behind my name (or lack thereof) means nothing in this venue.  If you dislike my points, argue against them, don't try this ad-hominem baloney.  Enforce a little rigor in your thinking.  

Second, if I admitted I'm a homeless man living on a grate in DC who posts from the local library between bottles of fortified wine, wouldn't you feel bad getting schooled by me? :)

Third, what you're asking is against the rules of this forum:

http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=1244&posts=21&start=1

User confidentiality.  Please stop asking.  If you don't like my arguments, prove me wrong in the arena of ideas.

As a note, I seem to agree with YOU a lot.  I wonder if you're really reading what I post? :D  



Quote
Copying and pasting text hardly qualifies you as an expert.

On the contrary, the large majority of the posts I make are not pasted text whatsoever.  I DO post many supporting links, but people are free to read those or not.  I try to make my own points,with varying degrees of success.


Quote
And your refusal to acknowledge that you are promoting nuclear devices, better yet NUCLEAR BOMBS, and deceitfully calling them "high energy propellants" is another

Have you read up on pulse units yet?  Do you understand how positron annihilations work yet?  I note with interest (and some small disappointment) that you have not answered my questions about whether or not positron annihilations are nuclear reactions.  Why not?  

But let's tackle this taboo head-on.  Let's say that I am an unapologetic advocate for nuclear bombs.  Is that inherently evil?

Nuclear weapons lead directly to the collapse of the Soviet Union, one of the most murderous regimes in history.  It was a tense and scary ride, but it ended well and saved who knows how many lives in the process.

If an asteroid was detected on the way to, say, Jakarta, and it was possible to break it up if we used nuclear weapons, would that advocation of nuclear weapons be also inherently evil?

As weapons go, nuclear weapons have really not killed many people, seen in the context of history.  If advocating nuclear weapons is so bad, isn't advocating ammonium nitrate even worse, due to the larger number killed by that substance?  How about guns?  Do you advocate the banishment of all guns?  For that matter, dam failures have killed at LEAST as many people as nuclear weapons, shoul we work to abolish all hydropower and remove all existing dams?

If not, why not?  Because dams are not weapons?  Neither are pulse units.
Title: Re: SSTO Thread
Post by: Dobbins on 10/28/2006 09:37 pm
Quote
mauk2 - 28/10/2006  11:48 AM

A while back, I asked for people to describe a viable, market-based transportation system based upon a fuel fraction of at least 90 percent.  I think folks misunderstood.

Typical. Pushers of junk science, and other fringe nonsense always try to steer the conversation away from the glaring weaknesses of their position by attacking minor points of more standard positions.

This along with the deceptive language (high energy propellants for nuclear devices) and baseless preemptive attacks on stronger positions (calling decades of accumulated knowledge on the effects of radiation a "superstition") is the sort of tactics you find shady shysters engaging in when they know they have a case that is a sure loser if they stick to factual information.

The fuel fraction is meaningless, the bottom line is cost of transportation, and chemical reaction rockets remain cheaper than nuclear reactor powered rockets and far cheaper than launchers powered by nuclear explosives.
Title: RE: SSTO Thread
Post by: Dobbins on 10/28/2006 09:47 pm
Quote
vt_hokie - 28/10/2006  11:52 AM

I do not believe that fear of radioactive nuclear reaction byproducts should be classified as "superstitious".

There is no doubt that some opponents of nuclear power have vastly overstated the dangers of radiation, but that is no excuse for this attempt to make the very real dangers that are present vanish by chanting "superstition" over and over like some kind of mantra.
Title: Re: SSTO Thread
Post by: mauk2 on 10/28/2006 10:47 pm

Hrrrm, even more good stuff here....

Quote
The baseline variable expansion ratio nozzle features a variable throat area translating plug, similar to how they throttle some solid motors. BTW, solids throttle "backwards" in that smaller throat areas increase thrust.

NEAT!  I never would have thought of that!  

Er, that does beg one question, though.  (Well, leaving aside instability questions, which I die to ask but figure you'll ignore as proprietary, and likely rightly so.)

Using this in a liquid fuel motor imples that you're constricting the throat at altitude, which means you have a working mechanism working inside the combustion chamber?   If so, is it something similar to this?  

http://www.freepatentsonline.com/3948042.html

Because that's kinda cool!  I saw that patent years ago and always wondered why nobody did anything with it.  The more I hear, the better I like!  You GO!   I still think it's doomed, but hey, I could be wrong! :D

Quote
Commercial space transportation is becoming very similar to other forms of transportation in that when someone want to move somebody or something somewhere, the two most important issues are--- a.) how much it will cost, and b.) how soon it will get there.

Ah, the UPS model.  Good!  Now, let's address this:   Who are the customers?  How do they make money moving these packages? (Not YOU, the carrier, THEY, the clients.) What size is that market?  How much growth?  Why?

The problem with the UPS model for spaceflight is that there really isn't any profit motive in LEO yet, and might never be.  (Iridium ring any bells?)  There are saleable/usable resources farther out, but we can't even get to LEO yet in any real way.  Now, the UPS model actually makes a modicum of sense for suborbitals, but the market for package delivery doesn't demand that much speed yet, and with the Internet, may never.

Quote
To get high-thrust, high-Isp nuclear propulsion implemented into an Earth-to-LEO launch system, the following things have to happen:

Just to clarify, I do not advocate ground launch of any system that produces fission products.  One of the reasons I am enjoying your low cost chemical efforts so much is because a similar (simplified) system would make a dandy lofter stage. :)

Quote
1. Government has to allow nuclear materials and technology to be used in propulsion development

Correct!  Combining the NRC and NASA would be an excellent first step, in my opinion.

Quote
... probability of this is near zero,

I strongly disagree.  I refer you to my last post in the "More Nuclear Material" thread to see the new US policy on this matter.  I refer you to Chapter Nine of the linked .pdf.  Conventional wisdom on this matter is increasingly divorced from reality.  I hope. :)

Quote
especially given the fact that nefarious jihadis want the proliferation of that technology worse than hardcore space cadets do.

I dunno, I want this REALLY, REALLY badly.  :)

More importantly, the "bad guys" are proliferating this ANYWAY.  See, any news about Iran or North Korea.  There is no way to keep this technology in a bottle, nuclear technology was blindingly hard in the 40's, but it's just not that hard these days, and is getting easier every day.  We need to address the underlying issues to end the jihadi problem, not bury our heads in the sand and spite our own face.  To mix a metaphor. :)

Quote
2. Government has to allow nuclear materials to be used in a launch operations... probability of this is near zero, since the environmental impact is so grave..

The government already does this, to launch Pu-238 powered RTG's.  The upcoming Mars rover is gonna have a MONSTER RTG on it, and the curies in those things are HUGE.  More importantly, back in the days of the Cold War, dozens of reactors got launched, and several crashed and burned.  Your characterization of high energy systems as having "grave" environmental impacts is a common fear, but not one based in reality.

Quote
3. Public opinion has to be supportive of nuclear launch vehicle operation... probability of this is near zero, maybe lower. You can call it superstition or paranoia, but it's real, and it won't go away by trying to talk people out of it.

I disagree.  Early on, atomic power was hugely popular.  Years of lies and propaganda by environmental organizations has poisoned that well, and a reasonable public education program would readily fix things.  Indeed, the government has recently launched EXACTLY such a propaganda campaign, in the vast anti-smoking campaign that is currently underway.  There is clear precedent for such things, and seen from the governments perspective, the access to resources real access to space would give is MUCH more important than stopping citizens from smoking.  More importantly, the nicotine addicition is MUCH stronger than being scared of the "N" word, yet it's getting hard to smoke anywhere but your own house these days.  Implying this situation is graven in stone is simply wrong.

Quote
4. The cost has to be significantly lower than existing launch systems... probability of this is near zero.. the actual probability is irrelevant because reasons 1, 2, and 3 are sufficiently insurmountable hurtles to preclude this from EVER happening.

This is incorrect on several points, but I'll just address this one:  There IS no existing launch system that can do the missions open to high energy propellants.  Barring some huge breakthrough, there is no competing system, so the point is moot.  Period.

Sorry.

Title: Re: SSTO Thread
Post by: Jim on 10/28/2006 11:08 pm
"Combining the NRC and NASA would be an excellent first step, in my opinion."

That is insane.  They are totally different agencies with different responsibilities adn should stay that way

"The upcoming Mars rover is gonna have a MONSTER RTG on it"

Wrong.  It is smaller than previous RTGs.  Also, the fuel is encased in a material that can survive entry,

"dozens of reactors got launched,"

Lying. Deceit by ommission .  The US did not launch them but a totalitarian gov't than had no regard for the environment

"the access to resources real access to space would give is MUCH more important than stopping citizens from smoking. "

Wrong.  In whose opinion.  Not mine.  I am sick of subsidizing other people's health care

"Yet it's getting hard to smoke anywhere but your own house these days"

that's the way it should be

Your comments about smoking just shows that you are fringe and weakens/cheapens any of your arguements.
Title: Re: SSTO Thread
Post by: dbhyslop on 10/28/2006 11:45 pm
Stop feeding the troll!
Title: Re: SSTO Thread
Post by: Dan Moser on 10/28/2006 11:50 pm
Quote
mauk2 - 28/10/2006  5:30 PM

Using this in a liquid fuel motor imples that you're constricting the throat at altitude, which means you have a working mechanism working inside the combustion chamber?   If so, is it something similar to this?  

http://www.freepatentsonline.com/3948042.html

not really, but the same principle.  Throttlable solids have been developed and used in small missile applications for many years, but they are still not that common.

Quote
mauk2 - 28/10/2006  5:30 PM

 I do not advocate ground launch of any system that produces fission products.  

then..  why in the hell are you posting on a thread named  "SSTO" ?... sheeesh!

Quote
mauk2 - 28/10/2006  5:30 PM
 Combining the NRC and NASA would be an excellent first step

Hah!.. makes about as much sense as combining Health & Human Services with DoD... good luck with pushing THAT one through Congress!  ... talk about utter futility!

Quote
mauk2 - 28/10/2006  5:30 PM

More importantly, the "bad guys" are proliferating this ANYWAY.  See, any news about Iran or North Korea.  There is no way to keep this technology in a bottle, nuclear technology was blindingly hard in the 40's, but it's just not that hard these days, and is getting easier every day.  We need to address the underlying issues to end the jihadi problem, not bury our heads in the sand and spite our own face.  To mix a metaphor. :)

.. man, you gotta be kiddin'!.. you're essentially saying "what the hell... why not let terrorists have nukes now because they'll probably have them eventually?" What an utterly stupid suggestion!.. by the same logic: if I have a cold, I may as well try to catch Bubonic plague and lung cancer as long as I'm sick anyway, huh?   Who's burying his head in the sand now?

Quote
mauk2 - 28/10/2006  5:30 PM

the government already does this, to launch Pu-238 powered RTG's.  The upcoming Mars rover is gonna have a MONSTER RTG on it, and the curies in those things are HUGE.  More importantly, back in the days of the Cold War, dozens of reactors got launched, and several crashed and burned.  Your characterization of high energy systems as having "grave" environmental impacts is a common fear, but not one based in reality.

Good point.. BUT.. the rather significant difference is.. DUH!...  You can't detonate an RTG.

Quote
mauk2 - 28/10/2006  5:30 PM
 There IS no existing launch system that can do the missions open to high energy propellants.  Barring some huge breakthrough, there is no competing system, so the point is moot.  Period.

Sorry.

Well.. don't be sorry because, once again, you got it totally backwards:  There IS no existing launch system with "high energy propellants."  Never will be, if by that you mean a string of mini fission detonations.. so.. it is your point that is truly moot.  Period.  Sorry.  

Launch systems that DO exist and burn chemical propellants have sent 4 spacecraft out of the solar system and recently boosted another spacecraft towards Pluto...and dozens of other interplanetary missions.. ain't those missions far out enough for ya?  
Title: Re: SSTO Thread
Post by: kevin-rf on 10/29/2006 06:20 am
Quote

Well.. don't be sorry because, once again, you got it totally backwards:  There IS no existing launch system with "high energy propellants."  Never will be, if by that you mean a string of mini fission detonations.. so.. it is your point that is truly moot.  Period.  Sorry.  

Launch systems that DO exist and burn chemical propellants have sent 4 spacecraft out of the solar system and recently boosted another spacecraft towards Pluto...and dozens of other interplanetary missions.. ain't those missions far out enough for ya?  

Four?

Pioneer 10
Poineer 11
Voyager 1
Voyager 2
Ulysses
New Horizons

Are all on there way out never to return to SOL.

And one can really quible if any of them have left the solar system. There are a few different metrics. They are all still under the sun's gravitational influence, but a few have passed the helio pause. Is New Horizons currently going fast enough to leave the solar system, or does it have to wait until after the jupiter flyby?

Also, since the thread has been hijacked by the split/squash/fuse/abuse atomic and sub atomic partcles any way you like just to get a high Delta V regardless of the cost. Why don't we split the thread into two or more. One on "high energy(nuclear) ReUsable Single Stage To Deep Space" and one on "chemcal S(T)STO". I for one would love to read more about what dan is doing without weeding through the nuclear debate that s gong on at the same time.

Title: Re: SSTO Thread
Post by: Kaputnik on 10/29/2006 08:04 am
Kevin, I totally agree with you. This thread has become mired in name-calling and is no longer a useful source of information.
Title: Re: SSTO Thread
Post by: hop on 10/29/2006 08:28 am
Quote
kevin-rf - 28/10/2006  11:03 PM

Ulysses
Ulysses is in a high inclination solar orbit, not on an escape trajectory, AFAIK. New Horizons and it's upper stage, OTOH, are on a one way trip.
Title: Re: SSTO Thread
Post by: Dan Moser on 10/29/2006 07:41 pm
Sorry, I admit my guilt in "feeding the troll."  I'll try my best to ignore "nuclear nonsense" from now on.
Title: RE: SSTO Thread
Post by: vda on 10/29/2006 10:23 pm
Nice forum. Hopefully here I can find some answers. :) For example:

Liquid first stage of typical ELV basically consists of powerful engines (expensive) and BIG tank (not expensive). So, doesn't it mean that it makes sense to recover and reuse the engines while discarding tank?

Detonate small explosive charges (similar to range safety system) and sever engine section from the tank, then use parachutes/airbags/whatever to land engines undamaged. Even if they are not recovered everytime in good condition, that gives you some benefits of RLV.

But this isn't done. Even old Atlas, which was dropping two of it's three first stage engines (for weight reasons), did not do it. Why?
Title: Re: SSTO Thread
Post by: Kaputnik on 10/30/2006 10:05 am
I asked a similar question but regarding whole rocket stages:
[/url]http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=3486&posts=13&start=1[/url]

I think liquid rocket engines are perhaps just too fragile to be recovered with a basic parachute/airbag system. Even a tiny bump to a turbopump could cause disaster on the next flight, so after recovery the whole thing would have to be stripped down and re-assembled, hugely reducing the cost saving. It wouldn't be like refuelling your car.
Title: Re: SSTO Thread
Post by: rfoshaug on 10/30/2006 01:38 pm
How about a "semi-SSTO" using drop tanks? Think of it as a space shuttle without the boosters (but with a larger external tank, some internal tanks as well, more engines and less payload capacity). The engines stay on the vehicle for the entire flight, but the tankage (or some of it) is dropped during ascent.

That way, you'd get the SSTO advantage of knowing that all engines work before committing to liftoff (as opposed to traditional staging), and the only thing you drop into the ocean is a relatively cheap tank. You'd need to carry many and/or large engines into orbit, but in return that would give you a very good and steady acceleration all the way (as the vehicle gets lighter you'd have to cut-off some of the engines during ascent to limit G-forces), as opposed to traditional staging where you drop back to 1.5 G's or something like that. The fewer minutes you need to reach orbit, the fewer minutes you'l have to fight gravity's 1G pull.

It wouldn't be SSTO, but it would have most of the advantages of SSTO while limiting the technical difficulties. Or would it?
Title: Re: SSTO Thread
Post by: Kaputnik on 10/30/2006 01:58 pm
A "semi-SSTO" with drop tanks has a number of disadvantages:
- Must use the same engines from sea level to vaccum;
- Must lug those engines all the way to orbit. Each kg of engine is one less kg of payload;
- To be of the greatest advantage, high acceleration is useful at the start of the flight, not the end;
- You still have integration and separation issues with the tank (and thus negate the basic advantage of SSTO).

There are endless permutations on this topic. Have a look at the Russian MAKS system, or browse the 'STS 2.0' thread.
Title: Re: SSTO Thread
Post by: Dan Moser on 10/30/2006 04:11 pm
Just ran a series of ascent simulations on the Eagle SSTO design using a starting altitude of 32,000 feet (~10 km), representing a typical air launch profile.  Even ignoring the benefit from the forward speed of the launch aircraft, the results were surprisingly good.  Payload increased about 40%, from 12,500 to 17,500 lb.  The main advantage is that Isp and thrust are signficantly higher at ignition, due to the lower ambient pressure and the low chamber pressure of this pressure-fed propulsion system design.  Aerodynamic drag was also greatly reduced, as the maxQ decreased by a factor of 4, roughly from 800 psf to 200 psf.

The main economic benefit is avoiding the government-owned launch range hassles, but that has to be balanced against the costs of the launch aircraft and getting the launch mechanics and cryogen storage systems developed.  Also, if you're going to do an airborne launch, one of the benefits of using an SSTO in the first place is lost, that being the avoidance of shedding spent booster stage hardware downrange.
Title: Re: SSTO Thread
Post by: meiza on 10/30/2006 04:53 pm
Does it fit into a C-17? ;)

I checked, nah, 170,000 lb is the aircraft's max payload and Eagle is 200,000... Airlaunch LLC:s Quickreach weighs 65,000 lb. So maybe with that weight you could orbit about 6,000 lb?
Title: Re: SSTO Thread
Post by: Dan Moser on 10/30/2006 05:10 pm
No, definitely not from the inside of a C-17, C-5, AN-225 or any other existing aircraft.  It wouldn't fit the length, diameter, or mass requirements.  This would probably have to be dropped from the bottom of modified 747, or a "clean sheet" aircraft design.  That's why I said (or at least implied) that the cost of the launch aircraft would diminish the attractiveness of this approach.
Title: Re: SSTO Thread
Post by: kevin-rf on 10/30/2006 05:28 pm
Quote
Dan Moser - 30/10/2006  11:53 AM

No, definitely not from the inside of a C-17, C-5, AN-225 or any other existing aircraft.  It wouldn't fit the length, diameter, or mass requirements.  This would probably have to be dropped from the bottom of modified 747, or a "clean sheet" aircraft design.  That's why I said (or at least implied) that the cost of the launch aircraft would diminish the attractiveness of this approach.

Makes a really good arguement for a very low performance booster that can loft the eagle to 32,000 ft and then be recovered and reused for the next eagle launch.

Ever given any thought to launching from a high altitude location instead of at sea level? Other than a payload fairing, what would you be shedding? What do the calculations say for Denver?

(I know jim is going to jump all over me for launching over a populated area)
Title: Re: SSTO Thread
Post by: Jim on 10/30/2006 05:41 pm
That's what Kistler's first stage was.  Launch Assist Platform.  Became more of a first stage later
Title: Re: SSTO Thread
Post by: josh_simonson on 10/30/2006 08:36 pm
Sure it's possible to build a nuclear powered launch vehicle, but you could build one out of rubber bands too if you got enough of them together.  The question is wether or not it is a viable, cost effective solution (which 1 trillion rubber bands is not..) and it is on that front that everyone is skeptical.
Title: Re: SSTO Thread
Post by: Dan Moser on 10/31/2006 12:16 am
Quote
kevin-rf - 30/10/2006  12:11 PM

Makes a really good arguement for a very low performance booster that can loft the eagle to 32,000 ft and then be recovered and reused for the next eagle launch.

Well, not really.  If you're doing a two stage vehicle anyway, why just go to 32,000 ft. with the first stage? Why not do an optimum mass split between first & second stage? That way, the upper stage is much easier to do than an SSTO-esque stage.  A low performance booster will cost just about as much as a high-performance booster because they have to do just about all of the same things.  Plus, with an optimized two-stager you have the option of doing away with liquid hydrogen fuel.. which is a bit of a troublesome fluid to manage.  

SSTOs are extremely performance sensitive.   They have to run right at peak performance through the entire burn, or they may not make it to orbit.   Multi-stage vehicles are generally more tolerant of slightly off-nominal stage performance.  A conclusion that many, including Kistler, have reached.
Title: Re: SSTO Thread
Post by: PlanetStorm on 10/31/2006 09:02 am
Quote
Dan Moser - 29/10/2006  12:33 AM

Quote
mauk2 - 28/10/2006  5:30 PM

 I do not advocate ground launch of any system that produces fission products.  

then..  why in the hell are you posting on a thread named  "SSTO" ?... sheeesh!

I think his point is that there are no fission products (at least not in any significant quanitity) from the SSTO designs he favours.

My question to mauk is, given that antimatter is unlikely to be feasible, there has to be some sort of nuclear reaction. Given that, and going back tp a question you actually asked yourself many posts ago, in the designs you favour, what spectrum of nuclides do you expect, what half-lives and in what quantities per launch? What is the likely distribution as a function of altitude in both a normal launch and a destructive failure? What is the dispersal pattern, what of the biological feedacks that can concentrate small quantities of, say, plutonium into large concentrations inside, say, a fish that one day you might eat? What makes you think you can convince people (across national boundaries) that long term exposures to even very low levels of activity released by relatively clean launches won't cause cancers?

Sorry if people think I am feeding the troll but I do think we ought to drop the name-calling and one liners and get to the heart of the science he is supporting.
Title: Re: SSTO Thread
Post by: kevin-rf on 10/31/2006 01:16 pm
Quote
PlanetStorm - 31/10/2006  3:45 AM

Sorry if people think I am feeding the troll but I do think we ought to drop the name-calling and one liners and get to the heart of the science he is supporting.

But there is already a thread for this, 'More Nuclear Materials' : http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=3615&posts=116&start=1

It is more of an attempt by mauk2 to draw in those of us who don't want to read the 'More Nuclear Materials' thread. This thread has twice the number of views as the other thread, hence twice the exposure.

Dan has been talking up a cool chemical design that is very on topic, but has been lost in the nuclide noise.

Actually, Dan question, I might have missed this in a previous post, but how are you funding your project, and how close to actually winding carbon fiber?
Title: Re: SSTO Thread
Post by: Dan Moser on 10/31/2006 05:18 pm
Quote
kevin-rf - 31/10/2006  7:59 AM

 how are you funding your project, and how close to actually winding carbon fiber?

Customer contracts are in place to build composite LOX tanks and common bulkhead tanks.  We have already wound fiber on subscale tanks.  The SSTO design effort is just an internally funded study at this time. Outside support is being sought as the opportunities arise.
Title: Re: SSTO Thread
Post by: hop on 10/31/2006 10:05 pm
Quote
Dan Moser - 30/10/2006  8:54 AM

Just ran a series of ascent simulations on the Eagle SSTO design using a starting altitude of 32,000 feet (~10 km), representing a typical air launch profile.  Even ignoring the benefit from the forward speed of the launch aircraft, the results were surprisingly good.  Payload increased about 40%, from 12,500 to 17,500 lb.
Some discussion of the pros and cons of various air-launch methods:
http://www.airlaunchllc.com/AIAA-2005-0621.pdf
http://mae.ucdavis.edu/faculty/sarigul/aiaa2001-4619.pdf
Title: Re: SSTO Thread
Post by: Dan Moser on 11/02/2006 04:24 pm
In the way of references on this subject, it's worth checking out the trapeze-lanyard airdrop designed and test-proven by the same guys at UC Davis and AirLaunch LLC.  It was proposed to NASA by t/Space, a COTS finalist, which was unfortunately not selected for further development funding, another NASA mistake, IMHO.

http://www.transformspace.com/document_library/media/AIAA-2006-1040.pdf
Title: Re: SSTO Thread
Post by: Jim on 11/02/2006 04:49 pm
T/space's concept was never viable
Title: Re: SSTO Thread
Post by: Dan Moser on 11/02/2006 08:53 pm
Quote
Jim - 2/11/2006  11:32 AM

T/space's concept was never viable

why not?
Title: Re: SSTO Thread
Post by: Jim on 11/02/2006 09:53 pm
Abort scenarios wrt Carrier airplane.  For example launch scrub and returning to base and the carrier plane has a landing gear problem.
Title: Re: SSTO Thread
Post by: Dan Moser on 11/02/2006 10:20 pm
Not at all.  Propellant mass is dumped prior to return to airstrip in an abort/ launch re-cycle scenario.
Title: Re: SSTO Thread
Post by: Jim on 11/02/2006 10:29 pm
crew can't get out
Title: Re: SSTO Thread
Post by: yinzer on 11/03/2006 01:08 am
If the carrier airplane can maintain level flight, why can't they open the hatch and jump?
Title: Re: SSTO Thread
Post by: Dan Moser on 11/03/2006 01:28 am
Quote
Jim - 2/11/2006  5:12 PM

crew can't get out

Nope!  You don't understand the concept.  Crew is last in / first out, and is able to easily jettison launch vehicle if need be from high altitude, which is a much easier abort procedure than ground-launch scenarios where escape motors need to be fired followed by critically-timed parachute deployment.

Title: Re: SSTO Thread
Post by: Jim on 11/03/2006 01:49 am
We don't need to keep bantering.  Obviously, I am right since it wasn't selected.  Plus what I heard, it wasn't that hard to select concepts since most weren't viable
Title: Re: SSTO Thread
Post by: Dan Moser on 11/03/2006 02:17 am
Quote
Jim - 2/11/2006  8:32 PM

We don't need to keep bantering.  Obviously, I am right since it wasn't selected.  Plus what I heard, it wasn't that hard to select concepts since most weren't viable

Hah!  Wrong again!.. Did it ever occur to you that NASA may have selected the least threatening proposals, rather than the most viable?  They are motivated by job preservation, first and foremost.  You are not proven right by who was selected.. that only proves.. well.. who was selected.  Your "crew can't get out" assertion was clearly erroneous and not grounded in facts.  I hope I'm not shattering your beliefs here, but NASA's motives are not "pure as the driven snow".. there are plenty of sleezey deals going behind closed doors.
Title: Re: SSTO Thread
Post by: mong' on 11/03/2006 10:16 am
how could a small cargo delivery capacity to LEO threaten NASA, now that it has set its sights on the moon ?
Title: Re: SSTO Thread
Post by: meiza on 11/03/2006 11:29 am
We don't need to resort to conspiracy theories... There are surely technical reasons provided by NASA as to why that air-launched corona capsule thingy was not selected. Are they public?
Title: Re: SSTO Thread
Post by: Jim on 11/03/2006 11:45 am
Quote
Dan Moser - 2/11/2006  10:00 PM

Quote
Jim - 2/11/2006  8:32 PM

We don't need to keep bantering.  Obviously, I am right since it wasn't selected.  Plus what I heard, it wasn't that hard to select concepts since most weren't viable

Hah!  Wrong again!.. Did it ever occur to you that NASA may have selected the least threatening proposals, rather than the most viable?  They are motivated by job preservation, first and foremost.  You are not proven right by who was selected.. that only proves.. well.. who was selected.  Your "crew can't get out" assertion was clearly erroneous and not grounded in facts.  I hope I'm not shattering your beliefs here, but NASA's motives are not "pure as the driven snow".. there are plenty of sleezey deals going behind closed doors.

Get real
Title: Re: SSTO Thread
Post by: Jim on 11/03/2006 11:46 am
Quote
meiza - 3/11/2006  7:12 AM

We don't need to resort to conspiracy theories... There are surely technical reasons provided by NASA as to why that air-launched corona capsule thingy was not selected. Are they public?

Never will be public.
Title: Re: SSTO Thread
Post by: Dan Moser on 11/03/2006 04:21 pm
We got off on a COTS award tangent...  So, getting back to the topic of SSTO:  the reference provided on prior page, AIAA 2006-1040, was relevant in that it outlines a test-proven airlaunching method called trapeze-lanyard air drop with a credible plan to launch vehicles up to 300,000 pounds gross mass using a modified 747 or a large custom built aircraft.  That is a lot higher gross mass than any current capability, which is around 80,000 pounds from the inside of a large cargo plane, such as a C-5.  There is also a size contraint on launch from internal stores.  The question is: is airlaunching worth it for an SSTO?  Some might say the aircraft is the first stage, so it's not truly an SSTO, but let just explore the worth of the aircraft launch without regard to purist's definitions for now.

On the pro side, launching from an aircraft provides a payload increase of approximately 40%, plus you can fly in just about all weather and avoid most of the hassles of ground based launch ranges.  

On the con side is the considerable cost of the launch aircraft and related support equipment (initial design-modification, propellant loading gear, on-board cryocoolers, etc.). A new 747 is roughly $300M without modifications, so a reasonable rough estimate for getting the large launch capability might be around $400M.  

So, if your payload cost is $1,000 per pound, and you're getting 4,000 pounds extra payload, then that's $4M in extra revenue.  So, you'd have to fly something like 100 times to pay back the cost of the aircraft launch capability, not counting operations costs and the cost of money.   To get the same payload increase from a ground launch system as you get from an aircraft launch system, the launch vehicle would have to be scaled up by 40% (in mass), or fly 40% more often, or adding a few strap-on boosters.   That may be cheaper than trying to amortise the cost of that launch aircraft, but it depends on how often you fly and what the expected profit per flight works out to be.  The trade-off boils down to sustainable flight rates based on market conditions.  The world's current launch market is less than one flight per week, so it seems there will have to be a MAJOR shift in market conditions before this large air launch capability would be justified.  Some believe space tourism IS that major shift, and I hope they are right, but I'm not betting on that just yet.
Title: Re: SSTO Thread
Post by: meiza on 11/03/2006 05:56 pm
If you're designing for a smaller payload though, launching from any existing unmodified aircraft of a certain type certainly sounds more attractive.

The 747 has the problem that it is designed for very fuel-efficient long distance people-hauling (and cargo). It's one of the reasons it's so expensive, because it's fine to cost millions more if you can shave off some fuel consumption. On the other hand, production runs of airliners are large because of other uses of the craft than hauling rockets to altitude, and that diminshes the costs.

If a 747 is expensive, it doesn't necessarily mean that any reusable vehicle is as expensive. You could, purely as an example, have a rocket-powered launch assist platform that just lifts the SSTO straight up to 30 km. Or 100 km. (Yeah or stage when there's still positive speed to reduce gravity losses etc, but these are details.) But the cost of such hardware, both building and operation, is hard to estimate.
Title: Re: SSTO Thread
Post by: publiusr on 11/03/2006 06:29 pm
Quote
HailColumbia - 20/9/2006  9:49 PM

I was just trying to point out that heavy lift is going to open the solar system back up, and hookie's RLV will not.

True-but Ross' Direct might allow for OSP type craft to be launched.

With the hybrid rocket of the old AMROC design, you had first and second stages that were simple fuel segments, with the oxidant tank up top feeding its own stage and the lower stages. If this were filled with LOX and was part of a small space craft (assuming you could evacuate the tank and use it as extra stowage space) You might have a simple reusable craft. If nothing else--all you would ever need to build are all-fuel lower stage solids with zero explosion risk. The space craft and the oxidizer tank both being reusable.

I wouldn't call it a half-stage to orbit exactly.

I wonder if there is ever going to be a way for a stage to burn down like a lit cigarette....
Title: Re: SSTO Thread
Post by: publiusr on 11/03/2006 06:32 pm
Quote
mauk2 - 25/9/2006  7:59 PM


But, pressure fed tanks are HEAVY.  Even high specific strength materials only gain us so much.

Luckily, some very smart guys have recently puzzled out a "third way" which compromises between the performance of the turbopumps and the simplicity of the pressure tanks:

http://www.flometrics.com/rockets/rocket_pump/rocketpump.htm

I recommend a a quick looksee at the concepts at that site.  Inspired simplicity, if I may say so myself. :)

Combine such "pistonless pumps" with extreme low-cost relaxed designs like TRW's ablative pintle engine and we may knock some of the ridiculous costs out of rocketry.

http://www.st.northropgrumman.com/media/SiteFiles/_docs/propulsion/092500_low_cost_engine.pdf

http://spaceflightnow.com/news/n0009/26trwpintle/


Sadly, we are still left with the low Isp of chemicals, but ehn, my feelings on that topic are likely well-known. :D


Still good for splashdown. Heavy pressure-fed tanks are better for ocean recovery, with simpler systems. Water recover for turbo-pumps what with the salt spray? I don't think so.
Title: Re: SSTO Thread
Post by: Jim on 11/03/2006 06:39 pm
"I wonder if there is ever going to be a way for a stage to burn down like a lit cigarette."

no
Title: Re: SSTO Thread
Post by: publiusr on 11/03/2006 06:50 pm
Quote
Dan Moser - 2/11/2006  5:03 PM

Not at all.  Propellant mass is dumped prior to return to airstrip in an abort/ launch re-cycle scenario.

A 747 on stilts? Not going to happen. Air launch is questionable--even with the greater lifting power of AN-225, which has a shoulder mounted wing and more suitable to both t/Space and Virgin--in that it could be used for standard cargo when not pressed into service as a first stage.

Virgin Cargo & Space.


Seriously, The nose of the rocket is very close to striking the back of the C-17.

t/Space is the one company out there that may get someone killed. If you have plans for the 747 STS ferry--t/Space has to go back to the drawing board or adopt something like Svityaz.
Title: Re: SSTO Thread
Post by: Dan Moser on 11/04/2006 01:06 am
Quote
publiusr - 3/11/2006  1:33 PM

A 747 on stilts? Not going to happen. Air launch is questionable--even with the greater lifting power of AN-225, which has a shoulder mounted wing and more suitable to both t/Space and Virgin--in that it could be used for standard cargo when not pressed into service as a first stage.

Of all the engineering challenges of launching things into space, you point to landing gear extensions on a 747 or DC-10 as a particularly difficult task?  Not at all!  It's a very straight forward application of exisiting technology.

Quote
publiusr - 3/11/2006  1:33 PM
Seriously, The nose of the rocket is very close to striking the back of the C-17.

Ample nose fairing clearance has already been demonstrated by AirLaunch LLC in multiple C-17 drop tests.  Your "very close" remark is relative and has no factual basis.  Besides, t/Space is proposing a bottom drop, not internal extraction, so nose clearance is irrelevant.

Quote
publiusr - 3/11/2006  1:33 PM
t/Space is the one company out there that may get someone killed. If you have plans for the 747 STS ferry--t/Space has to go back to the drawing board or adopt something like Svityaz.

That's your opinion, and a semi-slanderous one at that!  Serious risks are also present in ground and floating launches.  Air launching has many abort scenario safety advantages.

BTW, I may have overestimated the cost of the launch aircraft.  I've been told a new 747 is closer to $150 M, and a used DC-10 or L-1011 might be "only" a few Million in today's aircraft market.  So the return on investment could be much quicker than previously estimated.
Title: Re: SSTO Thread
Post by: kevin-rf on 11/04/2006 02:23 am
Quote
Dan Moser - 3/11/2006  7:49 PM

BTW, I may have overestimated the cost of the launch aircraft.  I've been told a new 747 is closer to $150 M, and a used DC-10 or L-1011 might be "only" a few Million in today's aircraft market.  So the return on investment could be much quicker than previously estimated.

Other than with all the airbus A380 delays, the market for used super jumbo's has gotten a little tight while arlines defer retirements until they get the delayed A380's.
Title: Re: SSTO Thread
Post by: Dan Moser on 11/04/2006 02:39 am
Quote
kevin-rf - 3/11/2006  9:06 PM

Quote
Dan Moser - 3/11/2006  7:49 PM

BTW, I may have overestimated the cost of the launch aircraft.  I've been told a new 747 is closer to $150 M, and a used DC-10 or L-1011 might be "only" a few Million in today's aircraft market.  So the return on investment could be much quicker than previously estimated.

Other than with all the airbus A380 delays, the market for used super jumbo's has gotten a little tight while arlines defer retirements until they get the delayed A380's.

A380 delays are irrelevant.  Hundreds of older 747s, DC-10, and L-1011s have already been retired, just waiting for a bargain-hunter.
Title: Re: SSTO Thread
Post by: ANTIcarrot on 11/20/2006 01:36 pm
Something not often considered in the phrase 'aircraft like operations' is the way companies like Boeing actually make a profit on them. Boeing doesn't sell seats, or flights, but whole aircraft and/or maintenance contracts - and they do so with almost anyone who can afford its products. If Boeing, or any other company, did develop a practical SSTO (or TSTO or anything like it) would they be able to do the same? Or would the government instantly pass a law forbidding foreign or domestic commercial sales the moment the company had succeeded?
Title: Re: SSTO Thread
Post by: Kelly Starks on 11/20/2006 02:51 pm
Quote
Dan Moser - 3/11/2006  11:04 AM

 The question is: is airlaunching worth it for an SSTO?  ==

On the pro side, launching from an aircraft provides a payload increase of approximately 40%, plus you can fly in just about all weather and avoid most of the hassles of ground based launch ranges.  

Well obviously it depends on the SSTO design.  Forexample I ran some numbers for a htol ramjet concept and found the rocket boost, and ramjet fuel consumption to get you up to 600 mph, waas about 10% of the initial mass.  Definatly a problem for a mass sensative SSTO.

However as the Pegasis launchers found, a air launched rocket based design might not really save you much.

Some (Like Rutan) have pointed out that airlaunch could be a lot safer, since a boster failure doesn't drop you onto the pad in secounds.


Quote
Dan Moser - 3/11/2006  11:04 AM
On the con side is the considerable cost of the launch aircraft and related support equipment (initial design-modification, propellant loading gear, on-board cryocoolers, etc.). A new 747 is roughly $300M without modifications, so a reasonable rough estimate for getting the large launch capability might be around $400M.  


But you can get a USED 747 (like the one NASA bought to fly carry the shuttles on) for $40-$50 million.  Airlines are very sensative to slight ineficencies of older designs, adn need a plane they can fly 10-20 hours a day year after year.  Neiather factor means much to launcher folks wanting some carry capacity to lift a LV every once in a whlie.

So what does it take to keep a old 747 runing (over head per year, per flight, etc) and what would it cost to mod it to lift your launch vehicle?
Title: Re: SSTO Thread
Post by: Dan Moser on 11/23/2006 11:29 pm
Quote
Kelly Starks - 20/11/2006  9:34 AM

you can get a USED 747 (like the one NASA bought to fly carry the shuttles on) for $40-$50 million.  Airlines are very sensative to slight ineficencies of older designs, adn need a plane they can fly 10-20 hours a day year after year.  Neiather factor means much to launcher folks wanting some carry capacity to lift a LV every once in a whlie.

So what does it take to keep a old 747 runing (over head per year, per flight, etc) and what would it cost to mod it to lift your launch vehicle?

Yes, Kelly, and as you might have noticed, I did revise the cost number downward for a used/retired jumbo jet.. Actually, you'll probably find a much better deal on L1011s and DC-10s, which have almost the same capacity as the earlier 747 models.  When comparing ground vs. aircraft launch costs, you have to account for the fact that air launching saves you the use costs on gov't controlled ground ranges, which is reportedly $1.5 M minimum, even if it's a tiny rocket.  Also, air launching increases your payload mass (and therefore revenue) per flight by something like 40% vs. the same size ground launch vehicle.  AND.. the obvious point.. ground launching also has significant fixed asset costs no matter how often you fly... propellant storage handling systems, assembly buildings, umbilicals, safety equipment, transporter/erector vehicles, exhaust buckets, and a permanent launch operations crew stationed at the pad... and to reach all orbital inclinations, you have to have two sets of launch pad infrastructure.  Finally, there is a significant cost associated with ground range-imposed holds and abort-recycle activities.. whether due to weather, maritime traffic, or.. as Elon Musk found out the hard way at Vandenberg.. the government suddenly deciding they won't let you fly there at all, no matter how much you have invested in launch facilities.   It is not sufficient to just look at the cost of buying and maintaining a 747 and deciding.. gee, that looks expensive.

