Author Topic: Zubrin's Falcon Heavy Mars Mission  (Read 83643 times)

Offline majormajor42

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #60 on: 05/15/2011 02:28 PM »
"Zubrin's" Falcon Heavy Mars Mission  ???

Musk risks his personal fortune and millions of NASA/taxpayer $$$
We triumphantly land on Mars.
Zubrin: "You're welcome"
...water is life and it is out there, where we intend to go. I believe that this nation should commit itself to achieving the goal, before this decade is out, of landing a man or machine on a body such as the Moon and harvest a cup of water for a human to drink or process into fuel for their craft.

Offline RocketEconomist327

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #61 on: 05/15/2011 03:55 PM »
"Zubrin's" Falcon Heavy Mars Mission  ???

Musk risks his personal fortune and millions of NASA/taxpayer $$$
We triumphantly land on Mars.
Zubrin: "You're welcome"

In comparison to the 11.1 Billion we wasted on Constellation or the 10 billion more we waste on the Senate Launch System, we are getting new capability and it is an acceptable risk.  Even if Musk was 10 years late it would still be better than the poppycock we are getting from NASA and congress.

VR
TPIS
RE327

You can talk about all the great things you can do, or want to do, in space; but unless the rocket scientists get a sound understanding of economics (and quickly), the US space program will never achieve the greatness it should.

Putting my money where my mouth is.

Offline Downix

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #62 on: 05/15/2011 04:51 PM »
Your array would loose 5% of it's total capability every 3 weeks.

brb calling Hubble team to find out how they still get pictures with the infinitesimal amount of power they have after considering radiation decay.
Hubble is still within the earths magnetic influence, hence is shielded from the majority of the degredation.  But even then, it still is loosing power, slowly.
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  Take that over two 6 month trips.  Figure out your power need, then work backwards and double it in case circuits are broken in between cells. 

Yep hayabusa sure lost half its power from broken circuits.
Hayabusa's power losses were greater than they anticipated, which is why it's arrival at Itokawa was delayed by months, lack of power for it's electrical thrusters. I actually used Hayabusa's power loss as one of the baselines to calculate out the rate of decay for extra-orbital panels.  And this was during a low point in solar activity.
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Let us do the math.  I will assume that this is a low-capacity 2-person mars mission, with a Dragon and an Almaz-sized/capability module with a propultion system which is chemical, not electric in order to reduce the power demands.  Almaz consumed 8500W/h, and Dragon's demands appear to be closer to 1500W/h, so let us get an aim-point of 10kW total demand after 12 months of exposure to solar radiation.

Holy donuts batman Almaz needed just 8500 watt hours of energy to run for a year.  Forget solar all together I can get that in about 500 lbs of lead acid batteries. 
As I put it as 8500 Watts per hour, I can only assume there is some ulterior motivation at work here.
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  What has been found is, per solar incident, solar panels decay at the rate of 2%.  During active periods (and we're entering into one right now), there are between 200-250 of these incidents per year.  So, let us calculate, 10kW, growing by 2% each time over 250 times, gives us  1484.13 kW.  Doubling that, we will need roughly 3MW of power in order to guarantee survival for return.
I thought you already mentioned this as the radiation decay of 5% per three weeks.  Also didn't we double because of all the circuit that will be destroyed from space magic. 
Have you ever built an electric circuit before?
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Each panel of the ISS generates 246kW of power, so we would need 6 of them to guarantee power supply.  When you take this with the weight of the panels, four of them with the truss needed to support them at 14mT.  Adding 50% more would result in 21mT.
Yeay ten year old tech getting 20 W/kg that must be the pinnacle of solar development... Just checked, you can get arrays around ten times the power density of that these days.
Well, if you want it floating out there without any support structure, wiring, or framework, go right ahead.  I prefer dealing with real world scenarios, where you need to hold something in place. 
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Offline Downix

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #63 on: 05/15/2011 04:54 PM »
Just what kind of solar cells are we talking about here?

