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

[Nicolas]

When posting arguments at the level of the pizza arguments, you must wonder why they have used protective covers on any launcher after the LEO Mercury/Gemini until now and also plan it for Orion. You must wonder what the chances are that your arguments are right versus all space engineers throughout history not having seen childishly simple ways of saving multiple tons on launch mass such as just leaving the BPC behind. Apollo: nobody thought about it (even though they did not use it on Gemini just before that, which alsso had a LAS tower; how dense do you think they are?). Soyuz: Nobody thought about it. New Soyuz TMA: nobody thought about it. Orion: nobody thinks about it, even though they have considered alternatives without the BPC (how dense do you assume they are if they still don't realize it then ???). But it's as simple as to think about a pizza to see a BPC is not necessary at all. Come on... You know just what it would mean if you'd come to your boss with a simple -working- plan that saves 2.5 tons or more on the capsule?

And no, the "boost" part in boost protective cover does not only refer to the tower. It refers to the boost phase, or powered ascent of the launch stack.We've given multiple sources to show that the BPC has more functions than protecting against a firing LAS tower.

You other claims are covered quite well by Bob B.

(just a hint: maybe you should consider that the air in the nice Italian pizza oven is rather stationary, which makes the quoted problem of heat channeling impossible, to name just one aspect that makes this analogy false)

[Bob B.]

even though they did not use it on Gemini just before that, which also had a LAS tower

Mercury and Apollo used a tower LAS but Gemini did not. The Gemini capsule was instead equipped with ejection seats that provided mode I abort within the first 50 seconds of powered flight. Gemini's solid retrorockets provided separation during mode II abort.

Ejection seats were determined acceptable for Gemini because the Titan II launch vehicle used nitrogen tetroxide/Aerozine 50 propellant, which burns rather than explodes. Since the Atlas and Saturn rockets used highly explosive LOX/kerosene, an escape tower was determined the better option for Mercury and Apollo because it could pull the capsule far away from the launch vehicle.

[Nicolas]

Ah, you're right.

I now see that Gemini had a nose protective cover/upper heat shield though
Mercury had a LAS tower, but as far as I know no BPC other than again something just around the nose.
Both were of course LEO craft. I don't know about the capsule's weight, but given the fact that everything since uses a BPC, it wouldn't surprise me if it was not optimal at all.

[gaetanomarano]

...pizza...

sorry you haven't appreciated the irony of my "pizza example"

...Mercury/Gemini...

two capsules launched without any BPC
.

[Nicolas]

Irony is nice, but not at the cost of facts. Especially when those facts are required to show the whole lot of space engineers indeed is doing a miserable job.

Gemini had a top cover/upper heat shield. Mercury also had a top shield. Indeed no full BPC though. However, Mercury and Gemini were not just "two capsules launched without full BPC". ("any" already is wrong). They were the first and last capsules to be launched without full BPC, and they were LEO only. There might have been a reason why they always opted for a BPC since mercury/gemini.

I still don't like the massively shortened qoutes. It makes unclear what arguments exactly you are replying to.

[gaetanomarano]

Irony is nice, but not at the cost of facts.

the FACT actually IS that fly 30 seconds at 400°C is NOT a problem for a capsule made of strong metals and alloys

Gemini had a top cover/upper heat shield.

there are LOTS of data about Gemini and Mercury on the web, so, everyone can search them and judge by himself
.

[Bob B.]

Mercury had a LAS tower, but as far as I know no BPC other than again something just around the nose.
Both were of course LEO craft. I don't know about the capsule's weight, but given the fact that everything since uses a BPC, it wouldn't surprise me if it was not optimal at all.

Mercury’s exterior was made of blackened heat radiating shingles. On the conical sides the shingles were made of a nickel-steel alloy and on the cylindrical nose they were made of beryllium. Mercury’s bottom heat shield was also made of beryllium and acted as a heat sink – it absorbed the heat and later radiated it away. The beryllium shield was heavier than later ablative heat shields.

Gemini’s exterior was also made of heat radiating shingles. At the base the shingles where made of Rene 41, a nickel based high-temperature alloy, and at the top they were made of beryllium. Gemini’s bottom was protected by a silicon elastomer ablative heat shield.