The aircraft launch platform is essentially a first stage RLV, and like in any RLV trade study, it is the the flight rate that determines cost feasibility.  Given the fact that today's payload demand is far less than today's launch capacity, a new launch system has to be far cheaper than the established competition, and/or focus on accommodating non-traditional payloads... such as space tourists... and there's plenty of risk on both of those fronts, to be sure!
Title: Re: SSTO Thread
Post by: Generic Username on 11/24/2006 12:26 am
Quote
"I wonder if there is ever going to be a way for a stage to burn down like a lit cigarette."

Yes, indeed. And such vehicles have actually *flown.*

There are two ways:

1: "Cigarette burners." Is pretty much what it sould like. Long slim cylindrical solid rocket motor with the propellant poured right in, no center perforation or fins or whatnot; conventional nozzle. Used a *lot* for various test motors... long burn time, rather pitiful thrust level.

2: Nozzleless rocket: Basically a  conventional center-perforated cylindrical solid rocket motor where someone appears to have forgotten to put on the aft closue and the nozzle. Just cone out the aft face of the propellant, and you're ready to go. Isp takes a substantial hit... call it 10%... but inert weight, cost and complexity go *way* down.

A video of such a rocket in flight, made by a feller I used to work with:
http://www.aerotech-rocketry.com/customersite/theatre/othermovies/ray_goodson_5_inch.mpg

Went to the edge of space for a few hundred bucks, back in the '60's.

Depending on how you design the nozzleless rocket, as the coned-out aft face of the propellant burns forward, the surrounding case wall material also burns away (especially true if it's paper phenolic or some such). In this way, the booster , not just the propellant, gets shorter as the motor burns.

United Tech studied and seriously proposed a Titan 34D-class nozzleless booster rocket to replace the existing boosters. Somewhat longer (due to lower Isp), but thought to be far cheaper.

I know nozzleless rockets have been successfully tested up to 18 inches diameter (the UTC TM-3 motor, frex), but I don't know if they've gone bigger'n that.

SSTO requires "hard and complex." But spaceflight need not. There are some *damned* simple options available.
Title: Re: SSTO Thread
Post by: simonbp on 11/24/2006 03:38 am
Quote
Generic Username - 23/11/2006  7:09 PM

SSTO requires "hard and complex." But spaceflight need not. There are some *damned* simple options available.

I guess that's the ultimate irony; cheap access to space will come not through an engineer's dream SSTO with turboscramjets, but with simple, cost effective boosters that give up a little bit of performance for a lot of cost...

Eschewing turbomachinery and cyrogenics might be a start...

Simon ;)
Title: Re: SSTO Thread
Post by: Generic Username on 11/24/2006 04:09 am
Quote
simonbp - 23/11/2006  9:21 PM

I guess that's the ultimate irony; cheap access to space will come not through an engineer's dream SSTO with turboscramjets, but with simple, cost effective boosters that give up a little bit of performance for a lot of cost...

Indeed. The likes of XCOR, who are devoting their efforts to making *reliable* and low cost rocket engines, will, IMO, be of greater value long-term than those seekign to make scramjets and the like.



Quote
Eschewing turbomachinery and cyrogenics might be a start...

What works. What works cheap.

Many complain that modern launch vehicles are jsut manned artillery. *IF* ONLY.* Artillery shells are made by the bajillions, and every single one is expended.  Recovering your transportation system is nice and all... but if it's *truly* cheaper to expend it... then do so. Minimum liftoff weight is nice... but if the vehicle that weighs twice as much costs a tenth as much to operate and one-hundedth as much to develop... then to hell with "advanced."
Title: Re: SSTO Thread
Post by: sbt on 11/25/2006 06:17 am

One word:

Martlet

:)

Title: Re: SSTO Thread
Post by: Generic Username on 11/25/2006 02:04 pm
Quote
sbt - 25/11/2006  12:00 AM


One word:

Martlet

:)


Difficult to send astronauts...
Title: RE: SSTO Thread
Post by: sbt on 11/25/2006 11:31 pm

True, true...

It all depends on your definition of 'Access to Space'

For small satellites the concept might be worthwhile, although something along the lines of 'Big Babylon' would be more useful. Building one at KSC would be an interesting problem though, maybe Vandenburg for Polar orbits?

Artillery has relevance to the more general discussion. Tube Artillery is very 'old technology' but still in widespread use. No newer technology has arrived to do its battlefield job with reasonable cost and infrastructure requirements. The Payload has been updated and is, in many cases, very sophisticated, and tweaks made to the Launch System but its still 'Back to the (16)60s' for even the most advanced nations.

Rick
Title: Re: SSTO Thread
Post by: Dan Moser on 11/26/2006 03:43 pm
The cannon-launched rocket approach is not used today for many good reasons.  Having done some engineering on cannon-launched missiles, I can tell you this is a very impractical approach, especially for space access.  The rocket motor design is much more problematic when the high-G, high-pressure cannon-launch environment is imposed.  How does 8,000 Gs and 30,000 psi sound?  As we found with the military applications, merely extending the first stage rocket motor by a modest amount and using conventional launch methods will do far more than a cannon-assist launch, and it's compatible with fragile payloads.  

In any case, this has nothing to do with SSTOs.  Perhaps a cannon-launch thread should be started if there are more details to be discussed on this approach..
Title: Re: SSTO Thread
Post by: publiusr on 12/22/2006 07:37 pm
Excalibur or Sea Dragon one day--I hope.
Title: Re: SSTO Thread
Post by: mong' on 12/22/2006 10:27 pm
I still have faith in good ole RLV's, I believe we have the technology to build a entirely reusable TSTO with a decent payload (10 tons) if we do it seriously, problem is it's going to have to fly a lot (and I mean a lot) in order to be competitive and reduce costs significantly, something like 50 flights/year.
right now we can't achieve that, there's just not that much payload in the entire world.

but I believe a moon base that needs constant resupply and a fuel depot in LEO as well as a permanent mars base can justify such high flight rates.
this along with reusable ascent/descent vehicle at both destinations (RLV's work better on the moon and mars) can significantly reduce not only LEO launch costs, but also that of interplanetary transport in general.

in the mid future (30-40 years) I can imagine using medium launch vehicles in the 40-50 metric tons range to send the big components of a mars ship, and mutliple small RLV's to fuel it. since we have 2 years between launch windows,we might as well use it.
I imagine that 2 medium launch vehicles + 10 RLV's could eventually cost less than 2 HLV's.
Title: Re: SSTO Thread
Post by: publiusr on 01/05/2007 06:27 pm
Quote
mong' - 22/12/2006  5:10 PM

 I can imagine using medium launch vehicles in the 40-50 metric tons range to send the big components of a mars ship, and mutliple small RLV's to fuel it. since we have 2 years between launch windows,we might as well use it.
I imagine that 2 medium launch vehicles + 10 RLV's could eventually cost less than 2 HLV's.

There are people who don't even want 40-50 ton range boosters, let alone HLLVs. RLVs are a dead end and I never had much faith iin them--esp for exploration.

Here is why I want to get larger rockets and a larger, non-comsat/milsat, etc. market for LVs.

Future fiber-optic cables.

For now, the big Asia Pacific market can only be serviced by Comsats, but as more fiber optic cables are called for--and more land-lines can be had---LVs may (in the more distant future) have even less of a market than they do now.

For now, comsat gigantism will keep LVs up in size.

Just remember theare are those mindsets in the military who wish the largest rocket out there to be in the Minuteman III size range---who do not want human spaceflight to grow.
Title: Re: SSTO Thread
Post by: Jim on 01/05/2007 06:47 pm
Quote
publiusr - 5/1/2007  2:10 PM

Just remember theare are those mindsets in the military who wish the largest rocket out there to be in the Minuteman III size range---who do not want human spaceflight to grow.


 Where is your proof?   Quote somebody.   Where is this documented?   These unsubstatiated  comments need to stop.  They are only from your uninformed viewpoint and based on nothing.

the military does not care what NASA does
Title: Re: SSTO Thread
Post by: Dan Moser on 01/07/2007 03:02 am
Quote
publiusr - 5/1/2007  1:10 PM

Quote
mong' - 22/12/2006  5:10 PM

 I can imagine using medium launch vehicles in the 40-50 metric tons range to send the big components of a mars ship, and mutliple small RLV's to fuel it. since we have 2 years between launch windows,we might as well use it.
I imagine that 2 medium launch vehicles + 10 RLV's could eventually cost less than 2 HLV's.

There are people who don't even want 40-50 ton range boosters, let alone HLLVs. RLVs are a dead end and I never had much faith iin them--esp for exploration.


GEEZ !... Can we please get off trying to use faith to control our launch vehicle decisions? This industry is -- or at least ought to be --  guided by science, engineering, and economics.  Subsidizing unnecessary launch vehicles for sentimental reasons is absolutely ludicrous!  (NASA... take note)  Rational decisions on launch vehicle designs MUST be based on technological maturity and launch market conditions .. not some space cadet's delusional wet dream!  Economics and technology will sort out the winner of SSTO vs. multi-stage and RLV vs. ELV vs. HLV.  Right now, with the launch market demand as it is... ELVs are the clear winner.  If there is an increase in demand, as is being predicted by some, then reusability may start to make sense.  NASA's attempt at cheap space access via launch vehicle reusability has generally been a failure, but others may have better success.
Title: Re: SSTO Thread
Post by: Jim on 01/07/2007 03:43 am
Quote
Dan Moser - 6/1/2007  10:45 PM

[Rational decisions on launch vehicle designs MUST be based on technological maturity and launch market conditions .. not some space cadet's delusional wet dream!  .

Hear, hear !!!
Title: Re: SSTO Thread
Post by: publiusr on 01/12/2007 05:39 pm
Need I remind any of you that any big liquid fueled vehicle can be considered a "wet dream" I'm sure Sergei Pavlovich heard that talk all the time

Quote
Jim - 5/1/2007  1:30 PM
 Where is your proof?   Quote somebody.   Where is this documented?

So...you're telling me there isn't hostility towards LVs? Don't tell me that there aren't folks who think anything bigger than a Min. III is a waste. That should be obvious just based on the "wet dream" comments alone.


At any rate---to avoid any complaints about being combative...let me ask you this.

If you were, say...NASA's Chief Administrator for life, what direction would you head NASA in, Jim?

Give me a run down of what you would like to see for, say, the next hundred years.


My guess is that it would not involve an SSTO (and rightfully so).

What payloads would you be an advocate for that otherwise would not be built....
Title: Re: SSTO Thread
Post by: kkattula on 02/08/2007 12:16 pm
I think you've mostly missed something important:

1) In a first stage, propellant density is more important than Isp.

2) SSTO is a first stage.


Using Dan Moser's earlier example:

>The shuttle ET weighs 59,500 pounds empty, and holds 1,589,000 pounds of LOX/hydrogen.
>3 RS-68 engines would generate 663,000 pounds SL thrust each, for a total of 1,989,000, with an Isp 359 >sec. SL and 409 sec. vacuum.
>Each engine weighs 14,876 pounds, for a total weight of 44,628 pounds for 3 engines.
>Throw in 10,000 pounds extra for added plumbing, structures & avionics, and an extended nozzle for the >one of the engines bringing its Isp to 450 sec vacuum. (conservative)
>Now put a 60,000 pound payload on top.
>Total GLOW = 59,500 + 1,589,000 + 44,628 + 10,000 + 60,000 = 1,763,128 pounds
>Propellant fraction = 1,589,000 / 1,763,128 = 90.1%
>Payload fraction = 60,000 / 1,763,128 = 3.4%

Re-working for LOX/RP-1 at volume O/F 2:1, using the same total tank volume:

The shuttle ET weighs 59,500 pounds empty, and holds 3,540,000 lbs LOX and 1,257,000 lbs RP-1.
7 RD-180 engines would generate 860,000 pounds SL thrust each, for a total of 6,020,000, with an Isp 311 sec. SL and 338 sec. vacuum.
Each engine weighs 11,889 pounds, for a total weight of 83,223 pounds for 7 engines.
Throw in 20,000 pounds extra for added plumbing, structures & avionics, (no extended nozzle), and stronger inter-tank and thrust structures, but remove the LH2 insulation and SRB thrust members.
Now put a 60,000 pound payload on top.
Total GLOW = 59,500 + 3,540,000 + 1,257,000 + 83,223 + 20,000 + 60,000 = 5,019,723 pounds
Propellant fraction = (3,540,000 + 1,257,000) / 5,019,723 = 95.56%
Payload fraction = 60,000 / 1,763,128 = 1.2%

Mass Ratio is 22.5.

At average Isp 330, (should be higher), delta V is 10,075 m/s. More than enough for LEO

And since delta V to LEO for high density propellant vehicles is lower, due to lower gravity & drag losses, such a vehicle could lift almost DOUBLE the payload (110,000+ lbs), with exactly the same (total) size tanks, but 40% heavier dry mass.

Interesting examination of propellant density and other subjects in this paper:
"Single Stage To Orbit Mass Budgets Derived From Propellant Density and Specific Impulse"

http://www.osti.gov/bridge/purl.cover.jsp?purl=/379977-2LwFyZ/webviewable/
Title: Re: SSTO Thread
Post by: Strato on 02/08/2007 01:03 pm

The problem is energy density.

Here ya go, this should give some insight:

http://ftp.fas.org/sgp/othergov/doe/lanl/lib-www/la-pubs/00191252.p...  


I remember an African engineer friend of mine who used to say: Ballistic is a headache.

But it is nice to see the maths ;)
Title: Re: SSTO Thread
Post by: PurduesUSAFguy on 02/08/2007 09:05 pm
Quote
publiusr - 12/1/2007  12:39 PM

Need I remind any of you that any big liquid fueled vehicle can be considered a "wet dream" I'm sure Sergei Pavlovich heard that talk all the time

Quote
Jim - 5/1/2007  1:30 PM
 Where is your proof?   Quote somebody.   Where is this documented?

So...you're telling me there isn't hostility towards LVs? Don't tell me that there aren't folks who think anything bigger than a Min. III is a waste. That should be obvious just based on the "wet dream" comments alone.


At any rate---to avoid any complaints about being combative...let me ask you this.

If you were, say...NASA's Chief Administrator for life, what direction would you head NASA in, Jim?

Give me a run down of what you would like to see for, say, the next hundred years.


My guess is that it would not involve an SSTO (and rightfully so).

What payloads would you be an advocate for that otherwise would not be built....

I've never run into anyone in the Air Force, from two stars on their shoulders all the way down to butter bars, that has animosity, much less hostility towards launch vehicles. The Air Force did fund the development of the Atlas V and Delta IV, both of which are quite a bit bigger then a Minuteman III. The Air Force also funded the development of the Delta IV Heavy, which other then the space shuttle is the heaviest lift rocket flying currently in the United States.

In fact, the Air Force almost ended up as the first operator of a space station, most people don't know how close the manned orbiting laboratory program came to become reality. Ditto the X-20. (Well, okay not so much on the X-20, but it wasn't exactly a pipe dream either)

My point is that the Air Force would be the biggest beneficiary of an RLV, or of cheap heavy lift. Your comment makes no sense, at all.
Title: Re: SSTO Thread
Post by: publiusr on 02/10/2007 06:00 pm
I am sure there are friends of HLLV and space in the Air Force. There are just a lot more folks who would rather spend money of fighters instead.
Things may be changing.

Let's hope so.
Title: Re: SSTO Thread
Post by: StoffelCorp on 02/22/2007 08:17 am
last year i did a study, design, fabricated, and static tested the possibility of a aerospike nozzle being compatible within a hybrid propulsion system. worked great! did a paper and translated into an independent study for credit at the university. right now, some fellow undergrads (friends/family) are working on a 4800lb thrust regeneratively cooled bi-propellant aerospike engine to static test this summer and for X Prize Cup 2008 when we apply to demonstrate. We'll most likely launch the hybrid aerospike at xprize cup, but current efforts to improve the hybrid propulsion system is underway. the regen aerospike is our main focus right now, and not sure if we'll have improvements on the hybrid yet by october this year (expected date of X Prize Cup). so stay tuned.... we have big plans for the aerospike and actual flight tests in the near future...

respectfully,

james
Title: Re: SSTO Thread
Post by: publiusr on 03/02/2007 07:12 pm
I remember talking to Seymour Bogdonoff, who has travelled to Russia not too long ago. He had an interest in a great many things.

Sadly, he died early in 05'
http://www.princeton.edu/~compub/pwb/05/0131/2a.shtml

Title: Re: SSTO Thread
Post by: TyMoore on 03/02/2007 08:45 pm
You built a hybrid aerospike engine? Wow, pretty impressive. Do you have any pictures?

What propellant combination did you use?

A long time ago I looked at some of the paper studies of the really big lifters done by Boeing, and McDonnel Douglas in the 1960's Almost all of them used aerospike engines with integral reentry heat shield. I looked at 'designing' (more of a rough design sketch!) such a vehicle myself that could loft 500 metric tons into a LEO orbit burning LOX and RP-1. The resultant 28,000 metric ton behemoth would have been very nearly 65 m in diameter at the base.  The liquid oxygen feed line alone was over 4 m in diamter! The liquid oxygen tank was three times thicker at the base than at the top to support the dynamic pressure column caused by so much liquid oxygen undergoing acceleration, and would have needed almost 600 metric tons of aluminum all by itself. The gross numbers gave me a real appreciation for just what it takes to make a big SSTO--and how bloody inefficient they are at delivering payload!
Title: Re: SSTO Thread
Post by: StoffelCorp on 03/02/2007 10:43 pm
Yes I do have pics and video, ill repost them in a few days and/or put them up on the website which is about 1/3 of the way complete. It was a 300lb thrust hybrid aerospike (conical full length). At the time, we used PVC and nitrious oxide. We're now looking into creating simple/complex geometrical grains, with a new high Isp fuel with similar characteristics as frozen pentane (done by USAF), and newly improved injector design. goal is to get it to gain similar Isp results as bipropellant engines with the added benefits of a hybrid propulsion system and aerospike nozzle. nitrous again as the oxidizer.
Title: Re: SSTO Thread
Post by: StoffelCorp on 03/02/2007 10:57 pm
this was the small motor we static tested. the next motor will be of designed 3000lb of thrust on a newly dedicated trailer and test stand.

http://img177.imageshack.us/img177/415/nozzletest1mayjune2006maw8.jpg
Title: Re: SSTO Thread
Post by: TyMoore on 03/03/2007 12:47 pm
Very nice. It's fun and all to discuss paper designs and theories. It's really nice to see hardware! 3000 lbf--that's a pretty hefty little engine!

Aerospike engines are fascinating because of the integral altitude compensation along with short nozzles. They may be able to offset some of the shortcomings of a gas generator cycle engine--allowing better performance (higher systemic Isp) with slightly lower chamber pressures, potentially reducing work load on a turbopump package...
Title: Re: SSTO Thread
Post by: halkey on 03/03/2007 07:57 pm
Quote
StoffelCorp - 2/3/2007  5:43 PM

Yes I do have pics and video, ill repost them in a few days and/or put them up on the website which is about 1/3 of the way complete. It was a 300lb thrust hybrid aerospike (conical full length). At the time, we used PVC and nitrious oxide. We're now looking into creating simple/complex geometrical grains, with a new high Isp fuel with similar characteristics as frozen pentane (done by USAF), and newly improved injector design. goal is to get it to gain similar Isp results as bipropellant engines with the added benefits of a hybrid propulsion system and aerospike nozzle. nitrous again as the oxidizer.

Awesome.  I can't wait to keep up with your blog/website once you finish it (hurry up and finish it!).  I've read a lot about aerospike nozzels and their advantages but have always been perplexed as to why very few rocket designs (and none which are commercial to my knowledge) incorporate them.  Is there some inherent difficulty in working with them or what is it exactly that causes them to be overlooked?  Just inertia of doing what has always been done?
Title: Re: SSTO Thread
Post by: aftercolumbia on 03/04/2007 04:54 am
I've never really been a fan of SSTO, and rather go "Aw, poo [or other expletive]! Here we go again."

There is one study that tried to give a huge variety of propellants a fair shake, primarily by assuming a constant propellant volume and fixed mass tanks and engines (he gave a small advantage to oxyhydrogen to make up for certain advantages resulting from its lack of density...such as the absence of slosh baffles.  He also made up for the reduced specific thrust of oxyhydrogen engines (low density LH2 means you need six times as much pump head to get the same pressure as for the next lowest density propellant, LNG.)

Hydrogen, both in the LOX and hydrogen peroxide families, came in dead last.

So, as a booster nut, I've found wanting the two touchstones of "modern" boosters: SSTO and liquid hydrogen, and now avoid both like Luke does rancors.  The major disadvantage I've found with SSTO boosters, even expendable SSTOs with dropaway fairings, is that one stage is doing all the work.  This isn't just a performance issue, but stretches to functionality.  One stage, once doing orbital maneuvers, has the problem of either running one or two of a large number of multiple engines, small dedicated maneuvering engines (possibly with separate propellant supplies) or really deep throttling of a single engine system.  The burnout accelleration of an SSTO with a non-throttling engine can be expected to be 12-14g.  It isn't likely structures built to such load factors would be light enough to allow an SSTO.

Dare I mention the ultimate SSTO wannabe, and the closest we've ever gotten to having one: the original MA-5 powered Atlas?  This booster can ascend to low energy orbit with a 2000lb (ish) payload operating from a single set of propellant tanks.  Because it drops its booster engine (one engine...one set of turbopumps feeds two motors) and pressurization system, it becomes a SAAHTO...can I say that?  (Stage-And-A-Half-To-Orbit)  Final note: it ran on oxykerosene.
Title: Re: SSTO Thread
Post by: meiza on 03/04/2007 07:39 pm
3000 lbf Stoffelcorp! That's very big if you're doing it as an experiment. Wouldn't it be easier to demonstrate a smaller one first? I don't know.
Title: Re: SSTO Thread
Post by: kkattula on 03/07/2007 01:08 pm
I'd prefer a stage and a half to orbit where you drop propellant tanks. Tanks can be cheap, and when empty will be very 'fluffy', so recovery for re-use is much more practical if you want to go to that much trouble. Something like this:

Core LOX/RP1 (2:1 volume ratio), MR 14, 5 engines: 2 low expansion ratio nozzles, 2 medium, 1 high. Hang 4 LOX & 2 RP-1 tanks around the core to increase tank volume by 55%. Fly a sub-sonic (250 m/s) profile to about 12 km altitude on 4 engines, drop 2 LOX & 1 RP-1 empty tanks. Throttle up the first 4 engines, start the 5th and drop the remaining 3 tanks at about 25 km, 700 m/s. From there the core would make orbit, shutting down lower ratio engines and some throttling to minimize g's.


Of course a Kistler style LAP would let the same size core put a lot more payload in orbit for the same amount of propellant, and it would fly itself back to the launch site too!
Title: Re: SSTO Thread
Post by: aftercolumbia on 03/12/2007 05:00 pm
Kkattula, I like that idea.  Also, engines have less convenient entry shapes.  I'd rather drop both, that way you have all the base area available for your lower expansion engines.
Title: Re: SSTO Thread
Post by: StoffelCorp on 03/23/2007 04:06 am
yes. i do agree with doing much smaller series of tests on a scalled down concept for our hybrid motor and biprop aerospike engine. in normal circumstances we would take this approach, not that our current size of engine isnt. which it is actually. there are other reasons currently unable to disclose, but are pushing with reasonability and safety first, the scale of this engine and demonstration of it this year. sorry, i havnt gotten a video up, besides the small pic of the first small scaled down 300lb hybrid aerospike, which will continue for a large scale hybrid aerospike 3000lb (but this motor is currently on the back side of the shop for the moment), and currently the one on the table and machine shop is the 4800lb regen clustered biprop aerospike engine. current tests and fabrication of the week is the torch spark igniters being used for each cluster. the website has been worked on some more and getting closer to being done. i dont have a definate date at the moment, but just that it is getting closer. stay tuned:O)

respectfully,

james
Title: Re: SSTO Thread
Post by: meiza on 03/23/2007 12:52 pm
One more thing about SSTO:s.
I know skis and hockey sticks nowadays use carbon nanotubes for increased strength. It's the latest thing in a long series of improvements: wood, fiberglass, carbon fibre and now nanotubes. Of course they are just a small part there, but nevertheless it could be interesting to do some research on their strengths and properties as additives in regular carbon fibre.
Title: Re: SSTO Thread
Post by: kevin-rf on 03/23/2007 01:28 pm
Quote
meiza - 23/3/2007  8:52 AM

One more thing about SSTO:s.
I know skis and hockey sticks nowadays use carbon nanotubes for increased strength. It's the latest thing in a long series of improvements: wood, fiberglass, carbon fibre and now nanotubes. Of course they are just a small part there, but nevertheless it could be interesting to do some research on their strengths and properties as additives in regular carbon fibre.

Yeah and bunch of people came out with titanium biners for rock climbing a few years back. Funny no one is selling them anymore, we all went back to Al and Stainless. It is more marketing spin, our product stands out because we use nano technology. How many beauty aids now have secret 'nano' particles ( usually gold or silver, old chemistry term coliodial suspension) in them that will cure everything from wrinkles to warts. How many sunglasses now have "nano coatings" to block that evil UV, same few nm thick coating that was always there, different name. The 'new' big thing in asia is silver nano particle coatings on everything. Silver really does cut down on the germs, the real reason why people use to give a baby a silver spoon.

The nano revolution for bulk materials is to see what you can do with these small particles/tubes in the bulk structure and coatings. A lot of cool stuff going on, but it is being over hyped ... Marketing spin has replaced good science. It is akin to the metal mono crystal turbine blade revolution that went into jet engines back in the seventies (stronger blade same mass).

Carbon Nanotubes have potential for lighter weight structures, but they still have to be sealed to keep the LH/LOX in. I wonder how much of an advantage they really have over carbon fiber... It is just a replacement for the carbon fiber in composites. If Carbon Nanotube fibers can be made cheap enough and strong enough maybe we could change the fraction enough for a SSTO.

Still if in using new materials we could increase the thrust to weight ratio of LH/LOX engines to that of Kero/LOX we could really make some progress on reducing the mass fractions.
Title: Re: SSTO Thread
Post by: meiza on 03/23/2007 01:42 pm
Yeah I know there is a lot of hype, but I know companies have invested a lot of money into this, and some that haven't, have been forced out of business.
The article is kind of unclear, is it a new resin that is used with regular carbon fibers?:
http://www.amroyinc.com/hybtonite/
Title: Re: SSTO Thread
Post by: kevin-rf on 03/23/2007 01:57 pm
I would be wary, they are talking carbon nanotube fibers in the epoxy to add strength to the structure...

Not apples to apples, but there is an interesting article out there on doing this with steal fibers instead of rebar in concrete domes. Not very much luck as you will read.

http://www.monolithic.com/pres/steel_fibers/index.html

Kinda reminds me of what happened with the X-33 composite tank failure. A zipper effect.

Title: Re: SSTO Thread
Post by: aftercolumbia on 03/25/2007 07:28 pm
Quote
kevin-rf - 23/3/2007  8:28 AM

The 'new' big thing in asia is silver nano particle coatings on everything. Silver really does cut down on the germs, the real reason why people use to give a baby a silver spoon.

Ironically, vampires have gone in the same direction with Star Trek...instead of vampires and silver bullets, you have Borg and nanites, all really the same flavour of creepiness if you stare at it long enough.

Quote
Still if in using new materials we could increase the thrust to weight ratio of LH/LOX engines to that of Kero/LOX we could really make some progress on reducing the mass fractions.

Why not consider using oxykerosene or some other propellant combination than oxyhydrogen?  Hydrogen isn't the only rocket fuel, and it is easier to attain lower dry mass fractions with denser fuels.

Hmm...I thought of something that might work not too badly as an SSTO, if it can be balanced properly, and of course, if the appropriate materials can be found.  It would use LOX/CH4+C2H6 (oxymethane+ethane; mixed fuel formulated to achieve a volumetric mixture ratio appropriate to the design, probably less than 1:1 assuming LOX on top, and the payload weighs more than the ascent engines...the empty CoG needs to be in the intertank.)

After burning most of the way to orbit like a conventional booster on oxyhydrocarbon engines mounted in the bottom of the vehicle, the hydrocarbon mixture fuel depletes.  The speed is probably in the ballpark of 6500m/s, leaving about 1300m/s left to orbital speed.  The booster turns sideways, opens a door in the intertank, and extends the nozzle of an oxyhydrogen engine, fed from the main LOX tank, and a toroidal LH2 tank in the intertank region.

A problem is that I can't see recovery (at least, not yet), because after the payload is released, the heavy end will be the engines.  Entering heavy end first, the ascent motors would act as ramscoops for entry plasma, and would be destroyed on entry (even if the tanks could be saved.)  The sucker would still need such insanely light construction that it would be far to expensive not to recover...but accomodating reuse might be too heavy to allow it to operate as an SSTO.  If one could stabilize it going sideways, the heating rates and dynamic pressures could be quite low (assuming entry angle isn't too steep), making it easy to implement a reusable TPS (assuming its light enough.)
Title: Re: SSTO Thread
Post by: tnphysics on 09/03/2007 04:33 am
Think again. Which would cost more?
Title: Re: SSTO Thread
Post by: bad_astra on 09/03/2007 06:24 am
Quote
kevin-rf - 23/3/2007  9:57 AM

I would be wary, they are talking carbon nanotube fibers in the epoxy to add strength to the structure...

Not apples to apples, but there is an interesting article out there on doing this with steal fibers instead of rebar in concrete domes. Not very much luck as you will read.

http://www.monolithic.com/pres/steel_fibers/index.html

Kinda reminds me of what happened with the X-33 composite tank failure. A zipper effect.


Actually there have been a lot of new tests done by ferrocement experimenters using sprayed concrete with very small steel pins to make preformed domes and from what I have heard, the results are promising.

 Monolithic sells a product and they do not want to loose business to thin-shell concrete, because they have their own process and selling it as the best is what makes them number one in a business where they are mostly competing with a few individuals. The ferrocement development of late has been more along the lines of open-source. I know this is out of the range of this discussion, although maybe for a lunar-habitat discussion. Anyway, just thought I'd add that bit.

In any case, for an SSTO to work there is going to have to be a very low weight ratio. It's either balloon tanks or unobtanium for that, and carbon nanotube might be it.
Title: Re: SSTO Thread
Post by: tnphysics on 09/15/2007 12:35 pm
What about an SSTO with a 8 SSMEs, modified to have plug nozzles, run stoichiometric, and be capable of serving as a heat shield?
Title: Re: SSTO Thread
Post by: meiza on 09/15/2007 01:30 pm
SSME:s would probably burn through if run stoichiometric. Also the cost of development and per flight would be humongous. I also doubt about your payload numbers. The Ares V has 5 RS-68 engines and solids plus the upper stage fires and still orbits less than 150 t.
Title: Re: SSTO Thread
Post by: TyMoore on 09/16/2007 02:02 am
Many years ago I played around with the idea of an 8.4 m modified ET core stage powered by 8 SSME's and 4 4-segment SRB's. I don't have the numbers infront of me, but it seems to me that I got a LEO payload of a little less than 200,000 Kg--good, but not super spectacular. And of course, I was interested in retrieving the propulsion module with all the SSME's in it for reuse. The trouble was, with a heat shield on one side and SSME's on the other, the sucker would want to tip over in an ocean splash down. So either I had to put about a 20,000 kg 'keel' ballast mass on a steel cable beneath the nose of the module to keep the heavier engines out of the water, or I had to let them get wet. And if you do that, you might as well not bother to reuse them!

Also, one little problem I anticipated was trying to figure out a good way to keep sea birds from resting on the upright engine bells and of course deficating inside (bird poop is really corrosive--very bad for reusable rocket engines!) I anticipated using a set of propane powered 'noise makers' to keep birds away until the propulsion module was recovered...

In short, I gained new respect for the folks that came up with the fairly straightforward SRB design--you have to admit its pretty good engineering!
Title: Re: SSTO Thread
Post by: tnphysics on 09/16/2007 02:55 am
What about giving the SSME's plug nozzles and making them the heat shield, using retro rockets for a land landing?

Flooding the oxygen tank immediately after splashdown would prevent tip over.
Title: Re: SSTO Thread
Post by: meiza on 09/16/2007 03:51 pm
It could be cool, but aerospike nozzles have never been flight tested. Spikes have been but aerospike fills the base with bleed air to prevent a low pressure area in the truncated spike end.
Title: Re: SSTO Thread
Post by: TyMoore on 09/18/2007 03:59 am
The trouble with using the SSME's in an aerospike configuration is that there is no aerospike!

Originally, aerospike rocket engines, as concieved, used a gas generator cycle wherin a seperate gas generator creates a gas flow from combustion of a fraction of the propellant flow, that drives gas-trubine rotors--which in turn spin the turbopumps. Spent gas was directed by low pressure ducts to the central part of the engine and dumped--this formed the gasseous part of the -aerospike- engine. The high pressure nozzle gasses first expanded against the curved part of the actively cooled plug nozzle, and then continued to expand against the lower pressure gas-turbine exhaust flow. In this sense you get altitude compensation and efficient expansion with across the entire base of the vehicle and not just the 'engine bells' of conventional deLevaal nozzles.

Since the SSME uses a high pressure, staged combustion system--there is no gas to dump--so technically you can't have an aerospike engine, only a plug nozzle engine. And without that ceontral low pressure gas, you'll end up with enough drage to 'uncompensate' your engine--so it will ultimately be no more and probably less efficient than using a conventional deLevaal nozzle.

A plug nozzle with an aerospike theoretically can give pretty good Isp performance (say between 350-400 sec) with reasonably low chamber pressures of say 1000 psia. However to get the higher performance (450 sec) you need to used a staged combustion cycle to achieve the much higher chamber pressure (3200-3500 psia), which eliminates the aerospike gas flow, and you end up with something similar to the SSME or RD-170 (if you go with RP-1/LOX.) If you go with some kind of auxiliary gas flow to re-establish the aerospike, the required mass flow will ultimately reduce your Isp from the higher staged combustion level--so the only advantage at all is the direct altitude compensation of the engine and possibly the utility of the engine as a large reentry heatshield--



Title: Re: SSTO Thread
Post by: meiza on 09/18/2007 08:37 am
Wasn't the initial Rocketdyne SSME competitor a J-2 derived plug nozzle engine? J-2 is a gas generator engine so it should work. (And was planned, built and tested again with the X-33!) In the end as we all know, a higher pressure staged combustion design was selected and you didn't have as much problems with that at low altitude so you could go with a conventional nozzle.
Title: Re: SSTO Thread
Post by: tnphysics on 09/18/2007 08:10 pm
A plug nozzle is not the same as an aerospike nozzle.

A plug nozzle can be an ordinary de Lavel nozzle with a plug inside.
Title: Re: SSTO Thread
Post by: MKremer on 09/18/2007 08:34 pm
Quote
tnphysics - 18/9/2007  3:10 PM

A plug nozzle is not the same as an aerospike nozzle.

A plug nozzle can be an ordinary de Lavel nozzle with a plug inside.

Guess what? As far as R&D and testing, followed by necessary additional R&D, plus all the money required to fund all of that... it doesn't make that much difference - it's still developing and thoroughly testing a new engine, regardless of how much hardware carries over (shades of the new J-2X based on old J-2 hardware).
Title: Re: SSTO Thread
Post by: tnphysics on 09/18/2007 08:38 pm
What if, to the turbopumps , the old nozzle behaves like the new nozzle?

As long as the turbopumps are unchanged, any other modifications are rather simple. (Unlike the F-1 which had serious combustion instability problems)
Title: Re: SSTO Thread
Post by: TyMoore on 09/18/2007 11:56 pm
Quote
tnphysics - 18/9/2007  1:10 PM

A plug nozzle is not the same as an aerospike nozzle.

A plug nozzle can be an ordinary de Lavel nozzle with a plug inside.

Actually they are pretty close relatives. An aerospike starts off as a plug nozzle which terminates prematurely. A gasseous plume in the center takes over the function of the 'spike': this is why it is called an aerospike engine...

And that is why aerospike engines have intrinsic altitude compensation: the pressure contours of the 'aerspike' continuously adjust to the plume pressure with which it is in approximate equilibrium...

Title: Re: SSTO Thread
Post by: tnphysics on 09/19/2007 12:14 am
Quote
TyMoore - 18/9/2007  7:56 PM

Quote
tnphysics - 18/9/2007  1:10 PM

A plug nozzle is not the same as an aerospike nozzle.

A plug nozzle can be an ordinary de Lavel nozzle with a plug inside.

Actually they are pretty close relatives. An aerospike starts off as a plug nozzle which terminates prematurely. A gasseous plume in the center takes over the function of the 'spike': this is why it is called an aerospike engine...

And that is why aerospike engines have intrinsic altitude compensation: the pressure contours of the 'aerspike' continuously adjust to the plume pressure with which it is in approximate equilibrium...


A plug nozzle looks, from the outside, just like a bell nozzle.

At least that is how the kind of nozzle I am refering to looks.
Title: Re: SSTO Thread
Post by: kraisee on 09/19/2007 02:22 am
Douglas engineer Phil Bono had an interesting idea for recovering large stages with engines - he proposed to deploy a large hydrogen-filled balloon to make the entire stage bouyant at a given altitude.   Using the heat of re-entry to boil some residual LH2 would be the obvious way to get your gas of course.

Assuming you can fast inflate a suitably large balloon, the only remaining trick would be the logistics of recovery and control of something that size and mass just "floating" in the air.   Getting it safely back on the ground would be a PITA.

Ross.
Title: Re: SSTO Thread
Post by: MrTim on 09/25/2007 07:09 am
Quote
kraisee - 18/9/2007  7:22 PM
Douglas engineer Phil Bono had an interesting idea for recovering large stages with engines - he proposed to deploy a large hydrogen-filled balloon to make the entire stage bouyant at a given altitude. Using the heat of re-entry to boil some residual LH2 would be the obvious way to get your gas of course.
It's a goofball idea that I have also proposed should be considered. It MIGHT be totally unworkable but could be worth some study. I do not however think one should aim for buoyancy at some altitude. You do not want to fly the thing. Just enough reduction in weight of the system would provide a soft-enough splashdown for re-use. Question is whether the additional weight of substituting a balloon of less gas permeable material, extra hydrogen, and extra hardware for inflation (all in place of simple chutes) is worth it.

Quote
kraisee - 18/9/2007  7:22 PM
Assuming you can fast inflate a suitably large balloon, the only remaining trick would be the logistics of recovery and control of something that size and mass just "floating" in the air.   Getting it safely back on the ground would be a PITA.
Ross.
I suspect the balloon would be shredded by the required rapid inflation if in atmosphere thick enough for much drag. The volume required for sufficent lift would be immense and the stage would be ballistic so inflation would need to be extremely rapid. If inflated high enough, then who knows? It might work. IF you made a big enough balloon and inflated it enough for actual buoyancy then it would probably be interceptable and towable by a large helicopter, with the balloon gently deflated by remote control after being towed to a landing spot.
Title: Re: SSTO Thread
Post by: tnphysics on 10/18/2007 12:08 am
The early Atlas rockets, which were stage-and-a-half, would be SSTO if the MA-2/5 engines were replaced with NK-33 engines. One for the Atlas D, two for the Atlas H. This would reduce payload, but the payload could be regained if one of the engines was redesigned to have two thust chambers (but with an unmodified turbopump) and jettisoned. One of two unmodified engines could be jettisoned if the other engine was sufficiantly gimbled or if a truss displaiced the engines from the vehicle CG, although it would no longer be SSTO.