Different types of solar cells have different degrees of radiation hardness,  and some newer types are pretty darned hard vs. older ones. p-n? Ga nitride? InGa nitride? InGaP/GaAs/Ge triple-junction? ???

Without specifying solar cell type comparing satellite A to space station B or telescope C isn't very helpful.
Indeed.  For simplicities sake I was using the ISS's panels.  If we were to discuss this seriously, first we'd need someone to discuss it with who is willing to hold an honest discussion and not just "SpaceX IZ GOD!!!" or some such nonsense.  We're not going to Mars in a Dragon capsule, nor in an Orion capsule.  We are going in a spaceship, which either one of these may attach to for crew access.
chuck - Toilet paper has no real value? Try living with 5 other adults for 6 months in a can with no toilet paper. Man oh man. Toilet paper would be worth it's weight in gold!

Online ugordan

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #64 on: 05/15/2011 05:01 PM »
Hubble is still within the earths magnetic influence, hence is shielded from the majority of the degredation.  But even then, it still is loosing power, slowly.

Again, what about GEO comsats as already pointed out? The solar degradation rates you talk of just don't pass the sniff test. You bring up Hayabusa, but don't mention the plethora of other interplanetary craft that suffered no such severe degradation due to solar flares.

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As I put it as 8500 Watts per hour, I can only assume there is some ulterior motivation at work here.

There's no ulterior motivation here. Watts per hour is a meaningless unit. Have your ever heard one talk about horsepowers per hour? Spacecraft power requirements are expressed in watts.
« Last Edit: 05/15/2011 05:02 PM by ugordan »

Offline Downix

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #65 on: 05/15/2011 05:43 PM »
Hubble is still within the earths magnetic influence, hence is shielded from the majority of the degredation.  But even then, it still is loosing power, slowly.

Again, what about GEO comsats as already pointed out? The solar degradation rates you talk of just don't pass the sniff test. You bring up Hayabusa, but don't mention the plethora of other interplanetary craft that suffered no such severe degradation due to solar flares.
I actually can't name any which did not suffer degradation.  The Solar Heliospheric Observatory lost 2% of it's solar generative ability in one day, for instance, from the solar event of Nov 4, 2001, with a total power loss of 8% from June to Dec 2001.  A paper from the University of Moscow titled "Analysis of Geostationary Spacecraft Solar Arrays Degradation" did a detailed study of GEO comstats, and found that they also suffer from the same issue.  They found several things.  One, the newer, lighter panels degraded faster than the older, due to more density of the solar array.  Two, that a GEO satellite is bombarded with enough radiation to cause a 7% loss of power within it's first 6 months of operation.  They also discussed how a GEO is mostly outside of the magnetic influence of the earth, but not completely so still does have some protection.
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As I put it as 8500 Watts per hour, I can only assume there is some ulterior motivation at work here.

There's no ulterior motivation here. Watts per hour is a meaningless unit. Have your ever heard one talk about horsepowers per hour? Spacecraft power requirements are expressed in watts.
Computer electronics are rated in watts per hour, solar panels are also rated in watts per hour.  Why are spacecraft exempt from this accepted EE system?
chuck - Toilet paper has no real value? Try living with 5 other adults for 6 months in a can with no toilet paper. Man oh man. Toilet paper would be worth it's weight in gold!

Offline Zubrin

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #66 on: 05/15/2011 05:52 PM »
Friends;
I apologize for not being able to include all the details of the proposed mission plan in my WSJ op ed, which had a 1000 word limit.

In answer to some of the objections raised in this forum, you may note the following:

1. There is no need for zero gravity exposure. Artificial gravity can be provided to the crew by tethering the Dragon off the TMI stage, in the same way as is recommended in the baseline Mars Direct plan.

