.

Tomorrow NASA will (finally) select the Orion prime contractor and (I hope) will reveal the full details of (both) the Lockheed-Martin and Northrop-Grummans/Boeing designs.

However, I hope the winner will not use the current cone-shaped design for the Orion but use a better "bell-shaped" design like I suggest in my latest article [ EggCEV - The "bell-shaped" Orion ] here: http://www.gaetanomarano.it/articles/012eggCEV.html

.

Why would a Bell shaped one be better? I am sure the designers will have thought about the shape, it wont be random.

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Eney meeny miny moo, cone shaped capsules, that'll do.
Eney meeny miny moo, bell shaped is for the Russian Co.

I might have a slightly wrong impression about engineering decision trees .

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On a more serious note, you argue that a bell shaped one probably is better from an aerodynamic POV.
Why then do the Russians have a cone fairing on their bell shaped soyuz at launch?

Or is you argument of aerodynamics solely from the reduced diameter, allowing for a smaller diameter of the fairing?
It wasn't fully clear to me from your website.

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I'm not sure the response will be either.

the bell shape give more internal space with less diameter and the same mass

why don't use a good idea? no matter if it come from Russia!

the main reason Russia used a bell shape is to add a few extra space (for three astronauts!) in its very little 2.5 mt. capsule!
the capsule is so little that in the first flight the astroanuts died for a decompression since the internal space was not sufficient for three astronauts WITH their spacesuits!
after the accident the capsule was modified so the astronauts can re-entry with the spacesuit
Soyuz needs a fairing since it has the Orbital Module on the top (and some non-aerodynamic antennas, etc.)
the EggCEV doesn't need any fairing since it has no orbital modules
the increased aerodynamic of the EggCEV come (1st) from its shape and (2nd) from its 4.5 mt. diameter that allows a reduced diameter for the 2nd stage tank

I have to admit, this has gotten me kind of curious about capsule shapes and tradeoffs.

Gaetano, do you know where I could find all the detailed technical analyses on reentry bodies that NASA has done over the decades? I'd love to get some technical details straight from the source, so to speak.

Also, if you know of any English-language translations of the large body of original Russian research, please let me know.

I'd love to be able to compare the two different design philosophies in context, with a full view of their respective advantages and disadvantages.

Thanks for stimulating my interest in such an interesting topic!

If I find anything out on my own, I'll be sure to come back and share it.


Thanks again!

Are you sure about the "same mass" part?

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no, but the difference may be in the range of +/- 5%... surely not "HALF" or "TWICE" the cone-CEV mass

Would you make calculations before putting a number on it? That way, you'll also know just how much room you win. Or do you already have a calculation lying around for that 30% number?

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I can try to search them, but I feel it's not easy to find something, since (both) NASA and Russia have done that research over 40 years ago in the early '60s
probably, some data can be found in the detailed Apollo press-kits (I've posted here a link to the Apollo 12 press-kit months ago but I must search the right post)

Less diameter with the same mass increases the ballistic coefficient, which affects how the capsule performs during reentry. The CEV probably has the diameter is does because that is what it needs to be to get the desired drag and lift characteristics. You can't start changing the shape and dimensions haphazardly without performing a complete analysis of the effects.

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no one can make an exact calculation about it since we don't know the final specs of the original CEV (that NASA changes every day) and the weight of the single parts
I've not made a calculation but only an evaluation since the bell-shaped CEV doesn't differ too much from the cone-CEV, then, I think that the difference may be in the range I've evaluated
also, consider that a bell-shaped CEV has more internal space but it may remains empty (to have a more comfortable habitat for the astronauts) or (part of it) can be used, then, the extra-mass can be calculated only when we will know HOW that extra space will be used
last, the bell-shaped CEV may weigh the same as planned at launch but more than planned at re-entry (with more lunar samples vs. the cone-CEV)
we can't "calculate" nothing without any "base-figures"!

Based on the most recent NASA illustrations I've seen, the CEV already has a smaller diameter than the Ares I second stage. Reducing the CEV diameter further will probably just change the adapter size without a producing reduction in the 2nd stage diameter.

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this is only a NASA decision if they want/need a more aerodynamic rocket
unfortunately, the problem come (again...) from the SRB used as first stage since it's too long and too thin... and that forces the Ares-I designers to build a rocket tall near the SaturnV !

