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Comparisons - expend./reusable,heavy/light,theory/practice

Posted by: Ekkehard Augustin - Thu Mar 30, 2006 8:38 am
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Comparisons - expend./reusable,heavy/light,theory/practice 
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Post    Posted on: Fri Jul 14, 2006 11:11 am
Hello, WannabeSpaceCadet,

this I didn't expect anymore because it menas that you are misunderstanding.

The share is a criterion but not a ratio I want to maximize so.

What I have in mind is to use the share or ratio as a criterion to distiguish families or kinds of vehicles. I am working on it a bit using the table I posted. I will have add some oxidator-propellant-combinations from another table under www.benrd-leitenberger.de that seem not to fit into the row of Isps but are essential regarding the share.

But doing so - using the share to distiguish families - doesn't have nothing to do with maximization. I don't have in mind maximizations or the like. The goal at present still is to establish comparability. The first measures to do that were to keep V constant and to make other variables constant too - the next measure will be to apply that share.

These are measures to be applied at the currect state - might be that later some constants will be made variables again or that I will shift from the share to something else. I don't know but at present the share will be my criterion.

The goal is not a ranking now.



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Post    Posted on: Fri Jul 14, 2006 1:11 pm
WannabeSpaceCadet wrote:
what we all want is much less expensive and much larger volume, access to space. The Payload Effciency (payload mass / total mass) is completely irrelevant to this goal.
If someone had a billion ton rocket that could only put one pound in orbit, that would not be less expensive than an Atlas, no matter how simple the billion ton rocket might be. At some point, Payload Efficiency is relevant.


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Post    Posted on: Mon Jul 17, 2006 8:48 am
campbelp2002 wrote:
WannabeSpaceCadet wrote:
what we all want is much less expensive and much larger volume, access to space. The Payload Effciency (payload mass / total mass) is completely irrelevant to this goal.
If someone had a billion ton rocket that could only put one pound in orbit, that would not be less expensive than an Atlas, no matter how simple the billion ton rocket might be. At some point, Payload Efficiency is relevant.


Such a vehicle would have already been eliminated by the $/kg (or $/lb ) criteria. But is a 100 ton rocket that puts 5 tons in orbit for $100 million better than a 400 ton rocket that puts 5 tons in orbit for $20 million? I think not, but I suspect LockMart & Boeing might have another opinion.

Incidentally, the fuel cost for 380 tons of LOX / Kero is on the order of only $200 thousand. How much for a light steel tank with a common bulkhead divider, a few valves, a rocket engine with a 100:1 T/W ratio, and a basic guidance package?


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Post    Posted on: Mon Jul 17, 2006 8:52 am
Ok, Ekkehard, I now see your goal. A list of all the common designs with their results over different categories. Should be interesting.


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Post    Posted on: Mon Jul 17, 2006 1:54 pm
WannabeSpaceCadet wrote:
is a 100 ton rocket that puts 5 tons in orbit for $100 million better than a 400 ton rocket that puts 5 tons in orbit for $20 million?
I have always suspected that the heavy lift crowd assumed that the bigger rocket would be cheaper per launch than the smaller rocket, so it is good to have that explicitly on record. But I just do not accept that assumption. I believe a more realistic assumption would be the 400 ton rocket putting 10 tons in orbit for $110 million. In other words, the cost per pound goes down with larger launch vehicles, but the cost per launch is still higher. You will never convince me that a rocket 4 times bigger can cost 80% less no matter how simple it is.


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Post    Posted on: Mon Jul 17, 2006 2:31 pm
In between I grouped the propellants by their normal state - gas, liquid, solid.

Here are the groups:

Code:
Oxidator                 Propellant           Isp

gas/gas ==> pressurization and cryogenics required

Oxygen                    Diborane            3374
Fluorine                  Ammonia             3500
Fluorine                  Diborane            3638
Oxygen                    Hydrogen            3830
Fluorine                  Hydrogen            4020

gas/liquid ==> propellant flows relatively freely abnd doesn't reqire cryogenics etc.

Oxygen                    Ethanol             2740
Oxygen                    Cerosene            2945
Oxygen                    ADMH                3010
Oxygen                    Hydrazine           3070
Fluorine                  Cerosene            3139
FLOX (Fluorine and LOX)   ADMH                3373
Fluorine                  Pentaborane         3530
FLOX (Fluorine and LOX)   Cerosene            3550
Fluorine                  Hydrazine           3560
Fluorine                  ADMH                3569

gas/solid ==> propellant doesn't require cryogenics etc. but doesn't flow freely also

Oxygen                    Lithium hydride     2569
Oxygen                    HTPB/Aluminum       (2776)
Fluorine                  Lithium hydride     3569
Oxygen                    Beryllium hydride   3628
Fluorine                  Beryllium hydride   3863
Fluorine                  Polyethylene        (4050)
Fluorine/Oxygen           Lithium hydride     (4335)
Ozone                     Beryllium hydride   (5248)

liquid/gas ==> oxydator flows relatively freely but the propellant requires cryogenics etc.