2. Cosmic ray radiation exposure for the crew is precisely THE SAME as that which would be received by those on any other credible Mars mission, all of which would use the 6 month Conjunction class trajectory to Mars, both because that is the point of diminishing returns (the "knee of the curve") where delta-V trades off against trip time, and because it is uniquely the trajectory that provides a 2-year free return orbit after launch from Earth. Assuming the baseline mission, the total cosmic ray dose would be no greater than that already received by a half dozen cosmonauts and astronauts who participated in long duration missions on Mir or ISS, with no radiation induced health effects having been reported. (Cosmic ray dose rates on ISS are 50% those of interplanetary space. The Earth's magnetic field does not shield effectively against cosmic rays. In fact, with a crew of 6, the current planned ISS program will inflict the equivalent of 30 man-years of interplanetary travel GCR doses on its crews over the next decade. This is an order of magnitude more than that which will be received by the crew of the mission proposed here. ) There are enough consumables on board to provide shielding against solar flares.

3. The preferred method of Mars capture is aerocapture, rather than direct entry. This means that the Dragon aeroshield, which has some lifting capability, may well be adequate. To see this with a back of the envelope calculation, consider a loaded Dragon system with an entry mass of 17000 kg, an effective shield diameter of 4 meters, a drag coeffecient of 1, coming in with an entry velocity of 6 km/s at an altitude of 33 km, where the Mars atmospheric density is 0.8 gm/m3. Setting drag equal to mass times deceleration, you can see that the system would decelerate at a speed of 42 m/s2, or a little over 4 gs. It could thus perform a 1 km/s deceleration in about 25 seconds, during which time it would travel about 140 km. This deceleration is sufficient to capture the spacecraft from an interplanetary trajectory into a loosely bound highly elliptical orbit around Mars. If the perigee is not raised, the craft will reenter again, and again, progressively lowering the apogee of its orbit, until either a desired apogee for orbital operations is achieved or the craft is committed to entry for purposes of landing. That said, if a larger aerobrake were desired, this could be created by adding either a flex-fabric or inflatable skirt to the Dragon core shield.

4. The habitable volume is admittedly lower than optimal. However it should be noted that with 5 cubic meters per crew member, it is 2.5 times higher than the 2 cubic meters per crew member possessed by Apollo crews. It could be expanded in space by the use of inflatable add-on modules. Extra space could be provided on the ground by using a 4th launch to preland another Dragon loaded with supplies, including one or more inflatable modules which could be set up by the crew after they land.

5. The mission architecture is much safer than any based on complex mega systems requiring orbital assembly, since the quality control of orbital assembly does not compare with that which can be accomplished on the ground. It would be better to have a crew of 4, but if we are to do it with Falcon 9 heavy's,  a crew of 2 is all we can do, and while it lacks a degree of redundancy otherwise desirable, it offers the counter benefit of putting the fewest number of people at risk on the first mission. It's quite true that not flying anywhere at all would be safer, but if you want to get to Mars, you have to go to Mars.

Robert





Online ugordan

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #67 on: 05/15/2011 05:53 PM »
There's no ulterior motivation here. Watts per hour is a meaningless unit. Have your ever heard one talk about horsepowers per hour? Spacecraft power requirements are expressed in watts.
Computer electronics are rated in watts per hour, solar panels are also rated in watts per hour.

What characteristic of theirs is rated in watts per hour?

http://en.wikipedia.org/wiki/Watt#Confusion_of_watts.2C_watt-hours.2C_and_watts_per_hour

Offline Downix

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #68 on: 05/15/2011 05:58 PM »
There's no ulterior motivation here. Watts per hour is a meaningless unit. Have your ever heard one talk about horsepowers per hour? Spacecraft power requirements are expressed in watts.
Computer electronics are rated in watts per hour, solar panels are also rated in watts per hour.

