Author Topic: Zubrin's Falcon Heavy Mars Mission  (Read 76345 times)

Online QuantumG

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Zubrin's Falcon Heavy Mars Mission
« on: 05/14/2011 01:17 AM »
http://on.wsj.com/mNABsj  (note that you may have to play "google the headline" to read this)

My summary:

Flight 1. Falcon Heavy puts Earth Return Vehicle into Mars orbit.
Flight 2. Falcon Heavy puts Mars Ascent Vehicle on Mars surface.
Flight 3. Falcon Heavy sends Crew Transfer Vehicle to Mars to precise landing.
Crew spends 500 days on the surface, uses the MAV to ascend to the ERV and return to an ocean landing.

The ERV has a LOX/Kero engine, presumably preloaded with kero only.

The MAV has a LOX/Methane engine and a chemical reactor to make oxygen from the Mars atmosphere (note that Zubrin isn't advocating making Methane on the surface.. presumably to keep the power requirements under 10 kW).

The CTV has maneuvering thrusters only and carries 2500 kg of provisions for a crew of two for 3 years.  There's no discussion of artificial gravity.

All three vehicles are Dragon derived.

Choice quotes:

   "we could send expeditions to Mars at half the cost to launch a Space Shuttle flight."

  "There is no question that this plan involves considerable risk, and a variety of missions, technology developments and testing programs in advance might reduce that risk. But if we try to do even a significant fraction before committing to the mission, we will never get to Mars.  [..] If we want to reduce risk to human life, there are vastly more effective ways of doing so than by spending $10 billion per year for the next two or three decades on a human spaceflight program mired in low Earth orbit."

I think the only more extreme position I've ever read is one-way-to-stay.
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Offline Michael Bloxham

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #1 on: 05/14/2011 01:45 AM »
I would assume that the 11 tonnes surface payload (from only 14.5 tonnes in orbit) would include the wet-mass of the descent stage. Otherwise such a high payload mass fraction (75%) is unrealistic. I think the current state-of-the-art (MSL) is less than 30%.

There is also the problem of constrained PLF size on the Falcon Heavy. If the same ballistic-coefficient at aero-entry as MSL were assumed, then an aeroshell with a diameter of at least 9 meters would be required. The current Falcon Heavy PLF is only 5.2m in diameter.

- Mike
Please help us to develop our high return-on-investment Humans-to-Mars architecture concept: http://forum.nasaspaceflight.com/index.php?topic=17360.msg636212#msg636212 Thanks!

Online QuantumG

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #2 on: 05/14/2011 01:50 AM »
Who knows how Zubrin came up with those numbers.. I expect dice were involved.

People have been telling him about the heat shield requirements for how many years now?  At least he's not talking about landing 30 tons on the surface with a heat shield this time.

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Offline Zed_Noir

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #3 on: 05/14/2011 02:00 AM »
I got a question about storing kerosene in a zero-G environment  for extended period of time. Have any experiment been done to find if the kerosene is usable after several months in Zero-G?

Offline Warren Platts

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #4 on: 05/14/2011 02:07 AM »
I got a question about storing kerosene in a zero-G environment  for extended period of time. Have any experiment been done to find if the kerosene is usable after several months in Zero-G?

Huh? Kerosine is kerosine: it doesn't care about gravity, within reason....
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Online QuantumG

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #5 on: 05/14/2011 02:28 AM »
To answer the question you meant to ask.. yes, kero is space storable.

When someone is wishing for a pony, there's little to be gained by suggesting a unicorn would be ever better.. ya know, unless it's sarcasm.

Offline wintermuted

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #6 on: 05/14/2011 03:11 AM »
To answer the question you meant to ask.. yes, kero is space storable.

You do have to keep it warm.  Not sure if it would return to usable form if you let it freeze/gel then thaw..

wm

Offline Patchouli

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #7 on: 05/14/2011 03:55 AM »
I would assume that the 11 tonnes surface payload (from only 14.5 tonnes in orbit) would include the wet-mass of the descent stage. Otherwise such a high payload mass fraction (75%) is unrealistic. I think the current state-of-the-art (MSL) is less than 30%.

There is also the problem of constrained PLF size on the Falcon Heavy. If the same ballistic-coefficient at aero-entry as MSL were assumed, then an aeroshell with a diameter of at least 9 meters would be required. The current Falcon Heavy PLF is only 5.2m in diameter.

