View Poll Results: Which Orion is better? A (smallSM) "CorkScrew Orion" or a (bigSM) "SwissKnife Orion&q

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Thread: Which Orion is better? A (smallSM) "CorkScrew-Orion" or a (bigSM) "SwissKnife-Orion"?

  1. #211
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    400s is atainable with H2/LOX, but I wouldn't put my money in achieving it with other fuels (that still provide high thrust as well). They don't tend to reach the 400 mark and development prospects don't suggest they "ever" will. I've researched literally 100 engines on this aspect. There doesn't tend to be a lot of Isp increase per fuel combi once initial development of the particular engine type is done anyway. Almost all of the Isp increase we still see in H2/LOX engines is due to increased nozzle size.

    There is only one fuel combination that is more energetic than H2/LOX, but you can't use it for environmental reasons (something like fluorine/LOX IIRC).

  2. #212
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    Quote Originally Posted by Nicolas View Post
    There doesn't tend to be a lot of Isp increase per fuel combi once initial development of the particular engine type is done anyway. Almost all of the Isp increase we still see in H2/LOX engines is due to increased nozzle size.
    Chemical and thermodynamic properties play a huge part in how much specific impulse a particular propellant can provide. No amount of technology can change this limitation. All the designer can do is change operating pressures, expansion ratios, etc.; however there are practical considerations that limit how far we can go here as well.

    For instance, there comes a point when the weight added by further extending a nozzle degrades performance more than the performance increase we receive from the higher expansion ratio. Another example is a pressure-fed system where an increase in chamber pressure means heavier propellant tanks. In this case it is generally better to operate at low chamber pressures and sacrifice some specific impulse in exchange for a lighter system.

    In general, today's propulsion systems are not particularly more efficient than those of the 1960s and 1970s. We've already gotten about all we can from chemical propulsions systems.

    Quote Originally Posted by Nicolas View Post
    There is only one fuel combination that is more energetic than H2/LOX, but you can't use it for environmental reasons (something like fluorine/LOX IIRC).
    Fluorine is generally burned with hydrogen, resulting in hydrofluoric acid (HF), but it does not react well with carbon. Fluorine can therefore be substituted for LOX when the fuel is H2, N2H4, or some other non-carbon containing compound. When the fuel is a hydrocarbon, such as kerosene, fluorine and LOX can be mixed in the appropriate ratio such that the F combines with H and the O combines with C. This mixture is called FLOX.

    Fluorine gives better performance than LOX, perhaps 10% depending on the fuel, but it is extremely reactive and toxic. The exhaust products are also very toxic and corrosive. Although fluorine burning engines have been built and tested, they have been pretty much abandoned because they're not worth the trouble.
    Last edited by Bob B.; 2007-Jan-29 at 08:53 PM. Reason: typo

  3. #213
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    Thanks for sparing my keyboard and some google time

  4. #214
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    Quote Originally Posted by Bob B. View Post
    Achieving the required L/D ratio has proven to be very problematic with such a shape.
    in the ESAS plan there are some studies of cone-shaped capsules with less slope than Orion ...my design just adds a second cone and truncate part of it
    .

  5. #215
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    Quote Originally Posted by Nicolas View Post
    Some problems that might arise:
    Q: *in ascent, the cp is located higher, which is less stable
    A: ascent stability problems of the capsule are minimal compared with the Ares-I stability problems

    Q: *the heat shield area is smaller; can it stand up to the re-entry? (same goes for L/D as Bob B points out)
    A: no, it has the same shape of the 5 m. Orion but reduced (in proportion) for a 4.5 m. capsule

    Q: *apparently you didn't take the increased size of the sides (due to the cornered double surface) into account
    A: it's minimal compared with the 20-25% weight-saving of the (surface/volume) smaller thermal shield

    Q: *your cg will be higher; this likely will make the craft less stable during descend
    A: my design is an hybrid of Soyuz/Shenzhou shape (that has near no-slope, but works safely on reentry) and Orion/Apollo shape

    Q: *I wouldn't be surprised if your ascent aerodynamic drag would increase
    A: the full vehicle will have the LAS fairing to be more aerodynamic

    Q: *your capsule is more prone to collapsing with this shape than a cone
    A: as said, it's an Apollo/Soyuz hybrid... nevers seen any of them "collapsed"

    Q: *is the heated flow detached enough from the lower sides of the capsule?
    A: that question needs real aerodynamic tests (but the near-zero-slope Soyuz has no problems on reentry)

    Q: Can you also present more detailed calculations on your weight saving figures?
    A: since great part of the weight-saving comes from a (surface/volume) smaller thermal shield, calculations need the extrapolated weight of the current 5 m. shield

    .
    Last edited by gaetanomarano; 2007-Jan-30 at 12:55 AM.