Hydrogenperoxide 95 %     Hydrogen            3187
Hydrogenperoxide 95 %     Diborane            3246
Dinitrogen tetroxide      Hydrogen            3353

liquid/liquid ==> both flow relatively freely

Nitric acid               Cerosene            2630
Dinitrogen tetroxide      Cerosene            2710
Nitric acid               ADMH                2710
Hydrogenperoxide 95 %     ADMH                2720
Hydrogenperoxide 95 %     Cerosene            2745
Hydrogenperoxide 95 %     Hydrazine           2760
Nitric acid               Hydrazine           2775
Dinitrogen tetroxide      ADMH                2804
Dinitrogen tetroxide      Aerozine 50         2820
Dinitrogen tetroxide      Hydrazine           2865

liquid/solid ==> the oxidator flows relatively freely but the propellant don't

Dinitrogen tetroxide      Lithium hydride     2441
Nitric acid               Polyurethane        (2490)
Nitirc acid               Polybutadiene       (2540)
Nitric acid               Lithium hydride     2549
Hydrogenperoxide 95 %     Lithium hydride     2559
Dinitrogen tetroxide      Polyethylene        2696
Dinitrogen tetroxide      Beryllium hydride   3432
Hydrogenperoxide 95 %     Beryllium hydride   3667

unknown/gas ==> can't say nothing about oxidator but the propellant requires cryogenics etc.

Difluoroxide              Diborane            3569
Difluoroxide              Hydrogen            4020

unknown/liquid ==> can't say nothing about oxidator but the propellant flows relatively freely

Difluoroxide              Cerosene            3196
Difluoroxide              Hydrazine           3383
Difluoroxide              ADMH                3442

unknown/solid ==> can't say nothing about oxidator but the propellant doesn't flow

Difluoroxide              Beryllium hydride   3746


I left away "Chlordifluoride Cerosene 2530" because the oxidator is liquid up to 21° C but gas above that temperature.

These groups are of meaning for one of the constants.

May be that there is a difference in how freely the different liquids flow but this shouldn't be the focus on at the moment.



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EDIT: I added the additional solid propellants I forgot yesterday and set the Isps into parenthesises because I am suspecting that they are valid for other burning cahmber pressurs, mix ratios or external pressures than those of al the other oxydator-propellant-combinations.

But my focus here is on the propellants and oxydators themselves - not on the Isps that much - at present.


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Post    Posted on: Thu Jul 20, 2006 7:27 am
campbelp2002 wrote:
You will never convince me that a rocket 4 times bigger can cost 80% less no matter how simple it is.

I don't see why not, if the cost of the propellants, raw materials, electronics, valves, wires, nut & bolts etc, is all a small fraction of the total cost, then complexity, & the search for the best possible payload fraction, must be the cost drivers.

NASA's Minumum Cost Design (MCD) studies of the 80's & 90's, proved this. But scrapping the Shuttle (and now Ares), proved politically impossible.


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Post    Posted on: Thu Jul 20, 2006 1:09 pm
I might agree that simplifying a design could cut the cost in half. You might get me to agree to a quarter for a really elegant design. But 4 times bigger AND 5 times cheaper is effectively 20 times cheaper for a given size. No way Jose!

Pegasus was supposed to be cheap, because it is all solid propellant and small. What could be simpler? Just a big model rocket; a steel tube filled with propellant. No pumps, valves, pipes, pressurizing gas, regenerative chamber cooling channels, slosh baffles, nothing. But it costs $30 million per launch, far more expensive than Falcon 1 which has a pump fed liquid fuel engine and can put a slightly larger payload into orbit.


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Post    Posted on: Fri Jul 21, 2006 5:14 am
Pegasus is small, but not simple. 3 stages, a wing, a converted airliner, (4 stages really). Solid rocket fuel (and hybrids) cost a lot more than most liquids, and require a lot of care and inspection in casting.

Similarly, Rutan's Spaceship-One was the quickest way to sub-orbital for an aircraft company sponsored by a billionaire. But it was nowhere near the cheapest at $200,000+ per flight. An upscaled version of Armadillo's VDR would have costs of around 5 to 10% of that.