What characteristic of theirs is rated in watts per hour?

http://en.wikipedia.org/wiki/Watt#Confusion_of_watts.2C_watt-hours.2C_and_watts_per_hour
Proof to me to not reply before my first cup of coffee.  I meant Watt-hours.  Stubborn me for not waiting.
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Offline Downix

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #69 on: 05/15/2011 06:03 PM »
Friends;
I apologize for not being able to include all the details of the proposed mission plan in my WSJ op ed, which had a 1000 word limit.

Fully understandable
Quote
In answer to some of the objections raised in this forum, you may note the following:

1. There is no need for zero gravity exposure. Artificial gravity can be provided to the crew by tethering the Dragon off the TMI stage, in the same way as is recommended in the baseline Mars Direct plan.
That is one way to do it, of course.  And for cheap-direct, it's a good one.
Quote
2. Cosmic ray radiation exposure for the crew is precisely THE SAME as that which would be received by those on any other credible Mars mission, all of which would use the 6 month Conjunction class trajectory to Mars, both because that is the point of diminishing returns (the "knee of the curve") where delta-V trades off against trip time, and because it is uniquely the trajectory that provides a 2-year free return orbit after launch from Earth. Assuming the baseline mission, the total cosmic ray dose would be no greater than that already received by a half dozen cosmonauts and astronauts who participated in long duration missions on Mir or ISS, with no radiation induced health effects having been reported. (Cosmic ray dose rates on ISS are 50% those of interplanetary space. The Earth's magnetic field does not shield effectively against cosmic rays. In fact, with a crew of 6, the current planned ISS program will inflict the equivalent of 30 man-years of interplanetary travel GCR doses on its crews over the next decade. This is an order of magnitude more than that which will be received by the crew of the mission proposed here. ) There are enough consumables on board to provide shielding against solar flares.
Wasn't that worried about human radiation exposure.  My concern was more on the solar panels, if they are used.  Personally I'd sooner use a 100kW MSTR or MLUR and skip the whole problem.
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3. The preferred method of Mars capture is aerocapture, rather than direct entry. This means that the Dragon aeroshield, which has some lifting capability, may well be adequate. To see this with a back of the envelope calculation, consider a loaded Dragon system with an entry mass of 17000 kg, an effective shield diameter of 4 meters, a drag coeffecient of 1, coming in with an entry velocity of 6 km/s at an altitude of 33 km, where the Mars atmospheric density is 0.8 gm/m3. Setting drag equal to mass times deceleration, you can see that the system would decelerate at a speed of 42 m/s2, or a little over 4 gs. It could thus perform a 1 km/s deceleration in about 25 seconds, during which time it would travel about 140 km. This deceleration is sufficient to capture the spacecraft from an interplanetary trajectory into a loosely bound highly elliptical orbit around Mars. If the perigee is not raised, the craft will reenter again, and again, progressively lowering the apogee of its orbit, until either a desired apogee for orbital operations is achieved or the craft is committed to entry for purposes of landing. That said, if a larger aerobrake were desired, this could be created by adding either a flex-fabric or inflatable skirt to the Dragon core shield.
Simple solution indeed.
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4. The habitable volume is admittedly lower than optimal. However it should be noted that with 5 cubic meters per crew member, it is 2.5 times higher than the 2 cubic meters per crew member possessed by Apollo crews. It could be expanded in space by the use of inflatable add-on modules. Extra space could be provided on the ground by using a 4th launch to preland another Dragon loaded with supplies, including one or more inflatable modules which could be set up by the crew after they land.
That is an approach I always appreciate, pre-landing your supply needs.
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5. The mission architecture is much safer than any based on complex mega systems requiring orbital assembly, since the quality control of orbital assembly does not compare with that which can be accomplished on the ground. It would be better to have a crew of 4, but if we are to do it with Falcon 9 heavy's,  a crew of 2 is all we can do, and while it lacks a degree of redundancy otherwise desirable, it offers the counter benefit of putting the fewest number of people at risk on the first mission. It's quite true that not flying anywhere at all would be safer, but if you want to get to Mars, you have to go to Mars.