Because of the high temperatures of a lunar return reentry, Apollo was surrounded by an ablative thermal protection system. The conical sides the capsule were covered by a pore seal, moisture barrier, and Mylar thermal control layers. (During coast to and from the Moon Apollo was exposed to a different thermal environment than previous Earth-orbiting capsules, it therefore required thermal control methods not previously used.) During boost the capsule was covered by a hard fiberglass cover with a cork ablator. This cover protected the capsule from the boost environment and aerodynamic heating.

[Bob B.]

the FACT actually IS that fly 30 seconds at 400°C is NOT a problem for a capsule made of strong metals and alloys.

The exterior is not strong metals and alloys. Please take your fingers out of your ears.

[Nicolas]

the FACT actually IS that fly 30 seconds at 400°C is NOT a problem for a capsule made of strong metals and alloys

Too bad such a capsule is heavier to the moon than a light one with a detachable BPC. Too bad such a capsule is not the best thing to take care of heat issues as encountered on Orion missions.

[Nicolas]

Mercury’s exterior was made of blackened heat radiating shingles. On the conical sides the shingles were made of a nickel-steel alloy and on the cylindrical nose they were made of beryllium. Mercury’s bottom heat shield was also made of beryllium and acted as a heat sink – it absorbed the heat and later radiated it away. The beryllium shield was heavier than later ablative heat shields.

Gemini’s exterior was also made of heat radiating shingles. At the base the shingles where made of Rene 41, a nickel based high-temperature alloy, and at the top they were made of beryllium. Gemini’s bottom was protected by a silicon elastomer ablative heat shield.

Because of the high temperatures of a lunar return reentry, Apollo was surrounded by an ablative thermal protection system. The conical sides the capsule were covered by a pore seal, moisture barrier, and Mylar thermal control layers. (During coast to and from the Moon Apollo was exposed to a different thermal environment than previous Earth-orbiting capsules, it therefore required thermal control methods not previously used.) During boost the capsule was covered by a hard fiberglass cover with a cork ablator. This cover protected the capsule from the boost environment and aerodynamic heating.

I would also like to note that Beryllium is quite toxic when it burns. That's why some people aren't too fond of Beryllium stereo speakers. I don't know in what amounts toxic Beryllium fumes would get into the atmosphere during a Mercury/Gemini re-entry though.

[Nicolas]

there are LOTS of data about Gemini and Mercury on the web, so, everyone can search them and judge by himself

This is not about "judging". It HAD a top shield. Or didn't you notice the white cover on the top during launch, remarkably absent while in orbit? As said, it didn't have a full area BPC though, for reasons mentioned in Bob B's detailed explanation (also including reasons why this wouldn't be optimal for Apollo/Orion).

[djellison]

Nic, Bob - you're wasting your time. He doesn't care about facts. He comes up with a silly idea and then no matter how wrong it is, how stupid it is, how implauable it is....he'll defend it to the hilt - and simply knock to one side any and all factual evidence, historical experience or laws of physics that counter his crazy ideas.

Doug

[gaetanomarano]

The exterior is not strong metals and alloys.

since we don't know in details how the Orion's surface will be made, we can define the Orion's external material as made of "something able to survive on re-entry (WITHOUT any BPC, Nose Cone and other protections) to temperatures 3-4 TIMES HIGHER and for a period 20-30 TIMES LONGER than the temperature+time of the brief (30-40 km. longer at 400°C for 20-30 seconds) Orion's ascent flight before the LAS+BPC will be jettisoned" (as explained in my posts #367, #384 and #386)

.

[Nicolas]

Answer 1 question Gaetano.

If The Apollo capsule had an exterior material (or materials) capable of surviving re-entry (and it had), why did they still put a BPC over it to protect it against ascent aerodynamic loads and heating?

(and to save you one try: don't say "simply to protect against the LAS tower firing" because we have already shown sources saying that was not the only reason)

I've got a bonus question for you: what is the difference in use of a capsule after ascent and after re-entry, and what are the consequences for the state in which it should be after said phases?