T/Space believe they can put a manned capsule, weighing almost 5 tons, in orbit, for $20m a flight, and they are still using a carrier aircraft and 2 stages.

A non man-rated, expendable BDR could be cheaper than that.


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Post    Posted on: Mon Jul 24, 2006 11:42 am
The groups of my recent table can partially can be aggregated to form the follwoing supergroups:

gas/gas
gas/liquid + liquid/gas
gas/solid
liquid/liquid
liquid/solid

unknown/gas
unknown/liquid
unknown/solid

Difluoroxide/Beryllium hydride

Leaving away the last four I at this point suspect - methodologically - the first group to require the most heavy equipment because for both the oxidator and the propellant crygenics and pressurization are required. The second requires less equipment because only one of the both requires cryogenics and pressurization.

The third group I expect additionally to not require equipment liquids need like pumps and valves.

The next two now don't need no cryogenics and pressurizations while the last of them may be the group requiring the least amount of equipment.

So these groups look as if they are groups of different kinds of rockets or vehicles because Klr and Klt are different in comparison to each other.

If the total weight of a rocket is 100% then the percentage of Klr and Klt at this point can be expected to differ between the groups more than within each group. As a consequence it can be expected that the percentage of payload-weight too differs in that manner.

Instead of 100% I could have used an absolute value - 100 mT for example. Then it can be seen directly that the expectation is that the payload-weight differs as described - so this may be a good criterion to distinguish 5 lifter-groups where according to the expectations the fifth group may be best fitted to heavy weights while the first may be best fitted to light weights but shouldn't be used for heavy weights.

These expections have to be checked later. Before that s going to be done another comparison is required also ...



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Post    Posted on: Mon Jul 31, 2006 11:18 am
In between I have ready a table providing a synopsis of the groups distinguished - but it doesn't fit into the post in parallel to keeping the table readable and understandable yet.

But what can be seen is that

1. the gas/gas-group, 75% of the gas/solid-group, four members of the gas/liquid-/liquid/gas-group and 25% of the liquid/solid-group have comparable Isps,
2. next there are eight members of the gas/liquid-/liquid/gas-group followed by
3. the liquid/liquid-group and at last
4. five members of the liquid/solid-group.

It seems that gases aren't required really and that non-gas-propellants allow for higher payload-shares of the total weight. But this depends on the distinct Isps merely. The issue might still hold because some Isps of solids are even higher than gas/gas.

I am going to find a modification of the table that fits into the requirements here - I will post it either here by EDIT or by a separate post.



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EDIT:

Here the table

I altered the names of the oxydators and propellants into short names first:

Translation Names into Short Names

Code:
Oxydator                  Propellant          Ox      Prop

Dinitrogen tetroxide      Lithium hydride     DT      Li hy
Nitric acid               Polyurethane        NA      Pol u
Nitric acid               Polybutadiene       NA      Pol b
Nitric acid               Lithium hydride     NA      Li hy
Hydrogenperoxide 95 %     Lithium hydride     HP      Li hy
Oxygen                    Lithium hydride     LOX     Li hy
Nitric acid               Cerosene            NA      Cero
Dinitrogen tetroxide      Polyethylene        DT      Pol e
Dinitrogen tetroxide      Cerosene            DT      Cero
Nitric acid               ADMH                NA      ADMH
Hydrogenperoxide 95 %     ADMH                HP      ADMH
Oxygen                    Ethanol             LOX     Ethl
Hydrogenperoxide 95 %     Cerosene            HP      Cero
Hydrogenperoxide 95 %     Hydrazine           HP      Hzine
Nitric acid               Hydrazine           NA      Hzine
Oxygen                    HTPB                LOX     HTPB
Dinitrogen tetroxide      ADMH                DT      ADMH
Dinitrogen tetroxide      Aerozine 50         DT      Ae 50
Dinitrogen tetroxide      Hydrazine           DT      Hzine
Oxygen                    Cerosene            LOX     Cero
Oxygen                    ADMH                LOX     ADMH
Oxygen                    Hydrazine           LOX     Hzine
Fluorine                  Cerosene            F       Cero
Hydrogenperoxide 95 %     Hydrogen            HP      LH2
Hydrogenperoxide 95 %     Diborane            HP      Dibo
Dinitrogen tetroxide      Hydrogen            DT      LH2
FLOX (Fluorine and LOX)   ADMH                FLOX    ADMH
Oxygen                    Diborane            LOX     Dibo
Dinitrogen tetroxide      Beryllium hydride   DT      Be hy
Fluorine                  Ammonia             F       Ammo
Fluorine                  Pentaborane         F       Penta
FLOX (Fluorine and LOX)   Cerosene            FLOX    Cero
Fluorine                  Hydrazine           F       Hzine
Fluorine                  ADMH;               F       ADMH
                          gas/solid-case:             g/s:
                          Lithium hydride             Li hy
Oxygen                    Beryllium hydride   LOX     Be hy
Fluorine                  Diborane            F       Dibo
Hydrogenperoxide 95 %     Beryllium hydride   HP      Be hy
Oxygen                    Hydrogen            LOX     LH2
Fluorine                  Beryllium hydride   F       Be hy
Fluorine                  Hydrogen            F       LH2
Fluorine                  Polyethylene        F       Pol e
Fluorine/Oxygen           Lithium hydride     F/LOX   Li hy
Ozone                     Beryllium hydride   Ozone   Be hy