A WBC would be SSTO if it was dropped from an airplane. This is only needed to reduce the atomspheric pressure surrounding the engines at ignition. It is not needed to provide energy to the vehicle.
Title: Re: SSTO Thread
Post by: meiza on 10/18/2007 12:12 am
The current Atlas isn't, even with the more advanced than NK-33 RD-180, I did some back of the envelope calculations in some other thread...
Title: Re: SSTO Thread
Post by: tnphysics on 10/18/2007 12:37 am
The early Atlas had lighter tanks.

Also the NK-33 has a higher thrust-to-weight ratio.
Title: Re: SSTO Thread
Post by: meiza on 10/18/2007 02:13 pm
True, I believe the NK-33 has the highest T/W of any engine ever.
Title: Re: SSTO Thread
Post by: BarryKirk on 10/18/2007 03:33 pm
Highest T/W ratio of any liquid rocket engine ever.

Looked it up

NK 33  T/W ratio of 136 and vac ISP of 331 seconds compared to
Merlin  T/W ratio of 96 and vac ISP of 304 seconds
RS-68 T/W ratio of 51.2 and vac ISP of 410 seconds

That NK 33 has some really impressive specs there!

Thanks for pointing that engine out to me.  I was unaware of it.


Title: Re: SSTO Thread
Post by: clongton on 10/18/2007 04:10 pm
Quote
MrTim - 25/9/2007  3:09 AM

Quote
kraisee - 18/9/2007  7:22 PM
Douglas engineer Phil Bono had an interesting idea for recovering large stages with engines - he proposed to deploy a large hydrogen-filled balloon to make the entire stage buoyant at a given altitude. Using the heat of re-entry to boil some residual LH2 would be the obvious way to get your gas of course.
It's a goofball idea that I have also proposed should be considered. It MIGHT be totally unworkable but could be worth some study. I do not however think one should aim for buoyancy at some altitude. You do not want to fly the thing. Just enough reduction in weight of the system would provide a soft-enough splashdown for re-use. Question is whether the additional weight of substituting a balloon of less gas permeable material, extra hydrogen, and extra hardware for inflation (all in place of simple chutes) is worth it.

Quote
kraisee - 18/9/2007  7:22 PM
Assuming you can fast inflate a suitably large balloon, the only remaining trick would be the logistics of recovery and control of something that size and mass just "floating" in the air.   Getting it safely back on the ground would be a PITA.
Ross.
I suspect the balloon would be shredded by the required rapid inflation if in atmosphere thick enough for much drag. The volume required for sufficient lift would be immense and the stage would be ballistic so inflation would need to be extremely rapid. If inflated high enough, then who knows? It might work. IF you made a big enough balloon and inflated it enough for actual buoyancy then it would probably be interceptable and towable by a large helicopter, with the balloon gently deflated by remote control after being towed to a landing spot.
What about deploying a balute rather than a balloon? It could be deployed at extreme altitude and would actually serve to decrease the re-entry speed, lowering the stress on any subsequently deployed recovery system. Once in the atmosphere, it would still do the functions that a balloon does. You could even deploy an actual balloon at lower altitude up thru the ring to provide better buoyancy. Or a parachute for either ground or mid-air recovery.

If we're willing to at least consider "goofball" ideas that might actually work, I think this qualifies as a possibility.
Title: Re: SSTO Thread
Post by: meiza on 10/18/2007 07:56 pm
Also, since any liquid first stage is light empty, much lighter than a SRB, a reasonable size ballute might be enough to slow the descent to the sea to some manageable speed, say, 20 m/s.

http://www.andrews-space.com/content-main.php?subsection=MjA4
Title: Re: SSTO Thread
Post by: MrTim on 10/19/2007 03:31 pm
Quote
clongton - 18/10/2007  9:10 AM
Quote
MrTim - 25/9/2007  3:09 AM
(the)Question is whether the additional weight of substituting a balloon of less gas permeable material, extra hydrogen, and extra hardware for inflation (all in place of simple chutes) is worth it.
I suspect the balloon would be shredded by the required rapid inflation if in atmosphere thick enough for much drag. The volume required for sufficient lift would be immense and the stage would be ballistic so inflation would need to be extremely rapid. If inflated high enough, then who knows? It might work.
What about deploying a balute rather than a balloon? It could be deployed at extreme altitude and would actually serve to decrease the re-entry speed, lowering the stress on any subsequently deployed recovery system. Once in the atmosphere, it would still do the functions that a balloon does. You could even deploy an actual balloon at lower altitude up thru the ring to provide better buoyancy. Or a parachute for either ground or mid-air recovery.
If we're willing to at least consider "goofball" ideas that might actually work, I think this qualifies as a possibility.
Did not have the time to fully expand on the theme when posted, else I would have thought to mention a ballute. (note: I encountered balutes (one "L") in the Philippines and I don't think that's what you meant  :laugh:  ) The balloon comment was really just a generic notion of a gas bag for bouyancy and you're right... it could be done as a ballute. The balloon would need to be huge to be useful and that means a LOT of LH to boil-off into it in a short time early in the ballistic arc (this is where the ballute comes-in, the thing could start as a ballute and continue inflating on the way down to become a balloon. Deploying the thing is another problem; needs to deploy AND inflate quickly and without tearing or you lose everything. There is one final complication: The only lift gas that makes sense is Hydrogen (best lift gas, and you have a booster full of it in dense liquid form) but the U.S. has never trusted hydrogen (see the U.S. Army airship Roma) and I *think* there is a ban on it post-Hindenburg. Silly really, given the hundreds of airships full of it that the Germans flew around the world in war and in peace before technology permitted the airplane to cross an ocean. As with all predictable but dangerous things, you simply need to pay the appropriate attention.  :cool:

There's a bundle of math to be done here if somebody cares to do it; I generally prefer to spend my spare time doing things I do NOT do for a living  ;)  Ultimately, as with most engineering, the simplest solution is best. I suspect that the plain-old parachute will win-out unless this scheme lets you save and re-use some VERY expensive engines etc. If you want to save stuff that is THAT worth saving, then I suspect wings or a lifting body will win-out as the way to do it. The other scheme that might make more sense is rotors. The rotary rocket guys may have just missed the mark by trying to use rotors on the spacecraft...the best use might have been on a re-usable 1st stage booster which has no re-entry issues. Proving any of this one way or the other would be a good exercise for a student...
Title: Re: SSTO Thread
Post by: chazmataz on 10/22/2007 09:11 am
Quote
BarryKirk - 18/10/2007  4:33 PM

Highest T/W ratio of any liquid rocket engine ever.

Looked it up

NK 33  T/W ratio of 136 and vac ISP of 331 seconds compared to
...


Actually, only the highest T/W of any cryogenic rocket engine.

check out the RD-261 from aeronautix.com - over 175:1 T/W, used on the Tsyklon 3.
It only has a 301 vac. ISP, but that is compensated by the smaller, lighter non-insulated tanks.

Dense liquid propellants make for higher T/W.  It is probably possible to build a hypergolic engine that exceeds 200:1 T/W.

If I were designing a SSTO, I would use a NK-33 for the main engine, a RL-10A-4 for the vacuum operations, and an  RL-10A-5 modified to use methane instead of LH2 as a landing motor, combined with a bolt-on ablative phenolic heat shield in the nose.  The vehicle would be designed to move the engines around during gliding flight and re-entry to properly align center-of-gravity and thrust.
Title: Re: SSTO Thread
Post by: tnphysics on 10/22/2007 12:06 pm
Why not an RL-10-B-2?

I assume that the NK-33 would be used primarily for lift-off, and the (probably multiple) RL-10s would provide most of the delta-V.
Title: Re: SSTO Thread
Post by: tnphysics on 10/22/2007 12:07 pm
Quote
tnphysics - 18/9/2007  8:14 PM

Quote
TyMoore - 18/9/2007  7:56 PM

Quote
tnphysics - 18/9/2007  1:10 PM

A plug nozzle is not the same as an aerospike nozzle.

A plug nozzle can be an ordinary de Lavel nozzle with a plug inside.

Actually they are pretty close relatives. An aerospike starts off as a plug nozzle which terminates prematurely. A gasseous plume in the center takes over the function of the 'spike': this is why it is called an aerospike engine...

And that is why aerospike engines have intrinsic altitude compensation: the pressure contours of the 'aerspike' continuously adjust to the plume pressure with which it is in approximate equilibrium...


A plug nozzle looks, from the outside, just like a bell nozzle.

At least that is how the kind of nozzle I am refering to looks.

I was referring to an expansion-deflection nozzle.
Title: Re: SSTO Thread
Post by: chazmataz on 10/22/2007 01:35 pm
Quote
tnphysics - 22/10/2007  1:06 PM

Why not an RL-10-B-2?

I assume that the NK-33 would be used primarily for lift-off, and the (probably multiple) RL-10s would provide most of the delta-V.

The RL-10-B2 gives you a bit more thrust and 11 seconds of ISP.  The downside is that it is substantially heavier, with a lower T/W, and larger - note that the RL-10A4 and the NK-33 are both about 150 cm. in diameter, while the B2 is a meter larger.  A larger engine would mean more complications during landing.

The idea would be to burn only the NK-33 until the g-loads get too high, then to shut it off, move the RL-104A into place, and fire it.  At that point, the overall T/W of the entire rocket would be just under 1:1, and you would start to lose vertical velocity while accelerating horizontally.  Using two or three RL-10's would get the T/W over 1:1 and improve the payload ratio, but would hurt the objective of reducing the empty weight of the SSTO for simplifying re-entry and landing.  The bigger advantage of using a pair of RL-10's during orbital injection is geometry - it would be simple to put the three engines in a straight line with the heavy NK-33 in the middle, and fire them without moving your engines around or gimballing.

By limiting the landing motor to a single modified RL-10-5, I am basically setting a hard limit on the landing weight to about 5 metric tons.  It helps to avoid creeping featuritis.
Title: Re: SSTO Thread
Post by: chazmataz on 10/22/2007 01:52 pm
Quote
tnphysics - 22/10/2007  1:06 PM

Why not an RL-10-B-2?

I assume that the NK-33 would be used primarily for lift-off, and the (probably multiple) RL-10s would provide most of the delta-V.

I noticed something while crunching the numbers.

A single NK-33 carrying two "dead weight" RL-10-4A motors still has an overall T/W of over 107:1, over 36% better than a plain RD-180.

A slight refinement of this design would use a 50/50 sub-cooled mixture of propane and propylene instead of kerosene as the fuel for the NK-33.  This would be expected to boost both the ISP and the T/W by about 2%
Title: Re: SSTO Thread
Post by: tnphysics on 10/22/2007 08:45 pm
An SSTO RLV (or any vehicle/spacecraft that needed a heat shield) could use a RCC heat shield material for both thermal protection and structure, if the skin of the vehicle was a load-bearing component, such as a tank wall.

This would actually lighten the tank.

Most other heat shield materials have much less strength AFAIK.
Title: Re: SSTO Thread
Post by: publiusr on 10/26/2007 03:08 pm
Would a submerged magrail/maglaunch system work?

I was looking over at Mark Wade's astronautix site and was interested in the large disk shaped ROOST HLLV-saucer.

We are familiar with hydrofoils and wing in ground effect--but would a magrail beneath the surface of the water be helpful as well. It would seem to eliminate complex landing gear (except for hydrofoils perhaps--and they might detach).

Such a disk shaped object filled with cryogenics might be the opposite of what we've seen with the small 'pill' of superconducting material. A few coil/slosh baffles (and a lot of insulation) might be enough to keep the disk elevated, and the water would serve as a cushion...

http://www.astronautix.com/craft/bonaucer.htm

Such a craft would be great at launching large, flat payloads that would further unfold to great surface area--making this concept superior to Sea Dragon with respect to SPSS deployment.

Saucers have drawbacks--but have advantages as well.
Title: Re: SSTO Thread
Post by: tnphysics on 10/27/2007 07:05 pm
Quote
chazmataz - 22/10/2007  9:35 AM

Quote
tnphysics - 22/10/2007  1:06 PM

Why not an RL-10-B-2?

I assume that the NK-33 would be used primarily for lift-off, and the (probably multiple) RL-10s would provide most of the delta-V.

The RL-10-B2 gives you a bit more thrust and 11 seconds of ISP.  The downside is that it is substantially heavier, with a lower T/W, and larger - note that the RL-10A4 and the NK-33 are both about 150 cm. in diameter, while the B2 is a meter larger.  A larger engine would mean more complications during landing.

The idea would be to burn only the NK-33 until the g-loads get too high, then to shut it off, move the RL-104A into place, and fire it.  At that point, the overall T/W of the entire rocket would be just under 1:1, and you would start to lose vertical velocity while accelerating horizontally.  Using two or three RL-10's would get the T/W over 1:1 and improve the payload ratio, but would hurt the objective of reducing the empty weight of the SSTO for simplifying re-entry and landing.  The bigger advantage of using a pair of RL-10's during orbital injection is geometry - it would be simple to put the three engines in a straight line with the heavy NK-33 in the middle, and fire them without moving your engines around or gimballing.

By limiting the landing motor to a single modified RL-10-5, I am basically setting a hard limit on the landing weight to about 5 metric tons.  It helps to avoid creeping featuritis.

You would be better off using the RL-10-A-4 engines to provide most of the delta-V, owing to its higher Isp.

This would increase the payload substantially.
Title: Re: SSTO Thread
Post by: chazmataz on 10/28/2007 08:07 am
Quote
tnphysics - 27/10/2007  8:05 PM

Quote
chazmataz - 22/10/2007  9:35 AM

The idea would be to burn only the NK-33 until the g-loads get too high, then to shut it off, move the RL-104A into place, and fire it.  At that point, the overall T/W of the entire rocket would be just under 1:1, and you would start to lose vertical velocity while accelerating horizontally.  Using two or three RL-10's would get the T/W over 1:1 and improve the payload ratio, but would hurt the objective of reducing the empty weight of the SSTO for simplifying re-entry and landing.  The bigger advantage of using a pair of RL-10's during orbital injection is geometry - it would be simple to put the three engines in a straight line with the heavy NK-33 in the middle, and fire them without moving your engines around or gimballing.
...

You would be better off using the RL-10-A-4 engines to provide most of the delta-V, owing to its higher Isp.

This would increase the payload substantially.

I think you are falling in to the same mental traps and misconceptions which have made NASA's recent designs so impractical and failure prone (i.e. the X-33).  You are optimizing for the wrong parameters in your rocket design.  Try to learn the lesson of the X-33, and don't make the same mistakes in your own concepts.

1) Use off the shelf components everywhere you can.  If you can use common hardware that you can just place an order and buy, then you don't have to spend three years and a couple of billion $ trying to develop a new engine with 5% better T/W , 3% better ISP, and twice the thrust.

2) Don't try to combine too many features of your rockent into one component in a way that has never been done successfully before in a effort to save weight.  The composite funny-shaped fuel tanks of the X-33 are a perfect example of what NOT to do.

3) Don't use toxic hypergolic fuels - the handling problems make it just too much hassle.

4) Don't build v1.0 of the rocket any bigger then you have to.  Very large rockets require more complicated and specialized launch facilities.  An ideal SSTO should be able to take off from almost anywhere.

5) Liquid hydrogen is extremely bulky, it can cause metals to become brittle over time, and it requires large, heavy, highly insulated tanks.  Try to avoid designing your rocket so that it uses too much of it.

6) Don't worry too much if v1.0 of your rocket has a tiny payload.  The object of a first generation SSTO is to prove the concept of a high flight-rate, highly re-usable, reliable rocket.  Remember that future refinements can boost the payload ratio significantly.

---

When I pointed out earlier that using sub-cooled propane/propylene mix as the fuel for the NK-33 engine would improve performance, I forgot to mention a possibly more significant reason for using it in a re-usable rocket.  There is a distinct advantage to using a fuel that always evaporates completely rather than one which leaves a greasy residue when you are planning on re-using your rocket engine.
Title: Re: SSTO Thread
Post by: gin455res on 10/28/2007 06:02 pm
Quote
tnphysics - 22/10/2007  7:07 AM

Quote
tnphysics - 18/9/2007  8:14 PM

Quote
TyMoore - 18/9/2007  7:56 PM

Quote
tnphysics - 18/9/2007  1:10 PM

A plug nozzle is not the same as an aerospike nozzle.

A plug nozzle can be an ordinary de Lavel nozzle with a plug inside.

Actually they are pretty close relatives. An aerospike starts off as a plug nozzle which terminates prematurely. A gasseous plume in the center takes over the function of the 'spike': this is why it is called an aerospike engine...

And that is why aerospike engines have intrinsic altitude compensation: the pressure contours of the 'aerspike' continuously adjust to the plume pressure with which it is in approximate equilibrium...


A plug nozzle looks, from the outside, just like a bell nozzle.

At least that is how the kind of nozzle I am refering to looks.

I was referring to an expansion-deflection nozzle.

I had an idea for a type of nozzle a week ago that I've never seen described. It looks like a bell nozzle, but has an add on that reduces the exit area. Imagine sticking another nozzle upside down on the bottom of the first, but with a very large throat. (looking like  a section of the neck of a cartoon character that has swallowed a bowling ball)

Once the rocket is out of the denser section of the atmosphere, the add on is jettisoned to leave a highly expanded nozzle.

Would this work and if so has it already got a name?
Title: Re: SSTO Thread
Post by: kkattula2 on 10/29/2007 02:01 am
Haven't heard of that one, but I have read of nozzles with one or more inserts that are ejected, or burnt off. Incrementally increasing the expansion ratio as the rocket ascends.

Though I imagine it would be hard to eject an insert if the motor thrust is pushing it back into the outer nozzle. Probably some form of  ablative inner nozzle would be easiest.
Title: Re: SSTO Thread
Post by: veedriver22 on 10/29/2007 02:03 am
The airline industry is economical because their engines can be run thousands of hours between engine rebuilds.  The shuttle engines have to be completely torn down between flights and cost more to rebuild than it costs to buy single use engines.   It seems to me that two things need to happen before SSTO will be practical.   Engines that can fly multiple missions between rebuilds,  and lighter weight materials to build the airframe and tanks out of.   Then the cost per flight will come way down.   I keep hearing that SSTO and reusable hardware are not ecomical because of low flight rates.  It seems to me that it is the other way around.   You have low flight rates because its so freakin expensive to launch.
Title: Re: SSTO Thread
Post by: chazmataz on 10/31/2007 08:25 am
Quote
veedriver22 - 29/10/2007  4:03 AM

The airline industry is economical because their engines can be run thousands of hours between engine rebuilds.  The shuttle engines have to be completely torn down between flights and cost more to rebuild than it costs to buy single use engines.   It seems to me that two things need to happen before SSTO will be practical.   Engines that can fly multiple missions between rebuilds,  and lighter weight materials to build the airframe and tanks out of.   Then the cost per flight will come way down.   I keep hearing that SSTO and reusable hardware are not ecomical because of low flight rates.  It seems to me that it is the other way around.   You have low flight rates because its so freakin expensive to launch.

The Shuttle was originally pitched to Congress as costing about $20 million per launch, at a flight rate of about 100 flights per year - which was extremely unrealisitic.  At its peak, the shuttle program was able to launch nine times in a year, with a fleet of four Orbiters.

The SSME was overambitious.  The high chamber pressure and the excessively powerful hydrogen turbopump resulted in an engine which requires a great deal of inspection after each use to detect and repair the cracks and leaks which frequently arise.  The RL-10 engine, on the other hand, can produce nearly the same ISP and T/W, without wearing out or excessive maintenance through hundreds of uses.

The TPS tiles are also a practical flop.  They are very easily damaged, and they require a very labor-intensive inspection/replacement after each flight.  The wings of the Orbiter are also a design liability.  Although they give the Orbiter a large useful cross-range on re-entry, they are heavy, and the sharp leading edges make the thermal problem of re-entry much worse than it should be.

The external tank was originally intended to function as a simple aluminum drop tank.  Currently there are two issues with the external tank - cost and foam shedding.  Because of weight growth, the tank was redesigned to use a lighter, but much more expensive alloy, which drove up the cost to over $60M.  The issue of foam shedding from the tank during ascent is only a safety issue because the Orbiter rides parallel to the tank instead of in front of it, exposing the delicate TPS to the debris.
Title: Re: SSTO Thread
Post by: meiza on 10/31/2007 07:14 pm
The toilet paper industry is successful and economical because every product is used only once. :)
Title: Re: SSTO Thread
Post by: tnphysics on 10/31/2007 10:38 pm
Quote
gin455res - 28/10/2007  3:02 PM

Quote
tnphysics - 22/10/2007  7:07 AM

Quote
tnphysics - 18/9/2007  8:14 PM

Quote
TyMoore - 18/9/2007  7:56 PM

Quote
tnphysics - 18/9/2007  1:10 PM

A plug nozzle is not the same as an aerospike nozzle.

A plug nozzle can be an ordinary de Lavel nozzle with a plug inside.

Actually they are pretty close relatives. An aerospike starts off as a plug nozzle which terminates prematurely. A gasseous plume in the center takes over the function of the 'spike': this is why it is called an aerospike engine...

And that is why aerospike engines have intrinsic altitude compensation: the pressure contours of the 'aerspike' continuously adjust to the plume pressure with which it is in approximate equilibrium...


A plug nozzle looks, from the outside, just like a bell nozzle.

At least that is how the kind of nozzle I am refering to looks.

I was referring to an expansion-deflection nozzle.

I had an idea for a type of nozzle a week ago that I've never seen described. It looks like a bell nozzle, but has an add on that reduces the exit area. Imagine sticking another nozzle upside down on the bottom of the first, but with a very large throat. (looking like  a section of the neck of a cartoon character that has swallowed a bowling ball)

Once the rocket is out of the denser section of the atmosphere, the add on is jettisoned to leave a highly expanded nozzle.

Would this work and if so has it already got a name?

Great idea! The only problem might be shock wave losses in in the aft convergient section.
Title: Re: SSTO Thread
Post by: MKremer on 11/01/2007 03:51 am
Quote
tnphysics - 31/10/2007  6:38 PM

Quote
gin455res - 28/10/2007  3:02 PM

I had an idea for a type of nozzle a week ago that I've never seen described. It looks like a bell nozzle, but has an add on that reduces the exit area. Imagine sticking another nozzle upside down on the bottom of the first, but with a very large throat. (looking like  a section of the neck of a cartoon character that has swallowed a bowling ball)

Once the rocket is out of the denser section of the atmosphere, the add on is jettisoned to leave a highly expanded nozzle.

Would this work and if so has it already got a name?

Great idea! The only problem might be shock wave losses in in the aft convergient section.

One of the main problems might be being able to handle the shock and extra heating by suddenly disrupting the existing, designed boundry layer between the regular expansion nozzle and hot combustion chamber gasses... IOW, disrupting the exhaust flow thru the regular nozzle - which is already designed for both maximum efficiency and minimum surface heating - by changing its exit parameters and drastically increasing the heating on whatever is a sudden obstruction.

A more efficient concept might be to use a drop-down nozzle extension (something like what the D-IV 2nd stage engine uses), but delayed until it can be of the most use for boost-phase ISP increases later on at the appropriate time.
Title: Re: SSTO Thread
Post by: gin455res on 11/01/2007 07:36 am
Quote
tnphysics - 31/10/2007  6:38 PM

Quote
gin455res - 28/10/2007  3:02 PM

Quote
tnphysics - 22/10/2007  7:07 AM

Quote
tnphysics - 18/9/2007  8:14 PM

Quote
TyMoore - 18/9/2007  7:56 PM

Quote
tnphysics - 18/9/2007  1:10 PM

A plug nozzle is not the same as an aerospike nozzle.

A plug nozzle can be an ordinary de Lavel nozzle with a plug inside.

Actually they are pretty close relatives. An aerospike starts off as a plug nozzle which terminates prematurely. A gasseous plume in the center takes over the function of the 'spike': this is why it is called an aerospike engine...

And that is why aerospike engines have intrinsic altitude compensation: the pressure contours of the 'aerspike' continuously adjust to the plume pressure with which it is in approximate equilibrium...


A plug nozzle looks, from the outside, just like a bell nozzle.

At least that is how the kind of nozzle I am refering to looks.

I was referring to an expansion-deflection nozzle.

I had an idea for a type of nozzle a week ago that I've never seen described. It looks like a bell nozzle, but has an add on that reduces the exit area. Imagine sticking another nozzle upside down on the bottom of the first, but with a very large throat. (looking like  a section of the neck of a cartoon character that has swallowed a bowling ball)

Once the rocket is out of the denser section of the atmosphere, the add on is jettisoned to leave a highly expanded nozzle.

Would this work and if so has it already got a name?

Great idea! The only problem might be shock wave losses in in the aft convergient section.

Wouldn't  these shock losses be the mechanism that induces the pressure increase needed to optimize low altitude operation. It's a question of whether these losses are significantly greater than the loss due to the decrease in area ratio alone.  

There wouldn't be a physical obstruction as the whole volume would be smoothly curving the whole way along. So I imagine any sudden obstruction would be the shock-wave?
Title: Re: SSTO Thread
Post by: ANTIcarrot on 11/08/2007 10:59 pm
Quote
chazmataz - 31/10/2007  10:25 AM
The Shuttle was originally pitched to Congress as costing about $20 million per launch, at a flight rate of about 100 flights per year - which was extremely unrealisitic.  At its peak, the shuttle program was able to launch nine times in a year, with a fleet of four Orbiters.

In all fairness, the high flight rate was based on a R&D budget of ten to fifteen billion dollars, and the (not entirely unreasonable) assumption that congress would be willing to spend money now to save it later. Then along came Mr Nixon, who decided that NASA should build a shuttle that would be cheap to develop and expensive to run; rather than the other way round. NASA then went to the USAF, who agreed to part fund the shuttle - if NASA would design it to carry 30 tons to orbit, and fly sideways 1500 miles during reentry.

I think these superfluous requirements were as responsible (if not more so) for the Phase C shuttle's under-performance than any amount of NASA over-optimism.

Though I agree the RL10 is a truly lovely engine. As is it's big brother, the RL60.
Title: Re: SSTO Thread
Post by: meiza on 11/09/2007 12:11 am
If you truncate a spike nozzle, uou have a low pressure area at the base that pulls the vehicle down, and of course the flows coming from the side tend to collide too since the wall is not there to keep them turning. So you introduce the turbopump exhaust to this low pressure area, and then you have a spike made of air - an aerospike! That's the idea. What's nice with that too is that the flow geometry varies with outside pressure: narrower with greater external pressure and wider with lower external pressure. How nice.
Title: Re: SSTO Thread
Post by: tnphysics on 11/13/2007 09:59 pm
What about using a thrust agmented nozzle?
Title: RE: SSTO Thread
Post by: alexterrell on 03/12/2008 10:11 pm
I've lost arguments before on SCRAMJets as a way to space. It seems its just not worth it. However, there may be a way to use scramjets.

There's been some development of missile based scramjets, for example the X51:
http://www.popularmechanics.com/technology/military_law/4203874.html

These appear capable of Mach 6 / Mach 7 or so.

There are a number of air launched SSTO proposals. Many are technically feasible, though apparantly not economically feasible.

Would it be possible to use two X51 missiles to accelerate an air launched space plane from Mach 0.7 to Mach 6? At this point the SCRAMJets would be jetisoned and the rockets take over.

The Scramjet missiles could be expendable or recovered, depending on economics.
Title: Re: SSTO Thread
Post by: Lampyridae on 03/12/2008 10:48 pm
Woooo, scramjets. It seems everybody thinks plain old ramjets are old hat and too useless for the modern era. Perhaps because they're nothing more than... well a pipe with a fuel injector and a cone in front if they're supersonic. No, the defence contractors can't field contracts for those, they're too cheap. Let's use scramjets instead and get government to pump in billions for research! At least with scramjets we can justify using hafnium diboride, complex fly-by-wire flight controls and algorithms, endless CFD and wind tunnel simulations and then fail to deliver a product at the end of the day!

Never mind that a plain old ramjet missile got out of control and flew past Mach 5 and was still accelerating when it ran out of fuel...
Title: RE: SSTO Thread
Post by: meiza on 03/13/2008 10:21 am
Quote
alexterrell - 12/3/2008  12:11 AM

I've lost arguments before on SCRAMJets as a way to space. It seems its just not worth it. However, there may be a way to use scramjets.

There's been some development of missile based scramjets, for example the X51:
http://www.popularmechanics.com/technology/military_law/4203874.html

These appear capable of Mach 6 / Mach 7 or so.

There are a number of air launched SSTO proposals. Many are technically feasible, though apparantly not economically feasible.

Would it be possible to use two X51 missiles to accelerate an air launched space plane from Mach 0.7 to Mach 6? At this point the SCRAMJets would be jetisoned and the rockets take over.

The Scramjet missiles could be expendable or recovered, depending on economics.

I don't think those scramjets can be started at Mach 0.7, nor produce much thrust all the way to Mach 6. The X-51 is boosted by a rocket you see:
"A rear-mounted Army Tactical Missile Systems rocket kicks in to propel the 1600-pound missile to Mach 4.5 and 100,000 ft. The rocket then drops away and the X-51's engine takes over."
So what does the scramjet do? Accelerate the thing from Mach 4.5 to Mach 5. And perhaps cruise at that speed for some time.

Scramjets and ramjets usually optimize for a narrow speed range for cruise. Space launch is the opposite of that, it's an acceleration mission and wants to get out of the atmosphere as fast as soon as possible. Hence scram- and ramjets aren't usually very useful for that.

Mach 4.3 was achieved with a *ramjet* already in 1960. Hydrocarbon fuel too. Lockheed X-7 with a Marquardt engine. It was another rocket-boosted air-launched test bed.
Title: Re: SSTO Thread
Post by: tnphysics on 03/13/2008 11:53 pm
There exist constant dynamic pressure paths, for which the scramjet is well suited.
Title: RE: SSTO Thread
Post by: alexterrell on 03/14/2008 07:08 pm
Quote
meiza - 13/3/2008  6:21 AM

I don't think those scramjets can be started at Mach 0.7, nor produce much thrust all the way to Mach 6. The X-51 is boosted by a rocket you see:
"A rear-mounted Army Tactical Missile Systems rocket kicks in to propel the 1600-pound missile to Mach 4.5 and 100,000 ft. The rocket then drops away and the X-51's engine takes over."
So what does the scramjet do? Accelerate the thing from Mach 4.5 to Mach 5. And perhaps cruise at that speed for some time.

Scramjets and ramjets usually optimize for a narrow speed range for cruise. Space launch is the opposite of that, it's an acceleration mission and wants to get out of the atmosphere as fast as soon as possible. Hence scram- and ramjets aren't usually very useful for that.

Mach 4.3 was achieved with a *ramjet* already in 1960. Hydrocarbon fuel too. Lockheed X-7 with a Marquardt engine. It was another rocket-boosted air-launched test bed.

I think your right. What I'm looking for is a "One and two quarter stages" to orbit.

- Air launch at Mach 0.7 at 50,000 ft.
- Wing mounted jets to go to Mach ? which then drop off. Probably ram jets, rather than SCRAMJets.

and the wing mounted jets borrowed from the military so we don't need to spend $1 billion developing them.

Trouble is, every time the analysis is done it seems drop off rockets work better.


Title: Re: SSTO Thread
Post by: hop on 03/14/2008 07:54 pm
This might be instructive: http://www.islandone.org/Propulsion/SCRAM-Spencer1.html
Title: RE: SSTO Thread
Post by: RanulfC on 03/16/2008 01:57 am
alexterrell, etc and all;

I'd thought I'd posted some or all of this under the V-Prize thread but I can't find it. (I might have made it under the Air-Launched SSTO thread but oh well :o)

"Scramjet" engines by definition must have supersonic flow through the entire jet engine and it is difficult to get that below speeds of around Mach-5 for the inlet air.
Ramjet engines can actually be started and run with thrust at any speed above zero for both the subsonic, (not designed to go past the speed of sound) and supersonic (designed to operate from subsonic speeds until a point where the internal air wants to remain supersonic) but none have been built to do so as of yet.

There are a great amount of mis-information on what ramjets can and can't do since they have pretty much always been used in specific 'niche' design modes for ceretain speeds and altitudes.

I would recommend that anyone looking into the possibilities of ramjets check out this website:
http://www.alt-accel.com/

The site owner, Mr. Glenn Olson has done a good bit of research on the promise and possibilities of ramjet propulsion. Specifically his “Ramjet Primer” (http://www.alt-accel.com/ramjet2.htm) is worth reading and his Pogo, and ARLA (Amateur Rocket Launch Assist) papers are highly recommended.

In line with the previoius posts I will note here some points that he makes;

-There is an often quoted ‘fact’ that ramjet engines can’t be started at speeds of less than Mach 1, this is incorrect as is another often quoted figure of 200mph. The actual “fact” is that ramjets cannot produce thrust at zero speed, but are capable of useful operation at any speed above zero.

- Since the majority of ramjet engines have been employed in ‘niche’ applications the majority of information is difficult to come by leading to an assumption that such applications are ‘all’ they can be used for.

- Generally Subsonic Combustion ramjets have been designed for either Subsonic or Supersonic speeds bur rarely for both applications. This has been a DESIGN limitation used for simplicity purposes to allow the use of fixed or ‘simple’ inlet design, and optimized performance at one or two, (occasionally three) “optimal” speeds. (The ASALM missile which had an optimized “fixed” inlet designed for a best-speed point of around Mach 4.5 but was accelerating beyond Mach 5.5 when its hydrocarbon (jet) fuel ran out)

- Many of the constraints on ramjet operations are design trade-offs made in attempts to constrain the ramjet to optimal speeds at specific altitudes. A properly designed subsonic ramjet engine, with some type of variable inlet system, (types would include ‘ramp’ inlets such as the F-15, or the moving spike type inlet of the SR-71) should be capable of speeds from under 200mph to at least Mach 7, if not more.
(Starts from ‘zero’ speed can be achieved through the use of ‘assists’ such as the turbojet engines on the ‘turboramjet’ SR-71 engines to injection of compressed or bleed air into a ramjet intake)

There are charts, data, and performance specifications on ramjets able to travel at Mach 6.5 enough for it to be a logical conclusion that someone has tested them at speeds at least this high. Speeds in excess of Mach 7 are only bound by the ability to continue to shock the air down below supersonic for feeding to the ramjet compressor section.
(Generally it would be easier and more efficient at Mach 7 to switch to supersonic combustion or ‘scramjet” engines

There are many more data points in the listed threads and articles but the bottom line is this:
Ramjets can be used if designed and constructed with proper design techniquies to operate from zero to speeds of around Mach-7 but it is DESIGN not inherent performance that determine ramjet performance.

Also there are a number of ways to bring ramjets “up-to-speed” as it were if you design them to operate more efficiently towards the upper Mach ranges; most of these types of engines being some type of “combined-cycle” propulsion system.

Examples would include using turbine engines to augment the ramjet for low speed operations, the turbo-ramjet J58 engines developed by Pratt-&-Whitney for propulsion on the A-12/SR-71 aircraft are a good example of this.
Below Mach-1 the turbojet operates as normal using the ramjet ducting as an afterburner but as speed increases more and more air is ‘by-passed’ past the turbojet and directly into the duct until at cruising speed over 75% of the thrust provided for the aircraft is by the ramjet ducting alone.

(Note: P-&-W has been working with NASA on a more advanced turbo-ramjet called the “Hyperburner” engine: gltrs.grc.nasa.gov/reports/2005/TM-2005-213803.pdf which is less complicated than the J58 was, and won’t require the special jet fuel blend that in the SR/A aircraft was used for everything from the engine hydraulics to lubricant before being fed into the combustion section :o)

The ‘downside’ of this type of engine is that they most often need either some sort of complicated ducting to bypass the turbojet sections during high-speed flight or some sort of active cooling of the turbojet components to survive the temperature extremes generated during high speed flight.

Another turbine based combined cycle engine uses cryogenic fuel in a similar manner to that used in the “expander” cycle rocket motor; by allowing the cryogenic fuel to warm the expanding fuel is used to turn a turbine which is connected to a compressor. The compressor operates like that in a normal jet-engine and compresses air and forces it into a combustion section though in this process that section is separate from the compressor/turbine section.

This allows the compressor/turbine to operate without being directly in the path of the air flow which at high speeds can become quite hot. Another advantage is that the cryogenic fuel can be circulated through heat exchangers in the compressor inlet to cool and densify the incoming air negating the need for added complications of active cooling within the compressor/turbine themselves and eliminates the need for ducting around the turbojet sections though you’ll still need ‘plumbing’ to get the compressed air into the combustor.

The cryogenic fuel can also be circulated around the ‘hot’ sections of the vehicle during boost/cruise and then pumped into the combustor as a gas which allows more thorough mixing and more efficient combustion.

Downsides? Well one of the most often brought up ‘faults’ is Liquid Hydrogen is bulky which increases your vehicle size, drag, etc. That of course ‘assumes’ one uses LH2 :o)
While LH2 engines have high ISP the bulk and extreme cold needed to liquefy it make it difficult to work with, cryogenic fuels such as Methane, Propane, or Ethylene are preferable.

(In my preference Ethylene or Propane are probably preferable because when cooled to LOX temperatures they are densified enough to almost match Kerosene with a much higher ISP :o)

Lastly there are the Rocket-Based Combined Cycle engines which use fuel rich rocket exhaust to ‘entrain’ air into the ramjet duct where they mix and are ignited creating thrust. Though most often based on ‘pure’ rockets using internal LOX until the ramjet engine can run on its own, research has also been done on using expander cycle compressor/turbines to inject air with the fuel in the rocket combustor which have yielded good results.
(http://caius.utias.utoronto.ca/rbcc.html)

One of the ‘neater’ things about RBCC engines is they usually require less powerful engines than a pure rocket would due to the mass of entrained air in the exhaust, so that instead of using a Merlin (for example) one could probably use a Kestrel engine run fuel rich exhausting into a ram-rocket duct to still achieve vertical take-off and acceleration to ramjet take-over speed.

I should also mention another aspect of the last engine; Liquid Air-Cycle Engines or LACE. These usually use a highly cryogenic fuel such as Liquid Methane or Liquid Hydrogen, (as opposed to the ‘softer’ cryogenic fuels such as Ethylene or Propane which only require LOX temperatures) to liquefy part of the incoming airstream burning some in the rocket combustor with fuel for thrust but also storing some as LOX for later use as a pure rocket. There have been variations suggested that use more mechanical liquefying process but the time required to ‘fill’ vehicle LOX tanks using these methods usually limit those to being used in some sort of Air-Launch scenario where the vehicle takes off with only fuel and collects its LOX while flying to the launch position or altitude.

"Lastly" of course is some type of booster arrangment which boost the ramjet vehicle up to speed and then drops away. Solids have been mentioned but there is also the possibility of using military class turbo or fan jet engines for short periods at full-military thrust with after burner in a similar method to smaller SRB type boosters. The engines can be "podded" with engines, fuel, and recovery gear all packaged in a 'strap-on' configuration that is dropped once they are no longer needed and recoverd down range.