[gaetanomarano]

Too bad such a capsule is heavier to the moon than a light one with a detachable BPC.

assuming (just a second) that you're right on this point... we must know HOW MUCH thick and heavy it must be ...well, I think that the solution is simple:

if the Orion external material will be non-ablative, we don't need to add any BPC (since the SAME material that survive 1200+ °C for 10+ MINUTES actually IS able to survive 1/3th the temperature for 1/20th the time)

if, instead, the external material used for the Orion external at re-entry will be ABLATIVE, we don't need to add a "protection of the protection" but (simply) increase its thickness

then, HOW MUCH thicker the Orion external protection must be to "survive" 20-30 seconds MORE at 400°C on ascent?

if we consider only the ablation time (20-30 sec. vs. 600-900 sec.) the answer is "around 3-5%" ...but we must consider that on re-entry the external temperature will be very much higher (and ablative) than on ascent... so, the Orion "re-entry external protection" must be increased a further 2% or less

then, if the Orion "external re-entry protection" will weigh (e.g.) 300 kg. ...the 2% extra-protection will weigh just a mere +6 kg.

also, since this 2% "extra-protection" will be "ablated" on ascent, it will be NOT an "extra-mass" sent to the Moon...

with or without an extra-protection, the underside-LAS still remains a clear winner!

.

[cjl]

You're missing the fact that the area of the capsule designed to take the heat is the opposite side from what would be taking the strain on boost. Your arguments are irrelevant unless you propose launching the capsule upside down.

[NEOWatcher]

... Your arguments are irrelevant unless you propose launching the capsule upside down.

Hold on, I need to do a search, but I'm pretty sure that was one of G's proposals.

[Nicolas]

with or without an extra-protection, the underside-LAS still remains a clear winner!

Call NASA

[Nicolas]

assuming (just a second) that you're right on this point... we must know HOW MUCH thick and heavy it must be ...well, I think that the solution is simple:

if the Orion external material will be non-ablative, we don't need to add any BPC (since the SAME material that survive 1200+ °C for 10+ MINUTES actually IS able to survive 1/3th the temperature for 1/20th the time)

if, instead, the external material used for the Orion external at re-entry will be ABLATIVE, we don't need to add a "protection of the protection" but (simply) increase its thickness

then, HOW MUCH thicker the Orion external protection must be to "survive" 20-30 seconds MORE at 400°C on ascent?

if we consider only the ablation time (20-30 sec. vs. 600-900 sec.) the answer is "around 3-5%" ...but we must consider that on re-entry the external temperature will be very much higher (and ablative) than on ascent... so, the Orion "re-entry external protection" must be increased a further 2% or less

then, if the Orion "external re-entry protection" will weigh (e.g.) 300 kg. ...the 2% extra-protection will weigh just a mere +6 kg.

also, since this 2% "extra-protection" will be "ablated" on ascent, it will be NOT an "extra-mass" sent to the Moon...

with or without an extra-protection, the underside-LAS still remains a clear winner!

.

Maybe you should start by considering
-the orientation of the capsule during ascent versus re-entry
-the tasks left to be done by the capsule after ascent versus after re-entry.

[gaetanomarano]

You're missing the fact that the area of the capsule designed to take the heat is the opposite side from what would be taking the strain on boost.

since you don't like my proposals, probably you don't read my posts... when I talk of "Orion's external temperature" on re-entry, I don't refer to the 2650°C on the TPS but to the ("lower") temperatures on the body and top of the capsule (as explained in my posts #367, #384 and #386)
.

[gaetanomarano]

Maybe you should start by considering
-the orientation of the capsule during ascent versus re-entry
-the tasks left to be done by the capsule after ascent versus after re-entry.

also if you increase 5, 10, 20 times the (estimated) Orion's ascent "extra-protection" mass, it still remains in the range of 30-100 kg.
.

[Nicolas]

If you increase a meaningless value 5, 10 or 20 times, it remains meaningless. Your proposals ignore some very important points. Multiplying a value doesn't change that a bit, in contrary.