Robert
Orbital Assembly is not a game-stopper, however.  Alternatively, you could pull a Skylab, and utilize the fuel tanks as living space from your departure stage, giving you the extra room you need.
chuck - Toilet paper has no real value? Try living with 5 other adults for 6 months in a can with no toilet paper. Man oh man. Toilet paper would be worth it's weight in gold!

Offline Zubrin

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #70 on: 05/15/2011 08:05 PM »
Friends;
Please see my answer to some of the issues raised on page 5 of this thread.
Thanks.
Robert


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.


Offline Cog_in_the_machine

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #71 on: 05/15/2011 08:28 PM »
Considering a previous remark made by Quantum in the Nautilus thread, I like where this is going.
^^ Warning! Contains opinions. ^^ 

Offline DaveH62

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #72 on: 05/15/2011 08:29 PM »
Private exploration is a different matter. There successful explorers assess the risk and take counter measures to reduce them to a level which *they* find acceptable. Then they go. Think of Frenchwoman Raphaela Le Gouvello who has crossed by wind surf the Atlantic, Pacific and Indian Oceans  or the two Aussie lads who Kayaked the Tasman.

The great think about the Zubrin/Dragon mission is that it reduce costs to a level were jut maybe private mission could be done. At the very least it brings that day closer.

ta

Ralph

Yeap that is one benefit to commercial space. It enables this kind of thing.

I think the private exploration element needs more discussion. What would the cost of a Amundsen/Scott type of exploration program to Mars. Is our technology baseline high enough to make the risk comparable to those Antarctic missions from the last century? Are there similar explorers today to risk life and fortune to expand the human frontier. NASA will likely require another 40 years to get to Mars with their collective risk aversion (Congressional and media oversight, changing priorities, changing presidents...). This could change if China challenges us and we choose to respond, but based on our current funding and support culture at NASA, it is difficult to see a human mission before the 2030's at best.
The only way for us to get to Mars in my lifetime is for a President to commit to it, and be willing to spend about 10 times the real mission cost, or private exploration. Would Paul Allen or someone be willing to spend $500 million to sponsor a mission? Branson has his money tied up in Virgin Space, or he would be a logical rich guy willing to risk his life guy. Could it be done for less than a billion? I see a lot of engineering math, but less financial math, and the more difficult to quantify math about personal risk. I know Musk wants to do this, but can he afford this without some big third party funding?
How little could a private mission be done with? Keep in mind, once an initial private mission is completed, more missions will follow and risks once defined empirically, can be better understood by politicians and our larger society.

Offline sdsds

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #73 on: 05/15/2011 08:45 PM »
And that's the fundamental disconnect.. Zubrin wants to get going already and the other camp wants to build the space equivalent of a Winnebago.

I doubt the implication underlying "the other camp."  There are not only two camps.  For example, I consider myself in the "aggressive flexible path" camp.  How does that fit into the implied dichotomy?
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Offline DLR

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #74 on: 05/15/2011 08:51 PM »
Interesting plan, albeit pretty limited capability-wise.

IMO adding a few more Falcon launches to add further redundancy/capability (for example by pre-positioning assets in Mars orbit and on the surface) or the addition of a high-energy upper stage to the Falcon Heavy to increase its trans-Mars throw mass will probably be necessary to make the plan "fly" politically (reducing risk), or if you want more than just a flags/footprints mission with two astronauts and a Dragon on Mars.
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Offline Adaptation

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #75 on: 05/15/2011 08:57 PM »
Zubrin I kinda like the new approach, good job and good luck with it.  I have always felt that radiation concerns about spaceflight where created by the man to keep us down.  Tether based artificial gravity has not really been worked on since Gemini and they had some problems with it, I know TMS had a cube sat they were working on to test it out but I haven't heard anything about it after newmars disappeared.  I really hope you can cut costs low enough that you can find a Warren Buffett to bankroll the mission.  I wonder if you would be willing to combine the first and second launch by using an array of hall effect thrusters to get to mars instead of chemical rockets.  You could have 10-20kW of the solar fold back up and reuse it on the surface, I like to pretend that I know how to come up with cool stuff (^_^) 
« Last Edit: 05/15/2011 09:02 PM by Adaptation »

Offline MikeAtkinson

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #76 on: 05/15/2011 09:24 PM »
Friends;
I apologize for not being able to include all the details of the proposed mission plan in my WSJ op ed, which had a 1000 word limit.