(The original concept came from some posts by Dani Edar where F100 engines were podded to vertically launch a Delta-II class orbital booster rocket with all parts recovered and reused after each mission)

I've seen a thesis that brings up an interesting point; in most air-breathing concepts that fly to orbit the focus has been on the 'air-breathing' portion being the booster or first stage of the vehicle while the orbital element was either an expendable rocket or a reusable stage rocket that went to orbit. The thesis noted that most of your technology and most of your 'cost' actually came from the first stage air-breather and the needed performance parameteres for such a stage was only a little less than needed to make the air-breather an orbital vehicle.
It went on to postulate the reversal of the 'normal' concept in having the Air-breathing vehicle ALSO being your orbital vehicle which was 'boosted' at the begining of flight by a simple and cheap rocket booster to give it the performance margins needed for making orbit with its own air-breathing and rocket engines.

Randy

Title: Re: SSTO Thread
Post by: kttopdad on 04/30/2008 06:55 pm
Quote
mauk2 - 9/9/2006  1:41 AM

Hiya Sonic!

I feel your frustration, dude, but Scotty is steering you right.  Barring huge breakthroughs, any sort of realistic SSTO is impossible with chemical fuels.  I'm sorry, but that's just the blunt truth.  

mauk2, that was a very helpful post.  I've had a rough idea of what the mass fraction is from context, but having it all laid out like that was nice.  Thanks for the time/effort to write up that post.  
Title: Re: SSTO Thread
Post by: mlorrey on 12/13/2008 10:41 pm
Hey guys, I've been on other projects for a few years, was just checking into to see how progress is moving. Any odds on Griffin and Ares getting the boot from Obama? Chances Obama will bring back RLV concepts? Discuss....
Title: Re: SSTO Thread
Post by: khallow on 12/13/2008 10:54 pm
There's a lot of discussion elsewhere in the forums. I don't see any indication that Obama's team will consider an SSTO or even an RLV. They certainly aren't asking the right questions, if they are considering such things.
Title: Re: SSTO Thread
Post by: clongton on 12/13/2008 11:08 pm
There's a lot of discussion elsewhere in the forums. I don't see any indication that Obama's team will consider an SSTO or even an RLV. They certainly aren't asking the right questions, if they are considering such things.

They are very focused on primarily two things - space-wise:
1. reducing the gap to as close to zero as possible in order to keep people working
2. either accelerating or replacing Ares in order to do that

Both of these indicate no interest at this time in a new technology development program, such as a RLV. They are asking "what do we already have that we can use to get this done" or "what can we put together, quickly, that achieves these goals". While being time-sensitive for the immediate future they are apparently not taking their eyes off the lunar program.
Title: Re: SSTO Thread
Post by: Jim on 12/14/2008 02:01 pm
Chances Obama will bring back RLV concepts?

No, not required at this time
Title: Re: SSTO Thread
Post by: spacedem on 12/14/2008 02:32 pm
Chances Obama will bring back RLV concepts?

No, not required at this time

Jim, could you expand on that?  I'm interested in why it's not required.  Not required for what?
Title: Re: SSTO Thread
Post by: Jim on 12/14/2008 05:01 pm
Chances Obama will bring back RLV concepts?

No, not required at this time

Jim, could you expand on that?  I'm interested in why it's not required.  Not required for what?

Current flight rates don't support the use of RLV's
Title: Re: SSTO Thread
Post by: spacedem on 12/14/2008 06:31 pm
Chances Obama will bring back RLV concepts?

No, not required at this time

Jim, could you expand on that?  I'm interested in why it's not required.  Not required for what?

Current flight rates don't support the use of RLV's

Not even something like an evolved DC-XA, something with the requirements of an SSX-2, perhaps with a recoverable booster stage?

I suppose it depends on what you are trying to accomplish, but why wouldn't we want something like that?

Title: Re: SSTO Thread
Post by: Jim on 12/14/2008 06:35 pm

I suppose it depends on what you are trying to accomplish, but why wouldn't we want something like that?

Not a matter of want but what we can afford.  RLV to replace EELV's and Shuttle are out of the question
Title: Re: SSTO Thread
Post by: clongton on 12/14/2008 06:48 pm

I suppose it depends on what you are trying to accomplish, but why wouldn't we want something like that?

Not a matter of want but what we can afford.  RLV to replace EELV's and Shuttle are out of the question

RLV's are extremely expensive to maintain, especially because of the design compromises that need to be made, at this time, due to the current state of the art in the TPS. The only way to make them economical, at this time, is extremely high flight rates. All the plans for the foreseeable future do not support flight rates that will do that. In addition, switching our efforts to a RLV in lieu of expendables would only exaserbate the gap problem, making it worse than it already is. The current focus is not on advancing the state of the art, but reducing the gap.
Title: Re: SSTO Thread
Post by: spacedem on 12/14/2008 07:12 pm

I suppose it depends on what you are trying to accomplish, but why wouldn't we want something like that?

Not a matter of want but what we can afford.  RLV to replace EELV's and Shuttle are out of the question

RLV's are extremely expensive to maintain, especially because of the design compromises that need to be made, at this time, due to the current state of the art in the TPS. The only way to make them economical, at this time, is extremely high flight rates. All the plans for the foreseeable future do not support flight rates that will do that. In addition, switching our efforts to a RLV in lieu of expendables would only exaserbate the gap problem, making it worse than it already is. The current focus is not on advancing the state of the art, but reducing the gap.

I'm not trying to be pedantic here, but I thought we had only spent $100 million on DC-X, and the proposed development budget for DC-Y was around $5 Billion.  Is all of the information out there on the Delta Clipper just flat-out wrong?

Title: Re: SSTO Thread
Post by: Jorge on 12/14/2008 07:32 pm

I suppose it depends on what you are trying to accomplish, but why wouldn't we want something like that?

Not a matter of want but what we can afford.  RLV to replace EELV's and Shuttle are out of the question

RLV's are extremely expensive to maintain, especially because of the design compromises that need to be made, at this time, due to the current state of the art in the TPS. The only way to make them economical, at this time, is extremely high flight rates. All the plans for the foreseeable future do not support flight rates that will do that. In addition, switching our efforts to a RLV in lieu of expendables would only exaserbate the gap problem, making it worse than it already is. The current focus is not on advancing the state of the art, but reducing the gap.

I'm not trying to be pedantic here, but I thought we had only spent $100 million on DC-X, and the proposed development budget for DC-Y was around $5 Billion.  Is all of the information out there on the Delta Clipper just flat-out wrong?



It may not be flat-out wrong but it is highly suspect.

DC-X was cheap but did not demonstrate any of the "hard" stuff (TPS, SSTO mass fraction) that DC-Y would have needed. DC-Y could have worked, but given the way the technical challenges were "back-loaded", it's highly unlikely it would have cost only $5 billion.
Title: Re: SSTO Thread
Post by: kevin-rf on 12/14/2008 09:09 pm

It also brings up the question of an RLV for an X-Plane program or an RLV as an ELV replacement.

There is no reason to say an X-Plane RLV is not needed at this time, but an ELV replacement maybe beyond the state of the art right now.

Though SpaceX is making an attempt at an orbital RLV. Then we have all those suborbital space tourist startups...

I just think when someone does crack the nut it will look nothing like what we imagined.
Title: Re: SSTO Thread
Post by: khallow on 12/15/2008 05:03 am

I just think when someone does crack the nut it will look nothing like what we imagined.

My take is that most of the barrier is economic not technical. There's simply not enough customers to justify the exotic proposals. My feeling is that once you're reached the point where a highly reusable RLV or an SSTO is viable, then you're a short ways away from other means of getting in space than chemical power rockets (rail/space gun launch, space elevators and rotovors, beamed power, etc). But at the moment, most of the launch industry is tied up in launch vehicle development rather than space launch.

So near future vehicles will look much as we expect. It's only when the physical properties of the vehicles become the bottleneck (rather than finding enough people customers to make the vehicle viable) will we deviate strongly from traditional ideas. Well, that's my take anyway.
Title: Re: SSTO Thread
Post by: Smoothie on 12/15/2008 06:38 am

I suppose it depends on what you are trying to accomplish, but why wouldn't we want something like that?

Not a matter of want but what we can afford.  RLV to replace EELV's and Shuttle are out of the question

I agree.

Only the Commercial sector will bother with an RLV eventually once there is a need for it and high flight rates to truly bring costs down.
Title: Re: SSTO Thread
Post by: Smoothie on 12/15/2008 06:41 am

It also brings up the question of an RLV for an X-Plane program or an RLV as an ELV replacement.

There is no reason to say an X-Plane RLV is not needed at this time, but an ELV replacement maybe beyond the state of the art right now.



We already have an Orbital RLV X-Plane.  It's called the Space Shuttle!  The shuttle is far more X-Plane then Space Transportation System.
Title: Re: SSTO Thread
Post by: jongoff on 12/19/2008 02:07 am
Current flight rates don't support the use of RLV's

Well, more correctly current flight rates combined with current ways of doing things don't support the use of RLVs.  There are actually ways that you could get enough flight rate to support an RLV even with only existing demand.  But it would take some change in the way some things are done.

~Jon
Title: Re: SSTO Thread
Post by: jongoff on 12/19/2008 02:10 am
Not a matter of want but what we can afford.  RLV to replace EELV's and Shuttle are out of the question

While I agree that there isn't enough demand for a Shuttle/EELV sized RLV out there, there's nothing that says RLVs have to be Shuttle or EELV sized. 

In fact there's a lot to be said for having first generation RLVs be a lot smaller than an EELV.  At least as small as 5 tons to orbit, possibly as small as 1 ton.

But admittedly it would take some changes in how things are done in order to close the case on a small RLV like that.

~Jon
Title: Re: SSTO Thread
Post by: jongoff on 12/19/2008 02:14 am
Then we have all those suborbital space tourist startups...

Hey!  Not all of us are focused on space tourism (and most of those who are prefer to use terms like "private spaceflight participant" instead of tourist).

Quote
I just think when someone does crack the nut it will look nothing like what we imagined.

More importantly, I don't think it will be doing anything like what most people currently imagine launch vehicles do.  Just as using composites as though they were "black aluminum" wastes much of their potential, running an RLV as though it was a reusable ELV also misses a lot of the point.

~Jon
Title: Re: SSTO Thread
Post by: Jorge on 12/19/2008 02:31 am

It also brings up the question of an RLV for an X-Plane program or an RLV as an ELV replacement.

There is no reason to say an X-Plane RLV is not needed at this time, but an ELV replacement maybe beyond the state of the art right now.



We already have an Orbital RLV X-Plane.  It's called the Space Shuttle!  The shuttle is far more X-Plane then Space Transportation System.

Too bad it wasn't designed that way.

Real X-planes don't have payload bays, they have instrument bays.

Real X-planes don't have crew cabins, they have cockpits.

The X-15 was a real X-plane. The shuttle design is way too over-specified to qualify as an X-plane, and its pattern of usage is not characteristic of an X-plane either.
Title: Re: SSTO Thread
Post by: Eerie on 12/19/2008 09:25 am
Don`t X-planes suppose to be experimental?

So, if you start using an X-plane to carry cargo, it`s not really experimental anymore...
Title: Re: SSTO Thread
Post by: Analyst on 12/19/2008 09:52 am
If the experiment is how to carry cargo ...

Analyst
Title: Re: SSTO Thread
Post by: Eerie on 12/19/2008 02:42 pm
If the experiment is how to carry cargo ...

For thirty years? And an experient on how to build an international spacestation, too?

Its like this japanese whaling for "scientific" reasons. Just admit you want to eat them, goddammit.
Title: Re: SSTO Thread
Post by: Smoothie on 12/19/2008 05:00 pm
I would seem I have everyone upset.   ;D  I was being mostly sarcastic but really the shuttle has never had the reusability it was intended to have.

The X-15's flew 199 times in about 9 years.

The shuttle has only flown 124 times in 27 years. (not including Enterprise test flights)

Sure, flight rate does not mean whether it is an x-plane or not but but it is sort of sad nonetheless.  We need a real reusable vehicle.  Be it SSTO or TSTO with the first stage being a fly back booster like Shuttle was originally conceived to fly on.

But no, the shuttle is not really an X-plane even though it will have flown less the the best of the X-planes ever made.
Title: Re: SSTO Thread
Post by: mlorrey on 12/20/2008 04:44 am
I would seem I have everyone upset.   ;D  I was being mostly sarcastic but really the shuttle has never had the reusability it was intended to have.

The X-15's flew 199 times in about 9 years.

The shuttle has only flown 124 times in 27 years. (not including Enterprise test flights)

Sure, flight rate does not mean whether it is an x-plane or not but but it is sort of sad nonetheless.  We need a real reusable vehicle.  Be it SSTO or TSTO with the first stage being a fly back booster like Shuttle was originally conceived to fly on.

But no, the shuttle is not really an X-plane even though it will have flown less the the best of the X-planes ever made.

Dont feel bad, if you aren't upsetting people you are not challenging them, and thus not advancing the pursuit of knowledge. Those who feel threatened by challenges should not be involved in a space program.

The shuttle was supposed to be a lot of things, but the cost cutting of the 70's hampered that. It was originally intended to have a hot structure, which would have cost twice as much. A hot structure would have allowed it to meet its performance objectives. Instead we got an aluminum structure covered with foam and a brick chimney that doubled the maintenance man hours required to turn it around each flight. A 5,000 USD per kg payload cost was turned into 20,000 USD per kg by this fact alone. Doubling the maintenance man hours due to TPS maintenance cuts the sortie rate by half and as a result to revenue to cost models quadruple the per unit price ($/kg payload).

Thus, you can blame Walter Mondale for the failure of STS (and the loss of one if not both shuttle crews).

Other failures: the SME design was too bleeding edge for a viable 'airline' style operation. Try running a taxi service with Formula 1 engines, it doesnt work. It would have been cheaper to design the engines to be inexpensive single use items. That would cut the shuttle turnaround maintenance costs and time by another 25%.

If you redesigned and rebuilt Shuttle with a hot frame and inexpensive single use engines today, you'd have a viable system. IMHO it should have been totally redesigned and rebuilt as such after the Challenger disaster.

And yes, part of the experiment was how to deliver cargo on a regular basis, and repair satellites in orbit, and even recover them for return to earth. All that was in the spec, things we'd never done before.
Title: Re: SSTO Thread
Post by: mlorrey on 12/20/2008 05:05 am
There's a lot of discussion elsewhere in the forums. I don't see any indication that Obama's team will consider an SSTO or even an RLV. They certainly aren't asking the right questions, if they are considering such things.

They are very focused on primarily two things - space-wise:
1. reducing the gap to as close to zero as possible in order to keep people working
2. either accelerating or replacing Ares in order to do that

Both of these indicate no interest at this time in a new technology development program, such as a RLV. They are asking "what do we already have that we can use to get this done" or "what can we put together, quickly, that achieves these goals". While being time-sensitive for the immediate future they are apparently not taking their eyes off the lunar program.

Well as much of a fan of SSTO and RLV as I am, I do think that having a sustained manned presence in space and on the moon are necessary precursors to create the demand for SSTO and RLV, so IMHO they are focusing on the right and pragmatic thing for now.

Personally I am biased against continued subsidies for the ICBM-industrial complex, I think the ESAS has heavy fingerprints of ATK and by political extension, VP Cheney and western republicans (not necessarily a bad thing for me, but problematic if ESAS is to survive a democratic administration).

Another problem NASA has IMHO (not intending to offend anybody in NASA here) is the same problem that the big three automakers have wrt UAW. Space exploration should not be constrained or treated as a jobs program, IMHO, and any decisions that smack of job security is not serving the greater interest. I think there are a LOT of highly talented and skilled people at NASA, just as there are many very talented former-NASA people working now in private industry such as at SpaceX, Orbital Sciences, SpaceDev, etc. HOWEVER I think those people could be far more effective doing what they do best if they were doing so in private space companies.

My personal vision for how space exploration should be done in the US is that the government should set up contract competitions and milestone prizes (a la the X Prize) but with amounts that actually reflect a significant return on investments made in development of the technology needed to attain the goals.

For instance, Scaled and Virgin Galactic's progress has slowed dramatically in part, IMHO, because there is no X Prize for VG to acheive profitable flight operations.

The COTS contracts are a great stimulant for companies like SpaceX, et al. Set up prizes and contracts for all levels of development and exploration: private manned launchers, RLVs, orbiting facilities, orbiting fuel plants, SPSs, SSTOs, lunar bases, and NASA should use its funds to stimulate private industry to make these things happen with both prizes and contracts once one or more parties achieve the goals set. Both prizes and contract competitions stimulate private capital to invest in ventures at a much higher level than currently.

As for Obama, I do not expect his team to have this level of vision. Obama wrt the wider economy, seems more New Deal oriented, so the old NASA-as-jobs-program paradigm will IMHO be retained. However given the past experience of seeing RLV/SSTO efforts maximized during democratic administrations, I think research money for these may be revived provided we dont suffer from fiscal crises that cause liberals to put entitlements before space.
Title: Re: SSTO Thread
Post by: clongton on 12/20/2008 03:05 pm

Thus, you can blame Walter Mondale for the failure of STS (and the loss of one if not both shuttle crews).

No, you can blame a NASA management that made safety decisions (if you want to call them that) in a lackadaisical fashion, and in both cases against the advise of the sme’s on the teams. In the case of Challenger, they even disregarded an ATK Technical Bulletin that specifically told them not to fly the SRB’s below a certain temperature. They just flat ignored it, as if to say “Huh, who do they think they are? We’re NASA. They can’t tell us what to do.” NASA management quite simply *chose* to ignore the people who actually knew what they were talking about as if, because they were NASA, and for no other reason what-so-ever, they knew best. The laws of physics wouldn’t dare contradict them.  The CAIB was *very* clear in it's condemnation of NASA management in this regard.


… NASA should use its funds to stimulate private industry to make these things happen with both prizes and contracts once one or more parties achieve the goals set.

NASA cannot use its funding for anything except what the Congress specifically authorizes. It has absolutely no wiggle room in that regard.

Quote
Both prizes and contract competitions stimulate private capital to invest in ventures at a much higher level than currently.

That takes much deeper pockets than most venture capitalist have available. There are probably only a small handful of such people in the world. Even the conglomerates with much more funding available won’t do it because they have stockholders to answer to who insist on a relatively secured return on investment. Stockholders are not in the habit of authorizing the expenditure of, for example, $5,000,000 to win a $500,000 prize, with no guaranteed $10,000,000 contracts for the winner. It’s a nice idea, but it is not a money-maker. If it doesn’t make money for the investor, the investments don’t happen.

Quote
As for Obama, I do not expect his team to have this level of vision. Obama wrt the wider economy, seems more New Deal oriented, so the old NASA-as-jobs-program paradigm will IMHO be retained.

There is no such thing, except in the minds of a few detractors, as “the old NASA-as-jobs-program”. There is the current condition where because of idiotic lack of real planning and ideological goals rather than goals of excellence and common sense, where we stand to decimate the only highly trained space workforce we have. We did that once, back when Saturn was shutdown. NASA, stupidly, fired them all believing that they could just rehire them when Shuttle was ready. That was stupid, really stupid, because not even one on ten came back. They had other priorities, like food, mortgages, families, so they went elsewhere, to more secure jobs. It took NASA over twenty years to rebuild the majority of the skill sets it lost by that move, and to this very day there are still things we did routinely back in the day that NASA still has no clue how to do.

For example look at their design efforts for cryogenic upper stages. The engineers working that at NASA are very smart people, but they still can’t match what we did on the Saturn because there is nobody there that has a clue how to duplicate that technology. It was lost when Saturn was shut down. What they have now is ok, and works, but when compared to what we did on Saturn, it pales in comparison in both weight management and efficiency. We had much better mass fractions. The NASA guys don't know how to duplicate it yet. They are trying to figure it out. That's a situation that should have never happened.

And guess what – they are fixing to do it again. Stupid, really stupid. So it’s not a “jobs program”. It’s a skill set retention program. Anyone who doesn’t get that doesn’t understand how unique that workforce is. It’s not even about the individual, specific skill that this worker or that worker has. It about the workforce as a whole, and what it is able to synergistically do, just like the human body. One’s right hand is very good at doing certain things. But loose the hand, and the rest of the body will compensate somewhat, but the overall loss to the body’s ability to function is reduced. Loosing the current workforce would be like a body loosing both hands, both feet, one eye and one ear. You can’t just replace those parts later, and the same goes with the workforce. There are *NO* schools or colleges that teach people how to work at a space launch complex or assembly facility. You can’t just go out and hire these people – they just do not exist on the outside.

From a program point of view, it is far better to retain them over the slow period, if you can, so that they are available when things get underway again. Ideally, you plan the incoming program in such a way that you can actually do something useful and necessary with the majority of them, so that you're not wasting your money. Sooner or later, what you pay them to do will be needed, so why not pay them now to go do that? So their specific skill needs to be retrained - so what? Do the training. Continual training & retraining should be happening anyway. They get to keep their jobs, you get the tasks done  that will be needed later and, more importantly, you keep the majority of the workforce and skill sets intact. If we don’t do that, more than 90% of them will not be available for rehire 6, 8 or 10 years from now. They will be gone. And we will be screwed, again.

When the VSE gets underway, there will be 2 basic parts to it; LEO and Lunar. The LEO part will use a smaller workforce than we have now, and that can be accomplished "mostly" thru normal attrition. But once the lunar program gets underway, the workforce will need to be much larger than it is now, much larger. We will need to hire a *lot* of skilled people and train them in the ways of the space program. Who's going to do that if you fire all the people today who should form the core of the skilled workforce later? They are not going to hang around for 6, 8 or 10 years waiting for the call while their homes and families go under. They will do the same thing that the Saturn people did; start new careers elsewhere in companies that won't treat them like so much excess meat.

Everybody wants to go to the moon and on to Mars. But nobody wants to pay for it. It's an EXPENSIVE thing to do people, very expensive; in terms of both workforce size and budget. It's going to cost a lot of money and will take many more people to do than we have today.

Title: Re: SSTO Thread
Post by: Jim on 12/20/2008 03:33 pm

Personally I am biased against continued subsidies for the ICBM-industrial complex,

That is an non existent entity.  There is no such thing. You  reduce the credibility of your posts with the belief this.

The shuttle is not the only launch vehicle the US uses and so your point is not applicable to the rest of the US fleet

ICBM's use solid motors, launch vehicle use liquid stages. ULA and OSC have no ties to the ICBMs.   Even before the merger, the Boeing group that did Minuteman refurb had no ties with the Delta launch vehicle group. As for Lockheed, it did SLBM's which have little to do with spacelaunch

Your bias is just as unsubstantiated as racism is.
It not based on any fact or evidence.
Title: Re: SSTO Thread
Post by: Eerie on 12/20/2008 04:40 pm
Jim, do you think VentureStar was possible?
Title: Re: SSTO Thread
Post by: spacedem on 12/20/2008 05:23 pm
Jim, do you think VentureStar was possible?

In particular, was the BF Goodrich TPS workable?  I wonder if it would have done the job for an SSX-like vehicle...
Title: Re: SSTO Thread
Post by: Jim on 12/20/2008 06:17 pm
Jim, do you think VentureStar was possible?

Just as the shuttle was, but will it be economical?
Title: Re: SSTO Thread
Post by: Smoothie on 12/20/2008 06:43 pm
Jim, do you think VentureStar was possible?

In particular, was the BF Goodrich TPS workable?  I wonder if it would have done the job for an SSX-like vehicle...

From what I have read the TPS was the best thing to come out of the whole program.  It just waits for a vehicle to use it now.
Title: Re: SSTO Thread
Post by: Eerie on 12/20/2008 06:47 pm
Just as the shuttle was, but will it be economical?

Well, it had no boosters and no ET, a true SSTO, so the only question is how expensive its maintenance would be...
Title: Re: SSTO Thread
Post by: Jim on 12/20/2008 07:22 pm
Just as the shuttle was, but will it be economical?

Well, it had no boosters and no ET, a true SSTO, so the only question is how expensive its maintenance would be...

and the size of the payload may have been small
Title: Re: SSTO Thread
Post by: mlorrey on 12/21/2008 05:24 am
Just as the shuttle was, but will it be economical?

Well, it had no boosters and no ET, a true SSTO, so the only question is how expensive its maintenance would be...

and the size of the payload may have been small

Payload was 10,000 kg right? Not small. Not as much as Shuttle, but still in the heavy lift arena. The frequency of heavier loads is so low that there really is no need for using a reusable launcher with that payload capacity. Lets look at how frequently Shuttle used its maximum payload capacity. You have any stats on the average payload carried by Shuttle? Even Hubble was only 11,000 kg. My scanning the stats at astronautix says most cargoes were between 6k-13k kg, anything over 10k kg involved multiple payloads, except for TDRS and military missions. The largest payloads were the TDRS satellites for NASA itself at 22k kg (these numbers do not include classified military payloads, for which there are no public stats).

Shuttle was never used for launching SDI battle stations, the main excuse back in the 80's for keeping it, and it only took 20 years to get around to its other main mission, building ISS, and shuttle will be retired upon its completion, if not sooner.

There really is no market need for a launcher over 10k kg payload, the frequency of need for such payloads speaks for using big low production rate expendables.

I agree Jim, that preserving the skill sets of NASA personnel is crucial. However that does not necessarily mean you have to keep people around, so his conclusion disputing my arguments is not supported. Thats what documentation is supposed to be for. We lost a lot of knowledge after the saturn program was cancelled because most records were destroyed and not archived. Any competent engineer documents everything about what they do, there is absolutely no excuse for engineers not documenting things out of some paranoid sense of job security.

Furthermore, Jim decrying the lack of skills being taught in our universities also speaks to a lack of documentation: those engineers should be seeing it as their sacred duty to document every scrap of knowledge they create and to teach it to the next generation. So dont give me arguments about keeping people around the cape as the only way to preserve that knowledge, thats hogwash. When I take a job, i see one of my primary duties to be so effective at what I do that I work myself out of a job. That includes documenting everything so if something happens to me, someone else can take up where I left off.
Title: Re: SSTO Thread
Post by: mlorrey on 12/21/2008 05:41 am

Thus, you can blame Walter Mondale for the failure of STS (and the loss of one if not both shuttle crews).

No, you can blame a NASA management that made safety decisions (if you want to call them that) in a lackadaisical fashion, and in both cases against the advise of the sme’s on the teams. In the case of Challenger, they even disregarded an ATK Technical Bulletin that specifically told them not to fly the SRB’s below a certain temperature. They just flat ignored it, as if to say “Huh, who do they think they are? We’re NASA. They can’t tell us what to do.” NASA management quite simply *chose* to ignore the people who actually knew what they were talking about as if, because they were NASA, and for no other reason what-so-ever, they knew best. The laws of physics wouldn’t dare contradict them.  The CAIB was *very* clear in it's condemnation of NASA management in this regard.

Well yes, but WHY did we have such a design in the first place? I agree launching Challenger in too cold climate was wrong and arrogant, but was that design arrived at in the first place out of economical cost cutting? If it was decided on for saving money on development, bingo, back to the penny pinchers.

That said, you completely ignore the Columbia disaster which IS the fault of Mondale and his cost cutters, who forced NASA to ditch the hot frame design which would have never suffered damage from some mere foam.



… NASA should use its funds to stimulate private industry to make these things happen with both prizes and contracts once one or more parties achieve the goals set.

NASA cannot use its funding for anything except what the Congress specifically authorizes. It has absolutely no wiggle room in that regard.

Of course. Frankly I think congress as a whole would be for such a proposal, although the handful of powerful senators and congressional committee chairmen who get their power from NASA money flowing to their districts I think would kill such proposals long before they reached a floor vote.

Quote
Quote
Both prizes and contract competitions stimulate private capital to invest in ventures at a much higher level than currently.

That takes much deeper pockets than most venture capitalist have available. There are probably only a small handful of such people in the world. Even the conglomerates with much more funding available won’t do it because they have stockholders to answer to who insist on a relatively secured return on investment. Stockholders are not in the habit of authorizing the expenditure of, for example, $5,000,000 to win a $500,000 prize, with no guaranteed $10,000,000 contracts for the winner. It’s a nice idea, but it is not a money-maker. If it doesn’t make money for the investor, the investments don’t happen.

You didnt read what i said. Firstly the efforts of Elon Musk  and Burt Rutan disprove some of your arguments, however, I was never talking about a piddly 10 million dollar prize for something that takes 10 billion to win. Paul Allen spent 30 million to win the 10 million dollar X Prize. He saw that as a decent payback because he also gained his stock in The Spaceship Company as well, plus whatever else he's got cooking with Scaled Composits or Virgin Galactic. The stock is going to pay him back a huge profit eventually.

But no, a 5 billion dollar project should have a prize of a billion dollars or more for being the first to achieve the goal. The investors get some immediate payback plus equity in the venture that gets to exploit that technology and market into the future. The government gets to see its goals reached for 10-30% of the full cost of achieving the goal, and the full cost of achieving the goal is minimized *safely and effectively* by capitalists who understand the numbers about minimizing risk in both terms of lives at stake and money invested.

Quote

Quote
As for Obama, I do not expect his team to have this level of vision. Obama wrt the wider economy, seems more New Deal oriented, so the old NASA-as-jobs-program paradigm will IMHO be retained.

There is no such thing, except in the minds of a few detractors, as “the old NASA-as-jobs-program”. There is the current condition where because of idiotic lack of real planning and ideological goals rather than goals of excellence and common sense, where we stand to decimate the only highly trained space workforce we have. We did that once, back when Saturn was shutdown. NASA, stupidly, fired them all believing that they could just rehire them when Shuttle was ready. That was stupid, really stupid, because not even one on ten came back. They had other priorities, like food, mortgages, families, so they went elsewhere, to more secure jobs. It took NASA over twenty years to rebuild the majority of the skill sets it lost by that move, and to this very day there are still things we did routinely back in the day that NASA still has no clue how to do.


Sorry, Jim, I meant my previous comments in my previous post for clongston here. You dont need to keep paying a paycheck to perserve a knowledge base, a competent engineering team will document everything they do, and a competent management team will preserve that stored knowledge as hard won intellectual capital.
Title: Re: SSTO Thread
Post by: clongton on 12/21/2008 02:04 pm
Mike:

I never indicated that the Shuttle design was optimal. That wasn't part of the equation. I was speaking about the immediate cause of the loss of the two crews. I contend, and the STS workforce will agree with me, that in spite of the suboptimal design, Shuttle *IS* safe to fly - when flown safely!

We agree on the Challenger. That is laid directly at the feet of an arrogant NASA management. As for Columbia, I contend the same thing. It wasn't Mondale's fault that NASA management *chose* to NOT image Columbia with the Hubble in spite of the fact that their safety organization officially recommended it after the high speed cameras clearly showed the foam hit. Had they done so, it is likely that the hole in the leading edge would have been seen and the crew would have remained aboard ISS for an extended time, saving their lives. The contention that Mondale influenced the tile-type TPS has nothing to do with NASA management's arrogance and stupidity. That's what caused the loss of Columbia's crew, not the TPS.

You speak as if I were recommending keeping the workforce around moving piles of dirt from one place at the cape to another until something useful comes along. Nothing, and I mean nothing, could be further from the truth. If that's all there is to do then furlough them - plain and simple. No, I'm speaking of rearranging the entire implementation and transition plan from STS to CxP in such a way that the majority of the workforce can be retained, and actually be working at stuff that CxP will actually need done. That's not a jobs program, because I do not advocate "making work" for them. I advocate them working a revised CxP transition schedule. I advocate downsizing the workforce, mostly thru normal attrition and retirements, and furloughing the rest, until you have a workforce that is properly sized to the tasks. But I want the schedule rearranged so that CxP actually gets work done that needs to be done. If that means that some of it is ahead of schedule, then so be it. But it's got to be stuff that would actually need doing. That is not a jobs program. That's being smart about retaining the skill sets and skilled labor in the industry. As a business owner, you should know that it is *always* less expensive to retain a skilled workforce thru lean times, if you can, than it is to fire them and then replace them later with people, while very smart people, who don't have a clue how to do this stuff. I want the CxP program rearranged to retain the workforce in that manner. Not welfare, and not a jobs program - real work.

Regarding your observations about documentation, it has to involve a lot more than "here's how it's done". It also needs to include "design intent". "I did it this way because .....". Here's where the designer's lifetime of experience comes into play and totally colors why the end result is what it is. It also includes why he or she did not do it differently, and includes all the failed attempts with a different methodology and the analysis of the failures with the resulting lessons learned. It keeps the new people from making the same mistakes all over again that the original designers made as they progressed toward the final design. This design intent knowledge would easily exceed the volume of "here's how to do this" documentation many times over. I run across this all the time in my own industry. We have tens of thousands of volumes of "here's how to do this" documentation, but it still requires the presence of someone who's been doing it for years to explain how to implement that to the new people, and more importantly: why. All industries recognize the validity of that. That's why most large companies of any size have mentoring programs that they gladly spend millions of dollars on. I'm sorry, but just having "good documentation" falls far short of the requirement. You need people around who have been doing it for years to explain it to the new people. Ten minutes spent with a highly experienced person can replace weeks of studying documentation.
Title: Re: SSTO Thread
Post by: sbt on 12/21/2008 02:56 pm
<snip> a competent engineering team will document everything they do, and a competent management team will preserve that stored knowledge as hard won intellectual capital.

I take it then that you believe that the Apollo era NASA team were incompetent? Because the Shuttle era team were unable to pick up all the skills from what the 'old guys' had written down.

In the real world things don't work like that.

For a start, whilst I'm no NASA engineer, I can't document the stuff I've picked up over time that suddenly comes to mind when I'm tackling a problem – I can't document stuff I don't know I know. Neither can I document the personal relationships that allow me to communicate with my nearest colleagues, particularly the mutual respect that is only built through seeing them in action year by year.

Nor do I have the time to document every last thing when I'm working on a fixed timescale set by outside forces – either I do the work with basic documentation or I document in incredible detail the work I would have done if I wasn't busy writing and the end user doesn't get what he needs. Neither would my successors have the time to read decades worth of documentation to pick up where I left off – they would either do the work without reading all the material or apologise to the end user about the project that failed because they never left the library.

Finally documenting a skill learnt through practice is of only limited utility. I can run my eyes across a list of military equipment and spot the mistake in a couple of seconds. I can, and do, document the issues but it still takes someone new to the job tens of minutes to make the same check – they lack two decades of experience.

Rick
Title: Re: SSTO Thread
Post by: indaco1 on 12/22/2008 12:01 am
Not a matter of want but what we can afford.  RLV to replace EELV's and Shuttle are out of the question

While I agree that there isn't enough demand for a Shuttle/EELV sized RLV out there, there's nothing that says RLVs have to be Shuttle or EELV sized. 

In fact there's a lot to be said for having first generation RLVs be a lot smaller than an EELV.  At least as small as 5 tons to orbit, possibly as small as 1 ton.

But admittedly it would take some changes in how things are done in order to close the case on a small RLV like that.

~Jon

Drag losses are much worst with small veichles.

A small RLV is even more difficult.
Title: Re: SSTO Thread
Post by: mlorrey on 12/22/2008 12:39 am
Not a matter of want but what we can afford.  RLV to replace EELV's and Shuttle are out of the question

While I agree that there isn't enough demand for a Shuttle/EELV sized RLV out there, there's nothing that says RLVs have to be Shuttle or EELV sized. 

In fact there's a lot to be said for having first generation RLVs be a lot smaller than an EELV.  At least as small as 5 tons to orbit, possibly as small as 1 ton.

But admittedly it would take some changes in how things are done in order to close the case on a small RLV like that.

~Jon

Drag losses are much worst with small veichles.

A small RLV is even more difficult.

Well, yes there are 'sweet spots' to scaling different sorts of designs. Huge vehicles require more structural support due to mass of what needs to be held up (something that is cheated by Atlas and Falcon by prepressurization of tanks, of course, and no reason not to figure out more such cheats).

I'm not too worried at the present time. Given further developments in polywell fusion, I think within a decade we'll be building the first fusion propelled SSTO RLV, with airline level mass fractions, capable of surface to surface Earth-Moon transit. That may sound a bit overoptimistic, and it may actually be so, but what i've seen so far has me hopeful. I would not be surprised to see Bussards theoretical performance fall short, but not significantly more than other technologies do.
Title: Re: SSTO Thread
Post by: Archibald on 12/22/2008 07:34 am
Quote


A hot structure would have allowed it to meet its performance objectives. Instead we got an aluminum structure covered with foam and a brick chimney that doubled the maintenance man hours required to turn it around each flight. A 5,000 USD per kg payload cost was turned into 20,000 USD per kg by this fact alone. Doubling the maintenance man hours due to TPS maintenance cuts the sortie rate by half and as a result to revenue to cost models quadruple the per unit price ($/kg payload).


Other failures: the SME design was too bleeding edge for a viable 'airline' style operation. Try running a taxi service with Formula 1 engines, it doesnt work. It would have been cheaper to design the engines to be inexpensive single use items. That would cut the shuttle turnaround maintenance costs and time by another 25%.

If you redesigned and rebuilt Shuttle with a hot frame and inexpensive single use engines today, you'd have a viable system. IMHO it should have been totally redesigned and rebuilt as such after the Challenger disaster.


Not sure about  the hot structure (Titanium tend to be horrendously expensive to manufacture). But (on the subject of cheaper engines) they thought about using J-2S instead of SSME.

They called that the Mark 1 / Mark 2 "phased" shuttle.

Mark I was to have J-2s and ablative heatshield... Mark II would have been upgraded with reusable heatshield and SSMEs.

Title: Re: SSTO Thread
Post by: Jorge on 12/22/2008 08:11 am
Mike:

I never indicated that the Shuttle design was optimal. That wasn't part of the equation. I was speaking about the immediate cause of the loss of the two crews. I contend, and the STS workforce will agree with me, that in spite of the suboptimal design, Shuttle *IS* safe to fly - when flown safely!

We agree on the Challenger. That is laid directly at the feet of an arrogant NASA management. As for Columbia, I contend the same thing. It wasn't Mondale's fault that NASA management *chose* to NOT image Columbia with the Hubble in spite of the fact that their safety organization officially recommended it after the high speed cameras clearly showed the foam hit. Had they done so, it is likely that the hole in the leading edge would have been seen and the crew would have remained aboard ISS for an extended time, saving their lives.

What the frack? Columbia was not on an ISS mission; it was in a 28.5 degree inclination orbit and there was no possibility of it ever reaching ISS. And Hubble was not capable of imaging Columbia; its pointing system is designed for celestial objects and cannot track a co-orbiting object.
Title: Re: SSTO Thread
Post by: KelvinZero on 12/22/2008 08:33 am
Drag losses are much worst with small veichles.

A small RLV is even more difficult.

I understand why that would make a small SSTO more difficult. What about a multiple stage RLV?

I have been wondering if there would be anything to learn from a small fully reusable multiple stage system with high flight rates.
Title: Re: SSTO Thread
Post by: mlorrey on 12/22/2008 09:32 am


Not sure about  the hot structure (Titanium tend to be horrendously expensive to manufacture). But (on the subject of cheaper engines) they thought about using J-2S instead of SSME.

They called that the Mark 1 / Mark 2 "phased" shuttle.

Mark I was to have J-2s and ablative heatshield... Mark II would have been upgraded with reusable heatshield and SSMEs.



Titanium airframe with inconel and such. As I recall reading, cost would have been 2-3 times as much as what we got. They still might have wound up using RCC for the leading edges, however if they had and Columbia still happened (foam airstrike), I doubt the titanium would have had problems standing up to ingress of hot gasses.

Conversely, having a hot frame would have allowed such a higher turn around rate and sortie rate that a loss of one crew would not have been seen as such a huge disaster. Still a tragedy, but not something that would bring everything to a halt.