  6. #216
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    Quote Originally Posted by gaetanomarano View Post
    in the ESAS plan there are some studies of cone-shaped capsules with less slope than Orion
    Correct, and those shapes were rejected because they couldn't provide the necessary L/D ratio.

    Quote Originally Posted by gaetanomarano View Post
    ...my design just adds a second cone and truncate part of it.
    Your design is very similar to the shapes that were found to be unsatisfactory.

  7. #217
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    I believe the highest Isp that has ever been achieved was a F/H/Li mix, and was somewhere in the mid 500's. The exhaust is nasty though, and liquid fluorine and lithium are slightly difficult to store...

  8. #218
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    Q: *in ascent, the cp is located higher, which is less stable
    A: ascent stability problems of the capsule are minimal compared with the Ares-I stability problems
    A2: but it adds to the total. A craft already having stability problems can do without extras.

    Q: *apparently you didn't take the increased size of the sides (due to the cornered double surface) into account
    A: it's minimal compared with the 20-25% weight-saving of the (surface/volume) smaller thermal shield
    Q2: A more fundamental question: do you have data on the total weight of a capsule and the weight of its heat shield?
    Q: *your cg will be higher; this likely will make the craft less stable during descend
    A: my design is an hybrid of Soyuz/Shenzhou shape (that has near no-slope, but works safely on reentry) and Orion/Apollo shape
    A2: still you'd have to test it for stability. Similar looks are not all there is to it. Certainly not when combining 2 designs. You can't really see where the cg is in other capsules, for a start.

    Q: *I wouldn't be surprised if your ascent aerodynamic drag would increase
    A: the full vehicle will have the LAS fairing to be more aerodynamic
    A2: And that fairing will not fit over your new design. See figure 3 on your website. Making it larger or cornered will add to the drag
    Q: *your capsule is more prone to collapsing with this shape than a cone
    A: as said, it's an Apollo/Soyuz hybrid... nevers seen any of them "collapsed"
    A2: maybe because they have an increased structure to prevent that = increased mass. Just going by shape, your design is more prone to collapsing than a cone.


    Not trying to break down your idea at all costs, but (possible) disadvantages need to be explored as well. And they did choose the cone over other shapes, some similar to yours, so that is an indication there may very well be disadvantages they stumbled upon.

  9. #219
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    Quote Originally Posted by cjl View Post
    I believe the highest Isp that has ever been achieved was a F/H/Li mix, and was somewhere in the mid 500's. The exhaust is nasty though, and liquid fluorine and lithium are slightly difficult to store...
    In practice, it's quite unusable indeed.

  10. #220
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    Quote Originally Posted by cjl View Post
    I believe the highest Isp that has ever been achieved was a F/H/Li mix, and was somewhere in the mid 500's.
    That is what I've heard as well, though I've had trouble reproducing that result analytically. Fluorine and lithium burn very hot but the resulting FLi has a molecular weight of 26, which is rather high for a high-performance propellant. I tried different mixture ratios but could never get a specific impulse higher than F and H alone. There is apparently something about tri-propellant systems I don't understand; I guess I should just stick to bipropellants.

    Quote Originally Posted by cjl View Post
    and liquid fluorine and lithium are slightly difficult to store...
    Lithium actually has the opposite problem of cryogenic propellants, to be stored in liquid form it must be kept hot (above 180.5 degrees C).

  11. #221
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    Quote Originally Posted by Nicolas View Post
    Q: *apparently you didn't take the increased size of the sides (due to the cornered double surface) into account
    A: it's minimal compared with the 20-25% weight-saving of the (surface/volume) smaller thermal shield
    Q2: A more fundamental question: do you have data on the total weight of a capsule and the weight of its heat shield?
    Due to the steeper sidewall of gaetanomarano’s design, the sides will be subjected to greater thermal loads during reentry. This will most likely result thicker thermal protection on the sidewalls. I suspect gaetanomarano’s design will have greater heat shield mass, not less as he claims.