I post here my reply to a similar question on another forum:

the Vostok capsule built with '50s Soviet technology was able of... "8 to 9 G re-entry, spherical capsule, 2500 to 3500 deg C re-entry temperatures" [ http://www.astronautix.com/craft/vostok.htm ]

"the astronaut would eject from the spacecraft at an altitude of 8 to 10 km." but the capsule landed with its parachutes [ http://www.astronautix.com/flights/vostok1.htm ]

if the Vostok (and the astronauts) survives such extreme conditions, then, also the bell-sized Orion can, since it's not another Vostok but looks close to the original CEV design... also, don't forget that the bell-shaped (and very reliable) Soyuz/Shenzhou have a 2.5 mt. only thermal shield!

probably, the re-entry speed of the EggCEV will be (a little) higher, but not dangerous; if the re-entry speed will be higher, the EggCEV may need larger "braking parachutes" but the main chutes will remain the same since the CEV mass dones't change so much with a bell shape

I don't suggest to launch the CEV (no matter its shape) and the astronauts without "performing a complete analysis of the effects" (and not even NASA thinks to do that!)

Wasn't a major reason for the Apollo capsule's shape its ability to handle reentry from a lunar return trip?

I'm still looking for the source, but I seem to recall reading a while back that the Apollo capsule could actually handle a high enough delta-v on reentry for use on a Mars return trip. So far, though, the closest I can find for actual numbers, though, is here:

http://www.astronautix.com/craft/cevcm.htm

Where they mention:

(Note - Earlier in the article, they mention the Block 2 CEV is the version that would be used on a lunar mission.)

Additionally, Georgia Tech has an interesting paper on reentry vehicle shape, trajectories, etc., which can be found here:

http://pweb.ae.gatech.edu/labs/ssdl/...20return%22%22

(Note, it's a 359 kb PDF)

There's a lot of good information there, and they explain (in great detail), the advantages of a conical lifting capsule shape like Apollo in handling reentry velocities of up to 14 m/s, when compared to other concepts.

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Wait, what?

Are you seriously telling me you've reached your conclusions about capsule shapes and tradeoffs without actually referring to the vast body of research on this topic?

And you don't even know where to find this body of research?

And you haven't even checked to see if NASA has done any recent work on this subject, what with them needing to design and build a new capsule from scratch for Orion? At the very least, shouldn't there be a recent NASA technical paper explaining how their current capsule design builds on the original Apollo design (or doesn't, as the case may be)? And wouldn't that paper be likely to have a juicy bibliography full of Apollo-era research that you could look into?

I'll be sure to let you know if/when I find these things. In the meantime, I'm concerned that your analysis may be very flawed.

Oh, I did find this, from the NASA website:

[/url]http://technology.nasa.gov/Technology_Detail.cfm?PKEY=2000286&category=Techno logy[/url]

It appears to be a summary of research done on "Subsonic Lift And Drag Characteristics Of Seven Blunt-Based Lifting Body And Wing-Body Reentry Vehicle Configurations".

Unfortunately, you need to have an account to access the article itself through the NASA website, but I did notice that the summary lists the seven different reentry vehicle configurations that were studied (M2-F1, M2-F2, HL-10, X-15, X-24A, X-24B, and Space Shuttle). I think further research into the these seven designs is probably the best place for me to start.

(Another option would be for me to start at the same place you did, Gaetano. What were your technical sources, Gaetano, if not NASA and Soviet program research papers?)

The summary I referred to seems to imply that the research paper itself does discuss some of the performance characteristics and tradeoffs of different designs. It probably doesn't address the "cone vs. bell" question directly, but I bet it's still a good place to start working on an understanding of the issues. It would probably also have some good leads on additional resources.

Unfortunately, a Google search for "DRC-098-071" was pretty fruitless for me. Can someone who is more knowledgeable about the NASA bureaucracy give me some pointers on how to get access to obscure technical papers?

it's interesting and appreciable to know more about capsules (like know more about why airplanes fly, why the earth has a day and a night, why a battery stores energy, etc.) but this is useless for a discussion about a (possible) bell-shaped CEV since it is not a "new thing" but a vehicle that have already made 100+ flights under the names "Soyuz" and "Shenzhou" (and still fly every year...)

but, if you have further doubts that a bell-CEV can safely return from space, look at the Shenzhou shape (below) that is a true "BELL" (much more than "my" EggCEV !!!)

shenzhoucapsule.gif

FLIGHT-DETERMINED SUBSONIC LIFT AND DRAG CHARACTERISTICS OF SEVEN LIFTING-BODY AND WING-BODY REENTRY VEHICLE CONFIGURATIONS WITH TRUNCATED BASES (PDF)

I just Googled on the title and got a hit on this paper. The title isn't precisely the same, but close.

