“Why are people convinced that aircraft and spacecraft have absolutely nothing in common?”

There is a difference between “nothing in common” and “everything in common”. Some of the differences are quite enough to make the cost estimates baseless in certain areas. My favorite being: Thermal Protection System. But the more general point is that the requirements for the design are very very different, some pointed out by Rand Simberg.

Nice to see that you’re into more amicable conversation mode.

“You will need to elaborate a bit on what you mean by high and low. The surface atmospheric density of Mars is comparable to the Earth’s atmospheric density at 100000 feet. Thus the Mars entry question is more one of shedding entry velocity than of thermal protection. Large shields are needed to get the required surface area and must be small L/D designs to maintain aero-stability.”

I will not elaborate more than that: Shedding velocity by definition (conservation of energy) will increase heating somewhere. So you will need TPS of one form or another. But it all depends where in the atmosphere you actually decelerate since the convective heat fluxes are dependent on density among other things. Now at this kind of velocity you will also have shock radiation heating wich will be substantial. As for L/D what you should really be concerned with is ballistic coefficient, ie. mass and drag, rather than L/D. We are not talking about cross range, down range and “precision” landing achieved via L/D. What you need is indeed stability but deployables by definition can take different shapes. What is the “best” shape? I don’t know. It’ll depend on what you can loft and what mission you are trying to achieve. You definitely don’t want to fly hypersonic at mountain top levels so to speak. Probes have usually not flown at any L/D, however (in)significant it might be. But humans will need entry forces relief. Anyway this is not a “simple” mission. But you cannot say you need L/D or anything in as much one cannot say we need an HLV to go places. Only mission requirements will tell and so far I have seen none. Another thing to consider is the Knudsen number…

“There are no heat loads to the payload through the fabric. Deployable entry shields typically have a conventional “nose-cone” (as it were) where the higher heat loads are experienced and the payloads are behind this region given the need to keep the mass close to the centerline. Thus heat leakage through the fabric to the payloads never occurs.”

I suppose, again, it all depends on the type and location of the deployable. I do not know any “typical” deployable for Mars entry. Even Earth entry does not really have any.

I’ll steal a line from Major Tom: FWIW…

http://www.directlauncher.com/documents/NASA-Compromise-Budget-Detailed.xls

That is not what the Orion contractors are telling me. Their only desire is that they get a little less ‘help’ from NASA which may be a component of the higher number. Their suggestion is to get more of NASA going on the Advanced Technology stuff. Getting rid of the uncertain vibrations environment and mass limitations imposed on them by the Ares-1 will also be a big help as well.

You might also review the document below that I submitted to the Augustine Committee concern their SDHLV cost numbers. Hint the CBO doesn’t agree with their cost assessment either and for the same reasons I provided. Producing a SDHLV estimate that approaches the cost of what it took to construct the entire Space Shuttle system (Orbiter and STS stack) from scratch should be strong sign that something is not right.

Unfortunately, at the point in time that these SDHLV cost numbers were being feed to Aerospace the Ares supporters still within NASA where trying desperately to save the PoR. As a result they were desperately trying to dumb down the Jupiter’s performance and increase the cost so that the obvious solution, (i.e. 2xSDHLV approach vs. the 1.5 ESAS, i.e. the best approach that was hidden in ESAS Appendix 6a from the public) didn’t look so obvious in ‘hindsight’.

http://www.nasa.gov/pdf/383305main_CostEstimates_SDHLV_Rev1.pdf

To be fair they also shanked the side-mount cost estimate as well so it was an equal opportunity shanking for all SDHLV approaches in order to not make Ares look so bad. Oh and they even managed to convince people on the commission to ignore the little fact, discovered by the induced environments group at MSFC over two years ago, that those RS-68 ablative nozzles would be long gone before we reached orbit due to the exhaust gases coming of the SRB.

Now, what to do about the performance numbers since the Aerospace Corp confirmed them. Hey I know let’s reset the performance bar to what a 2xAres-5 can do, thereby requiring 3xJupiter, yah that’s the ticket. It’s all right their baked right into the Augustine report for all too see, a fact I point out when I presented at the AIAA conference held November 2nd in one of the Senate Office buildings.

http://www.aiaa.org/content.cfm?pageid=835

I did.