The table I used to write this post is

Comparison of Isps using Short Names

Code:
hint         Ox      Prop.   gas/   gas/   gas/   liq/   liq/
                             gas    liq    soli   liq    soli

             DT      Li hy                               2441
             NA      Pol u                               2490
             NA      Pol b                               2540
             NA      Li hy                               2549
             HP      Li hy                               2559
             LOX     Li hy                 2569     
             NA      Cero                         2630   
             DT      Pol e                               2696
             DT      Cero                         2710   
             NA      ADMH                         2710   
             HP      ADMH                         2720   
gas/liquid   LOX     Ethl          2740         
             HP      Cero                         2745   
             HP      Hzine                        2760   
             NA      Hzine                        2775   
             LOX     HTPB                  2776     
             DT      ADMH                         2804   
             DT      Ae 50                        2820   
             DT      Hzine                        2865   
gas/liquid   LOX     Cero          2945         
gas/liquid   LOX     ADMH          3010         
gas/liquid   LOX     Hzine         3070         
gas/liquid   F       Cero          3139         
liquid/gas   HP      LH2           3187         
liquid/gas   HP      Dibo          3246         
liquid/gas   DT      LH2           3353         
gas/liquid   FLOX    ADMH          3373         
             LOX     Dibo    3374           
             DT      Be hy                               3432
             F       Ammo    3500           
gas/liquid   F       Penta         3530         
gas/liquid   FLOX    Cero          3550         
gas/liquid   F       Hzine         3560         
gas/liquid   F       ADMH;         3569   3569
or solid             g/s:
                     Li hy
             LOX     Be hy                3628     
             F       Dibo    3638           
             HP      Be hy                               3667
             LOX     LH2     3830           
             F       Be hy                3863     
             F       LH2     4020           
             F       Pol e                4050     
             F/LOX   Li hy                4335     
             Ozone   Be hy                5248     


Last edited by Ekkehard Augustin on Thu Aug 10, 2006 7:20 am, edited 2 times in total.



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Post    Posted on: Tue Aug 08, 2006 10:14 am
What has been left out of consideration during looking for and at groups is the density of propellants.

Since the density determines the required tank volume it determines the surface of the tank(s) and thus the weight provided the tanks have in common the material they are made of.

For comparison purposes I use a standard material - aluminum.

The density of the propellant(s) don't establish new groups but simply mean to turn back from the constants to the variables.



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Post    Posted on: Thu Aug 10, 2006 5:16 am
Some propellants are not compatible with aluminium. Fluorine for example. They require non-reactive liners. Cryogenic propellants require insulation of the tank, making it heavier.

Pressurization of the propellant initially allows the tank wall to be thinner, then thicker as pressure increases. The trade off with higher pressure (heavier) tanks, is you don't need a (heavy) turbo pump, but ISP is a bit less.

ISP varies, for any specific propellant combination, with the chamber pressure, whether produced by tank pressure (medium) or a turbo pump (high).

The surface area of the tanks depends on the the shape of the tank as well as the volume. A sphere has the least surface area for a given volume. Spherical tanks also require thinner walls to contain the same pressure.


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Post    Posted on: Thu Aug 10, 2006 1:04 pm
Hello, WannabeSpaceCadet,

under www.bernd-leitenberger.de there is an article explaining why spherical tanks aren't that advantageous but have more disadvantages than advatages.

But although spherical tanks are optimal regrading surface and thus material larger amounts of a particular propellant require a larger sphere too which menas more surface and thus more material.

The variation of the Isps by chamber pressure I remember to have mentioned when posting the propellant table the first time some posts ago on the previous page of this thread. The table(s) of propellants and Isp I am using up to now explicitly use a constant chamber pressure. At present I am not going to vary that pressure - variations simply would shift the values only I suppose.