Then again, I tend to like something I once read about the old Roman law wrt bridge and building contracting: you got paid half on completion, the other half if it was still standing 40 years later (and something about execution if it wasnt or something, not sure about that one).

IMHO anybody who makes a decision that directly causes a LOC should be prosecuted. I just don't understand how a bureaucrat (or a cop for that matter) can just walk on a wrongful death.
Title: Re: SSTO Thread
Post by: Archibald on 12/22/2008 11:11 am
Hubble was not capable of imaging Columbia; its pointing system is designed for celestial objects and cannot track a co-orbiting object.

Hubble no, but (dumb question probably...) what about a KH-11 or KH-12 ? Any chance ?
Title: Re: SSTO Thread
Post by: Kaputnik on 12/22/2008 12:19 pm
Titanium airframe with inconel and such. As I recall reading, cost would have been 2-3 times as much as what we got. They still might have wound up using RCC for the leading edges, however if they had and Columbia still happened (foam airstrike), I doubt the titanium would have had problems standing up to ingress of hot gasses.

Somebody asked, somewhere on the forum, how much longer Columbia would have lasted with a titanium structure rather than Alu. IIRC the answer, from CAIB, was about 15 seconds. Not enough to make any appreciable difference whatsoever to the crew's chances of survival.
Title: Re: SSTO Thread
Post by: Kaputnik on 12/22/2008 12:21 pm
Just as the shuttle was, but will it be economical?

Well, it had no boosters and no ET, a true SSTO, so the only question is how expensive its maintenance would be...

and the size of the payload may have been small

Payload was 10,000 kg right?

On paper, maybe. The payload was reducing more and more as the design got into deeper trouble. A externally mounted payload in a shroud, rather than in a PLB, was a last gasp effort to squeeze more performance out of the concept. Who knows what the actual paylaod might have wound up being.
Title: Re: SSTO Thread
Post by: mlorrey on 12/23/2008 06:18 am
Titanium airframe with inconel and such. As I recall reading, cost would have been 2-3 times as much as what we got. They still might have wound up using RCC for the leading edges, however if they had and Columbia still happened (foam airstrike), I doubt the titanium would have had problems standing up to ingress of hot gasses.

Somebody asked, somewhere on the forum, how much longer Columbia would have lasted with a titanium structure rather than Alu. IIRC the answer, from CAIB, was about 15 seconds. Not enough to make any appreciable difference whatsoever to the crew's chances of survival.

Thats debatable, and not that simple. I doubt the 15 second figure. Prior experience people go by for example is the plasma damage X-15 suffered on one flight when a test scramjet cause some serious damage simply from the shock wave plasma at hypersonic speed. You'd only get such damage in the internal airframe if the airflow actually caused hypersonic shock waves to be generated INSIDE the wing.

Plasma cutters achieve their cutting not just from the plasma but from the velocity of the ionized gas. If the speed of the plasma is too low, all you wind up doing is heating the metal up over a broad area. Hot enough to melt/cut aluminum like butter but nowhere near enough to cut titanium. I can melt aluminum with a lighter.

It takes the nozzle cup to generate shock waves and supersonic flow of the plasma to achieve a cut.

If the hole in the leading edge was large, you'd get shock wave impinging within the wing structure and you'd get cutting. If it wasnt so big, or just a crack, youd just get an ingress of plasma with no shock waves.

Also, keep in mind that even the existing wing has inconel behind the RCC leading edges.
Title: Re: SSTO Thread
Post by: kevin-rf on 12/23/2008 01:31 pm
Thats debatable, and not that simple. I doubt the 15 second figure. Prior experience people go by for example is the plasma damage X-15 suffered on one flight when a test scramjet cause some serious damage simply from the shock wave plasma at hypersonic speed.

The X-15 was an inconel airframe was it not? Not titanium...

Title: Re: SSTO Thread
Post by: mlorrey on 12/24/2008 05:33 am
Thats debatable, and not that simple. I doubt the 15 second figure. Prior experience people go by for example is the plasma damage X-15 suffered on one flight when a test scramjet cause some serious damage simply from the shock wave plasma at hypersonic speed.

The X-15 was an inconel airframe was it not? Not titanium...


It was both:
"The wing presented a difficult design problem, to account for uneven heating from leading edge to trailing edge and between lower and upper surfaces. At high angles of attack, inconsistent heating typically subjects the wing's lower surface to temperatures 400° F higher than those of the upper surface. The result of higher heating at the leading edge and lower surface is that these two surfaces try to expand faster than the rest of the wing. Thus, the wing structure had to be designed to allow for this expansion without deforming to a large extent, while, at the same time, carrying rather large airloads. A balance was achieved by allowing some expansion of skin to alleviate a part of the thermally induced stresses, and by the use of titanium internal structure, which has a higher elasticity than Inconel X. The internal structure provides enough restraint between attach points to give the hot wing surfaces a tufted-pillow appearance as they try to expand. Corrugations in the internal structure allow it to flex enough to keep skin stress within tolerable limits. "

Inconel was primarily the skin/TPS/leading edges. An all-inconel airframe would have been too heavy to fly, esp with those little wings, wing loading would have been huge, which would have increased thermal and structural stresses.

Shuttle wing structure:
http://spaceflight.nasa.gov/shuttle/reference/shutref/structure/wing.html
Title: Re: SSTO Thread
Post by: Kaputnik on 12/25/2008 05:34 pm
Here's the previous discussion about the extra time that would have been bought by a titanium airframe on Columbia:

http://forum.nasaspaceflight.com/index.php?topic=13302.msg289708#msg289708
Title: Re: SSTO Thread
Post by: jongoff on 12/26/2008 02:01 am
Drag losses are much worst with small vehicles.

Depends on how you do it.  As it is, drag losses are roundoff errors on typical launch vehicles (I think I was hearing ~200m/s for a typical EELV).  There are options like air launch or other things that can help deal with that.  Or you can just bite the bullet and deal with it.  Admittedly if you get *too* small, drag losses get truly heinous, but I'm not talking about a 5kg to orbit vehicle, a 1000kg to orbit vehicle is still a respectable sized craft, but small enough to keep the development cost cheap enough to be feasible.

Quote
A small RLV is even more difficult.

But it's easier on the one dimension that matters most--the financial one.  Raising hundreds of millions or billions of dollars for a bigger RLV is a lot harder than raising a smaller sum for a vehicle that is a lot smaller.  There still are technological challenges with small RLVs (especially if you try to go too small), but if you don't overcome the financial challenge, you don't get to even try on the technical side.  And quite frankly, I have higher confidence in being able to solve the technical issues than the financial ones.

~Jon
Title: Re: SSTO Thread
Post by: kkattula on 12/26/2008 02:26 am
Also it should be a lot easier to raise the money for a big RLV, once a small RLV has demostrated regular operations and retired most of the technical risk.
Title: Re: SSTO Thread
Post by: clongton on 12/26/2008 12:18 pm
Also it should be a lot easier to raise the money for a big RLV, once a small RLV has demonstrated regular operations and retired most of the technical risk.

In an oblique sort of way that was one of the unstated goals of the X-Plane program, specifically the X-15 and its intended successors.

I remember one of the pilots (I don't remember which one) gave a talk at my high school in 1963 and he said that someday people would fly into space and back on planes that were designed by things we learn from the X-15.
Title: Re: SSTO Thread
Post by: William Barton on 12/26/2008 12:35 pm
Drag losses are much worst with small vehicles.

Depends on how you do it.  As it is, drag losses are roundoff errors on typical launch vehicles (I think I was hearing ~200m/s for a typical EELV).  There are options like air launch or other things that can help deal with that.  Or you can just bite the bullet and deal with it.  Admittedly if you get *too* small, drag losses get truly heinous, but I'm not talking about a 5kg to orbit vehicle, a 1000kg to orbit vehicle is still a respectable sized craft, but small enough to keep the development cost cheap enough to be feasible.

Quote
A small RLV is even more difficult.

But it's easier on the one dimension that matters most--the financial one.  Raising hundreds of millions or billions of dollars for a bigger RLV is a lot harder than raising a smaller sum for a vehicle that is a lot smaller.  There still are technological challenges with small RLVs (especially if you try to go too small), but if you don't overcome the financial challenge, you don't get to even try on the technical side.  And quite frankly, I have higher confidence in being able to solve the technical issues than the financial ones.

~Jon

Many of the questions about small RLVs would have been answered by K-1, including viability of RTLS recovery and wings v. no wings. When people talk RLVs, it's usually winged rocketships no that different from Von Braun (or Tom Swift, Jr., for that matter), or maybe a DCX-like VTOL. Parachutes and airbags sometimes seems like a cheat, because you can't gas and go (like DCX) or restack, gas, and go (like a winged TSTO), but it still would have been an RLV is the general sense of the phrase.
Title: Re: SSTO Thread
Post by: kkattula on 12/26/2008 03:41 pm
People generally confuse RLV with SSTO.  A vehicle can be both, either or neither.
Both is the most difficult.

The big issues for SSTO are:

1)  High mass fraction
2)  Altitude compensation for nozzles.
3)  Thrust reduction (throttling) late in flight.

Going RLV helps with none of these, in fact it hurts 1 & likely 2 & 3.

Typically, staging is the solution for all three, at the cost of discarded hardware.
RLV first (& maybe second) stage has the potential to overcome that disadvantage.

In summary, IMO:

- RLV makes SSTO much harder & maybe a little cheaper.
- RLV makes TSTO much cheaper & maybe a little harder.
Title: Re: SSTO Thread
Post by: kevin-rf on 12/28/2008 01:13 pm
3)  Thrust reduction (throttling)

Only if it is manned. People also see SSTO, RLV, and assume manned.

The best first step RLV X program would be one that is designed to demonstrate reuse, rapid turn arround, and low man hours between flights.

Once that is done you can think about a follow on program with payloads.

The problem is someone would have to pay for something that has "zero" chance of "directly"  making money. It would be gen 2 or gen 3 before you "may" have a commercial vehicle.
Title: Re: SSTO Thread
Post by: tnphysics on 01/03/2009 04:11 pm
What about borane fuels? They were supposed to offer the performance of hydrogen at the density of kerosene, but I believe that their was a problem.
Title: Re: SSTO Thread
Post by: tnphysics on 01/03/2009 04:24 pm
The key to a gas-and-go SSTO RLV IMO is airbreathing engines-somewhat like the Forerunner V business jet proposed somewhere on the forum (afterburning ultra-high-bypass turbofan to Mach 8, then LNG scramjet to Mach 15, then switch to LH2 to Mach 20), with a small rocket added for EOI.  A metallic TPS should be used.
Title: Re: SSTO Thread
Post by: Eerie on 01/03/2009 04:38 pm
The key to a gas-and-go SSTO RLV IMO is airbreathing engines-somewhat like the Forerunner V business jet proposed somewhere on the forum (afterburning ultra-high-bypass turbofan to Mach 8, then LNG scramjet to Mach 15, then switch to LH2 to Mach 20), with a small rocket added for EOI.  A metallic TPS should be used.


That is really too complex.
Title: Re: SSTO Thread
Post by: mlorrey on 01/03/2009 04:49 pm
What about borane fuels? They were supposed to offer the performance of hydrogen at the density of kerosene, but I believe that their was a problem.

Boranes combustion products tend to be thick sticky/solid boron compounds which are generally impossible to remove from engine surfaces and make turbopumps impossible to use.

Kerosene/boron powder slurries offer similar performance without as much coking issues but still should only be used with pressure fed or piston pumps fed engines. If SpaceX used such a mix on, say, the Kestrel pressure fed engine, the Falcon 1 payload performance might be significantly increased.
Title: Re: SSTO Thread
Post by: mlorrey on 01/03/2009 04:53 pm
The key to a gas-and-go SSTO RLV IMO is airbreathing engines-somewhat like the Forerunner V business jet proposed somewhere on the forum (afterburning ultra-high-bypass turbofan to Mach 8, then LNG scramjet to Mach 15, then switch to LH2 to Mach 20), with a small rocket added for EOI.  A metallic TPS should be used.


That is really too complex.

Agreed. The GTX RBCC launcher (which would have launched by 2006 but was cancelled) would have demonstrated stage and a half air breathing rocket based combined cycle RLV technologies.

Personally I'd like to see a more basic POGO-like ram/rocket RLV, though IMHO provided polywell fusion moves along as expected, we'll be seeing fusion SSTO RLVs within a decade.
Title: Re: SSTO Thread
Post by: khallow on 01/03/2009 05:28 pm
The key to a gas-and-go SSTO RLV IMO is airbreathing engines-somewhat like the Forerunner V business jet proposed somewhere on the forum (afterburning ultra-high-bypass turbofan to Mach 8, then LNG scramjet to Mach 15, then switch to LH2 to Mach 20), with a small rocket added for EOI.

The gravity and air resistance losses would be much greater than for a standard rocket trajectory. But those are known weaknesses. Perversely, using the rocket to accelerate the vehicle to viable scramjet speeds may be better than adding a turbofan. It still means that a majority (as above) of your delta v comes from the scramjet. And you are carrying fewer systems as a result.
Title: Re: SSTO Thread
Post by: mlorrey on 01/04/2009 01:28 am
The key to a gas-and-go SSTO RLV IMO is airbreathing engines-somewhat like the Forerunner V business jet proposed somewhere on the forum (afterburning ultra-high-bypass turbofan to Mach 8, then LNG scramjet to Mach 15, then switch to LH2 to Mach 20), with a small rocket added for EOI.

The gravity and air resistance losses would be much greater than for a standard rocket trajectory. But those are known weaknesses. Perversely, using the rocket to accelerate the vehicle to viable scramjet speeds may be better than adding a turbofan. It still means that a majority (as above) of your delta v comes from the scramjet. And you are carrying fewer systems as a result.


Good point. Also note that air resistance losses are greatly mitigated by use of sharp design. Using SHARP materials for leading edges (hafnium diboride and zirconium diboride as is used in IRV steering fins) allows for mach 7 flight at sea level, mach 11 flight at 100k feet and minimal hypersonic plasma issues.
Title: Re: SSTO Thread
Post by: indaco1 on 01/07/2009 12:43 am
3)  Thrust reduction (throttling)

Only if it is manned. People also see SSTO, RLV, and assume manned.

......


Even for an unmanned launch, high g forces require a more robust, heavy and expensive structure. 

Expecially if you have an high mass ratio you can reach 7-8 g and more when the veichle has lost most of his mass but the thrust is the same. Very difficult to build something light that can bear these forces.

Also, I think insertion in orbit is slightly less efficient if you can't reduce thrust after coasting phase.

The optimal thrust to maximize payload is not full throttle at any time of the launch.  Thrust gently at the end is better.

But there's a very simple and easy way to solve this. 

Asymmetrical dual or multi engines.

You take off with two (or more) non thrustable engines on, one big and the other small, and you circularize the orbit using the small one only (the  "sustain engine").   

Note that this is a SSTO not a TSTO because both the engines are taken to orbit, nothing is jettisoned.

I think that just cut of some engines is a much more simple, cheap and efficient way than having thrustable engines like SSME, because the required thrust range (SSME allows just 60% reduction, not enough if you renounce boosters) and the many possible optimizations.

I still wonder why the designers of the Shuttle did't just cut off one of the three main engines at a certain point of the launch instead of require a 66% thrustability that is equivalent.....  I probably miss something.

Thrust reduction is not the worst problem to design a SSTO, anyway.
Title: Re: RE: SSTO Thread
Post by: LTABS on 01/07/2009 09:40 am
What you need to do is change the equation.  i.e. Create a launch vehicle or booster system that weighs nothing and has flyback capability for reuse. 

Impossible say's you?

see the "Airlaunch Using Hybrid Air Vehicles" post under Advanced Concepts.

As far as the dream of having a fully reusable SSTO that enables aircraft like opperation I think that is likley 50 years out, the rocket equation is a harsh mistress and as long as you are married to it it almost totally preclude a realistic SSTO RLV....



Title: Re: RE: SSTO Thread
Post by: mlorrey on 01/08/2009 02:27 am
What you need to do is change the equation.  i.e. Create a launch vehicle or booster system that weighs nothing and has flyback capability for reuse. 

Impossible say's you?

see the "Airlaunch Using Hybrid Air Vehicles" post under Advanced Concepts.

As far as the dream of having a fully reusable SSTO that enables aircraft like opperation I think that is likley 50 years out, the rocket equation is a harsh mistress and as long as you are married to it it almost totally preclude a realistic SSTO RLV....




Actually, there are tradeoffs. LH2 is too low a density for feasible SSTO RLV, it mandates too much vehicle mass and volume. Tripropellant systems like MAKS are feasible. Air breathing vs only rockets is another tradeoff issue: breathing air reduces LOX mass and tankage significantly but increases vehicle mass and TPS complexity.

The airlaunch for hybrid air vehicles post is about a two stage vehicle.

Achieving SSTO and RLV is indeed a very difficult problem with chemical engines. My current hopes are that polywell fusion is the holy grail.
Title: Re: SSTO Thread
Post by: Patchouli on 01/08/2009 03:05 am
3)  Thrust reduction (throttling)

Only if it is manned. People also see SSTO, RLV, and assume manned.

......


I still wonder why the designers of the Shuttle did't just cut off one of the three main engines at a certain point of the launch instead of require a 66% thrustability that is equivalent.....  I probably miss something.

Thrust reduction is not the worst problem to design a SSTO, anyway.
They would loose engine out capability the shuttle can loose an engine and throttle the remaining two back up this happened on STS 51-F.
Title: Re: SSTO Thread
Post by: Patchouli on 01/08/2009 03:12 am
This might have made a good mark I RLV vs the huge jump they made with the shuttle.
http://www.astronautix.com/lvs/sassto.htm
A plug nozzle engine of sufficient thrust was built and test fired back in the 60s as shown on the link.

Such a vehicle could be built today using a single SSME modified in the same manner the J2 was for the XRS-2000 or use the J2X from Ares/Direct.

An interesting note even though it's an RLV it also could be used to replace the S-IVB on the Saturn IB and would increase the IB's payload by 7938 to 9979Kg depending on whether the SASSTO was reused putting the vehicle into the EELV heavy class.

It might be a good idea to resurrect the concept since it has a lot of commonality with hardware used to return to the moon.
Title: Re: RE: SSTO Thread
Post by: LTABS on 01/08/2009 07:16 am
I concur with you on the two stage comment.  But I believe technically speaking that an air launch system is not classified as a stage by the keepers of the official records.  It will be interesting to see how they classify this one since it will potentially use rocket engines for power plants.


Actually, there are tradeoffs. LH2 is too low a density for feasible SSTO RLV, it mandates too much vehicle mass and volume. Tripropellant systems like MAKS are feasible. Air breathing vs only rockets is another tradeoff issue: breathing air reduces LOX mass and tankage significantly but increases vehicle mass and TPS complexity.

The airlaunch for hybrid air vehicles post is about a two stage vehicle.

Achieving SSTO and RLV is indeed a very difficult problem with chemical engines. My current hopes are that polywell fusion is the holy grail.
Title: Re: RE: SSTO Thread
Post by: mlorrey on 01/09/2009 05:16 pm
I concur with you on the two stage comment.  But I believe technically speaking that an air launch system is not classified as a stage by the keepers of the official records.  It will be interesting to see how they classify this one since it will potentially use rocket engines for power plants.


Actually, there are tradeoffs. LH2 is too low a density for feasible SSTO RLV, it mandates too much vehicle mass and volume. Tripropellant systems like MAKS are feasible. Air breathing vs only rockets is another tradeoff issue: breathing air reduces LOX mass and tankage significantly but increases vehicle mass and TPS complexity.

The airlaunch for hybrid air vehicles post is about a two stage vehicle.

Achieving SSTO and RLV is indeed a very difficult problem with chemical engines. My current hopes are that polywell fusion is the holy grail.

What is interesting is that altitude alone increases useful payload. Apparently the X-33 with a metal tank replacing the failed composite one would have had zero payload capacity when launched from sea level, but several thousand kg if launched from a high altitude site, like the White Sands launch site annex in Utah, or in White Sands itself, both locations at or above 4000 ft altitude.

Being air launched at 600 mph and 35,000 ft altitude saves you about 5% on your mass fraction, according to one thing I read from Mitchell Clapp.

Personally I still count a mothership as a stage of sorts, whether its drop launched, towed, or air refuelling the orbital vehicle.
Title: Re: RE: SSTO Thread
Post by: Patchouli on 01/09/2009 05:20 pm


Being air launched at 600 mph and 35,000 ft altitude saves you about 5% on your mass fraction, according to one thing I read from Mitchell Clapp.

Personally I still count a mothership as a stage of sorts, whether its drop launched, towed, or air refuelling the orbital vehicle.

Who cares if it's counted as a stage all that matters is that it's safe, affordable , and most important of all works.
Air launching also eliminates the need for the engines to operate at sea level and even aerospikes suffer from a loss of ISP during sea level operation.

If you can get to have an extra 15 to 20 sec/kg of isp on the first 40 seconds of operation plus the small speed and altitude boost from being air launched it will help the mass fraction a lot.
Title: Re: SSTO Thread
Post by: indaco1 on 01/09/2009 06:14 pm
In theory the best place on Earth surface for a launch is the top of Chimborazo Mount, Ecuador.

It's the farthest point from the center of the Earth and, being exactly on the equator, rotation speed of Earth is maximized. 

I know that what's important is air density for engine efficiency and drag. Altitude and distance from the center "per se" are much less important.

(http://upload.wikimedia.org/wikipedia/commons/thumb/b/bf/Chimborazofromwest.JPG/300px-Chimborazofromwest.JPG)

http://en.wikipedia.org/wiki/Chimborazo_(volcano)

I don't even try to guess if the payload increase could compensate the costs and troubles of a launching pad on the top of a vulcan very far from everything.   Probably not.
Title: Re: SSTO Thread
Post by: KelvinZero on 01/09/2009 11:38 pm
In theory the best place on Earth surface for a launch is the top of Chimborazo Mount, Ecuador.

It's the farthest point from the center of the Earth and, being exactly on the equator, rotation speed of Earth is maximized. 

I know that what's important is air density for engine efficiency and drag. Altitude and distance from the center "per se" are much less important.

I don't even try to guess if the payload increase could compensate the costs and troubles of a launching pad on the top of a vulcan very far from everything.   Probably not.

Looks like a nice location to put something like the hopper :)

http://en.wikipedia.org/wiki/Hopper_(spacecraft)

I was really surprised when I saw this. How serious was this Hopper idea?

Title: Re: SSTO Thread
Post by: mlorrey on 01/09/2009 11:52 pm
In theory the best place on Earth surface for a launch is the top of Chimborazo Mount, Ecuador.

It's the farthest point from the center of the Earth and, being exactly on the equator, rotation speed of Earth is maximized. 

I know that what's important is air density for engine efficiency and drag. Altitude and distance from the center "per se" are much less important.

(http://upload.wikimedia.org/wikipedia/commons/thumb/b/bf/Chimborazofromwest.JPG/300px-Chimborazofromwest.JPG)

http://en.wikipedia.org/wiki/Chimborazo_(volcano)

I don't even try to guess if the payload increase could compensate the costs and troubles of a launching pad on the top of a vulcan very far from everything.   Probably not.

Oh what you do there is assemble your rocket horizontally, like soyuz and falcon do, your launch tower is a big honking train car with afterburning jet engines on the sides, it launches horizontally and uses a track that starts down on the altiplano and runs up the side of the volcano. Main question is whether the stages can handle the extra g's laterally from the ramping upward. Talk about holy rollercoasters....
Title: Re: RE: SSTO Thread
Post by: Kaputnik on 01/11/2009 12:34 pm
Apparently the X-33 with a metal tank replacing the failed composite one would have had zero payload capacity when launched from sea level

Was the X33 supposed to have a payload?
Title: Re: RE: SSTO Thread
Post by: mlorrey on 01/12/2009 03:11 am
Apparently the X-33 with a metal tank replacing the failed composite one would have had zero payload capacity when launched from sea level

Was the X33 supposed to have a payload?

X-33 was not designed to carry a payload or even to reach orbit, it was a scale proof-of-technology of what would have been the Venturestar launcher. It was only intended to reach Mach 15 originally.

X-33 was to have 2 XRS-2200 linear aerospike engines and the Venturestar was to have six times the thrust of the X-33 (and twice as long and wide). Venturestar's payload was to be 59,000 lb.

Later on, Popular Mechanics came out with their "the new area 51" article claiming a site in Utah was where the air force was launching a secret copy of the X-33 as a first stage RASCAL-type booster flying pop-up missions:

http://www.popularmechanics.com/technology/military_law/1281151.html?page=4
Title: Re: SSTO Thread
Post by: kkattula on 01/12/2009 09:10 am
I was going to mention tri-propellant & MAKS too.  Although given the throttling issue, you might just be better off with 2 or more high thrust LOX/Kero engines, which are shut down at altitude, then fire up a lower thrust, high Isp LOX/LH2 engine. 3 tanks; 1 Kero & 1 LH2 about the same size, and a LOX tank more than twice as big.

For an almost SSTO, put some or all of the Kero in drop tanks, which are a well-developed technology for aircraft.

Title: Re: SSTO Thread
Post by: William Barton on 01/12/2009 10:46 am
In theory the best place on Earth surface for a launch is the top of Chimborazo Mount, Ecuador.

It's the farthest point from the center of the Earth and, being exactly on the equator, rotation speed of Earth is maximized. 

I know that what's important is air density for engine efficiency and drag. Altitude and distance from the center "per se" are much less important.

(http://upload.wikimedia.org/wikipedia/commons/thumb/b/bf/Chimborazofromwest.JPG/300px-Chimborazofromwest.JPG)

http://en.wikipedia.org/wiki/Chimborazo_(volcano)

I don't even try to guess if the payload increase could compensate the costs and troubles of a launching pad on the top of a vulcan very far from everything.   Probably not.

Oh what you do there is assemble your rocket horizontally, like soyuz and falcon do, your launch tower is a big honking train car with afterburning jet engines on the sides, it launches horizontally and uses a track that starts down on the altiplano and runs up the side of the volcano. Main question is whether the stages can handle the extra g's laterally from the ramping upward. Talk about holy rollercoasters....

What you're talking about is Fireball XL-5 (or the Pan Am Clipper from "2001")...
Title: Re: RE: SSTO Thread
Post by: Kaputnik on 01/12/2009 12:32 pm
Apparently the X-33 with a metal tank replacing the failed composite one would have had zero payload capacity when launched from sea level

Was the X33 supposed to have a payload?

X-33 was not designed to carry a payload or even to reach orbit, it was a scale proof-of-technology of what would have been the Venturestar launcher. It was only intended to reach Mach 15 originally.

X-33 was to have 2 XRS-2200 linear aerospike engines and the Venturestar was to have six times the thrust of the X-33 (and twice as long and wide). Venturestar's payload was to be 59,000 lb.

Later on, Popular Mechanics came out with their "the new area 51" article claiming a site in Utah was where the air force was launching a secret copy of the X-33 as a first stage RASCAL-type booster flying pop-up missions:

http://www.popularmechanics.com/technology/military_law/1281151.html?page=4

Then what did you mean when you said "Apparently the X-33 with a metal tank replacing the failed composite one would have had zero payload capacity" ???
Title: Re: RE: SSTO Thread
Post by: mlorrey on 01/12/2009 07:18 pm
Apparently the X-33 with a metal tank replacing the failed composite one would have had zero payload capacity when launched from sea level

Was the X33 supposed to have a payload?

X-33 was not designed to carry a payload or even to reach orbit, it was a scale proof-of-technology of what would have been the Venturestar launcher. It was only intended to reach Mach 15 originally.

X-33 was to have 2 XRS-2200 linear aerospike engines and the Venturestar was to have six times the thrust of the X-33 (and twice as long and wide). Venturestar's payload was to be 59,000 lb.

Later on, Popular Mechanics came out with their "the new area 51" article claiming a site in Utah was where the air force was launching a secret copy of the X-33 as a first stage RASCAL-type booster flying pop-up missions:

http://www.popularmechanics.com/technology/military_law/1281151.html?page=4

Then what did you mean when you said "Apparently the X-33 with a metal tank replacing the failed composite one would have had zero payload capacity" ???

I had misremembered what I had read, but the idea was that the X-33 could be used as a first stage to launch an upper stage and a good sized payload of several thousand kg IF it was launched from an altitude like 4000-4500 ft, but if launched from sea level its ability to orbit any meaningful payload on a second stage was deemed negligible. Given it was never even intended for such a mission, it was meant as a technology demonstrator (ostensibly), that should never have been a factor in any cancellation, however IMHO the potential for such a mission should have at least merited the USAF pursue the concept for the RASCAL program.
Title: Re: SSTO Thread
Post by: kevin-rf on 01/18/2009 11:27 pm
After watching the latest Delta IV launch with ablative nozzles I was wondering. Has anyone thought about handling the sea level to vac nozzle problem with an ablative? Something that melts or burnss away to change the expansion ratio from sea level optimized to vac optimized.

Just thinking about it, any thoughts?

Lining the nozzle with solid rocket fuel maybe 8)

Title: Re: SSTO Thread
Post by: mlorrey on 01/19/2009 12:32 am
After watching the latest Delta IV launch with ablative nozzles I was wondering. Has anyone thought about handling the sea level to vac nozzle problem with an ablative? Something that melts or burnss away to change the expansion ratio from sea level optimized to vac optimized.

Just thinking about it, any thoughts?

Lining the nozzle with solid rocket fuel maybe 8)

Um, isnt the mark of a vac nozzle a higher expansion ratio between the neck of the de laval nozzle and the end of the bell? If so, it wouldn't be possible to do what you suggest. Erosion of a solid fuel lining would open up the neck more than the end of the bell and reduce expansion ratio.

Having the nozzle be lined to be thicker toward the end and erode the end outward would increase the expansion ratio however the nozzle length would not change and you would thus have some issues with whether the exhaust will expand fast enough in that distance.

Finally, whatever material you use there to line the nozzle would be highly resistant to combustion to last over a minute, thus it would likely be a heat absorber, not emitter, and reduce performance of the fuel combustion.
Title: Re: SSTO Thread
Post by: HMXHMX on 01/19/2009 06:34 am
After watching the latest Delta IV launch with ablative nozzles I was wondering. Has anyone thought about handling the sea level to vac nozzle problem with an ablative? Something that melts or burnss away to change the expansion ratio from sea level optimized to vac optimized.

Just thinking about it, any thoughts?

Lining the nozzle with solid rocket fuel maybe 8)



If one builds a high area ratio nozzle with a jettisonable ring at the sea level (or actually 40K ft altitude) point, you get the right results.  The ring is dispatched when the time is right but until then forces the flow to cleanly trip from the wall.  If desired, one can inject gas behind the ring or even vent the nozzle to ambient, but that tends to complicate the system.

I call it a "Stiennon Ring" after a colleague who first described the idea to me in the 1980s, but I believe the Russians (as usual) may have thought about it first, and I also think I subsequently saw similar US concepts from the fertile 1960's.  The dual bell approach is another attempt to implement the clean separation notion.
Title: Re: SSTO Thread
Post by: DeepSpaceorbust on 01/19/2009 07:39 am
Obviously the technology for SSTO is quite far off, but an effective alternative may be provided by photonic laser propulsion. Currently the maximum weight to even get an object airborne is around 10kg, but if vastly improved, the technology could take the place of the first stage, or provide support for the entire launch.
Title: Re: SSTO Thread
Post by: kevin-rf on 01/19/2009 12:51 pm
If desired, one can inject gas behind the ring or even vent the nozzle to ambient, but that tends to complicate the system.

A good place inject TAN propellants?

Quote
I call it a "Stiennon Ring" after a colleague who first described the idea to me in the 1980s, but I believe the Russians (as usual) may have thought about it first, and I also think I subsequently saw similar US concepts from the fertile 1960's.  The dual bell approach is another attempt to implement the clean separation notion.

So you could place a larger more vac optimized bell on an RS-68 and greatly improve it's vac ISP using the Stiennon Ring. Interesting thought.
Title: Re: SSTO Thread
Post by: HMXHMX on 01/19/2009 06:37 pm
If desired, one can inject gas behind the ring or even vent the nozzle to ambient, but that tends to complicate the system.

A good place inject TAN propellants?

Quote
I call it a "Stiennon Ring" after a colleague who first described the idea to me in the 1980s, but I believe the Russians (as usual) may have thought about it first, and I also think I subsequently saw similar US concepts from the fertile 1960's.  The dual bell approach is another attempt to implement the clean separation notion.

So you could place a larger more vac optimized bell on an RS-68 and greatly improve it's vac ISP using the Stiennon Ring. Interesting thought.

If you do TAN injection, you don't need the ring any more.  The dual point of TAN is to increase thrust and allow for a high area ratio nozzle.

Regarding your second point, yes, I believe that would be feasible.


Title: Re: SSTO Thread
Post by: jongoff on 01/19/2009 07:58 pm
If one builds a high area ratio nozzle with a jettisonable ring at the sea level (or actually 40K ft altitude) point, you get the right results.  The ring is dispatched when the time is right but until then forces the flow to cleanly trip from the wall.  If desired, one can inject gas behind the ring or even vent the nozzle to ambient, but that tends to complicate the system.

I call it a "Stiennon Ring" after a colleague who first described the idea to me in the 1980s, but I believe the Russians (as usual) may have thought about it first, and I also think I subsequently saw similar US concepts from the fertile 1960's.  The dual bell approach is another attempt to implement the clean separation notion.

There are a few other approaches to forcing flow separation, that have been experimentally demonstrated over the years.  One or two of them were particularly interesting because they offer the potential for continuous flow separation control without being heinously complicated.  There is even one or two ways to possibly do a passive system based on some ancient Aerojet research that I stumbled on a while back.

~Jon
Title: Re: SSTO Thread
Post by: jongoff on 01/19/2009 08:01 pm
If you do TAN injection, you don't need the ring any more.  The dual point of TAN is to increase thrust and allow for a high area ratio nozzle.

Regarding your second point, yes, I believe that would be feasible.

Well, not for a traditional rocket.  But if you're talking about a reusable SSTO, it still might be useful to have both TAN and flow separation control.  If you have to throttle down the engine in the atmosphere (for powered landing for instance), FSC techniques allow you to do that without sacrificing expansion ratio for your in-space operations, or requiring separate landing engines.

~Jon
Title: Re: SSTO Thread
Post by: tnphysics on 01/20/2009 11:50 am
Current flight rates don't support the use of RLV's

Well, more correctly current flight rates combined with current ways of doing things don't support the use of RLVs.  There are actually ways that you could get enough flight rate to support an RLV even with only existing demand.  But it would take some change in the way some things are done.

~Jon

What are those methods? PDs or putting everything on one launcher?
Title: Re: SSTO Thread
Post by: jongoff on 01/20/2009 03:35 pm
What are those methods? PDs or putting everything on one launcher?

One idea presented by a friend of mine out in UK was that most of the mass on orbit of a satellite bound for GEO is the propellant to boost it there.  The "beginning of life" mass--the mass of a satellite after the circularization burn is complete--of the most massive GEO birds today is only around 5mT, with many of them being much smaller than that.  However, the total mass needed in LEO to get that much mass into GTO is typically 3-4x that, once you include the kick stage and all the propellants.  His initial thought he presented was to prelaunch 2-4 "propulsion modules", dock them together, and then launch the actual satellite itself on the last launch, dock it with the stack in LEO, and then send it off to GEO.  Each of the pieces could fit on a small RLV (5mT to orbit would cover pretty much the biggest stuff on the market).  By capturing only 1/4-1/2 of the existing GEO market, his theory was you could get flight rates high enough to make that work--and the kicker is that doing it that way wouldn't require any changes to the actual satellite other than not loading the circularization burn propellants during payload processing.

Now, there are better methods (small depot tanks up the kick stage instead of doing tinkertoys modules, eventually having a reusable kick stage, etc) but that's the basic concept.  The big challenge is that GEO sat customers are really conservative.  While they definitely will go with lower launch cost options once they are proven (people still launch on Protons and Zenits, both of which have worse records than some other more expensive but less used launchers), they're sticklers about not being the first or second customer for something.  Now, if NASA did the smart thing, and acted as an anchor tenant for such services by using them to send a probe or two to the Moon or Mars, that might pave the way...

But there's a lot of work between here and there--both propellant transfer and RLVs.  Personally, I find depots to be the less daunting of the two (though my day job is working on the other problem).

~Jon
Title: Re: SSTO Thread
Post by: kevin-rf on 01/20/2009 03:48 pm
If you have to throttle down the engine in the atmosphere (for powered landing for instance), FSC techniques allow you to do that without sacrificing expansion ratio for your in-space operations, or requiring separate landing engines.

With the ejectable ring doesn't that require inserting a new ring in the engine before coming back for a landing? ...
Title: Re: SSTO Thread
Post by: jongoff on 01/20/2009 04:26 pm
With the ejectable ring doesn't that require inserting a new ring in the engine before coming back for a landing? ...

I wasn't suggesting using that method.  There are other approaches for flow separation control that can potentially allow you to turn the flow separation control on and off.

~Jon
Title: Re: SSTO Thread
Post by: A_M_Swallow on 01/21/2009 12:56 am
{snip}

Now, there are better methods (small depot tanks up the kick stage instead of doing tinkertoys modules, eventually having a reusable kick stage, etc) but that's the basic concept.  The big challenge is that GEO sat customers are really conservative.  While they definitely will go with lower launch cost options once they are proven (people still launch on Protons and Zenits, both of which have worse records than some other more expensive but less used launchers), they're sticklers about not being the first or second customer for something.  Now, if NASA did the smart thing, and acted as an anchor tenant for such services by using them to send a probe or two to the Moon or Mars, that might pave the way...

But there's a lot of work between here and there--both propellant transfer and RLVs.  Personally, I find depots to be the less daunting of the two (though my day job is working on the other problem).

~Jon
Depots and RLV are not incomparable.

The probe's LV upper stage could be refuelled by the depot allowing a single reuse as a kicker stage.  This saves launching the mass of an engine, tanks and heat shield for a kicker stage.

The tanker to fill the depot could be launched on an RLV.  Since the tanker does not need its solar panels exposed for the next 5 years it may be able to keep is faring.  The faring could then be used as part of the heat shield, if a suitable material can be found.  Alternatively the faring could be the outer wall of the fuel tank.
Title: Re: SSTO Thread
Post by: cheesybagel on 01/25/2009 03:25 pm
What about borane fuels? They were supposed to offer the performance of hydrogen at the density of kerosene, but I believe that their was a problem.

The rockets proposed at the time used Fluorine as oxidant and Borane as fuel. The problems were toxicity, corrosion and clumping IIRC. There are ways of improving the ISP of kerosene rockets slightly. e.g. the Russians pre-chilled kerosene to make it denser, and used sintin (synthetic kerosene) which allegedly is only made of some specific hydrocarbon compound instead of the mix-mash that is regular kerosene. Then there are the middle ground hydrocarbons between kerosene and hydrogen. Proposals to use liquid propane or methane are often bandied around.

As for LOX/LH2 you can increase thrust at the cost of ISP by, varying the mixture ratio, adding more LOX. LOX has a much higher density than LH2 so you get higher overall propellant density. Having a variable mixture ratio LOX/LH2 engine reduces a lot of the advantage of going for a LOX/LH2/LCH4 tri-propellant engine for example.
Title: Re: SSTO Thread
Post by: William Barton on 01/25/2009 04:02 pm
What about borane fuels? They were supposed to offer the performance of hydrogen at the density of kerosene, but I believe that their was a problem.