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I'm not entirely sure what your point is here: we've already established that both "bell-shaped" and conical capsules can safely return from space.

What you have not established, though, is whether the "bell" shaped capsule you advocate can safely reenter the atmosphere at the kinds of velocities that a lunar or Mars return trip requires. As the links I've provided show, an Apollo-style conical capsule can handle the 11 m/s and 14 m/s velocities. If that wasn't enough, we have the benefit of several Apollo missions that show Apollo's conical command module handling the energy from an 11 m/s reentry just fine.

So, if you want to push the "bell" capsule as an alternative, the burden of proof is on you to prove that the "bell" shape can handle it. Given that, despite the number of successful flights done by Soyuz and Shenzhou, not one "bell-shaped" vehicle has flown a manned lunar return mission, the successful Soyuz flights do not constitute proof.

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Thanks, Gaetano, but I was hoping for something a little more technically detailed then "well, the Russians have used the bell shape successfully, so it must be the best solution".

I'm especially interested in the reasoning of actual NASA and contractor engineers, who are actually putting pens to paper and hands to tools, as to why they've chosen to use the cone design (which also has has a history of successful use).

I really wish you would provide that level of analysis, either on your own, or by referencing first-hand accounts from people who have performed that level of analysis.

Meanwhile, I'll keep searching myself.

D'oh!

Thanks, 01101001! I'll begin reading right away!

You can make an accurate calculation of the interval volume of both shapes, so you have something to back up that 30%.

You can calculate the surface of each capsule, which could be a rough indication for its mass.

Anything is better than throwing with percentages as if they're calculated, while they're just guesses.

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The suspected rounded-triangle Orion logo shape screams conical.

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Soyuz and Shenzhou reenter from Earth orbit where the velocity is 7.8 km/s. A vehicle returning from the Moon will be going 11 km/s and even faster from Mars. Nonetheless, it is true the Soviet Zond capsule, which was a modified Soyuz, did make at least a couple lunar returns in 1968. Thus the bell-shaped (I've also heard it called "headlight" shaped) Soyuz is apparently capable of 11 km/s reentries, though probably with a beefed up heat shield.

The problem comes in scaling up the vehicle. When the vehicle is enlarged the mass increases faster than the area of the base. This increases the ballistic coefficient and, therefore, the reentry characteristics. You may end up with an unsatisfactory flight profile. If a lower ballistic coefficient is required then the area of the base must be increased, which may lead us away from a bell shape toward a conical shape.

I'm not saying a bell-shape won't work, but at this point we simply don't know without an intensive study. The best you can do, gaetanomarano, is to urge a study into the feasibility of a bell-shaped CEV. I'm okay with that; but I'm not okay with you recommending the use of a bell-shaped CEV without first knowing the results of such a study.

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I've read many times from many sources that (both) Soyuz and Shenzhou are designed for a direct lunar re-entry, despite (you're right in that) they have never accomplished this kind of flight in the reality
also, I've read that the most important points to design a capsule for a direct lunar re-entry are the thickness and the material of the thermal shield
about Mars... as I've stated many times here... I don't think that a Mars mission (30+ years from now) will accomplished with the same toys (literally) used to come back on the moon, then, it's a nonsense and a waste of time and money to design (now) the CEV for a direct Mars reentry!

not the best solution, only a solution that (already) works (and can work also with the CEV)
the reason (I believe) is NOT thecnical but psychological
they must accomplish that mission but have fear to fail... then, they are xerox-copying step-by-step the Apollo missions and hardware (with only small changes) to be sure they will be successful...
it's curious (for me) to read that NASA engineers look at the old Apollo hardware in museums the same way, in some sci-fi movies (like Independence Day) the scientists examine an alien ship to try to seize its hidden secrets...
if I find something interesting, I'll post here