[gaetanomarano]

Your proposals ignore some very important points.

no, YOUR critics ignore a VERY important point: LAS-like solid rocket's propellent burns at 1500+ °C ...so, the MAIN (I think the ONLY) purpose/thickness of the Apollo/Orion BPC was/will be to protect the capsule from THIS temperature, NOT from a mere 400°C on ascent... and, also if you add a FULL BPC (that is completely unnecessary) the total mass of my LAS still remains about HALF of a tower-LAS...
.

[Nicolas]

What you think means nothing when the knowledgeable sources state other things.

Think about the purpose of a BPC all you will, but if sources such as the designers explaining the use of Apollo's and Orion's BPC say something different, wonder who's wrong. So ignore mode on: the BPC is only there to protect against a LAS tower firing.

And "a mere 400°C" can be a huge concern for a structure. But ignore those comments as well if you will. So ignore mode on: there is no such thing as heat channeling, thermal overload, aerodynamic loads, ascent impacts, increased mass to lunar orbit, and the like.

I for one do not ignore these things and thereby must conclude that this discussion is getting pointless.

[Bob B.]

no, YOUR critics ignore a VERY important point: LAS-like solid rocket's propellent burns at 1500+ °C ...so, the MAIN (I think the ONLY) purpose/thickness of the Apollo/Orion BPC was/will be to protect the capsule from THIS temperature, NOT from a mere 400°C on ascent... and, also if you add a FULL BPC (that is completely unnecessary) the total mass of my LAS still remains about HALF of a tower-LAS...

If you have to abort then you really don't care how badly the exhaust scorches the capsule exterior because the mission is over anyway. The problem with the Apollo LAS was that the jettison motor exhaust would soot the windows. This could have been solved with some sort of detachable window covering, not an entire boost protective cover. The reason for the BPC went well beyond keeping the windows clean. It protected the capsule's exterior from aerodynamic loads and heating.

Why do you refuse to acknowledge that Apollo had, and in all likelihood Orion will have, a fairly delicate thermal control layer on top of the more robust ablative thermal protection system? This outer layer is critical to a spacecraft's operation and must be protected during boost. You simply cannot continue to ignore this issue and make a valid argument. (Please take your fingers out of your ears.)

[gaetanomarano]

...heat channeling, thermal overload...

I don't agree that these problems (if real) are so bigger on ascent than reentry... however, assuming that a BPC is necessary ALSO for that purpose, we must slice the BPC thickness/mass between "1500°C abort motors burning" and "400°C ascent temperature" protection... maybe, we can guess a 70% for the first vs. 30% for the latter... well, the Orion's external protection "extra-mass" will be in the range of 300 kg. of (ablative) protection material ...then, my LAS still remains the winner!
.

[gaetanomarano]

The problem with the Apollo LAS was that the jettison motor exhaust would soot the windows.

no, the 1500+ °C (of the tower-LAS Abort Motors' DIRECT burn) are TOO MUCH for the ENTIRE capsule (not only for its windows) since it's HIGHER than the HIGHEST external/windows temperature the Orion will face on re-entry
.

[Nicolas]

I don't agree that these problems (if real) are so bigger on ascent than reentry...

You still don't get it. Listen very carefully. If you burn your hands a minute before you die, it's not a problem. If you burn your hands a minute before your calligraphy exam, it is.

After re-entry, it doesn't matter that much in what shape the capsule is. If it's a splashdown, it still needs to float, and that's about it. After ascent, the capsule and all its vulnerable parts, such as thermal control layers, need to be in optima forma. Is it that hard to understand?

[Nicolas]

no, the 1500+ °C (of the tower-LAS Abort Motors' DIRECT burn) are TOO MUCH for the ENTIRE capsule (not only for its windows) since it's HIGHER than the HIGHEST external/windows temperature the Orion will face on re-entry
.

So now duration suddenly is not an issue? Besides, that comment was not what Bob B is saying but what Apollo designers were saying. Apparently you also know the failure modes of Apollo better than its designers? Amazing....

[Nicolas]

well, the Orion's external protection "extra-mass" will be in the range of 300 kg. of (ablative) protection material ...then, my LAS still remains the winner!

Assuming -and I'm on very rough terrain here- that your assumptions are correct, you call a craft that has to take 300 kg more of structural weight to the moon the winner? The BPC is detached, your fixed layer is not.