You will need to elaborate a bit on what you mean by high and low. The surface atmospheric density of Mars is comparable to the Earth’s atmospheric density at 100000 feet. Thus the Mars entry question is more one of shedding entry velocity than of thermal protection. Large shields are needed to get the required surface area and must be small L/D designs to maintain aero-stability. There are no heat loads to the payload through the fabric. Deployable entry shields typically have a conventional “nose-cone” (as it were) where the higher heat loads are experienced and the payloads are behind this region given the need to keep the mass close to the centerline. Thus heat leakage through the fabric to the payloads never occurs.

If you had bothered to read the original post closely, you would have seen that I was not talking about the price of the payloads. I was only discussing the price of the spacecraft (its subsystems, integ. & test, etc.). Any payload related costs are above and beyond the $300M development (non-recurring) and first unit price (recurring) of the spacecraft typical of first-of-a-kind or one-of-a-kind spacecraft, be it a com-sat or a manned spacecraft. Thus if I ignore the payloads costs, the SpaceX numbers are still insufficient to develop and fly a manned spacecraft, let alone the LV mods that go along with it. Next time, read the post carefully and understand the basis of the argument before you reply.

Simberg – “Manned spacecraft don’t have to operate in high-gee environments on all axes. Manned spacecraft don’t have to carry and deliver ordnance….”

Perhaps this was directed at Common Sense, but one of your earlier posts also directed a similar comment to me so let me respond, from the viewpoint of the argument I was putting forth. First, I didn’t compare manned spacecraft to fighter aircraft. You made that leap of faith all on your own. What I did put forth was the argument that piloted aircraft compared to unpiloted aircraft, and in a similar fashion manned spacecraft compared to unmanned spacecraft, are more complex, have greater design requirements associated with them, and require a higher level of reliability, fault tolerance, and safety. All of these aspects result in higher cost to the system. Thus the cost numbers put forth by SpaceX are laughable. You couldn’t get an unmanned, first/one-of-a-kind spacecraft, with no payloads, designed, built, tested, and launched for the numbers he is quoting let alone a human-rated spacecraft and its launch vehicle as he claims.

Simberg – “oops ..” Damn, and here I had another barrel locked and loaded to unload on you a third time for not reading posts closely. Oh well, 2 out of 3 aint bad.

It’s not clear even if deployables can’t be made to work because it’s not certain large aeroshells for landing large payloads will work. You may need a lot of hypersonic retropropulsion even with a large aeroshell. Both the aeroshell and the hypersonic retropropulsion will require a lot of R&D with uncertain results. The only solution that’s known to work may be supersonic (but not hypersonic) or even subsonic retropropulsion.

I’d give that honor to ISRU.

A useless refrain for human space flight, where historically — from Apollo to Shuttle to Freedom to ISS to Constellation — the President leads and Congress follows.

“Based on what’s been said so far in the Committee hearings, it looks like this plan, while not DOA, is clearly on life support.”

What lawmakers actually write into legislation is much more important that what they blow hard about. Despite all the sturm and drang, both draft authorization bills provide every dollar in every NASA account that the President’s FY 2011 budget request asks for and contain every major human space flight element from the President’s FY 2011 budget request.

“Except for Congressman Dana Rorabacher, everyone’s been skeptical at least, and outright hostile at most.”

Not true. For example, Mollohan, the House appropriations chair who is ultimately responsible for originating NASA’s spending bill, gave an opening statement at this week’s hearing that was arguably supportive of the President’s budget request for NASA.

“If Sen. Bill Nelson has his way, a lot of the Commercial Crew money will go to a capsule (very likely that Orion will be revived) and accelerated HLV development.”

If Nelson was really serious about this, it would be reflected in the draft Senate authorization bill. It’s not. The bill only asks NASA to study further HLV acceleration and does not dictate the use of Shuttle-derived or Constellation components.

“Whatever new plan comes out of this, the companies that were involved in Constellation are going to have to have some pieces of the pie, as it’s essential politically.”

It has little to do with the politics, and everything to do with aerospace industry consolidation over the past couple decades and the limited number of companies in the business. Boeing and LockMart are arguably givens. Even ATK will probably be involved in solid rocket motors for launch escape systems, if nothing else.

FWIW…