    Quote Originally Posted by Nicolas View Post
    Q: *your cg will be higher; this likely will make the craft less stable during descend
    A: my design is an hybrid of Soyuz/Shenzhou shape (that has near no-slope, but works safely on reentry) and Orion/Apollo shape
    A2: still you'd have to test it for stability. Similar looks are not all there is to it. Certainly not when combining 2 designs. You can't really see where the cg is in other capsules, for a start.
    It is my understanding that the Soyuz/Shenzhou shape is somewhat more stable during reentry than the Orion/Apollo shape, however this requirement was deemed secondary to the need for a high L/D ratio, which the bell shape could not provide. There were two things NASA was trying to achieve in their concept studies – monostability and an L/D ratio of 0.4.

    Monostability means that during reentry there is only one aerodynamically stable attitude and the craft will seek this stable position on its own without any input from the crew. A good example of monostability was the Vostok capsule, which once separated from the service section, had no attitude control. It oriented itself into a heatshield down attitude simply because of its offset center of gravity. Russia claims that Soyuz is monostable and NASA’s studies seemed to support that monostability is likely achievable with the shape. The Apollo shape had two stable positions – heatshield down and nose down – and attitude control was necessary to assure correct orientation. Although monostability is desirable, it is not an overriding requirement.

    More important to NASA is the L/D ratio. Since NASA wants to make land recovery an option with Orion, it was determined that an L/D ratio of 0.4 is required for Orion to reach in its potential landing sites within the continental United States on missions returning from the ISS. It was determined that the Soyuz shape or other steep sidewall shapes simply could not achieve an L/D ratio this high. The Apollo shape offered the best chance to achieve the high L/D ratio, and even that was proving to be difficult at the time of the ESAS report. According to the data released in August-06, Orion has a hypersonic L/D ratio of 0.34. It therefore appears they have fallen short of the 0.4 goal. I’m not sure what this means for Orion. Perhaps they found a way to make the lower L/D ratio work or perhaps the possibility of land recovery is at risk. I’m sure we will eventually learn the answer.

    As a side note, NASA initially favored a steep sidewall design but abandoned it when acquiring the desired L/D ratio proved too problematic. I suppose it is possible NASA may go back to the shape if land recovery is abandoned in favor of water recovery, thus lessening the need for the high L/D ratio. As we have said many times, this thing is still in the early design phase and trades are continuing to be made.
    Last edited by Bob B.; 2007-Jan-30 at 07:51 PM.

  12. #222
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    Quote Originally Posted by Bob B. View Post
    That is what I've heard as well, though I've had trouble reproducing that result analytically. Fluorine and lithium burn very hot but the resulting FLi has a molecular weight of 26, which is rather high for a high-performance propellant. I tried different mixture ratios but could never get a specific impulse higher than F and H alone. There is apparently something about tri-propellant systems I don't understand; I guess I should just stick to bipropellants.


    Lithium actually has the opposite problem of cryogenic propellants, to be stored in liquid form it must be kept hot (above 180.5 degrees C).
    Just a guess, but did you take high temperature dissociation effects into account? It can cause a huge increase in Cp and a small decrease in mixture temperature.

    If you use tables such as Zucrow (gas dynamics volume 1, p56-57 IIRC) provides up to 3000 K, they apparently don't account for that. The CEA database does. I haven't used the latter though.

    Also the number of radicals formed plays a role, though that can be marginal. Don't know about this case.

    btw you wrote "with any crew input" in the other post, I assume that is "without"?

  13. #223
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    Quote Originally Posted by Nicolas View Post
    Just a guess, but did you take high temperature dissociation effects into account?
    Yes I did. I use a freeware program called STANJAN to calculate the equilibrium mixture of combustion products and the flame temperature.

    Determining the optimum mixture ratio when there are only two reactants is pretty easy, but doing so with three gets trickier. I played around with it for a while but could never find a combination that produced a specific impulse higher than a fuel-rich fluorine/hydrogen mixture. Every time I added lithium it brought the Isp down because of the higher molecular weight of the exhaust gases.

    Quote Originally Posted by Nicolas View Post
    btw you wrote "with any crew input" in the other post, I assume that is "without"?
    Thanks, I fixed it.

  14. #224
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    Quote Originally Posted by Bob B. View Post
    Your design is very similar to the shapes that were found to be unsatisfactory.
    no, my TBS-Orion is very much similar to a 4.5 m. Orion (with only slightly changes in the shape)
    .