The rockets proposed at the time used Fluorine as oxidant and Borane as fuel. The problems were toxicity, corrosion and clumping IIRC. There are ways of improving the ISP of kerosene rockets slightly. e.g. the Russians pre-chilled kerosene to make it denser, and used sintin (synthetic kerosene) which allegedly is only made of some specific hydrocarbon compound instead of the mix-mash that is regular kerosene. Then there are the middle ground hydrocarbons between kerosene and hydrogen. Proposals to use liquid propane or methane are often bandied around.

As for LOX/LH2 you can increase thrust at the cost of ISP by, varying the mixture ratio, adding more LOX. LOX has a much higher density than LH2 so you get higher overall propellant density. Having a variable mixture ratio LOX/LH2 engine reduces a lot of the advantage of going for a LOX/LH2/LCH4 tri-propellant engine for example.


Are there any advantages to LNG as a fuel? It's easy to come by, relatively cheap, and a large manufacturing base exists, including fleets of specially equipped tankers. It wouldn't cost that much to put a sea delivery terminal/pipe offshore from Canaveral or Wallops.
Title: Re: SSTO Thread
Post by: kevin-rf on 01/25/2009 06:54 pm
It wouldn't cost that much to put a sea delivery terminal/pipe offshore from Canaveral or Wallops.

I would be willing to bet natural gas (methane) is available at both the cape and wallops. At most all you would need to do is install a chiller to chill it into it's liquid form.

I think it is more an issue of no one has actually flow a Methane rocket (yet).
Title: Re: SSTO Thread
Post by: Nascent Ascent on 01/26/2009 02:19 am
You could also generate relatively easily Hydrogen from the Methane too.
Title: Re: SSTO Thread
Post by: Proponent on 01/26/2009 09:51 am
I think it is more an issue of no one has actually flow a Methane rocket (yet).

Actually, the very first liquid-fuel rocket in Europe (about 75 years ago) burned methane and lox!  But certainly no current system uses methane.

What I wonder, though, is why everybody is so excited about methane and not propane.  According to Bruce Dunn (http://www.dunnspace.com/alternate_ssto_propellants.htm) and others, propane generally outperforms methane, and it's less cryogenic to boot.

The one place where I can see methane being preferable is for in situ fuel production, because it's probably easier to manufacture methane than propane.  This consideration, however, is irrelevant for earth launch and is far in the future for any other system, except maybe on the moon.
Title: Re: SSTO Thread
Post by: kevin-rf on 01/26/2009 12:33 pm

Actually, the very first liquid-fuel rocket in Europe (about 75 years ago) burned methane and lox!  But certainly no current system uses methane.

What I wonder, though, is why everybody is so excited about methane and not propane.  According to Bruce Dunn (http://www.dunnspace.com/alternate_ssto_propellants.htm) and others, propane generally outperforms methane, and it's less cryogenic to boot.

The one place where I can see methane being preferable is for in situ fuel production, because it's probably easier to manufacture methane than propane.  This consideration, however, is irrelevant for earth launch and is far in the future for any other system, except maybe on the moon.

Though people are playing with methane and propane as we type...

I would argue if you are going to use LOX (I can not see a chemical SSTO without it) you have to handle Cryo fuels anyway. Methane does have a slightly higher ISP but lower density than propane so we it is as always a tradeoff.

Not to pull us off topic, but the only "in situ" methane production I can think of is mars. Both Carbon and Hydrogen are scare on the moon, so it makes sense to use the H2 directly. At this point we have detected methane releases on mars. Meaning we (big unknown what form it really is in and how it is locked up) might be better off drilling for natural gas on mars. Big drilling rig vs. big plumbers wet dream ;)
Title: Re: SSTO Thread
Post by: jongoff on 01/26/2009 02:50 pm

Actually, the very first liquid-fuel rocket in Europe (about 75 years ago) burned methane and lox!  But certainly no current system uses methane.

What I wonder, though, is why everybody is so excited about methane and not propane.  According to Bruce Dunn (http://www.dunnspace.com/alternate_ssto_propellants.htm) and others, propane generally outperforms methane, and it's less cryogenic to boot.

The one place where I can see methane being preferable is for in situ fuel production, because it's probably easier to manufacture methane than propane.  This consideration, however, is irrelevant for earth launch and is far in the future for any other system, except maybe on the moon.

Though people are playing with methane and propane as we type...

I would argue if you are going to use LOX (I can not see a chemical SSTO without it) you have to handle Cryo fuels anyway. Methane does have a slightly higher ISP but lower density than propane so we it is as always a tradeoff.

Not to pull us off topic, but the only "in situ" methane production I can think of is mars. Both Carbon and Hydrogen are scare on the moon, so it makes sense to use the H2 directly. At this point we have detected methane releases on mars. Meaning we (big unknown what form it really is in and how it is locked up) might be better off drilling for natural gas on mars. Big drilling rig vs. big plumbers wet dream ;)

An interesting thing to note is that "sub-cooled" propane (propane cooled down to just above LOX temperature) has a density greater than Kerosene, has almost as good of Isp as methane, is an amazing coolant, and is cold enough that the merkapten stenchants all fall out during chill-down.  With the differences in mixture ratio to get the best Isp, a LOX/sub-cooled propane rocket ends up having tanks with the exact same proportions as a LOX/Kero rocket.

And there was at least one company here in Mojave firing big ~20-24klbf LOX/Propane (not subcooled) rockets up until recently...

~Jon
Title: Re: SSTO Thread
Post by: relyon on 01/26/2009 08:42 pm
... has almost as good of Isp as methane ...

I understand everything except this statement. The C/H mass ratio of propane (~36:4) is higher than methane (~12:4) and that of the exhaust products correspondingly similar. With consistent mixture ratios across a range of inlet fuel temperatures, I'd expect Isp to stay relatively constant. Is the mixture ratio in "sub-cooled" propane engines altered to make use of the different thermal properties of the fuel (cooling) or is there something else I'm missing?

Bob
Title: Re: SSTO Thread
Post by: khallow on 01/26/2009 09:36 pm
Hmmm, if ethane isn't too hard to produce from methane, then that's another Martian fuel choice. It has somewhat better handling properties and density for a touch less isp. And of course, from ethane you can make ethylene, base stock for the plastics industry.
Title: Re: SSTO Thread
Post by: yinzer on 01/26/2009 09:40 pm
... has almost as good of Isp as methane ...

I understand everything except this statement. The C/H mass ratio of propane (~36:4) is higher than methane (~12:4) and that of the exhaust products correspondingly similar. With consistent mixture ratios across a range of inlet fuel temperatures, I'd expect Isp to stay relatively constant. Is the mixture ratio in "sub-cooled" propane engines altered to make use of the different thermal properties of the fuel (cooling) or is there something else I'm missing?

If you burn stoichiometrically, the average molecular weight of the exhaust is 29.1 for propane (3 CO2 @ 44, 4 H2O @ 18) and 26.7 for methane (1 CO2 @ 44, 4 H2O @ 18), and 31 for RP-1 (1 CO2, 1 H2O).  For LH2/LOX it's 18.

If you run fuel-rich to leave some unburned hydrogen the numbers change a bit, but not a huge amount.  Propane is roughly halfway between methane and kerosene, and all are a lot higher than liquid hydrogen.
Title: Re: SSTO Thread
Post by: Lampyridae on 01/26/2009 10:36 pm
Propylene is another one, it also has similar characteristics to RP-1 when you subcool it. Trouble is, you start getting plastics forming in your turbopumps and cooling channels! Garvey Aerospace has been messing around with propylene and aerospikes.

http://www.astronautix.com/engines/garspike.htm

This one uses ethanol.

http://www.csulb.edu/colleges/coe/mae/views/projects/rocket/news_2008/aerospike06252008.shtml
Title: Re: SSTO Thread
Post by: relyon on 01/27/2009 04:19 am
If you burn stoichiometrically, the average molecular weight of the exhaust is 29.1 for propane (3 CO2 @ 44, 4 H2O @ 18) and 26.7 for methane (1 CO2 @ 44, 4 H2O @ 18), and 31 for RP-1 (1 CO2, 1 H2O).  For LH2/LOX it's 18.

If you run fuel-rich to leave some unburned hydrogen the numbers change a bit, but not a huge amount.  Propane is roughly halfway between methane and kerosene, and all are a lot higher than liquid hydrogen.

Precisely what I was thinking. Higher exhaust velocities could potentially offset the [average] molecular mass of the combustion products, but I don't see that being possible given the energy potentials of the fuel/oxidizer combinations being discussed (see http://www.engineeringtoolbox.com/adiabatic-flame-temperature-d_996.html (http://www.engineeringtoolbox.com/adiabatic-flame-temperature-d_996.html)) for some comparative adiabatic flame temperatures, albeit at room conditions).

Bob
Title: Re: SSTO Thread
Post by: jongoff on 01/27/2009 04:55 am
... has almost as good of Isp as methane ...

I understand everything except this statement. The C/H mass ratio of propane (~36:4) is higher than methane (~12:4) and that of the exhaust products correspondingly similar. With consistent mixture ratios across a range of inlet fuel temperatures, I'd expect Isp to stay relatively constant. Is the mixture ratio in "sub-cooled" propane engines altered to make use of the different thermal properties of the fuel (cooling) or is there something else I'm missing?

Honestly, I'm not a propellant chemist, but most numbers I've seen only give LOX/Methane a ~2-3% higher Isp than LOX/propane.  Which in my mind is really not worth it when you look at how much worse bulk density LOX/Methane has.

~Jon
Title: Re: SSTO Thread
Post by: jongoff on 01/27/2009 04:58 am
If you burn stoichiometrically, the average molecular weight of the exhaust is 29.1 for propane (3 CO2 @ 44, 4 H2O @ 18) and 26.7 for methane (1 CO2 @ 44, 4 H2O @ 18), and 31 for RP-1 (1 CO2, 1 H2O).  For LH2/LOX it's 18.

If you run fuel-rich to leave some unburned hydrogen the numbers change a bit, but not a huge amount.  Propane is roughly halfway between methane and kerosene, and all are a lot higher than liquid hydrogen.

Precisely what I was thinking. Higher exhaust velocities could potentially offset the [average] molecular mass of the combustion products, but I don't see that being possible given the energy potentials of the fuel/oxidizer combinations being discussed (see http://www.engineeringtoolbox.com/adiabatic-flame-temperature-d_996.html (http://www.engineeringtoolbox.com/adiabatic-flame-temperature-d_996.html)) for some comparative adiabatic flame temperatures, albeit at room conditions).

I guess it just depends on how loosely you use the term "almost".  To me, 10s worth of Isp is not a lot of difference.  You can easily have a situation where you could get a LOX/Propane engine with better performance than a LOX/CH4 one just because of design details.  To me that's "almost as good of Isp".

~Jon
Title: Re: SSTO Thread
Post by: Proponent on 01/27/2009 01:09 pm
[T]he only "in situ" methane production I can think of is mars. Both Carbon and Hydrogen are scare on the moon, so it makes sense to use the H2 directly

We do know that neutron spectrometer on Lunar Prospector produced evidence of hydrogen at the lunar south pole.  People tend to tie that result Clementine and Arecibo data suggesting the presence of water ice, but I wonder whether the hydrogen might not be in the form of organic (carbon-bearing) molecules.  This isn't my idea, BTW, but I don't remember where I saw it.

But, I agree with you that in situ propellants are still pretty far in the future.
Title: Re: SSTO Thread
Post by: Proponent on 01/27/2009 01:24 pm
To me, 10s worth of Isp is not a lot of difference.  You can easily have a situation where you could get a LOX/Propane engine with better performance than a LOX/CH4 one just because of design details.  To me that's "almost as good of Isp".

That's exactly what I think--a few seconds' worth of lost specific impulse seems a small price to pay for a density that's 60% higher.

It's not like propane is an exotic chemical: its properties are well known and it's cheap.  So, I ask, why is there so much excitement about methane and so little about propane?  For that matter, might one not wonder why propane was not (as I am aware) ever considered as a fuel in the 1950s or even earlier as a successor to alcohol.  It was readily available even then and its use might have obviated the need to develop RP-1.

I got to thinking about propane again, BTW, after reading a post last month by Gary Hudson on your blog.  He mentioned that methane was better for a VaPaK system, but didn't comment on non-VaPaK applications.

I'm a huge fan of your blog, BTW--it's a great resource for us all.
Title: Re: SSTO Thread
Post by: kkattula on 01/27/2009 01:33 pm

Actually, the very first liquid-fuel rocket in Europe (about 75 years ago) burned methane and lox!  But certainly no current system uses methane.

What I wonder, though, is why everybody is so excited about methane and not propane.  According to Bruce Dunn (http://www.dunnspace.com/alternate_ssto_propellants.htm) and others, propane generally outperforms methane, and it's less cryogenic to boot.

The one place where I can see methane being preferable is for in situ fuel production, because it's probably easier to manufacture methane than propane.  This consideration, however, is irrelevant for earth launch and is far in the future for any other system, except maybe on the moon.

Though people are playing with methane and propane as we type...

I would argue if you are going to use LOX (I can not see a chemical SSTO without it) you have to handle Cryo fuels anyway. Methane does have a slightly higher ISP but lower density than propane so we it is as always a tradeoff.
...

Armadillo Aerospace have hovered a tethered rocket on LOX/Methane for 60 seconds at least 5 times. But this news is a month old, so they could have improved a lot since then at the rate they develop.

http://www.armadilloaerospace.com/n.x/Armadillo/Home/News


Airlaunch LLC are developing a 2-stage, air-launched, LOX/Propane rocket called the QuickReach. I'm not sure if it's sub-cooled propane. I suspect not since they use VAPAK, but I could easily be wrong.

http://www.airlaunchllc.com/index.htm
Title: Re: SSTO Thread
Post by: William Barton on 01/27/2009 01:37 pm
Wasn't somebody (maybe in Denver) working on a silane-propellant SSTO idea ten or fifteen years back? I have some vague memory it was a group associated with an NSS chapter, but I can't seem to recover it enough to try a lookup.
Title: Re: SSTO Thread
Post by: Proponent on 01/27/2009 01:38 pm
I was going to ask about propane's non-pre-chilled cooling properties, but then I answered my own question by looking at this old thread (http://yarchive.net/space/rocket/fuels/propane.html).

And there was at least one company here in Mojave firing big ~20-24klbf LOX/Propane (not subcooled) rockets up until recently...

Would you be at liberty to tell us which company?  What the intended application was?  Why firings stopped?
Title: Re: SSTO Thread
Post by: Proponent on 01/27/2009 02:54 pm
Airlaunch LLC are developing a 2-stage, air-launched, LOX/Propane rocket called the QuickReach. I'm not sure if it's sub-cooled propane. I suspect not since they use VAPAK, but I could easily be wrong.

http://www.airlaunchllc.com/index.htm

Thanks--that is interesting.  But now I am really confused.  This is, as you say, a propane-fueled vehicle.  It also uses VaPak propellant pressurization.  Gary Hudson is deeply involved.  But, on Selenian Boondocks Gary Hudson mentions (http://selenianboondocks.com/2008/12/target-fixation) that methane is better than propane for VaPak for operational reasons.  Perhaps AirLaunch recently switched from propane to methane and the information on the AirLaunch site is out of date?
Title: Re: SSTO Thread
Post by: HMXHMX on 01/27/2009 04:47 pm
Airlaunch LLC are developing a 2-stage, air-launched, LOX/Propane rocket called the QuickReach. I'm not sure if it's sub-cooled propane. I suspect not since they use VAPAK, but I could easily be wrong.

http://www.airlaunchllc.com/index.htm

Thanks--that is interesting.  But now I am really confused.  This is, as you say, a propane-fueled vehicle.  It also uses VaPak propellant pressurization.  Gary Hudson is deeply involved.  But, on Selenian Boondocks Gary Hudson mentions (http://selenianboondocks.com/2008/12/target-fixation) that methane is better than propane for VaPak for operational reasons.  Perhaps AirLaunch recently switched from propane to methane and the information on the AirLaunch site is out of date?

I'll try to clarify.

AirLaunch traded propane and methane (LNG, actually) in 2003.  Performance defined as payload deployed was within 1% of each other; as many others have noted there is not much difference between the two propellants.   But we chose propane since it was non-cryogenic and we thought that would be beneficial with regard to pressure/temperature control while in the aircraft.  We already had to deal with a cryogen (LOX) and didn't want to complicate the issue. Finally, we thought that propane would be easier to obtain and store than LNG for the particular application.

After development and testing, however, what we found was LNG would make it much easier to control temp and pressure.  This turns out to be a universal truth: if one is using VaPak propellants, the operational temperature of the propellants should be well below ambient.  In propane's case, it might be necessary to cool it on a hot day or warm it on a cold day.  For a pure cryogen, it is only necessary to vent to control temperature.  In hindsight, this is perhaps obvious, but sometimes we can be denser than our propellants...

AirLaunch then demonstrated firing the same engine on LNG, and that works fine.  If Falcon has gone forward we would have argued for a change to LNG.  For purely space launch missions, if VaPak is the pressurization scheme, I would use LNG, especially for external-carriage air-launching.  But there are definitely vehicle concepts where propane is desirable in place of LNG; I leave discovery of those as an exercise for the interested.
Title: Re: SSTO Thread
Post by: jongoff on 02/06/2009 07:05 am
We do know that neutron spectrometer on Lunar Prospector produced evidence of hydrogen at the lunar south pole.  People tend to tie that result Clementine and Arecibo data suggesting the presence of water ice, but I wonder whether the hydrogen might not be in the form of organic (carbon-bearing) molecules.  This isn't my idea, BTW, but I don't remember where I saw it.

It may have been Henry Spencer, or myself repeating him.  Basically the idea goes that if the volatiles are of cometary origin, there's a good chance that at least some of it is in the form of light hydrocarbons or ammonia (since those are also comet constituents).  Or, if it's merely concentrated solar wind, then you'd likely see large amounts of N and C because while rarer, those are much easier to trap in a cold-trap than Hydrogen.

But it's all wild speculation until we get more data.

~Jon
Title: Re: SSTO Thread
Post by: jongoff on 02/06/2009 07:15 am
That's exactly what I think--a few seconds' worth of lost specific impulse seems a small price to pay for a density that's 60% higher.

It's not like propane is an exotic chemical: its properties are well known and it's cheap.  So, I ask, why is there so much excitement about methane and so little about propane?  For that matter, might one not wonder why propane was not (as I am aware) ever considered as a fuel in the 1950s or even earlier as a successor to alcohol.  It was readily available even then and its use might have obviated the need to develop RP-1.

The big problem with Propane is that at room temperature, you have to store it at relatively high pressure for a pump-fed vehicle, its density isn't that great for a pressure-fed vehicle, and in order to solve either of those issues you have to subcool it.  There really are benefits to having a liquid propellant that's nice and easy to handle, storable, and relatively low vapor pressure.  There's a reason why Masten is using LOX/IPA so far--it's just not worth the hassle for what we're trying to do.

And because of those initial issues, RP-1 now has a lot more experience built up with it.  Other than a few RL-10 tests, and Gary's work, I'm not aware of anyone else that has done LOX/Propane tests of any seriousness.  When you go to start a new rocket engine for a company like SpaceX, are you really going to go for a science experiment?  Or are you going to go with something that there is decades of experience using?

I like Propane, and think it makes a lot of sense in some cases, but I can't fault others for sometimes disagreeing.

Quote
I got to thinking about propane again, BTW, after reading a post last month by Gary Hudson on your blog.  He mentioned that methane was better for a VaPaK system, but didn't comment on non-VaPaK applications.

The real place propane shines is as a subcooled (near LOX temp) liquid in a pump-fed rocket--preferrably using an expander cycle.  There you take maximum advantage of its wide liquid range, its excellent thermodynamic properties, its density, and its performance.

Quote
I'm a huge fan of your blog, BTW--it's a great resource for us all.

:-)  Thanks.  I'm glad you've found it interesting!

~Jon
Title: Re: SSTO Thread
Post by: jongoff on 02/06/2009 07:18 am
I would argue if you are going to use LOX (I can not see a chemical SSTO without it) you have to handle Cryo fuels anyway. Methane does have a slightly higher ISP but lower density than propane so we it is as always a tradeoff.

To be fair, a cryogenic fuel is a much bigger pain in the backside than a cryogenic oxidizer (and both John and some of my friends at XCOR agree).  GOX vapors can't burn in air--methane or propane vapors can.  While dealing with those issues isn't a show-stopper, it is a lot more of a hassle than dealing with LOX leaks.

~Jon
Title: Re: SSTO Thread
Post by: kkattula on 02/06/2009 06:09 pm
Airlaunch LLC are developing a 2-stage, air-launched, LOX/Propane rocket called the QuickReach. I'm not sure if it's sub-cooled propane. I suspect not since they use VAPAK, but I could easily be wrong.

http://www.airlaunchllc.com/index.htm

Thanks--that is interesting.  But now I am really confused.  This is, as you say, a propane-fueled vehicle.  It also uses VaPak propellant pressurization.  Gary Hudson is deeply involved.  But, on Selenian Boondocks Gary Hudson mentions (http://selenianboondocks.com/2008/12/target-fixation) that methane is better than propane for VaPak for operational reasons.  Perhaps AirLaunch recently switched from propane to methane and the information on the AirLaunch site is out of date?

I'll try to clarify.

AirLaunch traded propane and methane (LNG, actually) in 2003.  Performance defined as payload deployed was within 1% of each other; as many others have noted there is not much difference between the two propellants.   But we chose propane since it was non-cryogenic and we thought that would be beneficial with regard to pressure/temperature control while in the aircraft.  We already had to deal with a cryogen (LOX) and didn't want to complicate the issue. Finally, we thought that propane would be easier to obtain and store than LNG for the particular application.

After development and testing, however, what we found was LNG would make it much easier to control temp and pressure.  This turns out to be a universal truth: if one is using VaPak propellants, the operational temperature of the propellants should be well below ambient.  In propane's case, it might be necessary to cool it on a hot day or warm it on a cold day.  For a pure cryogen, it is only necessary to vent to control temperature.  In hindsight, this is perhaps obvious, but sometimes we can be denser than our propellants...

AirLaunch then demonstrated firing the same engine on LNG, and that works fine.  If Falcon has gone forward we would have argued for a change to LNG.  For purely space launch missions, if VaPak is the pressurization scheme, I would use LNG, especially for external-carriage air-launching.  But there are definitely vehicle concepts where propane is desirable in place of LNG; I leave discovery of those as an exercise for the interested.

Falcon SLV is cancelled then? I hadn't heard. What a shame.  Are you continuing to develop QuickReach? Seeking alternative funding?
Title: Re: SSTO Thread
Post by: Proponent on 02/07/2009 11:33 am
To be fair, a cryogenic fuel is a much bigger pain in the backside than a cryogenic oxidizer (and both John and some of my friends at XCOR agree).  GOX vapors can't burn in air--methane or propane vapors can.  While dealing with those issues isn't a show-stopper, it is a lot more of a hassle than dealing with LOX leaks.

This is all very interesting, and I think I've learned more from your posts and from HMXHMX's posts in this thread than just about any others I've ever read.

If I could ask a couple of other questions about sub-cooled propellants....

In practice how would one keep the propellant cool in a largish vehicle launched from the earth's surface?  From HMXHMX's posts about the AirLaunch Falcon, it sounds like insulation alone would probably not be sufficient  If cooling is needed, would it be done by circulating propellant or by building a refrigerator around the vehicle?  Or something else entirely...?

Secondly, is the large thermal expansion as a densified propellant warms up to the boiling point a major engineering issue?  I mean, if you're using a cryogen at its boiling point, then as long as your vents don't freeze shut, I would imagine that the worst that's likely to happen is that the tank boils dry.  But if I've got a tank of sub-cooled propane and cooling fails and I can't detank for some reason, do I have a time bomb on my hands?  Picture a tank of propane that's warming up and spurting liquid propane through its vents and may still burst.

EDIT: Corrected attribution of quote
Title: Re: SSTO Thread
Post by: kevin-rf on 02/07/2009 03:17 pm
If cooling is needed, would it be done by circulating propellant or by building a refrigerator around the vehicle?  Or something else entirely...?

The delta uses a heater plus recirculator to keep the fuel at the correct elevated temp.

Something else to think about is to use the lox as a refrigerant for the propane. Centuar uses the LH to keep the LOX from boiling off and only vents H2 during normal flight operations. Assuming the LOX tank is above the Propane tank you should have a LOX pipe that goes through the Propane tank, if you have no insulation on that pipe it will cool your propane and you could use the LOX boiloff to keep everything at the right temp.

btw. I think you are reffering to jongoff and not me in your last post (your quoting is a little messed up). Both he and HMXHMX make excellent contributions I do agree. Now if I could just bring myself to quit my day job and join one of these startups out in the california desert I think I would learn quite a bit.
Title: Re: SSTO Thread
Post by: Proponent on 02/07/2009 04:29 pm
Quote from: kevin-rf link=topic=3915.msg363312#msg363312
I think you are reffering to jongoff and not me in your last post (your quoting is a little messed up).

Quite right; I've now edited my previous post.  And BTW I'm very happy to be reading your posts too!
Title: Re: SSTO Thread
Post by: jongoff on 02/07/2009 04:48 pm
If I could ask a couple of other questions about sub-cooled propellants....

In practice how would one keep the propellant cool in a largish vehicle launched from the earth's surface?  From HMXHMX's posts about the AirLaunch Falcon, it sounds like insulation alone would probably not be sufficient  If cooling is needed, would it be done by circulating propellant or by building a refrigerator around the vehicle?  Or something else entirely...?

You're talking about keeping the propellants subcooled on the pad?  If so, look up a company called Sierra Lobo.  I think they have some papers on their site about densified propellants (another term for subcooled propellants).

Quote
Secondly, is the large thermal expansion as a densified propellant warms up to the boiling point a major engineering issue?  I mean, if you're using a cryogen at its boiling point, then as long as your vents don't freeze shut, I would imagine that the worst that's likely to happen is that the tank boils dry.  But if I've got a tank of sub-cooled propane and cooling fails and I can't detank for some reason, do I have a time bomb on my hands?  Picture a tank of propane that's warming up and spurting liquid propane through its vents and may still burst.

Yeah, that's the one big issue I can see with subcooled propellants.  I've never actually messed with them in person myself, and as far as I know nobody's actually tried to make a stage out of them.  But yes, that expansion from the subcooled density to the boiling point density is an issue that would have to be dealt with.  I honestly haven't put much thought into it yet (since we've stuck with plain-jane Isopropanol so far at Masten).


~Jon
Title: Re: SSTO Thread
Post by: HMXHMX on 02/08/2009 04:25 am
Airlaunch LLC are developing a 2-stage, air-launched, LOX/Propane rocket called the QuickReach. I'm not sure if it's sub-cooled propane. I suspect not since they use VAPAK, but I could easily be wrong.

http://www.airlaunchllc.com/index.htm

Thanks--that is interesting.  But now I am really confused.  This is, as you say, a propane-fueled vehicle.  It also uses VaPak propellant pressurization.  Gary Hudson is deeply involved.  But, on Selenian Boondocks Gary Hudson mentions (http://selenianboondocks.com/2008/12/target-fixation) that methane is better than propane for VaPak for operational reasons.  Perhaps AirLaunch recently switched from propane to methane and the information on the AirLaunch site is out of date?

I'll try to clarify.

AirLaunch traded propane and methane (LNG, actually) in 2003.  Performance defined as payload deployed was within 1% of each other; as many others have noted there is not much difference between the two propellants.   But we chose propane since it was non-cryogenic and we thought that would be beneficial with regard to pressure/temperature control while in the aircraft.  We already had to deal with a cryogen (LOX) and didn't want to complicate the issue. Finally, we thought that propane would be easier to obtain and store than LNG for the particular application.

After development and testing, however, what we found was LNG would make it much easier to control temp and pressure.  This turns out to be a universal truth: if one is using VaPak propellants, the operational temperature of the propellants should be well below ambient.  In propane's case, it might be necessary to cool it on a hot day or warm it on a cold day.  For a pure cryogen, it is only necessary to vent to control temperature.  In hindsight, this is perhaps obvious, but sometimes we can be denser than our propellants...

AirLaunch then demonstrated firing the same engine on LNG, and that works fine.  If Falcon has gone forward we would have argued for a change to LNG.  For purely space launch missions, if VaPak is the pressurization scheme, I would use LNG, especially for external-carriage air-launching.  But there are definitely vehicle concepts where propane is desirable in place of LNG; I leave discovery of those as an exercise for the interested.

Falcon SLV is cancelled then? I hadn't heard. What a shame.  Are you continuing to develop QuickReach? Seeking alternative funding?

QR is terminated, unless another customer comes along.  I don't do investors, so it would have to be gov't funding.

I'll try to get to everyone else's comments/questions in the next few days but can't guarantee when.
Title: Re: SSTO Thread
Post by: mlorrey on 02/08/2009 05:06 am


QR is terminated, unless another customer comes along.  I don't do investors, so it would have to be gov't funding.

I'll try to get to everyone else's comments/questions in the next few days but can't guarantee when.

Um why don't you 'do investors'??
Title: Re: SSTO Thread
Post by: kkattula on 02/08/2009 07:54 am


QR is terminated, unless another customer comes along.  I don't do investors, so it would have to be gov't funding.

I'll try to get to everyone else's comments/questions in the next few days but can't guarantee when.

Um why don't you 'do investors'??

My guess is bad experiences with Rotary Rocket. 

They tend to want ironclad guarantees of high returns in the short to medium term, and don't handle delays very well. I don't imagine SpaceX would have survived to reach orbit, if it had depended on venture capital.
Title: Re: SSTO Thread
Post by: kkattula on 02/08/2009 08:15 am
There are a lot of good ideas out there, that could be explored for less than 1% of NASA's annual Ares I development budget. Yet NASA ignores what should be one of their prime goals. New launch vehicle technology.
Title: Re: SSTO Thread
Post by: HMXHMX on 02/09/2009 04:58 am


QR is terminated, unless another customer comes along.  I don't do investors, so it would have to be gov't funding.

I'll try to get to everyone else's comments/questions in the next few days but can't guarantee when.



Um why don't you 'do investors'??

Short answer: if you draw a Venn diagram of the solution set of the interests of investors and the interests of customers, the intersection of the sets is a small sliver of barely overlapping circles.  Investors are concerned with the next rounds of funding, technology demonstrations to obtain that funding, exit strategies and generally, only short term problems.  Customers have short term concerns as well, true ... they want their product or service as soon as possible and working as promised.

I decided in 2000 that rather than "sell" a product twice, I'd sell it only once, to the end user.  Unfortunately, that currently (largely) means selling to the government, since they have been the customer most likely to finance the development.  That's why I came up with the concept that led to NASA COTS, i.e., get the end user (NASA) to finance the development of a commercial human spaceflight capability.  That's another story, and getting off topic.

I guess that was the long answer after all.
Title: Re: SSTO Thread
Post by: mlorrey on 02/09/2009 07:57 am


QR is terminated, unless another customer comes along.  I don't do investors, so it would have to be gov't funding.

I'll try to get to everyone else's comments/questions in the next few days but can't guarantee when.



Um why don't you 'do investors'??

Short answer: if you draw a Venn diagram of the solution set of the interests of investors and the interests of customers, the intersection of the sets is a small sliver of barely overlapping circles.  Investors are concerned with the next rounds of funding, technology demonstrations to obtain that funding, exit strategies and generally, only short term problems.  Customers have short term concerns as well, true ... they want their product or service as soon as possible and working as promised.

I decided in 2000 that rather than "sell" a product twice, I'd sell it only once, to the end user.  Unfortunately, that currently (largely) means selling to the government, since they have been the customer most likely to finance the development.  That's why I came up with the concept that led to NASA COTS, i.e., get the end user (NASA) to finance the development of a commercial human spaceflight capability.  That's another story, and getting off topic.

I guess that was the long answer after all.

Well thats fair. I have enough experience myself with government contracting, and heard enough from others, that the idea of the governments regulatory and paperwork burden being less costly than that of investors seems rather nonsensical, although I can imagine it really matters who the investors are. If the investors are purely financially motivated and operate on short term time frames, I agree entirely.

I suppose that people like Elon Musk, Paul Allen, and Richard Branson, who are not solely money motivated and are not trapped in short term mindsets, are not the run of the mill investor. The type of investors I have seen in the microcap world, i.e. on the pink sheets, are far more bother than they are worth and are more than likely to be more interested in playing some sort of game on your company than being truly interested in its long term future.

A VC who considers $50-100 million a small amount to risk I suppose is in rather rare company. It is unfortunate though that the government, which does see that as chump change, still will burden you with so much regulatory BS that has nothing to do with being successful and wisely handling the money invested that you wind up needing several times more capital than you would otherwise need. The excuses of "making sure money isn't wasted" tends to excuse a lot more waste in bureaucratic expense than would otherwise be wasted.
Title: Re: SSTO Thread
Post by: HMXHMX on 02/13/2009 05:16 am
Airlaunch LLC are developing a 2-stage, air-launched, LOX/Propane rocket called the QuickReach. I'm not sure if it's sub-cooled propane. I suspect not since they use VAPAK, but I could easily be wrong.

http://www.airlaunchllc.com/index.htm

Thanks--that is interesting.  But now I am really confused.  This is, as you say, a propane-fueled vehicle.  It also uses VaPak propellant pressurization.  Gary Hudson is deeply involved.  But, on Selenian Boondocks Gary Hudson mentions (http://selenianboondocks.com/2008/12/target-fixation) that methane is better than propane for VaPak for operational reasons.  Perhaps AirLaunch recently switched from propane to methane and the information on the AirLaunch site is out of date?

I'll try to clarify.

AirLaunch traded propane and methane (LNG, actually) in 2003.  Performance defined as payload deployed was within 1% of each other; as many others have noted there is not much difference between the two propellants.   But we chose propane since it was non-cryogenic and we thought that would be beneficial with regard to pressure/temperature control while in the aircraft.  We already had to deal with a cryogen (LOX) and didn't want to complicate the issue. Finally, we thought that propane would be easier to obtain and store than LNG for the particular application.

After development and testing, however, what we found was LNG would make it much easier to control temp and pressure.  This turns out to be a universal truth: if one is using VaPak propellants, the operational temperature of the propellants should be well below ambient.  In propane's case, it might be necessary to cool it on a hot day or warm it on a cold day.  For a pure cryogen, it is only necessary to vent to control temperature.  In hindsight, this is perhaps obvious, but sometimes we can be denser than our propellants...

AirLaunch then demonstrated firing the same engine on LNG, and that works fine.  If Falcon has gone forward we would have argued for a change to LNG.  For purely space launch missions, if VaPak is the pressurization scheme, I would use LNG, especially for external-carriage air-launching.  But there are definitely vehicle concepts where propane is desirable in place of LNG; I leave discovery of those as an exercise for the interested.

Falcon SLV is cancelled then? I hadn't heard. What a shame.  Are you continuing to develop QuickReach? Seeking alternative funding?

QuickReach is mostly at CDR level but unless there is a new customer, it won't be built.  I'm open to doing something with it, but frankly won't spend a lot of effort seeking new funding.  The FALCON program had some very specific good points that attracted me in 2003, when "FALCON" became "Falcon"* and lost the strike mission, the rationale for continuing the program really disappeared.

(*no relation to SpaceX Falcon)
Title: Re: SSTO Thread
Post by: HMXHMX on 02/13/2009 05:21 am
To be fair, a cryogenic fuel is a much bigger pain in the backside than a cryogenic oxidizer (and both John and some of my friends at XCOR agree).  GOX vapors can't burn in air--methane or propane vapors can.  While dealing with those issues isn't a show-stopper, it is a lot more of a hassle than dealing with LOX leaks.

This is all very interesting, and I think I've learned more from your posts and from HMXHMX's posts in this thread than just about any others I've ever read.

If I could ask a couple of other questions about sub-cooled propellants....

In practice how would one keep the propellant cool in a largish vehicle launched from the earth's surface?  From HMXHMX's posts about the AirLaunch Falcon, it sounds like insulation alone would probably not be sufficient  If cooling is needed, would it be done by circulating propellant or by building a refrigerator around the vehicle?  Or something else entirely...?

Secondly, is the large thermal expansion as a densified propellant warms up to the boiling point a major engineering issue?  I mean, if you're using a cryogen at its boiling point, then as long as your vents don't freeze shut, I would imagine that the worst that's likely to happen is that the tank boils dry.  But if I've got a tank of sub-cooled propane and cooling fails and I can't detank for some reason, do I have a time bomb on my hands?  Picture a tank of propane that's warming up and spurting liquid propane through its vents and may still burst.

EDIT: Corrected attribution of quote

AirLaunch's quickReach was not using sub-cooled propellants.  Just the opposite.  VaPak propellant are warmed to reach a particular desired vapor pressure, then maintained at the temperature until ignition.  But if one was using sub-cooled propellant, you'd just insulate appropriately.  No big deal.

Regarding your second question: just vent.  One always needs to size the vent to accommodate the gas flow that might result from the condition you describe. 
Title: Re: SSTO Thread
Post by: space_man on 04/09/2009 03:08 pm
Great posts guys! I had a few ideas myself and just wanted to know what you think. As previously mentioned the key technologies necessary for SSTO are:

- lightweight structures
- hypersonic flight capability for airbreathing mode
- high specific impulse for rocket mode

I did some calculations and propose the following for an SSTO vehicle (possibly winged aircraft)

-Hybrid Engine with an airbreathing and a rocket mode. The airbreathing mode is capable of sustaining speed of Mach 4 and has a specific impulse of 2000sec. The rocket mode is based on tri-propellant combustion of flourine, berillium, and hydrogen and has a specific impulse of 700sec.

-Composite structure with a mass ratio of 2.5:1
Title: Re: SSTO Thread
Post by: GI-Thruster on 04/09/2009 05:58 pm
Great posts guys! I had a few ideas myself and just wanted to know what you think. As previously mentioned the key technologies necessary for SSTO are:

- lightweight structures
- hypersonic flight capability for airbreathing mode
- high specific impulse for rocket mode

I did some calculations and propose the following for an SSTO vehicle (possibly winged aircraft)

-Hybrid Engine with an airbreathing and a rocket mode. The airbreathing mode is capable of sustaining speed of Mach 4 and has a specific impulse of 2000sec. The rocket mode is based on tri-propellant combustion of flourine, berillium, and hydrogen and has a specific impulse of 700sec.

-Composite structure with a mass ratio of 2.5:1


And who were you going to get to handle the Fluorine?  You'd need more than just one mother-in-law. . .
Title: Re: SSTO Thread
Post by: MKremer on 04/09/2009 06:17 pm
Great posts guys! I had a few ideas myself and just wanted to know what you think. As previously mentioned the key technologies necessary for SSTO are:

- lightweight structures
- hypersonic flight capability for airbreathing mode
- high specific impulse for rocket mode

I did some calculations and propose the following for an SSTO vehicle (possibly winged aircraft)

-Hybrid Engine with an airbreathing and a rocket mode. The airbreathing mode is capable of sustaining speed of Mach 4 and has a specific impulse of 2000sec. The rocket mode is based on tri-propellant combustion of flourine, berillium, and hydrogen and has a specific impulse of 700sec.

-Composite structure with a mass ratio of 2.5:1


And who were you going to get to handle the Fluorine?  You'd need more than just one mother-in-law. . .

Also, what sorts of combustion byproducts would be generated? Not many people or governments would be very happy having tons of hydrofluoric acid dumped into the upper atmosphere with every launch.
 
Title: Re: SSTO Thread
Post by: space_man on 04/09/2009 06:23 pm
Yes, I have read the thread on tri-propellants. I realize this generates tons of harmful chemicals, and the floruine is a nasty element to store.

