"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"
Quote from: Downix on 05/14/2011 06:37 pmYour 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.
Your array would loose 5% of it's total capability every 3 weeks.
Quote from: Downix on 05/14/2011 06:37 pm 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.
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.
Quote from: Downix on 05/14/2011 06:37 pmLet 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.
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.
Quote from: Downix on 05/14/2011 06:37 pm 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.
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.
Quote from: Downix on 05/14/2011 06:37 pmEach 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.
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.
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.
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.
As I put it as 8500 Watts per hour, I can only assume there is some ulterior motivation at work here.
Quote from: Downix on 05/15/2011 04:51 pmHubble 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.
QuoteAs 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.
Quote from: ugordan on 05/15/2011 05:01 pmThere'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.
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.
Quote from: Downix on 05/15/2011 05:43 pmQuote from: ugordan on 05/15/2011 05:01 pmThere'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
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
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.
Quote from: Ralph Buttigieg on 05/14/2011 10:36 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.taRalphYeap that is one benefit to commercial space. It enables this kind of thing.
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.taRalph
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.
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.
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
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?