  15. #225
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    Quote Originally Posted by gaetanomarano View Post
    no, my TBS-Orion is very much similar to a 4.5 m. Orion (with only slightly changes in the shape).
    No, your shape is getting closer to those that had undesirable L/D ratios.

  16. #226
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    Quote Originally Posted by gaetanomarano View Post
    no, my TBS-Orion is very much similar to a 4.5 m. Orion (with only slightly changes in the shape)
    .
    Note that "slight changes in shape" at hypersonic velocity can make VERY large differences in the stability and aerodynamic properties of the object.

  17. #227
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    1 degree can easily make an engine going from running smoothly to stalling, and then I'm just talking about M2 -M8. The problem is twofold: there is the huge dynamic pressure, and then there's shock patterns that are quite sensitive to angles.

    Now for a flat plate L/D things are quite ok, the higher the mach number the larger the range of AOA around optimal L/D. But return capsules are not flat plates, and L/D isn't everything. Stability is a nice variable as well, to name just one .

  18. #228
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    [QUOTE=Nicolas;915577]Q: *in ascent, the cp is located higher, which is less stable
    A: ascent stability problems of the capsule are minimal compared with the Ares-I stability problems
    A2: but it adds to the total. A craft already having stability problems can do without extras.
    A: that "extra" is minimal

    Q: *apparently you didn't take the increased size of the sides (due to the cornered double surface) into account
    A: it's minimal compared with the 20-25% weight-saving of the (surface/volume) smaller thermal shield
    Q2: A more fundamental question: do you have data on the total weight of a capsule and the weight of its heat shield?
    A: the goal is to save 1-2 mT with a 25% lighter TPS, less capsule diameter, less structure at its top, etc. (of course, when LM will release detailed data of the Orion's parts we can calculate the exact saving)

    Q: *your cg will be higher; this likely will make the craft less stable during descend
    A: my design is an hybrid of Soyuz/Shenzhou shape (that has near no-slope, but works safely on reentry) and Orion/Apollo shape
    A2: still you'd have to test it for stability. Similar looks are not all there is to it. Certainly not when combining 2 designs. You can't really see where the cg is in other capsules, for a start.
    A: clearly, my design (like every design) needs very much wind-tunnel tests and some changes

    Q: *I wouldn't be surprised if your ascent aerodynamic drag would increase
    A: the full vehicle will have the LAS fairing to be more aerodynamic
    A2: And that fairing will not fit over your new design. See figure 3 on your website. Making it larger or cornered will add to the drag
    A: again, it needs some wind-tunnel tests to know the better LAS-fairing shape and how much it adds to drag (I think not so much since the drag exists only in the first 30 km. of the flight)

    Q: *your capsule is more prone to collapsing with this shape than a cone
    A: as said, it's an Apollo/Soyuz hybrid... nevers seen any of them "collapsed"
    A2: maybe because they have an increased structure to prevent that = increased mass. Just going by shape, your design is more prone to collapsing than a cone.
    A: the drawings of these capsules don't show any "increased structure"

    Not trying to break down your idea at all costs, but (possible) disadvantages need to be explored as well. And they did choose the cone over other shapes, some similar to yours, so that is an indication there may very well be disadvantages they stumbled upon.
    maybe there are some... but I only suggest to evaluate and test my proposal
    .

  19. #229
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    Quote Originally Posted by Bob B. View Post
    Due to the steeper sidewall...
    the near-cylindric Soyuz doesn't have so heavy structures (and my TBS-Orion is NOT a Soyuz)
    ...bell shape...
    my TBS-Orion is NOT a (Soyuz-like) "bell-shaped" capsule
    ...monostability and an L/D ratio of 0.4...
    REAL wind-tunnel tests of my (NON-Soyuz) may show if that design matches the NASA requirement
    Monostability
    great part of the TBS-Orion weight is near its bottom, while its top is shorter and used mainly as a living space, then, it may have a lower CG and will be much more "monostable" than (both) Apollo and Orion
    ...other steep sidewall shapes simply could not achieve an L/D ratio this high...
    that problem doesn't exist with the TBS-Orion since it's NOT Soyuz-shaped
    ...the possibility of land recovery is at risk...
    why? ...soil landing needs only big parachutes and good airbags
    ...NASA initially favored a steep sidewall design but abandoned it when acquiring the desired L/D ratio proved too problematic...
    I've never read the claims you quote ...apparently, the real (and only) reason was that a bigger CEV was too big, too heavy and too expensive than a 5.5 m. (now reduced to 5 m. for the same weight/price reason) small capsule ...also, they realized that a so big CEV needs a very big Ares-I...
    .