But what about using regular propellants in the atmosphere and then engaging the tri-propellant engine in space where the pollutants would no longer be released into the actual atmosphere?
Title: Re: SSTO Thread
Post by: clongton on 04/09/2009 06:28 pm
A better idea, once the nation finally gets over its mamby pamby fears, is to go nuclear. The exhaust is not radioactive. It’s practically impossible to make hydrogen radioactive, just very, very hot with lots of thrust and high isp.
Title: Re: SSTO Thread
Post by: GI-Thruster on 04/09/2009 06:29 pm
Yes, I have read the thread on tri-propellants. I realize this generates tons of harmful chemicals, and the floruine is a nasty element to store.

But what about using regular propellants in the atmosphere and then engaging the tri-propellant engine in space where the pollutants would no longer be released into the actual atmosphere?

Well you can get more bang for your buck using these odd options but, you need to understand the practical reasons folks don't normally mess with Fluorine.  It's just a nightmare to deal with and that is never going to lead to a cost effective transport system.  We need to reduce support infrastructure in order to bring costs down, not create more infrastructure needs.

This is one of the reasons QR is such a good idea, the entire first stage is nothing like "rocket science."  It has the same safe, quick, convenient and economical advantages as all modern air transport.  Gary had basically a two stage rocket with the hassles of only a one stage rocket.  That was a VERY good idea.  I'm surprised that no one else wants to pick up that ball and run with it.  No one in Europe?  India? 

Just out of curiosity, if HMX is still around; I'd love to know why solids were passed over for QR.  That would have added a huge convenience to the entire concept.  Did solids just not have the get-up-and-go power you needed?

I'm also curious whether anyone ever considered the crazy option of carrying the rocket externally, pulling the plane up and releasing, then winging over the aircraft to get it away from the rocket quickly.  I know this sounds like a crazy stunt but in fact, B-47 pilots used to practice this maneuver to literally "throw" their payload at the target and get as far away as possible before the boom.  For anyone who has an interest, there's a DVD out there that describes this. I had occasion to view it myself since I picked it up for my father who crewed an RB-47 during the Korean conflict.  Very fun video and a little suprising to consider a bomber acting like a fighter.
Title: Re: SSTO Thread
Post by: space_man on 04/09/2009 06:34 pm
A better idea, once the nation finally gets over its mamby pamby fears, is to go nuclear. The exhaust is not radioactive. It’s practically impossible to make hydrogen radioactive, just very, very hot with lots of thrust and high isp.

I am curious, do you plan to pump hydrogen through exposed plutonium? (In which case temperature will be too high for modern nozzle materials)
Title: Re: SSTO Thread
Post by: Jim on 04/09/2009 07:36 pm

But what about using regular propellants in the atmosphere and then engaging the tri-propellant engine in space where the pollutants would no longer be released into the actual atmosphere?

Still have to deal with them on the ground and then there is the accident scenario
Title: Re: SSTO Thread
Post by: HMXHMX on 04/10/2009 04:35 pm
Yes, I have read the thread on tri-propellants. I realize this generates tons of harmful chemicals, and the floruine is a nasty element to store.

But what about using regular propellants in the atmosphere and then engaging the tri-propellant engine in space where the pollutants would no longer be released into the actual atmosphere?

Well you can get more bang for your buck using these odd options but, you need to understand the practical reasons folks don't normally mess with Fluorine.  It's just a nightmare to deal with and that is never going to lead to a cost effective transport system.  We need to reduce support infrastructure in order to bring costs down, not create more infrastructure needs.

This is one of the reasons QR is such a good idea, the entire first stage is nothing like "rocket science."  It has the same safe, quick, convenient and economical advantages as all modern air transport.  Gary had basically a two stage rocket with the hassles of only a one stage rocket.  That was a VERY good idea.  I'm surprised that no one else wants to pick up that ball and run with it.  No one in Europe?  India? 

Just out of curiosity, if HMX is still around; I'd love to know why solids were passed over for QR.  That would have added a huge convenience to the entire concept.  Did solids just not have the get-up-and-go power you needed?

I'm also curious whether anyone ever considered the crazy option of carrying the rocket externally, pulling the plane up and releasing, then winging over the aircraft to get it away from the rocket quickly.  I know this sounds like a crazy stunt but in fact, B-47 pilots used to practice this maneuver to literally "throw" their payload at the target and get as far away as possible before the boom.  For anyone who has an interest, there's a DVD out there that describes this. I had occasion to view it myself since I picked it up for my father who crewed an RB-47 during the Korean conflict.  Very fun video and a little suprising to consider a bomber acting like a fighter.

We traded out solids because of the DARPA/USAF cost target.  No way to get to to the target being captive to essentially only one manufacturer.  You also need three or more stages, adding to the overall cost. Since each stage is about as expensive as another, irrespective of size.

I have heard of a number of non-U.S. air-launch studies and programs.  I expect the idea is not dead.

We did look at external carriage, but there were reasons (that I can't get into) for the choices we made for FALCON.  t/Space did use external carriage and AirLaunch was assigned a patent on specifics of that approach last fall.  I'm fairly familiar with the B-47 maneuver you mention and in fact, I know of at least one air-launch concept that used it as the starting point for analysis.  It's hard on heavier vehicles and airframes, however.

By the way, getting the airplane away quickly is really only a problem for solids (that can detonate) versus airborne liquids that can really only deflagrate.  In flight, there is not a mechanism for propellants to mix (witness Challenger).


Title: Re: SSTO Thread
Post by: mmeijeri on 05/28/2009 01:34 am
Hmmm, if ethane isn't too hard to produce from methane, then that's another Martian fuel choice. It has somewhat better handling properties and density for a touch less isp. And of course, from ethane you can make ethylene, base stock for the plastics industry.

You can make higher hydrocarbons, even diesel, from methane, see

Gas to liquids (http://en.wikipedia.org/wiki/Gas_to_liquids)
What is Gas to Liquids? (http://www.shell.com/home/content/shellgasandpower-en/products_and_services/what_is_gtl/gas_to_liquid/whatisgtl_0112_1532.html)

I don't know how well this process could be adapted to Martian ISRU, if at all. Next time I bump into some old colleagues, I'll ask them.
Title: Re: SSTO Thread
Post by: Proponent on 07/14/2015 02:40 pm
Having a little spare time during the summer lull, I've had a quick look at the effect of variable mixture ratios on lox-hydrogen SSTO.

I began by reproducing Dunn's results for 1000-m3 SSTO.  In Dunn's approximation, finding the payload to LEO is simply a matter of finding the burn-out mass that yields an ideal delta-V of 9500 m/s and then subtracting 20,000 kg plus 3% of the propellant load (that's for hydrogen; for other fuels he uses 25,000 kg and 2%).  Like Dunn, I use 90% of the vacuum Isp for the given mixture ratio, though my Isp figures come from RPA Lite (http://www.propulsion-analysis.com/index.htm) 1.2.8.0 rather than from ProPEP.  As the table below shows, my payload figure for the mixture ratio of 6 that he asumed is similar to his (9350 kg).

Scenario      MR   Payload
            (mean)    (kg)
Max Isp      5.281    7389
Dunn         6.000    9333
Opt Fixed    7.622   11488
Variable     7.719   11873
Stoich       7.937   11270
Max Impulse 17.192  -12427

The table gives us a reminder that maximizing performance is not the same thing as maximizing Isp, as people so often assume.  Even Dunn's unusually-lean mixture ratio turns out to have been too low: bumping the MR all the way up to 7.6 adds more than 20% to the payload.

I then divide the 1000-m3 propellant volume into 100 equal slices, each of which consists of liquid oxygen and hydrogen in an arbitrary ratio.  I numerically adjust the mixture ratio in each slice to maximize the payload to orbit.  The resulting MR profile is a shown in the attached figure.  The mean MR of 7.7 is what is reported in the table, above.  The horizontal line in fhe figure shows the MR for the optimal fixed-MR case.

Frankly I'm disappointed that the variable MR appears to boost the payload by just a few percent over the optimal fixed-MR case.  I do suspect, though, that the benefit of variable-MR is understated, because the oxygen-rich mixture burned at lift-off would produce high thrust, thus reducing gravity losses.  (On the other hand, there's the complexity of building an engine which can handle a large range of MRs -- that's well beyond the scope of this simple calculation).

It must be the case in principle that right at lift-off, the optimal MR is that which maximizes the density impulse (density times Isp).  The reason is that the initial infinitesimal volume of propellant does not need to be accelerated of lifted off the pad, so the volume it occupies in the tanks might as well be packed as full of impulse as possible*.  I presume the fact that the present calculation does not show the MR rising that high at lift-off is that the optimal MR falls very quickly to lower values.
(http://forum.nasaspaceflight.com/data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAABLgAAAKdCAIAAACvdke+AAAAA3NCSVQICAjb4U/gAAAACXBIWXMAAA7EAAAOxAGVKw4bAAAgAElEQVR4nOzdd3jVhaH/8ZNFCDuEFaZMARliFBGQUcImgEIExGK9coF6b29alSGOi6NW1N6WXq2Fi1ZREQoiFYqiLHG0VqmioGxlyJARIGFD8vvjtNTDDysq5HuSvF5/+Jyck8CHPu0j735XTH5+fggAAAD+ITboAQAAAEQXoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAEAEoQgAAECE+KAHFJwpU6YsWrQo6BUAAADnJCEh4emnn05ISCj437oYheLSpUvvv//+KlWqBD0EAADgmw0dOvTIkSNC8YIrX758cnJy0CsAAAC+WSCJGOYaRQAAACIIRQAAACIIRQAAACIIRQAAACIIRQAAACIIRQAAACIIRQAAACJEXSjm5+cfPHhw3759+fn5QW8BAAAojqIlFDds2DBu3LiGDRsmJSWVL18+JSWlZMmS9evXHzt27MaNG4NeBwAAUIzEBz0gFAqF3nvvvfT09DJlyvTp06dp06YVK1bMz8/fv3//2rVrZ86cOXny5CVLllx22WVBzwQAACgWoiIUx4wZ06pVq/nz55cpU+aMj/7nf/5n0KBBo0ePXrx4cSDbAAAAipuoOPX0b3/72w9/+MP/vxJDoVBiYuLw4cNXrFhR8KsAAACKp6gIxYsvvnjp0qVfd/eaJUuWXHzxxQU8CQAAoNiKilNPR48ePWjQoJ07dw4ePLhp06bJyckxMTHZ2dlr1qyZM2fOggULZs6cGfRGAACA4iIqQjEzM7NUqVK//OUv//3f//2Mjzp37vzyyy/37t07kGEAAADFUFSEYigU6t27d+/evffu3fvFF1/s2rUrFApVqVKlZs2aKSkp5/6L7Nu3b/bs2V/36UcffXTs2LHzsBUAAKBIi5ZQDEtJSflWZXiGhISE5OTkr/t09+7d2dnZderU+c6/PgAAQHEQXaH4PZUtWzYzM/PrPr399ttjY6Pi5j0AAADRTDgBAAAQISqOKN5+++3f+D2PPvpoASwBAAAgKkIxJibmySefzM7Orlix4tddZCgUAQAACkZUhOIjjzwyYsSIJk2a3HHHHedydBEAAIALJ1quUWzYsOGVV14Z9AoAAACi44hi2C9+8YuKFSsGvQIAAKC4i6JQ7NChQ9ATAAAAiJpTTwEAAIgSQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQhEAAIAIQrGgrV+//rHHHgt6BQAAwNcSigWtQYMG77///rPPPhv0EAAAgLMTigUtJibm//7v/1544YXFixcHvQUAAOAs4oMeUBwlJCTMmDGjT58+VapUad68edBzAAAAIjiiGIxy5cq98MILI0aM2LZtW9BbAAAAIgjFwNSoUWPKlCnDhg3Lzc0NegsAAMA/CcUgNW/efMyYMddff/3JkyeD3gIAAPB3QjFgPXr06Nev349//OOghwAAAPydUAzezTffXK1atQcffDDoIQAAAKGQUIwS99133/r166dNmxb0EAAAAKEYHWJiYqZMmTJz5sxFixYFvQUAACjuPEcxWiQkJEyfPr1Pnz6pqamXXHJJ0HMAAIDiyxHFKFK+fPnp06cPHz7cwxUBAIAACcXoUqtWralTpw4ePDg7OzvoLQAAQDEVdaF45MiRLVu25OTkBD0kMJdccsnPf/7zwYMHHz16NOgtAABAcRQtofj+++8PGzYsOTm5VKlSderUKVeuXJkyZVq3bv3b3/72wIEDQa8raB07drz55puHDBly6tSpoLcAAADFTlSE4ptvvtm+ffvt27ffddddP/7xj+Pj4++888577733oosuGj16dMuWLTdv3hz0xoJ23XXXde3a9Sc/+UnQQwAAgGInKu56etddd/Xu3Xv27NkxMTGhUKhp06aTJk1au3ZtbGzs1q1bu3Xrdtdddz377LNBzyxot9xyy+jRox9++OExY8YEvQUAAChGoiIUP/jgg9/97nfhSgyFQhkZGT/5yU/WrVvXuHHjWrVqZWVlPfDAA+fy6+zZs+epp57Kz88/66c5OTknT548b6MLxMMPP3zTTTc988wzN954Y9BbAACA4iIqQrFq1aobN248/eWOHTtCoVB8/N+37dmz5xx/naSkpPr16+fl5Z310/j4+NjYqDjV9tzFxMT83//93zXXXFOtWrXu3bsHPQcAACgWoiIUBw8e/PDDD9evX/8HP/jB5s2bb7nllkaNGtWrV2/Pnj133nnn73//+9tvv/1cfp3SpUsPGDDg6z69/fbbC10ohkKhhISEF154oU+fPpUrV77sssuCngMAABR9URGKd91118aNG4cOHRr+slatWnPmzImNjV21atXMmTPHjBlzzz33BLswWGXLlp0xY0a/fv2ef/75hg0bBj0HAAAo4qIiFBMTE6dPn37PPfd89NFHKSkpbdq0KV26dCgUatOmzZ49e06fg1qcpaamTp8+fdiwYXPnzq1SpUrQcwAAgKIsihqscePGjRs3/uo7JUuWDGpMFGrQoMGjjz46ZMiQl19+ORzSAAAAF0Lhu2avOGvbtu0dd9yRmZl57NixoLcAAABFllAsZNLT04cPHz506NBC96gPAACgsBCKhc+1117bpUuX4cOHf90TIwEAAL4PoVgo/fjHP65fv/748eODHgIAABRBQrGwuvvuu0+cOPHII48EPQQAAChqhGIh9sgjj6xdu3bq1KlBDwEAAIoUoViIxcTETJ48+fXXX581a1bQWwAAgKJDKBZucXFxzz777DPPPLNw4cKgtwAAAEVEfNAD+L5KlCgxffr0jIyMsmXLtm3bNug5AABAoeeIYlFQrly5F198cezYsZ988knQWwAAgEJPKBYRlSpVev7554cPH75ixYqgtwAAAIWbUCw6ateu/dJLL912223z588PegsAAFCICcUipWrVqn/605+efPLJJ554IugtAABAYSUUi5rSpUvPnj171apVWVlZeXl5Qc8BAAAKH6FYBMXFxT3++OP16tW7/vrrjx49GvQcAACgkBGKRVZWVtaAAQMGDBhw4MCBoLcAAACFiecoFmWZmZmVKlXq3bv39OnTa9euHfQcAACgcHBEsYjr3Lnz5MmTBw0a9MEHHwS9BQAAKByEYtF3ySWXzJ49Oysra9GiRUFvAQAACgGnnhYLNWrUmD9//oABA2JiYrp06RL0HAAAIKoJxeKiXLlyL774YkZGRsmSJdu1axf0HAAAIHo59bQYCbfi6NGjP/zww6C3AAAA0UsoFi+VKlWaNWvWyJEj165dG/QWAAAgSgnFYqdGjRrPP//8sGHDtmzZEvQWAAAgGgnF4qhBgwZTp04dNGjQl19+GfQWAAAg6gjFYqp58+a/+tWvBg8enJOTE/QWAAAgugjF4qtNmzZ33nnnddddd/To0aC3AAAAUcTjMYq1Ll265OTkXH/99TNnzkxISAh6DgAAEBUcUSzu+vfv379//3/7t3/Ly8sLegsAABAVhCKhYcOGtWrV6r/+67+CHgIAAEQFoUgoFArdeuutFSpU+O///u+ghwAAAMETivzdAw88sH///l/96ldBDwEAAAImFPmnX/3qV3/961+ffvrpoIcAAABBEor8U2xs7LRp0+bMmbNgwYKgtwAAAIHxeAwiJCQkzJgxo1+/fuXKlWvfvn3QcwAAgAA4osiZSpUqNWPGjDFjxnz44YdBbwEAAAIgFDmLlJSUWbNm3XLLLZ999lnQWwAAgIImFDm7GjVqTJs27YYbbti5c2fQWwAAgAIlFPlaDRo0+O1vf3vddddlZ2cHvQUAACg4QpF/pWXLlvfee++AAQMOHToU9BYAAKCAuOsp36Bz58779u274YYbZsyYkZiYGPQcAADggnNEkW82YMCAwYMH9+nTZ8+ePUFvAQAALjihyDkZNGjQ/fff37dv308//TToLQAAwIUlFDlXbdq0ef755//93/99yZIlQW8BAAAuIKHIt1C3bt1XXnll0qRJTzzxRNBbAACAC0Uo8u2ULVv2xRdfXL16dVZWVl5eXtBzAACA808o8q3Fx8c/9thj9erVGzx48OHDh4OeAwAAnGdCke8oKyvrpptu6tGjx7Zt24LeAgAAnE9Cke+uZ8+ejz32WGZm5gcffBD0FgAA4LwRinwvLVq0mDVr1k9/+tM//elPQW8BAADOD6HI91WzZs0FCxb8/ve/nzBhQtBbAACA80Aoch6ULl161qxZoVBo6NChR48eDXoOAADwvQhFzo+YmJgJEyb07du3T58+u3btCnoOAADw3QlFzqdBgwY98MADGRkZbm8DAACFl1DkPGvTps1LL7106623/vGPfwx6CwAA8F0IRc6/GjVqzJ8//9lnn3V7GwAAKIyEIheE29sAAEDhJRS5UMK3t+nVq1dGRsbOnTuDngMAAJwrociFNXTo0J///OfXXHPNkiVLgt4CAACcE6HIBde6deuFCxdOnjx53Lhxp06dCnoOAADwDYQiBaFcuXIzZsxITU3t1avXjh07gp4DAAD8K0KRAhITE5OVlRU+DfX1118Peg4AAPC1hCIF6vLLL1+4cOHUqVMnTJiQl5cX9BwAAOAshCIFrXz58jNmzEhOTu7Vq5e7oQIAQBQSigQgfBrq/fff379//0WLFgU9BwAAiCAUCcwVV1zxpz/96bHHHpswYcKJEyeCngMAAPydUCRIKSkpc+fOrVevXqdOnVauXBn0HAAAIBQSikSDYcOGPf/88+PGjZs4caIHLQIAQOCEIlHhoosuWrBgQXJycvfu3devXx/0HAAAKNaEItEiJiZmxIgRv/nNb26++eZJkybl5+cHvQgAAIopoUh0adq06ZIlS44ePZqRkbFt27ag5wAAQHEkFIk68fHxY8eOffDBB4cOHTplypSg5wAAQLEjFIlSLVq0WLhw4bp166699tqtW7cGPQcAAIqR+KAHwNcqWbLko48++uGHHw4bNqxHjx633XZbfLz/xgIAwAXniCLR7tJLL128eHFycnLnzp3ffffdoOcAAEDRJxQpBGJjY0eMGDFz5swnnnhi5MiRBw8eDHoRAAAUZUKRQqN69epPP/10nz59unfvPm3atKDnAABAkSUUKWQyMjIWL178ySef9O/ff/PmzUHPAQCAIsitQSh8SpUq9dBDD61YseLGG2/s3Lnzf/7nf6akpAQ9CgAAig5HFCms0tLSlixZctlllw0aNGjkyJHr168PehEAABQRQpFCLDY2NiMjY9GiRT/84Q9Hjx7dt2/f999/P+hRAABQ6Dn1lKKgffv27du3/+ijjx599NGtW7feeuutGRkZQY8CAIDCyhFFio4WLVpMmzbt97///aJFi66++upp06adOnUq6FEAAFD4CEWKmosuumjSpElz5szZsGFD+/bt77777jVr1gQ9CgAAChOhSNFUuXLl++677+233+7evfuvfvWrNm3aTJw4cefOnUHvAgCAQsA1ihRlsbGx4csXjxw5Mn/+/FGjRh07dmzIkCHXXnttmTJlgl4HAABRyhFFioWkpKTMzMy5c+c++eSTu3fv7tWr10033bRkyZK8vLygpwEAQNQRihQv1atXv+2225YvX37bbbe9+uqr7dq1Gz9+/Keffhr0LgAAiCJOPaWYatas2cMPP5yXl/fOO+/8+te/Xrly5TXXXHPTTTdVqVIl6GkAABAwoUixdsZFjCNGjAhfxDhw4MBSpUoFvQ4AAILh1FMIhb5yEeOUKVO++OKLrl273nLLLe+++27QuwAAIABCESLUqlXrjjvuePvtt3/0ox8988wz7dq1e/jhh3fs2BH0LgAAKDhOPYWza926devWrY8dO/baa6/97Gc/O3DggFNSAQAoJhxRhH8lMTExIyNjxowZTz75ZHZ2ds+ePUeOHPnWW28FvQsAAC4goQjnpHr16llZWW+88caPfvSjZ599tn379g8++ODnn38e9C4AADj/nHoK385VV1111VVXhU9JveeeezZv3nzttdcOHjy4atWqQU8DAIDzwxFF+C7Cp6ROmzbt5ZdfTk5OHjlyZOfOnadMmZKTkxP0NAAA+L7OEoo7duyYMWPGzJkzc3Nzw+/k5uZ+9tlnK1asmDdvXufOnQt2IUS18uXLDxs2bO7cudOnTz98+HBGRsaQIUPmzp2rGAEAKLzOPPX03Xff7d69+4EDB0KhUMOGDZctW3bLLbfMmzcvLy8v/A2xsQ5Cwlmkpqb+9Kc//elPf7p+/frZs2c/8cQTJ0+ebNu2bZcuXa666qrExMSgBwIAwLmKyc/P/+rXXbt2/fjjj5988skqVaqMHTt27dq1R48eHT9+fOPGjePj41NTUxs1alSyZMmg5n4fderUmTdvXosWLYIeQnFx8uTJlStXLlq06O233z558mTr1q3bt2/fsWPHhISEoKcBAFAI9OvX79lnny1XrlzB/9ZnHlH829/+9pOf/KR3796hUGjixImtW7d+4oknRo0aVfDLoLCLj49PS0tLS0sLhUIHDhxYtmzZvHnz7r333sqVK3fq1Klz587NmjWLiYkJeiYAAJzpzFDct29frVq1wq9r164dCoXq169f0KOgyClfvny/fv369esXCoV27ty5bNmyxx9/fPXq1VWrVg1HY9OmTUUjAABR4iyPx4iLi/vqC395hfOrWrVqgwcPHjx4cCgU2rFjx7Jly37zm9+sXr26evXqHTt27NSpU5MmTVwMDABAgDxHEYKUmpo6ZMiQIUOGhEKh7du3L126dNKkSZ9++mmZMmWuuOKK1q1bX3nllZUrVw56JgAAxUv0huL+/ft37NhRv379EiVKBL0FCkL16tWHDh06dOjQUCiUm5v74Ycfrlix4g9/+MPGjRsrVqzYvn37du3apaWlJSUlBb0UAIAi7sy7nsbExMTHx4dPOs3Pzz9+/PjpL087evToed/x8ssvP/XUU8eOHbvhhhuGDh06ceLEe+655/jx4yVKlLjjjjvuvvvuMzZ8B+56SuG1ZcuWd9999y9/+cuHH3544sSJ2rVrt2jRonnz5s2bN69Zs2bQ6wAAuCCi6K6nd955Z8GPmDlz5uDBg6+44oqqVavedNNN77zzzlNPPXXPPfdcdtllb7zxxgMPPJCamjpy5MiCHwZRonbt2rVr187MzAx/+fnnn3/88ccffvjhM88888UXXyQmJjZu3Dicjo0bN05OTg52LQAAhd2ZRxQDcemllzZv3nzatGkxMTEzZswYMmTIL37xi3HjxoU//clPfrJ8+fKVK1d+z9/FEUWKquPHj3/yyScff/zxqlWr1q5du2/fvri4uLp16zZs2LBhw4aNGjVq2LChE1YBAAqdKDqiuGrVqm/8mWbNmp3fEevWrRs9enT49qo9evQIhUJXXXXV6U/btWv31FNPncuv8+WXX/7+97//uk9zcnJOnjz5vcdC1ClRosSll1566aWXnn7n1KlTmzdvXrdu3bp165YtW7Zhw4YjR44kJibWqVOndu3aderUCb+oWbNmQkJCgMsBAIhOZ4Zi8+bNv/FnzvtByJo1a3788cfh1x999FEoFFq/fn3Hjh3D76xfv/4cr8IqW7Zs+OHmZ1WiRInvf6EjFApxcXH16tWrV69e+P95CTt27NjmzZu3bNmyZcuWpUuXfv7551988cWJEydiY2OrVatW+ytq1arl/FUAgOLszFCMi4s7depUixYtBg4cePXVV8fHF8RtUYcPHz5+/Pj9+/dXqVJl8uTJrVu3vueee+rUqdOqVas33njj0Ucf/Y//+I9z+XWSkpLS09O/7tPExETPhKQ4S0xMbNSoUaNGjc54Pz8/f8eOHZs3b966devatWtff/31LVu27Nu3LzY2NjExsVatWrVq1apTp07NmjWrV69eq1atMmXKBLIfAIACc2YH7tq1649//OOLL774wAMPlCtX7pprrhkwYEDnzp0v6DMqbr311kOHDk2dOvX48eM//OEPH3744UGDBnXr1i38ae/evQO5xQ4UEzExMdWrV69evfpXT/kOO3r06JYtW7Zt27Z169Z33nln+/bt27Zty8nJiY2NjY+PD3djampqrVq1qlSpkpqaWqlSpVKlSgXypwAA4Dz62pvZHDhwYP78+S+++OKrr76amJjYr1+/gQMHpqenlyxZ8sKtyc/PDx/0y8/PX758+ebNmy+55JLLLrvsvBwJdDMbOI+OHz++ffv2L774Ytu2bTt27Ni2bdvu3bt3796dm5sbCoXi4uLKli1buXLlqlWrVqlSpVKlSsmREhMTg/4TAABEuwBvZvPNdz09dOjQK6+88uKLL/7pT38KhUJ9+vSZPn16gWw7z4QiFKScnJwdO3bs2bMnHJDZkY4dO3b6O8uVK1ehQoXy/1DhH776pbAEAIqhqA7FsF27ds2YMWPChAn79++PhidqfAdCEaLTga/Yv3//V1/s/4evhmWZMmUqVKiQnJwc/mfFr0hJSalYsaJbuQIARUMUPR7jDDt37nzppZdmzZr1xhtvVK1a9YYbbhg4cGDBLAOKifCRw3P//tzc3P3792dnZ4f/uW/fvg0bNuzbt2/fvn179+7du3fviRMnwt9ZokSJcDqG//nVmAy/cCdkAICzOnsobt++fc6cObNnz16+fHmNGjUGDBhw3333tW3bNjY2toD3AZyhTJkyZcqUOZen5hw/fvx0QIZfrFu3Lvw6/M+8vLzTp0iULVv29Jmu4XZNTk4uXbp06dKlw8cww6/Lli17gf98AADBOzMUf/Ob38yaNevtt9+uXbv2wIEDH3roodatW+tDoDAqUaJEtWrVqlWrdi7fnJOT89XzXQ8cOJCdnb1p06ZDhw4dOnQofBgz/Do2NvbkyZP5+fmJiYnHjh0rWbJkhQoVkpKSkpKSvvqiTJky4bY8Izg9pwcAiH5nXqMY/htMixYtLr/88q/728zUqVMLYtr55hpF4EI4evTokSNH9u/ff+TIkdMvDh8+vH///tzc3HBbZmdnnw7O48ePh38wJiYmPj6+XLlyZcuWLfcPFSpUCL84/WZycnLZsmUL5qm2AEBUiaJrFNPS0sIvVq5cWeBjAAqfkiVLlixZMjk5+Tv8bH5+fvjo5cGDB3Nycg4ePHjw4MEDBw5s27bt4D/k5OQcOHDgdF7GxsbGxMQkJSWVLl26fPnySUlJpUqVOn0kMzk5OT4+vmzZsomJiaVKlSpVqlRiYmK4Mx3MBADO3Zmh+P777weyA6AYiomJCT9Y8tv+YE5OzpEjR3Jzc3Nycg4fPnzo0KGDBw8eOXIkOzs7Nzf3xIkTBw4cOHXq1P79+0+ePJmTkxM+7Hns2LHwkcmTJ0/GxsbGxcWFOzM5OTn8InxxZvgq0LJly1aoUKFs2bLh1y7OBIBixblMAIVPuNyqVKnyPX+dcF4eOnQofMZsTk5O+FrN3bt35+Tk5Obmnj7amZubGxcXd+rUqfAFCyVKlAhfhxleUq5cuXBhhu/3E/4orEKFCufjTwwAFCihCFB8hS+D/A4/eOLEidzc3Ozs7HBbho9thgszfGVm+NhmWF5eXl5eXigUSkhIOHny5Fnv8VOqVKnSpUuH95QuXTp8Pm2ZMmU8FRMAAiEUAfjWEhISvttJs6FQ6Kz3+Nm/f//evXsPHz4cvjIz/P7pizPj4+PDtZmUlHT66GVYcnJyuUjhx5y4IBMAvg+hCECBCgfed/vZ01dmhm8qm5ubGw7LzZs3H4wUDstwLoZv/FPhK5KTk8OPyjzNg6AA4KuEIgCFRvjmrpUrV/5WPxW+CPOrzwTIiZ8AACAASURBVMncvXv3+vXrs/9h3759px8WdfpgaUpKSsWKFStWrHjGixIlSlyAPxkARBehCEARF74YskaNGufyzSdOnDhdj3v37t23b99nn332/vvv79u3L/zOsWPHQqFQfn5+UlJSOB1TIlWqVCklJSWQZ14BwPkiFAHgnxISEqpUqXIud5Q9fvz43khbtmw5/frgwYPhb4uJiUlJSalSpcpXS7JSpUpVqlSpVKlS6dKlL/AfCAC+C6EIAN9FiRIlUlNTU1NT//W3nTp16nQ97tmzZ+/evStXrty9e/eePXv27Nlz6NCh8C1hS5UqVekfqlWrVrVq1cqVK6emplapUiUpKalA/kAA8E9CEQAuoLi4uHM5RHn06NFwOu7atevLL79cv3798uXLv/zyy/AzLePi4mJiYpKTk2vUqFGtWrWaNWvWqFGjevXqNWvWdI4rABeCUASA4JUsWbJmzZo1a9b8F9+ze/fu3bt3f/HFF9u3b//LX/6yY8eOrVu3HjhwIC4uLjY2NtyNderUueiii+rWrVunTp3ExMQC2w9AESMUAaBwqFy5cuXKlZs2bfr/f3TixImdO3du3br1888/X7FixYsvvrh58+ajR4/GxcXVqFHjoosuCtdj3bp1a9WqFR/v3/4AfAP/qgCAQi8hIaFWrVq1atVq27btV9/Py8vbvn37Z5999tlnn7311lvTpk3bunXryZMnS5YsWbdu3XpfUaFChaDGAxCFhCIAFFmxsbHhM1qvvvrqr75/9OjRzz77bNOmTZs2bXr77bc3bdq0f//+UChUvXr1Bg0a1K9fv379+g0aNPjGW/UAUFQJRQAodkqWLNmkSZMmTZqc8f727ds3bNiwcePGhQsXPv744zt27AiFQikpKfXr12/YsGGDBg0aNmxYs2bNmJiYIFYDUHCEIgDwd9WrV69evXqHDh2++ubevXs3bty4YcOG5cuXP/nkk9u2bQuFQpUqVTqdjg0bNqxevXpAkwG4IIQiAPCvpKSkpKSktG7d+qtv7tmzZ8OGDevWrVu0aNETTzwRPvZYvXr1iy+++OKLL27UqFGjRo3Kli0b0GQAvi+hCAB8a5UqVapUqVKbNm2++ua2bdvWrVu3bt265557bu3atYcOHUpMTKxXr97FF1/ctGnTiy++uE6dOk5bBSgUhCIAcH6Eb5zzgx/84PQ7x48f37Bhw5o1a1asWPHcc89t2bIlFArVqFGjadOmjRs3bty4caNGjUqUKBHcZADOTigCABdKiRIlmjZtesazH7ds2bJ27do1a9YsXrx448aNhw8frlKlSpMmTZo1axa+xU5iYmJQgwEIE4oAQIGqXbt27dq1u3btevqdvXv3rlq16tNPP506deq6detOp2Pz5s3Dxx4ddQQoYEIRAAhYSkpKx44dO3bsePqdPXv2rF69+pNPPvnd7363du3a48eP16xZs2XLls2aNWvWrNlFF10U3FiAYkEoAgBRp1KlSmek45YtW1atWvXxxx+/8MILW7dujY+Pv/jii1u2bNmyZcvmzZuXKVMmwLUARY9QBAAKgfAJq7169Qp/eeLEiTVr1qxatWru3Ln33XffoUOHqlWr1qpVq3A61qhRI9i1AIWdUAQACp+EhITmzZs3b958yJAh4Xd27NixcuXKlStXTps2bfv27aVKlWrevHmrVq1atWrVqFGjuLi4YAcDFC5CEQAoClJTU1NTU3v06BH+8vDhwx9//PEHH3zw61//eu3atbGxsU2aNAl3Y/Pmzd0dB+BfE4oAQBFUqlSpK6+88sorrwx/efLkyU8++eSDDz549tlnV61adeLEifr161922WVpaWktW7YsVapUsGsBoo1QBACKvvj4+BYtWrRo0eLGG28MhUL5+fkbN25csWLFSy+9NGHChMOHD5/uxksvvbR06dJB7wUImFAEAIqdmJiYBg0aNGjQYNCgQeF3Nm7c+Le//W3evHkPPPBAbm5u3bp1L7/88ssvv/zSSy91vBEohoQiAECofv369evXz8zMDH/52Wefvf/++3/84x8nTJhw9OjRRo0ahbuxRYsWrm8EigOhCABwprp169atWzfcjfn5+evWrXv//feff/75sWPH5uXlNWnSpHXr1q1bt27cuHFsbGzQYwHOv5j8/PygNxSQatWqjRgxombNmkEPAQAKsby8vB07dnz++eefffbZzp074+PjL/qHChUqBL0OKFKeeOKJZcuWlS9fvuB/62J0RDEmJqZcuXLJyclBDwEACreUlJRmzZqFXx87dmzTpk0bNmyYO3fuvn37ypcv37Bhw4YNG9avXz8xMTHYnUBhl5CQENRvXYxCsUSJEt26dWvRokXQQwCAImvXrl1//etf33333WnTph09erR58+ZXXnllmzZtGjVqFPQ0oPB57rnnYmJiAvmti1EoAgBcaFWrVs3IyMjIyAiFQqdOnVq9evWf//znX/ziF+vXr09OTr7yyiuvuuqq1q1bly1bNuilAP+KUAQAuCDi4uLCD28cOXJkKBTKzs7+y1/+snz58kceeeTw4cMtW7a86qqr2rdvX7t27aCXApxJKAIAFITk5OSePXv27NkzFAqdOnVqzZo1b7/99l133bVp06bk5OT27du3a9eudevWHr8BRAOhCABQ0OLi4i655JJLLrlkxIgRoVBo69atb7311syZM8ePH1+mTJm2bdt27NjxiiuuKFmyZNBLgWJKKAIABKxWrVpDhgwZMmRIKBTKzc39y1/+snjx4gcffDAnJyd8pPHqq6/27A2gIAlFAIAoUqZMmfT09PT09FAodOTIkfBljY899tiJEyfS0tI6derUoUMH98IBLjShCAAQpZKSkjp37ty5c+dQKHTixIn33ntv2bJl//u//3v8+PG2bdv+4Ac/aNu2rdNTgQtBKAIAFAIJCQlt27Zt27bt+PHjT548uXLlykWLFj3yyCMHDhzo0KFDenp6hw4d3AgHOF+EIgBAIRMfH5+WlpaWljZ27Njc3Nw33njjlVdeue+++ypWrNitW7fu3bvXr18/6I1A4SYUAQAKsTJlyvTu3bt3796hUGjPnj1Lly59+OGHP/300yZNmqSnp3fr1q18+fJBbwQKH6EIAFBEVKpUKTMzMzMzMxQKrV69ev78+YMHDz5w4EC3bt0yMjIuu+yymJiYoDcChYNQBAAogsLPaRw7duzBgweXLFkyderUDz/8sEWLFhkZGV26dElKSgp6IBDVhCIAQFFWrly5/v379+/fP/SPw4yTJk2KjY3t1avXgAEDatasGfRAIBoJRQCA4uL0YcY9e/YsWLDg1ltv3bp1a8eOHfv06dOuXTsnpgKnxQY9AACAglapUqVhw4b94Q9/WLp0aceOHadPn962bdtbbrnltddeO378eNDrgOA5oggAUHyVLFmyZ8+ePXv2DP3jxNRf/vKXiYmJAwcO7Nu3b4UKFYIeCARDKAIAEAp95cTUzZs3L1y48Kabbjpw4ED37t2vvfbahg0bBr0OKFBCEQCACHXq1BkxYsSIESP27du3YMGC8ePH7969Oz09/ZprrrnkkkuCXgcUBKEIAMDZVaxY8YYbbrjhhhuOHTv25ptvTpky5b333rviiisyMzPd/AaKNqEIAMA3SExMTE9PT09Pz8vLe+edd+bPnz9mzJgGDRpkZmb26NEjISEh6IHAeSYUAQA4V7Gxse3bt2/fvn1+fv6KFSvmzJkzceLERo0aDRgwoGvXriVKlAh6IHB+CEUAAL61mJiYyy+//PLLLw+FQp988sns2bMfeuihunXrZmZmduvWLTExMeiBwPfiOYoAAHwvTZs2veeee9588817771306ZNGRkZffv2nTZtWm5ubtDTgO9IKAIAcH7UrVs3Kyvrtdde++Uvf/nFF1/06dNnyJAhc+bMOXr0aNDTgG9HKAIAcJ41bNjwjjvuWLZs2c9//vN169Z169bt5ptvXrx48alTp4KeBpwToQgAwIVSr169cePGLV++/LbbbnvzzTc7d+6clZX11ltv5efnBz0N+FeEIgAAF1zTpk0nTJiwfPnyYcOGzZo1q02bNuPGjVu3bl3Qu4Czc9dTAAAKTlpaWlpa2okTJ1599dUJEybs2rVr8ODBgwcPLlu2bNDTgH9yRBEAgIKWkJCQkZExffr0l156KT8//9prr73uuusWLVoU9C7g74QiAACBKVeu3IgRI15//fUJEyYsWrSoffv2EydO3LNnT9C7oLgTigAABK9p06YPPfTQokWL6tWr96Mf/WjQoEGLFi1yzxsIilAEACBalCxZMjMzc/78+RMmTHjllVfat28/adKkgwcPBr0Lih2hCABA1GnSpMkvf/nLJUuWVK9efcCAASNHjly9enXQo6AYEYoAAESpxMTEzMzM119/fcSIEY888kivXr1mzZp16tSpoHdB0ScUAQCIdmlpaU8//fSTTz65evXq8A1vsrOzgx4FRZlQBACgcEhNTZ0wYcKSJUtSUlL69u3705/+dM2aNUGPgqJJKAIAUJgkJSUNHz78zTffvOaaa+69994ePXrMmDHj+PHjQe+CIkUoAgBQKHXs2PGFF1544YUXdu3a1bZt26ysrI0bNwY9CooIoQgAQCGWnJyclZX117/+NSMj48477wzf8ObEiRNB74LCTSgCAFDoxcbGpqenz5gxY+rUqWvWrOnQocM999zz+eefB70LCiuhCABA0VG9evW77777rbfeat269c9+9rNevXrNnDnz2LFjQe+CQkYoAgBQ1MTFxfXp0+ell1566qmndu7cmZ6ePnLkyA8++CDoXVBoCEUAAIqsatWqZWVlvfnmmyNGjPjd737XsWPHSZMm7du3L+hdEO2EIgAARV9aWtrkyZNffvnlxMTEa6+99kc/+tGbb76Zn58f9C6IUkIRAIDionz58qNGjVq2bNmtt946e/bsdu3aTZw4cefOnUHvgqgjFAEAKHZatGgxadKkpUuX1qtXb9SoUT169PBQDfgqoQgAQDGVmJiYmZk5d+7cJ598ctOmTR07dszKylq1alXQuyB4QhEAgOKuRo0aY8eOfeutt3r16nX//fd369Zt+vTpx48fD3oXBEYoAgBAKBQKxcbGdu/efebMmdOnT9+2bVvHjh3vuuuubdu2Bb0LAiAUAQAgQqVKlcaMGfP222936tTp9ttv79Gjx7x589wilWJFKAIAwFnExsamp6fPmDHj8ccff/vtt9u2bTtx4sTs7Oygd0FBEIoAAPCv1K9f/6GHHlq8eHFKSkq/fv1uueWWNWvWBD0KLiyhCAAA36xUqVLDhw9fvnz50KFD77rrroEDB7777rtBj4ILRSgCAMC30K5du9mzZ0+cOHH69Oldu3Z1+SJFklAEAIBvrX79+pMmTXruuedWrFjRqVOnadOmnTx5MuhRcN4IRQAA+I6qVq06YcKEefPmZWdnd+zYcdKkSYcPHw56FJwHQhEAAL6XcuXKZWVlLVq0KD4+vkuXLhMnTszNzQ16FHwvQhEAAM6DpKSk//iP/3jzzTdTU1O7dev24IMP5uTkBD0KviOhCAAA5018fPywYcPeeuuthg0bpqenjxs3bv/+/UGPgm9NKAIAwHkWGxubmZn55z//uV27dn379h03blx2dnbQo+BbEIoAAHBBxMbGZmRkLFu2rF27dv379x83bty+ffuCHgXnRCgCAMAFFM7FpUuXXn755f369bv77rvlItFPKAIAwAUXGxs7cODA5cuXt2rVql+/fnfeeeeePXuCHgVfSygCAEABiYmJufbaa5cvX96mTZvMzMysrKydO3cGPQrOIipC8fDhw3Pnzt2xY0fQQwAA4IKLiYkJn4yakZExZMiQrKwsfxMm2kRFKH755ZfXXHNNy5YtX3nllaC3AABAAUlPTw/n4tChQ+UiUSUqQjHsuuuuu/nmm3/84x9/+eWXQW8BAIACkp6evmTJkm7dul1//fW33XabvwwTDaIoFNPT01euXLl79+769evfd999/hcCAEDx0bt376VLl3bp0uW6664bM2bM7t27g15EsRYf9IAIlStXnj179htvvDF69OgHHnigb9++Q4YM6dChQ+XKlc/lx3ft2jVp0qS8vLyzfnrgwIGTJ0+e170AAHA+9erVq1evXosWLcrMzGzZsuX48eOrVq0a9CiKo+gKxbCOHTu+++67S5YsefzxxwcNGnTq1KnGjRt/+umn3/iD5cuX79KlS35+/lk/ffrpp+Pi4s73WAAAOM/S09PT09MXLVo0aNCgli1b3nnnnVWqVAl6FMVLNIZiKBSKiYnp0qVLly5dvvzyy1dffXXBggXn8lMlS5bs0qXL132amJgYExNz/jYCAMAFlJ6e3qVLl/nz52dmZl511VVjx45NTk4OehTFRRRdo3hWVapUGTZs2IwZM4IeAgAABe30gzTS0tIyMjLuu+++nJycoEdRLERFKFatWvX1119v27Zt0EMAACDqxMbGZmZmLl++vEGDBt26dfv1r3997NixoEdRxEVFKCYlJaWnpzvxGgAAvk5sbOz111+/fPnyUqVKdejQYcqUKe7UyIUTFaEIAACci4SEhBEjRixdujQ7O7tDhw6zZs36uls5wvchFAEAoJApVarU2LFjFy5cuGnTpq5duy5atCjoRRQ1QhEAAAqlsmXLjh079tlnn50zZ06vXr3ee++9oBdRdETp4zEAAIBzkZqa+tvf/nbjxo3//d//nZeX9/Of/7xu3bpBj6LQE4oAAFDo1a9f/7nnnluxYsWoUaMuuuii+++/360i+T6cegoAAEVEWlrawoULMzMzr7vuuokTJx49ejToRRRWQhEAAIqU9PT0JUuWpKamduzYccqUKXl5eUEvovARigAAUNTExsYOGzYs/BSN9PT0pUuXBr2IQkYoAgBA0RR+isbzzz8/Y8aM/v37f/LJJ0EvotBwMxsAACjKUlNTJ0+evHr16nHjxtWoUWPChAlVq1YNehTRzhFFAAAo+i655JKXX3554MCBAwcOHDduXG5ubtCLiGpCEQAAiosuXbq88cYbaWlp3bt3nzJlyqlTp4JeRJQSigAAUIzExsZmZma+/vrr2dnZV1999SuvvBL0IqKRUAQAgGInfJ+bl19++dVXX+3Zs+fHH38c9CKii5vZAABAMVWpUqVJkyatWrXqjjvuqFu37oQJEypWrBj0KKKCI4oAAFCsNWvWbN68eX379u3fv//EiROPHz8e9CKCJxQBAIBQenr6kiVLkpOTf/CDH8yaNSvoOQRMKAIAAKFQKBQfHz9ixIh58+atWLGid+/eLlwszlyjCAAA/FNycvJDDz20bt26sWPHVqlS5YEHHqhcuXLQoyhojigCAABnatSo0UsvvdS/f//+/fv/5je/OXnyZNCLKFBCEQAAOLuePXsuW7bs1KlTXbp0WblyZdBzKDhCEQAA+FoJCQk/+9nPnnnmmTvvvHPcuHFHjx4NehEFQSgCAADf4KKLLpo/f35aWlqnTp2WLl0a9BwuOKEIAACck8zMzD/+8Y/PPPPMyJEjDx48GPQcLiChCAAAnKuqVas+/fTTffv27dq160svvRT0HC4UoQgAAHw7vXv3fu2115YtWzZ48ODdu3cHPYfzTygCAADfWvny5SdNmjRq1Kh+/frNmjUr6DmcZ0IRAAD4jjp16rR48eIVK1YMHjx47969Qc/hvBGKAADAd5eUlPTQQw/953/+Z9++fefNmxf0HM4PoQgAAHxf7du3f+WVV+bPn3/jjTfm5OQEPYfvSygCAADnQbly5SZPnjx48OAePXosW7Ys6Dl8L0IRAAA4b3r27Dl37tzHH3985MiRhw8fDnoO35FQBAAAzqfKlSvPmjUrPT29e/fuK1asCHoO30V80AMAAIAiKDMz86qrrho1atSll1561113lSxZMuhFfAuOKAIAABdEzZo158+f37Jly86dOy9atCjoOXwLQhEAALiAMjMzFyxYMGvWrEGDBu3ZsyfoOZwToQgAAFxYycnJkydPvuWWW/r27TtlypSg5/DNhCIAAFAQOnbsuHjx4u3bt/fo0WPdunVBz+FfcTMbAACggCQlJU2YMOGjjz4aNWpUhw4d7rzzzoSEhKBHcRaOKAIAAAWqRYsWr7/+enJycnp6+nvvvRf0HM5CKAIAAAUtLi4uKyvrueeee/TRR0eOHLl3796gFxFBKAIAAMGoVavWzJkzBw8e3L9//0mTJp06dSroRfydUAQAAILUuXPnJUuWhEKhLl26/PnPfw56DqGQUAQAAAKXkJCQlZU1ffr0yZMn33jjjV9++WXQi4o7oQgAAESF6tWrP/300zfddNOAAQOciRosoQgAAESRTp06LVmy5Pjx4126dHFP1KAIRQAAILokJCSMHj36ueeeu//++8ePH3/s2LGgFxU7QhEAAIhGNWvWfPnll1u1atW1a9f3338/6DnFi1AEAACiV2Zm5syZMx988MFx48Y5tFhghCIAABDVUlNT58yZk5aW1rVr1xUrVgQ9p1iID3oAAADAN8vMzGzduvWoUaNatmx53333lShRIuhFRZkjigAAQOFQp06dBQsW1KtXr3Pnzh988EHQc4oyoQgAABQaMTExI0aMeO6558aNGzdx4sS8vLygFxVNQhEAAChk6tat++qrr5YsWbJ3797bt28Pek4RJBQBAIDCJyYmJisr6/777x84cOD8+fODnlPUCEUAAKCwuvzyyxcuXPiHP/whKyvLwzPOI6EIAAAUYmXLlp02bVpaWlqnTp1WrVoV9JwiQigCAACF3rBhw6ZPn/5f//VfkyZNCnpLUSAUAQCAoqBu3boLFy7Mzs4eNGjQ/v37g55TuAlFAACgiEhISJgwYcKNN97Ys2fPv/71r0HPKcTigx4AAABwPvXq1atVq1bDhw+/+uqr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)