- Mike

There is a way around that an inflatable aeroshell.

I seen NASA plans where a scaled up version is used to land 60 to 80 tons on Mars.
http://www.prlog.org/10316724-ilc-dover-celebrates-successful-irve-inflatable-aeroshell-flight-test.html

Offline Michael Bloxham

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #8 on: 05/14/2011 04:36 AM »
Inflatables are even less mass-efficient than rigid aeroshells.
Please help us to develop our high return-on-investment Humans-to-Mars architecture concept: http://forum.nasaspaceflight.com/index.php?topic=17360.msg636212#msg636212 Thanks!

Online QuantumG

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #9 on: 05/14/2011 04:46 AM »
Before this dissolves into a debate of technology.. and I thoroughly admit to having started that debate.. I have to say I would much rather hear people's opinions on the quotes.  Zubrin doesn't get up on stage or write for the newspapers to convince the technical audience.  In fact, I'm not terribly sure I've ever heard Zubrin say much to convince the technical audience. 

As I see it, his argument is simple: risk to astronaut life, be it immediate mission failure risk or long term health risk, is worth it to go to Mars.. and he typically goes on to say that the possibility of finding life is the best reason to go to Mars, with eventual colonization being a distant second.

How do you feel about that?  Is his "right stuff" mentality correct?  Is NASA way too cautious these days?  Or is he just shouting into the wind?

(for anyone who cares, my personal belief is that NASA will never do another mission with the level of risk of Apollo 8.. and their biggest fear is that another set of astronauts will some day die and the entirety of HSF will be shut down.  Whether or not you think that is good or bad is irrelevant, it's the way it is, deal with it.)
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Offline Michael Bloxham

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #10 on: 05/14/2011 05:04 AM »
"There is no question that this plan involves considerable risk, and a variety of missions, technology developments and testing programs in advance might reduce that risk. But if we try to do even a significant fraction before committing to the mission, we will never get to Mars."

This statement is both foolish and redundant. Risks to human life must be qualified to a humanstic degree in any scenario. Not attempting a dangerously premature human mission to Mars doesn't mean we will never get there. I agree with the above poster; the risk is just the opposite.

- Mike
Please help us to develop our high return-on-investment Humans-to-Mars architecture concept: http://forum.nasaspaceflight.com/index.php?topic=17360.msg636212#msg636212 Thanks!

Offline Michael Bloxham

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #11 on: 05/14/2011 05:20 AM »
With that said, I think the better way forward is to rely on well-developed and reliable technologies - e.g. low-ballistic coefficient rigid aeroshells such as the type used for robotic probes - rather than less-understood hypothetical technologies. If Zubrin wants a Humans-to-Mars mission on the cheap, then I would suggest the development of a small man-rated lander utilizing a progression of MSL-type technology - rather than relying on completely new and untested technologies. That means a capsule-shaped entry vehicle with a large diameter rigid heatshield. E.g. 9m - far larger than what Falcon Heavy can accomodate, but within the bounds of SLS, etc. Although I admit there may be potential for a much larger PLF on Falcon Heavy. But could it be big enough?

- Mike
« Last Edit: 05/14/2011 05:21 AM by Michael Bloxham »
Please help us to develop our high return-on-investment Humans-to-Mars architecture concept: http://forum.nasaspaceflight.com/index.php?topic=17360.msg636212#msg636212 Thanks!

Online QuantumG

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #12 on: 05/14/2011 05:43 AM »
Well, Zubrin has already made the argument for bigger rockets.. how does these technical objections change the basic philosophy?

What is worth the risk of astronaut's lives?  How much risk is acceptable?  These are deep questions that I wish Zubrin would ask, instead of declaring answers, because so many people object to his answers and then feel no need to ask themselves the questions.
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Offline Downix

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #13 on: 05/14/2011 05:50 AM »
  "There is no question that this plan involves considerable risk, and a variety of missions, technology developments and testing programs in advance might reduce that risk. But if we try to do even a significant fraction before committing to the mission, we will never get to Mars.  [..] If we want to reduce risk to human life, there are vastly more effective ways of doing so than by spending $10 billion per year for the next two or three decades on a human spaceflight program mired in low Earth orbit."
And at this point I had to start laughing, for I know what $10 billion per year with the shuttle program would deliver, using some pieces of work Zubrin himself even discussed in the past.