In answer to some of the objections raised in this forum, you may note the following:

1. There is no need for zero gravity exposure. Artificial gravity can be provided to the crew by tethering the Dragon off the TMI stage, in the same way as is recommended in the baseline Mars Direct plan.

Agreed, but I think you have not allocated enough mass for spin-up/down, tether & related systems.

2. Cosmic ray radiation exposure for the crew is precisely THE SAME as that which would be received by those on any other credible Mars mission, all of which would use the 6 month Conjunction class trajectory to Mars, both because that is the point of diminishing returns (the "knee of the curve") where delta-V trades off against trip time, and because it is uniquely the trajectory that provides a 2-year free return orbit after launch from Earth. Assuming the baseline mission, the total cosmic ray dose would be no greater than that already received by a half dozen cosmonauts and astronauts who participated in long duration missions on Mir or ISS, with no radiation induced health effects having been reported. (Cosmic ray dose rates on ISS are 50% those of interplanetary space. The Earth's magnetic field does not shield effectively against cosmic rays. In fact, with a crew of 6, the current planned ISS program will inflict the equivalent of 30 man-years of interplanetary travel GCR doses on its crews over the next decade. This is an order of magnitude more than that which will be received by the crew of the mission proposed here. ) There are enough consumables on board to provide shielding against solar flares.

Agreed, radiation is no worse than for most other mission architectures I've seen.

3. The preferred method of Mars capture is aerocapture, rather than direct entry. This means that the Dragon aeroshield, which has some lifting capability, may well be adequate. To see this with a back of the envelope calculation, consider a loaded Dragon system with an entry mass of 17000 kg, an effective shield diameter of 4 meters, a drag coeffecient of 1, coming in with an entry velocity of 6 km/s at an altitude of 33 km, where the Mars atmospheric density is 0.8 gm/m3. Setting drag equal to mass times deceleration, you can see that the system would decelerate at a speed of 42 m/s2, or a little over 4 gs. It could thus perform a 1 km/s deceleration in about 25 seconds, during which time it would travel about 140 km. This deceleration is sufficient to capture the spacecraft from an interplanetary trajectory into a loosely bound highly elliptical orbit around Mars. If the perigee is not raised, the craft will reenter again, and again, progressively lowering the apogee of its orbit, until either a desired apogee for orbital operations is achieved or the craft is committed to entry for purposes of landing. That said, if a larger aerobrake were desired, this could be created by adding either a flex-fabric or inflatable skirt to the Dragon core shield.

Agree that aero-capture into Mars orbit is the best solution and seems possible for Dragon.

I am worried however about EDL, a heatshield of the size of Dragon is not sufficient to slow the mass of Dragon enough to deploy parachutes, there does not seem to be enough mass allocated for propulsive descent.

I'm also worried about landing the Mars Ascent Stage and its fuel and O2 manufacturing kit.

You seem to be assuming that it is possible to land about 12 tonnes of useful payload from an initial mass in Mars orbit of 17 tonnes. That is not possible with any EDL system that I have heard of.

4. The habitable volume is admittedly lower than optimal. However it should be noted that with 5 cubic meters per crew member, it is 2.5 times higher than the 2 cubic meters per crew member possessed by Apollo crews. It could be expanded in space by the use of inflatable add-on modules. Extra space could be provided on the ground by using a 4th launch to preland another Dragon loaded with supplies, including one or more inflatable modules which could be set up by the crew after they land.