I might have a look on the thickness or thinness of the tank walls later when I am ready with the propellants and thus the connection between ve and Mve for the first time. At this point I only want to hint to the circumstance that the weight of the tanks is a constant Klt here.

In between there are five groups of Klt here - but Klt will be kept a constant but not turned into a variable Mlt again.

This all is so simply because the focus is on the connection between ve and Mve at present - which must be kept yet.



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

EDIT:

Another hint regarding Fluorine and aluminum. At present I am still focussed on theory. This means that I can neglect such incompatibilities - they simply have to be handled later in practice. There might be solutions like thin protecting layers of non-aluminum materials. Each tank might have such layers and it might be possible to select them so that the comparability of the tank weight isn't removed. And LOX-tanks have insulations for wires inside because of the requirement to set the LOX to motion from time to time.

What's of meaning at present simply is to apply tanks in these theoretical considerations that are made of the same material or of materials that weight nearly the same at nearly identical amounts.


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Post    Posted on: Tue Aug 15, 2006 11:24 am
In the following table the Isps are replaced by average densities I got from www.bernd-leitenberger.de.

Code:
hint         Ox      Prop.   gas/   gas/   gas/   liq/   liq/
                             gas    liq    soli   liq    soli

             DT      Li hy                                 ? 
             NA      Pol u                               1.391
             NA      Pol b                               1.384
             NA      Li hy                                 ? 
             HP      Li hy                                 ? 
             LOX     Li hy                   ?       
             NA      Cero                         1.35   
             DT      Pol e                                 ? 
             DT      Cero                         1.26   
             NA      ADMH                         1.25   
             HP      ADMH                         1.24   
gas/liquid   LOX     Ethl          1.1           
             HP      Cero                           ?     
             HP      Hzine                        1.26   
             NA      Hzine                        1.28   
             LOX     HTPB                  1.34       
             DT      ADMH                           ?     
             DT      Ae 50                        1.2     
             DT      Hzine                        1.22   
gas/liquid   LOX     Cero          1.2           
gas/liquid   LOX     ADMH            ?           
gas/liquid   LOX     Hzine         1.7           
gas/liquid   F       Cero            ?           
liquid/gas   HP      LH2             ?           
liquid/gas   HP      Dibo            ?           
liquid/gas   DT      LH2             ?           
gas/liquid   FLOX    ADMH            ?           
             LOX     Dibo      ?             
             DT      Be hy                                 ? 
             F       Ammo    1.18             
gas/liquid   F       Penta           ?           
gas/liquid   FLOX    Cero            ?           
gas/liquid   F       Hzine         1.31           
gas/liquid   F       ADMH;           ?      ? 
or solid             g/s:
                     Li hy
             LOX     Be hy                  ?       
             F       Dibo      ?             
             HP      Be hy                                 ? 
             LOX     LH2     0.28           
             F       Be hy                  ?       
             F       LH2     0.45           
             F       Pol e                1.31       
             F/LOX   Li hy                1.327     
             Ozone   Be hy                  ?       


The order of the propellants is left unchanged.

It turns out that the high densities are concentrated at the propellants with low or medium Isps as far as I found densities listed. Four higher densities only are to be found in the high-Isp-region of the tables. The highest density is to be found in the gas/liquid-column while the only high-density/high-Isp combinations can be found in the gas/solid-column.

From this it seems that high Isps are not necessaryly not-outweighed by larger tank-weights.

I consciously say "From this" because I might get different results considering it from another perspective - here I still look at the functional links and connections between ve and Mve. Lighter tanks with less Isps - heavier tanks with higher Isps - four exceptions of that only: In general an increase of the ve will be partially consumed by an increase of the weight of the tank(s) and so on - except for 4 exceptions. The conclusion from this seems to tend to be that the slope of the function f(ve) = Mve is not negative.

Please note that I am still considering the theory-aspect. The results are weak regarding the function f(ve) = Mve since a lot of average densities aren't available to me at present and they would have to be given under the conditions I listed in an earlier post.



Hello, WannabeSpaceCadet,

although I am not yet at the point to look at the tanks one hint here. Larger spherical tanks would have a larger diameter. So the rockets using larger spherical tanks would be wider and thus tend to suffer more resistance by the air in front of it/them. This in turn would increase the required amounts of propellant - which again would increase the tank diameter.

The shape of rockets might be changed to solve such problems - but this too is or would be a problem to be considered later.

...



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)


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