  20. #230
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    Quote Originally Posted by Bob B. View Post
    No, your shape is getting closer to those that had undesirable L/D ratios.
    you can't claim that since the TBS-Orion is different from (both) the Soyuz and the NASA concepts ...then, it needs some REAL wind-tunnel tests to know the answer
    .

  21. #231
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    Quote Originally Posted by cjl View Post
    Note that "slight changes in shape" at hypersonic velocity can make VERY large differences in the stability and aerodynamic properties of the object.
    that's true, but we can't know if the TBS-Orion may have or not any "stability and aerodynamic" problems without hundreds REAL wind-tunnel tests
    .

  22. #232
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    .

    to-day Andrews Space has proposed its Olympus Commercial Orbital Transportation System

    I agree with the Andrews Space (4.6 m. Command Module + Mission Module) design since it looks VERY CLOSE to the (4.5 m. Reentry Module + INFLATABLE Orbital Module) "BigelowOrion" I've suggested in my Jan. 14, 2007 article

    however, the INFLATABLE Orbital Module is a better choice since it can be BIGGER, its weight may be a FRACTION of a solid module (that's very important to have more payload) and its price will be very competitive, so, it can be added in EVERY mission

    also, I agree with the choice to build it as "FedEx carrier" as I've suggested in the point #7 of my "Empirical Law of Private Space Industry"

    I've updated my TBS-Orion article adding a further water/oxygen/fuel tanks' allocation drawing and some (possible) thermal shield's shapes

    .
    Last edited by gaetanomarano; 2007-Feb-05 at 01:51 PM.

  23. #233
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    Sorry for interrupting the big people, what's L/D?

  24. #234
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    lift to drag ratio, is equal to "glide ratio" for unpropelled craft. A certain non-propelled shape at a certain angle of attack and flight conditions (speed, air density...) generates a lift force and drag force. Divide them gives you L/D. L/D = 5 means that, if everything including speed remains constant, you'll glide 10 km far from 2 km altitude. Drag is measured along the glide path, lift perpendicular to it.

  25. #235
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    Quote Originally Posted by gaetanomarano View Post
    I've never read the claims you quote ...
    Perhaps you should. It's in the ESAS report.

  26. #236
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    Quote Originally Posted by Bob B. View Post
    Perhaps you should. It's in the ESAS report.
    IIRC, the ESAS text you've linked months ago said a cone is better, but not that a different shape can't work or is unsafe, also, I don't remember any (really tested) biconic (nor truncated biconic) shape ...however, I still think that "budget" was the most important factor in the (conservative) 5 m. Apollo-like choice (rather than "aerodynamics")
    .

  27. #237
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    You do realize that if a shape was aerodynamically superior, it would be superior in the budget too, right?

  28. #238
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    Quote Originally Posted by cjl View Post
    You do realize that if a shape was aerodynamically superior, it would be superior in the budget too, right?
    in the (20+ years) Orion project, great parts of the funds will go to engineers, employees, infrastructures, etc. while, "raw materials" and "aerodynamic tests" costs will be minimal ...so, build a "cone-shaped" or "cylinder-shaped" or "cube-shaped" vehicle, may have modest (or no) influence on the Orion's price
    .

  29. #239
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    Quote Originally Posted by gaetanomarano View Post
    in the (20+ years) Orion project, great parts of the funds will go to engineers, employees, infrastructures, etc. while, "raw materials" and "aerodynamic tests" costs will be minimal ...so, build a "cone-shaped" or "cylinder-shaped" or "cube-shaped" vehicle, may have modest (or no) influence on the Orion's price.
    Of course the shape can affect cost. Consider for instance your proposed shape versus the Apollo-like shape. With steeper sidewalls your capsule will most likely experience greater thermal loads on the sides, thus require thicker thermal protection in this area. This could make your capsule heavier, thus reducing the amount of passengers/cargo delivered to orbit. Also since Orion is to be a reusable vehicle, a heavier thermal protection system could increase the cost of refurbishment. Furthermore, if the packaging of your shape makes it impossible to achieve the higher L/D ratio, then land recovery may not be possible for ISS missions. This means a costlier water recovery technique will be neccessary. All of these higher operational costs begin to add up to a large amount of money.

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    The only place that shape does not matter is in the vacuum of space of which the utilization of what is available is all that matters.

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