The 10m^3 of Dragon would need to hold 2.5 tonne of supplies (assume at least 3m^3 with packaging), air and water recycling systems, even assuming 100% efficiency a buffer supply of water and gas, spare clothing, tools, equipment, Mars suits (+ space suits?). I would be surprised if there were more than 4 m^3 available for crew use

5. The mission architecture is much safer than any based on complex mega systems requiring orbital assembly, since the quality control of orbital assembly does not compare with that which can be accomplished on the ground. It would be better to have a crew of 4, but if we are to do it with Falcon 9 heavy's,  a crew of 2 is all we can do, and while it lacks a degree of redundancy otherwise desirable, it offers the counter benefit of putting the fewest number of people at risk on the first mission. It's quite true that not flying anywhere at all would be safer, but if you want to get to Mars, you have to go to Mars.

Using a rendezvous of a 53 tonne EDS with Earth integrated payload (2 FH launches, for 6 in total) or an empty EDS + payload launched on a single FH and refuelled at a propellant depot seem better options. That would allow enough payload mass for a reasonable hab volume, 3+ crew, EDL and extra margins all round.


Robert

Offline Nathan

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #77 on: 05/15/2011 09:34 PM »
Thank you Robert. The falcon 9 heavy does provide an excellent means of enabling a mars mission at last. The specifics of the architecture would obviously depend on whom is paying.

In the architecture proposed, how is edl handled by dragon? Inflatables or supersonic retro propulsion? Or other means?
Given finite cash, if we want to go to Mars then we should go to Mars.

Offline mlorrey

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #78 on: 05/15/2011 11:54 PM »

Computer electronics are rated in watts per hour, solar panels are also rated in watts per hour.  Why are spacecraft exempt from this accepted EE system?

Because electronics are NOT rated in watts per hour, they are rated in watt*hours. Multiplication, not division.

Offline Zubrin

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Re: Zubrin's Falcon Heavy Mars Mission
« Reply #79 on: 05/15/2011 11:55 PM »
Friends;
Here are further answers relating to concerns that have been advanced.

1. Habitable volume.
As noted, if the Dragon capsule alone is used, this provides 5 m3 living volume per crew member, which compares to 2 m3 per crew on an Apollo capsule, 9 m3 per crew member on the Space Shuttle, or 8 m3 per crew member on a German U-Boat (Type VII, the fleet workhorse) during WWII. This would be uncomfortable, but ultimately, workable by a truly dedicated crew. However these limits can be transcended. The Dragon has a 14m3 cargo area hold below the aeroshield. Into this we could pack an inflatable hab module, in deflated form, but which if inflated, could be as much as 8 m in diameter and perhaps 10 m long, thereby providing 3 decks, with added volume of 502 m3 and a total floor space equal to 1.5 times as much as that in the Mars Society's MDRS or FMARS stations, which have proved adequate in size for crews of 6. After Trans Mars injection, the Dragon would pull away from the cargo section and turn around, then return to mate its docking hatch with one in the inflatable. It would then pull the inflatable out of the cargo hold, much as the Apollo command module pulled out the LEM. The inflatable could then be inflated. The other end of the inflatable would be attached to the tether, which is connected to the TMI stage, for use in creating artificial gravity.
Upon reaching Mars the inflatable could either be expended, along with the tether system and TMI stage, prior to aerocapture. Alternatively, and optimally, the tether and TMI stage alone would be expended, but the inflatable deflated and retained for redeployment as a ground hab after landing.

2. EDL
Using just its aeroshield for deceleration, the Dragon would have a terminal velocity of around 340 m/s on Mars at low altitude (air density 16 gm/m3). So we could either give it a rocket delta-V capability of 600 m/s (a 20% mass hit assuming storable or RP/O2 propulsion, Isp~330 s) to land all propulsive, or we could use a drogue to slow it down (a 20 m diameter chute would slow it to ~70 m/s) and then employ a much smaller rocket delta-V for landing.

Robert

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