In the 1990's, General Dynamics proposed a program called "Early Lunar Access" using a pairing of Shuttle and ELV to deliver a lunar program for low cost and rapid development.  Studying this, and applying todays capabilities, let us explore what can be done.

Let us assume that we push the Shuttle to maximum capability, as many launches as we can safely, considering we have only one launch pad and three orbiters. As a Shuttle takes 2 months to turn it around on average, that means each shuttle can be launched 6 times per year, maximum.  I'll divide that by half, as these are old vehicles, for a total of 9 launches.  Knowing the numbers for the Space Shuttle, this would cost a grand total of $5.1 billion per year.  Now, we need to be able to afford the craft, so I will take an approach of adapting the Nautilus-X program and cost projections to this combined Shuttle/EELV approach.  It's cost is $3.7 billion for R&D and construction, with testing of equipment on the ISS.  Because we still have the Shuttle, the spacecraft does not require automated assembly systems, which means speeding up of development.  Now, 8 assembly launches will not have a complete system, but it will have all of the components *but* the inflatable habs and the fuel units.  $10 billion a year, subtracting the Shuttle and vehicle costs comes to $8.8 billion.  The inflatable habs, fuel, and the lander would be lifted with traditional EELV's, requiring 3 heavy launches (two Delta and one Atlas 551) to accomplish the final assembly in the 2 weeks after the initial crew launch, utilizing the crew left by the last Shuttle launch, all three vehicles utilizing both Cape EELV launch sites and the Vandenburg launch site.  This would cost $1.1 billion, making the whole cost of the Mars mission $9.9 billion.  No new launch vehicles, and no use of technology we do not have within the near future.

Now, let us compare to Zubrin's plan here.  Unlike the Shuttle, which has the tools and capability for on-orbit assembly, Falcon is just a BFR.  You'd have more launches to reach the same capability, even if each launch could lift more, due to the need for on-orbit assembly.  By a calculation, for the same level of craft as the Nautilus-X, it would take 20 Falcon 9 Heavy launches to reach the same level of capability.  While yes, the launch strength of F9H is higher, it lacks any kind of on-orbit assembly system, requiring an automated deploy, tug, and assembly, which would increase the weight of each payload.  Based on the automated Russian assembly of modules for both Mir and ISS, and comparing to the weight of those brought by the Shuttle with their capability for the ISS, each module would have to add approximately 40% weight to reach the same level of capability based on history with not one, but 4 space agencies.  This of course means the craft would need a more powerful engine, which adds even more weight to the process, further increasing the number of flights.  It would need 12 flights for the main structure, 3 more for the habitat, and 5 for the fuel, totalling 20 flights. At $150 million per launch, that comes to $3 billion.  The turnaround for Falcons is not fast enough, nor do they have the number of pads needed to enable a staffed spaceship to handle the final stage of assembly. And adding to it, the development cost of the vehicle would itself be higher, due to it's need to self-assemble.  You'd be looking, based on experience we've had with the ISS, at the craft itself having the cost at least doubled, bringing it to $7.4 billion.  So, $3 billion + $7.4 billion == More expensive than the Shuttle + EELV program.

Welcome to space flight.  You're talking a Mars mission, and claiming superiority of one system over another over cost, while ignoring the full capability of the other system.  This is the exact kind of mission the Shuttle is ideal for.  You're not going to Mars in a capsule, you need a full spaceship.  And a full spaceship is not going to be all-up, but assembled on-orbit. For on-orbit Assembly, nothing beats the Space Shuttle.
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Offline Michael Bloxham

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #14 on: 05/14/2011 06:06 AM »
FWIW, Zubrin is proposing vehicles that accomodate a crew of only 2 each. With the 53 tonne throw-weight of the Falcon Heavy, it is not implausible that these could be each delivered to Mars in one piece - without requiring orbital assembly. (See http://forum.nasaspaceflight.com/index.php?topic=17360.msg685877#msg685877 and http://forum.nasaspaceflight.com/index.php?topic=24909.0)

Edit: Also, Nautilus-X is a joke. :D

- Mike
« Last Edit: 05/14/2011 06:12 AM by Michael Bloxham »
Please help us to develop our high return-on-investment Humans-to-Mars architecture concept: http://forum.nasaspaceflight.com/index.php?topic=17360.msg636212#msg636212 Thanks!

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