* Steven Pietrobon previously used this argument (http://forum.nasaspaceflight.com/index.php?topic=30103.msg972101#msg972101) in approximate form to show that density impulse is relatively more important for first stages.  Here I'm using it in exact form for an infinitesimal first stage.

EDIT: Added a parenthetical about Dunn's assumptions for non-hydrogen fuels and fixed typos.  Expanded description of the figures and on argument about the density impulse for the initial slug of propellant.  Corrected parenthetical description of Dunn's mass model in the second sentence.
Title: Re: SSTO Thread
Post by: john smith 19 on 07/15/2015 09:03 am
Having a little spare time during the summer lull, I've had a quick look at the effect of variable mixture ratios on lox-hydrogen SSTO.
This technique has been applied.

It was written up in a paper by Logsdon & Africano on improving payload to the Moon with the Saturn V, along with several other techniques.

Variable MR was estimated to be responsible for 1/2 of the 5% improvement in payload to lunar orbit and needed no hardware changes, just valve settings to the J2. They describe it as a "gear change," a move from 1 valve setting to another, not a gradual sweep.
Quote
Frankly I'm disappointed that the variable MR appears to boost the payload by just a few percent over the optimal fixed-MR case.  I do suspect, though, that the benefit of variable-MR is understated, because the oxygen-rich mixture burned at lift-off would produce high thrust, thus reducing gravity losses.  (On the other hand, there's the complexity of building an engine which can handle a large range of MRs -- that's well beyond the scope of this simple calculation).
This was L&A's point. The lower Isp dumps more of the heavier O2 molecules lower in the trajectory, so the vehicle accelerates faster. BTW they noted that in the early 70's the cost per unit mass of payload to the Moon was more than the equivalent mass of Gold.

A 2.5% improvement is pretty good.
Quote
It must be the case in principle that right at lift-off, the optimal MR is that which maximizes the density impulse (density times Isp).  The reason is that the initial infinitesimal volume of propellant does not need to be accelerated of lifted off the pad, so the volume it occupies in the tanks might as well be packed as full of impulse as possible*.  I presume the fact that the present calculation does not show the MR rising that high at lift-off is that the optimal MR falls very quickly to lower values.
By extension there is an optimal MR for every point on the trajectory that maximizes a particular parameter, depending on what parameter that is.

Sadly they were not able to apply the technique to the Saturn V 1st stage.

In an atmosphere the trades are different. You want to get the engine nozzles to the design altitude fast, OTOH your peak dynamic pressure rises the lower in the atmosphere you are when you hit M1, so you don't want to accelerate too fast
Title: Re: SSTO Thread
Post by: hkultala on 07/16/2015 11:47 am
Yes, I have read the thread on tri-propellants. I realize this generates tons of harmful chemicals, and the floruine is a nasty element to store.

But what about using regular propellants in the atmosphere and then engaging the tri-propellant engine in space where the pollutants would no longer be released into the actual atmosphere?

Practically all the exhaust you use to reach orbit will reach atmosphere. It will have much less velocity than the orbital velocity, as you are shooting it backwards.
Title: Re: SSTO Thread
Post by: docmordrid on 07/18/2015 08:57 am
Interesting....we'll see.

Escape Dynamics beamed power SSTO

http://escapedynamics.com/edispacelaunch/
Title: Re: SSTO Thread
Post by: Asteroza on 07/20/2015 03:55 am
Escape Dynamics seems to have a press release for an end-to-end demo of a 100KW microwave beamed power thermal rocket, which is a step up beyond the demos done by Parker. Good to see some of the beamed power thermal thruster work progressing.

The other major beamed power groups have gotten quiet though. Lasermotive certainly hasn't been saying very much as of late.
Title: Re: SSTO Thread
Post by: Devilstower on 07/20/2015 03:52 pm
Short article on Escape Dynamics announcement in popular press. Includes embedded video.

http://www.engadget.com/2015/07/20/escape-dynamics-microwave-spacecraft/
Title: Re: SSTO Thread
Post by: A_M_Swallow on 07/20/2015 04:09 pm
Short article on Escape Dynamics announcement in popular press. Includes embedded video.

http://www.engadget.com/2015/07/20/escape-dynamics-microwave-spacecraft/

If building microwave transmitters throughout the world is too difficult politically what is this system like as a first stage?
Title: Re: SSTO Thread
Post by: Devilstower on 07/20/2015 06:28 pm
Personally, I'd go with an equator-girdling series of barge-mounted Masers over broad arrays of more conventional focused microwave sources on land. It's a daunting project either way, but pocket change compared to many suggestions for delivering material to orbit.
Title: Re: SSTO Thread
Post by: spacenut on 07/20/2015 07:56 pm
I've read that Nasa did a study one time about using electromagnetic propulsion on a mile long runway with a ramp at the end.  Something like an X-33 shuttle could be launched using this ramp to achieve about 600 mph at lift off, thus saving 20% of extra fuel needed to achieve orbit.  The craft would launch horizontal and land horizontal on a runway.  I do not know why this was never used in conjunction with the X-33 for SSTO craft. 
Title: Re: SSTO Thread
Post by: john smith 19 on 07/21/2015 12:06 am
I've read that Nasa did a study one time about using electromagnetic propulsion on a mile long runway with a ramp at the end.  Something like an X-33 shuttle could be launched using this ramp to achieve about 600 mph at lift off, thus saving 20% of extra fuel needed to achieve orbit.  The craft would launch horizontal and land horizontal on a runway.  I do not know why this was never used in conjunction with the X-33 for SSTO craft.
I've no idea of this but there was a Boeing proposal for a $1Bn single SSME powered crewed SSTO using magnetic  sled as a launch assist technology.

What was astonishing was this was a fixed price contract proposal to the USAF (not NASA) , suggesting that Boeing were very confident that it could work.

The problem is that $1Bn is still a lot of money to commit, especially when the X30 was the programme of record at the time (mid to late 80's IIRC). That rail also commits you to take offs only on that axis, the alternative being multiple catabults or some way of spinning the several mile long launcher. Not entirely impossible, but verydifficult.  :(
Title: Re: SSTO Thread
Post by: john smith 19 on 07/21/2015 12:06 am
Personally, I'd go with an equator-girdling series of barge-mounted Masers over broad arrays of more conventional focused microwave sources on land. It's a daunting project either way, but pocket change compared to many suggestions for delivering material to orbit.
Unnecessary.

If you figure that getting to orbit is roughly a 1/4 circle starting at the launch point then at a point down range equal to the altitude you want to reach you're roughly in orbit you don't need a girdle of microwave stations.

Maser technology was not really developed in the way laser tech was. By their operating principles such devices always hae pretty poor conversion efficiency as they have to achieve population inversion before energy release. 

Probably the biggest recent advance in MASER technology was the development in the UK of a room temperature design using laser pumping to get the inversion in an organic crystal before inputting a microwave signal.

But current microwave sources are 80%+efficient, whereas the most efficient lasers (LED driven crystals) are about 25-35%/

At high power levels (and this stuff is all high power) you that means 2.5x-3x more heat to get rid of.

Title: Re: SSTO Thread
Post by: spacenut on 07/21/2015 01:14 pm
One catapult could have been built at Vandenburg for polar orbits.  One at the cape for ISS orbit.  At least one vehicle would mean less complexity.  Also the entire vehicle would return for inspection.  Maybe a third catapult at Texas for a different orbit. 
Title: Re: SSTO Thread
Post by: Paul451 on 07/21/2015 07:25 pm
I've no idea of this but there was a Boeing proposal for a $1Bn single SSME powered crewed SSTO using magnetic  sled as a launch assist technology. [...]
The problem is that $1Bn is still a lot of money to commit, [...] That rail also commits you to take offs only on that axis, the alternative being multiple catabults or some way of spinning the several mile long launcher.

Meh, at a $1b a pop, you prove it works in one trajectory then build others to follow demand. (Maybe start with polar, since this was USAF.) How much has the US spent on launchers since the '80s?

My guess is that you'd have a pretty broad range of orbital planes you can reach with the SSTO from any given "first stage" trajectory. You might only need two for polar, one for due East, and maybe two more NE and two SE for everything in between. $7b for a full spread. Plus a few billion for backup sites. Bargain.

One catapult [...] at the cape for ISS orbit.

Two, one for the NE leg, one for the SE leg. (Also, since it was the '80s, it would have been Freedom, not ISS. And since the station hadn't been built yet, you'd optimise the station for the catapult, not the catapult for the station.)
Title: Re: SSTO Thread
Post by: RobLynn on 07/22/2015 03:05 am
The future availability of SpaceX's Raptor methane/lox reusable staged combustion engine that at the moment looks to like it will have something like 2500kN thrust and probably something like Isp=320s SL, 350s Vac has got to make the feasibility of SSTO much more likely.  T/W is of course critical, but with the Proton's staged combustion UDMH/N204 RD275M T/W at nearly 180:1 and 50 year old RP1/LOX NK33 at 140:1 it suggests that T/W >130 may be on the cards even with methane's lower density (25% lower density than RP1 partially compensated for by 5% higher Isp).

In a few more years Aerojet's Thrust Augmented Nozzles will come out of patent - and with their massive increase in T:W at lift off, with only slight depression in SL Isp as well as boost in Vac Isp (due to more optimal higher expansion ratio nozzle) they could work very well for an SSTO based on the Raptor or other LOX/methane engine.

Also SpaceX's demonstration of propulsive landing will lower the perceived risk of VTOL designs to spare the complexities compromises and (likely?) higher development costs of VTHL designs.

I still like the idea of launch tower catapults to provide a relatively deltaV saving boost at liftoff - even if it is only 50-100m/s, the saving of 150-300m/s deltaV could make all the difference for an SSTO, and may only add a few 100 million to development costs.

With current expendable launchers looking to be in serious trouble from SpaceX's lower costs, maybe one of the more deep-pocketed govt backed providers (china, russia, india, ESA) will take the plunge on SSTO to leap-frog SpaceX's TSTO.
Title: Re: SSTO Thread
Post by: tl6973 on 07/23/2015 12:12 pm
Just wondering - is the principal point of having these very large ground infrastructure installations (rails, catapults, laser/ maser barges etc.) to make an SSTO vehicle FEASIBLE, or to have a simpler/ cheaper launch vehicle than by other concepts?

Could anyone comment on whether the ongoing operations and maintenance cost (lots of salaries to pay I'm assuming, along with hefty electricity bills) of these devices actually does make it either cheaper, more capable or reliable than using expendable rockets?

Also, one could make the argument that since these devices play a large part in providing the energy to orbit, they are in fact the first stage of a TWO stage vehicle...

A bit odd to think that your first stage is disconnected from the orbiter and permanently attached to the ground I suppose :)
Title: Re: SSTO Thread
Post by: Paul451 on 07/23/2015 07:51 pm
Just wondering - is the principal point of having these very large ground infrastructure installations (rails, catapults, laser/ maser barges etc.) to make an SSTO vehicle FEASIBLE, or to have a simpler/ cheaper launch vehicle than by other concepts?

AIUI, the former. It's to bring the mass-fraction requirements of the SSTO back within realistic materials and construction.

Also, one could make the argument that since these devices play a large part in providing the energy to orbit, they are in fact the first stage of a TWO stage vehicle...

That is actually a long and thread-locking argument over SSTOs.

For example, is an SSTO still an SSTO if it has drop-tanks? What about boosters? Does a ballistic once-around RTLS SSTO, requiring an upper-stage to put the payload into an actual orbit, still qualify because it gives 90% of the orbital energy?

(The same arguments can be had over two vs three stages, of course, but there seems to be less emotional investment in the issue so those are less likely to turn into heated arguments.)
Title: Re: SSTO Thread
Post by: Asteroza on 07/23/2015 11:43 pm
Just wondering - is the principal point of having these very large ground infrastructure installations (rails, catapults, laser/ maser barges etc.) to make an SSTO vehicle FEASIBLE, or to have a simpler/ cheaper launch vehicle than by other concepts?

The very large systems (this includes large and very large conventional SSTO's) generally are fighting the payload margin issue through some kind of brute force method. Large conventional SSTO's try to beat the mass ratio issue by going physically larger, under the general assumption that using larger physical components eases manufacturing, and parts count drives costs more than cost of materials so going large doesn't hurt you overall. This leads to extreme Big Dumb Booster concepts like Sea Dragon which uses thick maraging steel welded by former submarine builders.

SSTO-ish systems relying on some sort of ground infrastructure heavily prioritize payload throughput and capacity utilization. The underlying assumption being that the infrastructure is expensive but is generally an up-front capital expense, with assumed low operating expense pushing you to use the infrastructure as much as possible. Operating concepts start resembling railway operations more than airline operations. Though for any transportation system, you are trying to reduce CapEx and OpEx, with tempo linked to OpEx.


This is why raw ground launchers like gun launch (railguns, staged combustion guns, etc) prefer high firing rates, generally trying to ship bulk payloads (much like a railroad) like fuel and hardy consumables, ideally to some sort of receiver propellant/cargo depot. The pain of high CapEx means you must design for exceptionally low OpEx from the beginning. For beamed power style systems, there is the added benefit/issue that depending on the ground location and layout, you may have some azimuth choices for launch. Also depending on the ground layout, there may be the option between unmanned cargo and passengers (a lot of beamed power systems initially are designed as 100-1000Kg payload systems with a 20G burnout acceleration, which is generally unacceptable for humans).

I suppose as an extension of the OpEx issues, the moving but non-cargo portions of the systems need to be minimized, and possibly reusable, so are in some sense lower cost. Railgun systems have a fairly minimal shell design with a kick stage, some design are recoverable with the expectation that they are brought back in batches somehow. Beamed systems do have expendable capsule designs (higher mass margin) but many are reusable, generally a spaceplane look due to a broad underside available as a heatshield for reentry, which internally may be simpler than a conventional rocket thus being cheaper than a "normal" VTHL/HTHL SSTO. Though how well that works out depends on design, as there could be a fairly complex turbopump arrangement which means you end up having half a conventional rocket engine in essence.


As a footnote, many beamed systems don't talk much about the actual launch. There is a bit of an assumption that the rocket is within line of sight of the first beaming station, and in that situation, at least enough power is delivered to get positive thrust to get it higher and easier to see from the first or other ground stations. I think in practice, unless the rocket has some sort of assist to get some altitude above the horizon of the first beaming station, it will be hard to site the launchpad and first beaming station. There have been some interesting proposals to the solve the first kilometer problem, usually air launch from a mothership, some sort of catapult, making the rocket external air breathing initially (ATR), and even reflecting power from a beam redirector array in orbit from the first beaming station. My personal favorite is a beam assisted Skylon, as it can self-launch and gain the necessary altitude and can change azimuth by changing the approach vector to the beaming station.
Title: Re: SSTO Thread
Post by: john smith 19 on 07/24/2015 12:23 am
Just wondering - is the principal point of having these very large ground infrastructure installations (rails, catapults, laser/ maser barges etc.) to make an SSTO vehicle FEASIBLE, or to have a simpler/ cheaper launch vehicle than by other concepts?
The only thing that people are very confident about SSTO is that the structural mass (and hence the payload) are strictly limited. Those who've believed that either it it's simply too difficult to build a vehicle with that mass fraction (or equally difficult guarantee the vehicle will hit that within its design margins). The more concerned they have been the bigger the level of "launch assist" they have looked at using.

As a general point there is a spectrum of launch vehicle architecture options starting at pure SSTO, then "assisted" SSTO, then full TSTO. Assistance can be applied to an LV of any number of stages, most famously with the plane launch of the Pegasus XL, 2 or 3 stage ELV.
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Could anyone comment on whether the ongoing operations and maintenance cost (lots of salaries to pay I'm assuming, along with hefty electricity bills) of these devices actually does make it either cheaper, more capable or reliable than using expendable rockets?
All open questions until someone builds one.  :(
Historically most ELV's have failure rates around 1 in 50  and few have racked up enough launches to go below 1 in 100 (IIRC Soyuz is the exception).

The only data points here are aircraft and the Shuttle. Aircraft went from <100mph top speeds and the flying of the English Channel being a major event to long distance flight at M3 in less than 60 years. In a similar period Rockets have not really made equivalent progress. The Shuttles 2 failures happened to the parts that were either expendable or heavily rebuilt after each launch.

These suggest that expendable parts (and in an ELV all parts are expendable) have severe effects on reliability, as does being able to examine a vehicle after flight. Possible with aircraft, impossible for all ELV's.
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Also, one could make the argument that since these devices play a large part in providing the energy to orbit, they are in fact the first stage of a TWO stage vehicle...
True, although the usual nomenclature is "launch assist" as the planned delta V is usually much smaller than a stages delta V (IE 1/3 to 1/2 of orbital velocity).
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A bit odd to think that your first stage is disconnected from the orbiter and permanently attached to the ground I suppose :)
You might also note that the vehicle is at its heaviest at takeoff. At this point you spend the most propellant mass to get the least increase in velocity (because the LV is at its heaviest. Vertical or horizontal does not really matter).

Hence the attraction of systems that only provide a little delta V (100s of m/s) so it's already moving when you have to start pushing it harder. Being ground based also means the launch assist is not mass limited. It can be as heavy as needed.

Note electricity is cheap, relative to propellant. It takes something like 63 Mj to orbit a Kg, that 's 17.5 Kwh.

You might like to check the price of Kwh in your location.
Title: Re: SSTO Thread
Post by: Asteroza on 07/24/2015 06:43 am

Note electricity is cheap, relative to propellant. It takes something like 63 Mj to orbit a Kg, that 's 17.5 Kwh.

You might like to check the price of Kwh in your location.

The flip side of that though is Dr Kare's rule of thumb for beamed SSTO; beam power needs to be around 1MW per Kg of payload...
Title: Re: SSTO Thread
Post by: john smith 19 on 07/24/2015 10:18 am

Note electricity is cheap, relative to propellant. It takes something like 63 Mj to orbit a Kg, that 's 17.5 Kwh.

You might like to check the price of Kwh in your location.

The flip side of that though is Dr Kare's rule of thumb for beamed SSTO; beam power needs to be around 1MW per Kg of payload...
A fair point but is that for using lasers to directly heat air only?

I'm guessing a low molecular weight gas (IE anything below 28g/mol)  is much more effective.  Obviously LH2 is the lightest but I'd bet the trade would be quite tight with Methane if cost were a factor.
Title: Re: SSTO Thread
Post by: chipguy on 07/24/2015 04:35 pm
It takes something like 63 Mj to orbit a Kg, that 's 17.5 Kwh.

You might like to check the price of Kwh in your location.

I think your figure is high by a factor of two.

OTOH, while ground based captive electromagnetic launchers can be very efficient (probably over 90%
with recovery of energy/regenerative braking of the captive portion/moving platform) for the tiny initial
energy input the beamed approach is very inefficient with significant losses in beam generation, beam
transmission, beam spreading, recovery of beam energy in launch vehicle, and conversion of energy into
propulsion.
Title: Re: SSTO Thread
Post by: JasonAW3 on 07/24/2015 06:54 pm
It takes something like 63 Mj to orbit a Kg, that 's 17.5 Kwh.

You might like to check the price of Kwh in your location.

I think your figure is high by a factor of two.

OTOH, while ground based captive electromagnetic launchers can be very efficient (probably over 90%
with recovery of energy/regenerative braking of the captive portion/moving platform) for the tiny initial
energy input the beamed approach is very inefficient with significant losses in beam generation, beam
transmission, beam spreading, recovery of beam energy in launch vehicle, and conversion of energy into
propulsion.

chip,

     You maybe more right than you know.  I was just reading an article about a superconductor that super cunducts at up to 77C, or about 150F.  This is way beyond room temperature super conducting, however the fragile nature of the conductor and the complex processing needed would still cause problems.

     On the other hand, if this can be made cheaply, less fragile, and in massive quantities, then the linear acellerator becomes VERY practicle.

     (Of course, this would also make electrical motors VASTLY more effecient!)
Title: Re: SSTO Thread
Post by: chipguy on 07/24/2015 07:49 pm

chip,

     You maybe more right than you know.  I was just reading an article about a superconductor that super cunducts at up to 77C, or about 150F.  This is way beyond room temperature super conducting, however the fragile nature of the conductor and the complex processing needed would still cause problems.

     On the other hand, if this can be made cheaply, less fragile, and in massive quantities, then the linear acellerator becomes VERY practicle.

The fly in this ointment is critical current density and critical magnetic flux density. Exceed either and your superconductor is no longer a superconductor. But given its useful application in other areas this may not be a problem. However with the short operating time and low duty cycle of an electromagnetic launch system conventional materials would likely be far more cost effective while still meeting requirements.

Quote
     (Of course, this would also make electrical motors VASTLY more effecient!)

Electrical motors can easily exceed 90% efficiency today so "VASTLY" really depends on how you look at it.

Consider increasing the efficiency of a motor from 92 to 96%.

From the viewpoint of converting electrical energy into mechanical energy efficiency only increased 4.3%.

From the viewpoint of designing the cooling system efficiency doubled - heat generated within the motor is halved for the same power in.

However if this improvement required supeconductors the cooling system will likely end up far more problematic despite halving the waste heat to remove.
Title: Re: SSTO Thread
Post by: Paul451 on 07/25/2015 05:59 am
I was just reading an article about a superconductor that super cunducts at up to 77C, or about 150F.

Unlikely. The current record for a normal superconductor is about -130C. The "open" record is for a material pressurised to 30GPa, which appears to still superconduct at -70C (~200K).

The only superconductors above that are claims by fringe researchers. (One in particular who's been inventing new materials every few months for 20 years which he claims are above-RT superconducting, but only for a few domains within the bulk material, and therefore only detected by micro dips in his Ohmmeter.)
Title: Re: SSTO Thread
Post by: john smith 19 on 07/25/2015 07:39 am
It takes something like 63 Mj to orbit a Kg, that 's 17.5 Kwh.

You might like to check the price of Kwh in your location.

I think your figure is high by a factor of two.

OTOH, while ground based captive electromagnetic launchers can be very efficient (probably over 90%
with recovery of energy/regenerative braking of the captive portion/moving platform) for the tiny initial
energy input the beamed approach is very inefficient with significant losses in beam generation, beam
transmission, beam spreading, recovery of beam energy in launch vehicle, and conversion of energy into
propulsion.
Oh dear, I've forgotten the 1/2 in the KE equation. Again.   :(
It does show that in energy terms getting to orbit is not that hard (but applying that energy is).

Are you confusing beamed power with heating? This was done by Raytheon in the early 60s to drive a model helicopter and you've got
AC --> microwaves --> transmitter aerial loss --> receiver aerial loss --> rectification --> motor drive
Even then JPL were I think expecting about 60-80% from solar panel (for satellite solar) to output to the grid, using phase locked microwave oven magentrons for the job (no one thought you could do that with such cheap hardware at the time).
but this system does
AC --> microwaves --> transmitter aerial loss -->Absorbance by load (IE the heat exchanger).

I'd expect a properly dimensioned HX could be very absorbent of microwave power than heat the fluid very efficiently.
Title: Re: SSTO Thread
Post by: RobLynn on 07/26/2015 05:54 pm
If looking at launch assist for SSTO (or other launchers) electromagnetic accelerators are extremely expensive, and probably a very bad choice until get up to speeds around Mach 1 or beyond.

Steel belts used in moving floor windtunnels can operate at up to 100m/s, and aircraft carrier cable arrestor systems operate reliably at 70m/s.  Fiber reinfoced composite belts or cables with lower density and higher strength can probably go much faster providing the pulleys are large enough diameter.  It is very simple to accelerate to 2x the speed limit set by the speed of the cable going around the pulley (attach one end of cable to rocket, other to ground and accelerate the pulley), suggesting that with steel belts 200m/s is possible.

Steam rockets, V8 crate engines and large falling weights are probably the cheapest ways to provide the ~GW's of power needed for low flight rate subsonic catapult launch assist.  Though looking around there seems to have been little work done on the general concept of launch assist systems (too low tech to excite space agencies, or just not worth hassle for TSTO?).
Title: Re: SSTO Thread
Post by: john smith 19 on 07/28/2015 07:11 am
If looking at launch assist for SSTO (or other launchers) electromagnetic accelerators are extremely expensive, and probably a very bad choice until get up to speeds around Mach 1 or beyond.

Steel belts used in moving floor windtunnels can operate at up to 100m/s, and aircraft carrier cable arrestor systems operate reliably at 70m/s.  Fiber reinfoced composite belts or cables with lower density and higher strength can probably go much faster providing the pulleys are large enough diameter.  It is very simple to accelerate to 2x the speed limit set by the speed of the cable going around the pulley (attach one end of cable to rocket, other to ground and accelerate the pulley), suggesting that with steel belts 200m/s is possible.
The issue with all such systems.Does the launch velocity reduction outweigh the cost and expense of developing this system. The trouble is full orbital is about M23. The question (like with air breathing) is can you lower the gross mass enough to improve the mass fraction enough to make the construction task easier.
Quote
Steam rockets, V8 crate engines and large falling weights are probably the cheapest ways to provide the ~GW's of power needed for low flight rate subsonic catapult launch assist.  Though looking around there seems to have been little work done on the general concept of launch assist systems (too low tech to excite space agencies, or just not worth hassle for TSTO?).
Actually this has also been looked at using a pneumatic system.
Title: Re: SSTO Thread
Post by: msat on 07/31/2015 01:05 pm
For catapults, I figured a option would be to build a rocket powered sled which has the advantage of not requiring the propulsion system to be flight weight, so should be cheaper to build and more robust, and use heavy rail techniques for the track, which is well established and relatively cheap. That would make launch sites cheaper to build, maintain and operate than a lot of other potential systems. The speed record using conventional rail is over 300mph, so it seems there is some potential there.
Title: Re: SSTO Thread
Post by: Asteroza on 08/03/2015 01:11 am

Note electricity is cheap, relative to propellant. It takes something like 63 Mj to orbit a Kg, that 's 17.5 Kwh.

You might like to check the price of Kwh in your location.

The flip side of that though is Dr Kare's rule of thumb for beamed SSTO; beam power needs to be around 1MW per Kg of payload...
A fair point but is that for using lasers to directly heat air only?

I'm guessing a low molecular weight gas (IE anything below 28g/mol)  is much more effective.  Obviously LH2 is the lightest but I'd bet the trade would be quite tight with Methane if cost were a factor.

I understood the rule of thumb to apply to LH2 propellant HX beamed systems, and not like Myrabo's lightcraft using outside air. I imagine aside from the exhaust velocity, there would be coking issues with hydrocarbons in the HX.

As for the first kilometer issue to get above the horizon for beamed systems, a mountain ramp steam rocket catapult sled would be an interesting alternative. If thermal energy stores are used to provide a heatsink for beaming infrastructure, that heat can be hauled as insulated hot gravel tank cars. Have the tank cars take the long way around the mountain and provide heat for the steam plant to load the steam rocket sled.
Title: Re: SSTO Thread
Post by: Asteroza on 08/03/2015 06:28 am
Now for added fun, the NTTR, a NTR SERJ-ish SSTO! Well, more like an NTR ejector tipfan ramrocket, with some possible scramjet action. Or an NTR ATR turbofan rocket. NTR hydrogen output gets exhausted out linear aerospike shaped trailing edges of the fan blades to burn with air. Variable pitch blades, so as a rocket fan it eventually stops turning for pure rocket mode.

http://arc.aiaa.org/doi/abs/10.2514/6.2015-3958 (http://arc.aiaa.org/doi/abs/10.2514/6.2015-3958)

I expect SERJ fans to come spinning out of the vacuum any moment now...

Title: Re: SSTO Thread
Post by: john smith 19 on 08/03/2015 05:32 pm
Now for added fun, the NTTR, a NTR SERJ-ish SSTO! Well, more like an NTR ejector tipfan ramrocket, with some possible scramjet action. Or an NTR ATR turbofan rocket. NTR hydrogen output gets exhausted out linear aerospike shaped trailing edges of the fan blades to burn with air. Variable pitch blades, so as a rocket fan it eventually stops turning for pure rocket mode.

http://arc.aiaa.org/doi/abs/10.2514/6.2015-3958 (http://arc.aiaa.org/doi/abs/10.2514/6.2015-3958)

I expect SERJ fans to come spinning out of the vacuum any moment now...
This briefly came up on the Skylon thread.

It really did sound like an idea unencumbered by any actual knowledge of the subject. :(
Title: Re: SSTO Thread
Post by: Nilof on 08/03/2015 05:39 pm

Note electricity is cheap, relative to propellant. It takes something like 63 Mj to orbit a Kg, that 's 17.5 Kwh.

You might like to check the price of Kwh in your location.

The flip side of that though is Dr Kare's rule of thumb for beamed SSTO; beam power needs to be around 1MW per Kg of payload...

Let's see...

At 800s Isp and 100% efficiency, the power consumption is roughly 4 kW/N, or 40 kW per kg of liftoff thrust. As a first approximation we can increase that to 100 kW per kg to account for >1 initial T/W and inefficiencies.

If the payload to initial mass ratio is 10, that does indeed lead to 1 MW per Kg payload, it should be fairly good as an order of magnitude estimate for "typical" beamed power SSTO proposals with hydrogen propellant.

The one thing that people seem to miss however is that you do not need a power plant designed to give that much peak power, since the power is only needed for a few minutes. Li-Ion batteries can discharge their full load in a 20 minute time-frame. 125 million dollars' worth of Tesla powerpacks should be enough to power a launcher with a one-tonne payload, and could easily be recharged by grid power if the launch rate is less than once a day.

The beaming equipment price and operation is the real bottleneck. The first mile problem could be handled with something akin to LANTR, where one initially injects LOX into the combustion chamber to increase thrust. Alternatively, winged vehicles could be towed into the air by another aircraft.