Did you not see in my comment that I said that very thing? Look at this passage in my comment:
“It takes about 4.5 days from the time we first see a CME until its outflow reaches Earth orbit. This several days of warning is one good argument for a large true spacecraft such as Nautilus-X which would have a safe area for astronauts to go to surrounded by the ship’s water supply that would give very good protection against both CMEs and cosmic ray bursts. If you are in Orion, you would just have to put your head between your legs and kiss your ass goodbye.”

“It is a case of NASA being risk adverse. PICA carries the risk that the gap fillers won’t work….but the trouble with being risk adverse is that nothing is gained”

This is a little underestimating the risk on your part. The differential ablation will most likely cause hypersonic boundary layer tripping. The problem is that in turn you get high heating locally.So much so you might end up with a burn through of your thermal protection system.

Now remember Robinson under the Shuttle removing the gap fillers before entry?

http://www.nasa.gov/returntoflight/crew/EVA_gapfiller.html

Why did he do that? Well generally speaking there an army of people running simulations when something like that occurs. A lot of computational fluid dynamics and possibly experiments. The CFD most likely showed the tripping of the boundary layer and the potential risks. So they sent the astronaut to remove the gap fillers.

Yeah well atmospheric entry is a little tricky… Some people are lucky others not so much.

What occurs much more frequently and is potentially very lethal are the Sun’s occasional CMEs (Coronal Mass Ejections) and often associated solar flares, both of which may eject large volumes of charged particles at incredibly high energies.

What is typical particle energy spectrum for CMEs? Although CMEs produce very high flux they occur for limited time periods, and with even a brief warning crew could take cover in a small shielded volume, or “storm cellar” on the spacecraft.

It should also be noted that there is no evidence weightlessness alone limits flight duration. Although exercise equipment for spacecraft remains suboptimal, reasonably intense exercise can clearly limit bone and muscle loss to a degree that doesn’t significantly increase the risk of serious injury.

Dragon was designed with an eye towards BEO missions. Orion was designed for lunar ones. One problem with mars missions is that there are questions as to if people can survive the high speed of direct reentry. A direct reentry after a mars mission will pull more g’s than Apollo. There are questions as to wither or not you might need something with more lift than a capsule to survive.

IMHO it is not wise to design anything with Mars in mind at this point in time as no mars mission has been selected.

CXP Orion was going to support a crew of 4 for 21 days, be able to wait 6 months by itself without a crew as well as wait 6 months at a space station. However CXP Orion also lacks the delta V to both enter and leave lunar orbit(it was going to use Alter to handle breaking into lunar orbit). About the only deep space mission you could do with CXP Orion would be a high earth orbit or a L point mission and Orion became both high priced and disposable. Orion has radation harderned electronics and a bit more radationshielding than dragon but there is nothing preventing dragon to be likewise upgraded.

Honestly the only thing a capsule can do on a deep space mission is be a crew return vechile or maybe a crew transfer vechile(I.e. transport the crew to a waiting larger spacecraft) and who knows what the MPCV will do as there are plans to cut some of this ability and I have a feeling that not much work has been done on Orion’s service module to date as the 2013 test won’t test a real service module.

in Orion’s defense they did automate this process. However PICA is still less labor intensive. Hence why Space X would risk using PICA (i.e. if it works you have a better heat shield and a cheaper to make one…and for LEO missions if they can do land landings one that is possible reusable too(it ablates a lot less than Avcoat and could do more than one LEO mission).

It is a case of NASA being risk adverse. PICA carries the risk that the gap fillers won’t work….but the trouble with being risk adverse is that nothing is gained(i.e. Avcoat will increase your mission costs and masses more than PICA. ). Every new technology was once a risk and sometimes you can’t advoid risk at all….The current version of Avocoat is not the same as the Apollo one..

“If this is not 100% automated it must be just super man hour intensive.”

It is crazy and NASA had planned to use a robot to fill the honeycomb. I don’t know what happened to that though.

“Another reason for the choice?”

Nope. Not that I know. It flew human back from the Moon, AVCOAT that is, is a pretty good reason. However know that the new AVCOAT is not quite the Apollo AVCOAT… Yet the gap filler problem is not solved. That I know any way. So which one is best? I would say the one that flies and comes back with data… So long the data is being used for analysis and validation/verification…

I did some reading, looking at who manufactured each, who’s district they were in, the timeline for the decision. It looks like when land landing and reusability were scrapped pica was also. Avcoat is directly attached and if the capsule is only used once and the moon was the only target, they went with one that was easiest.

I was surprised at how many honeycombed cells had to be filled. 400,000 for the Apollo capsule and 600,000 – 700,000 cells for the MPCV. Each cell gets individually filled and if a bubble occurs they have to drill a small hole and pump more resin in.

If this is not 100% automated it must be just super man hour intensive. Another reason for the choice?

Here: Slide 22 for example. Have fun!

https://smartech.gatech.edu/xmlui/bitstream/handle/1853/26408/78-98-1-PB.pdf?sequence=1

PICA is tiled to cover a large surface. The problem comes from the gap fillers. So yes PICA can sustain the very high speed reentry but it is not know if the gap fillers will behave. Actually experiments have shown it may not. There is a presentation somewhere. AVCOAT has flown and is de facto human rated (Hey Rand? ) or so was the feeling. PICA has not. Actually had not before Dragon. There is a host of issues that are unsolved with tiled PICA.

Hope this helps.

“I thoughtOrion was intended to eventually go to Mars, and still is today.”

Only in the Lockheed Martin marketing brochures. It was designed for keeping a crew of four alive for 21 days during a lunar mission, with no exercise facilities. Maybe it will serve lifeboat duty on a true spaceship that is going to Mars, but because of it’s high price, I doubt it.

Dennis wrote @ September 2nd, 2011 at 12:01 pm

“MPCV is the newer designated name, but I think Orion still has been kept. Even the Congress men call it Orion.”

What about Congress women?

Look, people that can process new information call the MPCV the MPCV. People that can’t process new information will call it Orion. But the MPCV has different capabilities than the Orion, so it’s not just a matter of what they are called.

Don’t be a lemming. Call the MPCV the MPCV.