Quote from: alexw on 05/14/2011 07:48 pmWhat's a "W/h" intended to mean?Watt/hour. Basic electricity term to determine power demand.
What's a "W/h" intended to mean?
Who needs the shuttle when we have ISS? Why not use capsules to ISS on the cheap and space walk from ISS to do on orbit assembly? That way we don't have to pay to launch an entire on orbit assembly platform in the shape of shuttle when we have one that sits up in space and cost us $100 billion. Lets use the ISS!
You'd have to increase the side of the ISS crew in order to turn it into an assembly location, plus the arm does not have a long enough reach as it is, so you would need to expand the ISS a bit to handle this kind of role. Not saying it can't be done, but do understand that it will need more work for this.
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
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.)
Your array would loose 5% of it's total capability every 3 weeks.
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.
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.
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.
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.
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. 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.
Quote from: Downix on 05/14/2011 08:03 pmQuote from: alexw on 05/14/2011 07:48 pmWhat's a "W/h" intended to mean?Watt/hour. Basic electricity term to determine power demand. I think you mean Watt-hour (W·h). Power divided by time doesn't make much sense. Power multiplied by time on the other hand is a measure of energy, which I assume is what you're thinking of.
Quote from: Downix on 05/14/2011 06:37 pmWhat 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. 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.These numbers do not make any sense. GEO comsats are mostly outside the earth magnetic field, so they get the full brunt of all "solar events". Yet they manage with a loss of power of <30% over the typical lifetime of 15 years. If you use the same kind of cells on a mars mission, your power loss due to radiation would be almost negible for a 900 day mars mission.
{snip} Actually, it is mildly amusing to try to think of situations where W/h -- some form of power acceleration -- would be a sensible unit. Perhaps the slow ramping up of (say) a hydroelectric dam to meet shifting grid demand.
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.
Don't be too disappointed if the "details" are nothing more than hobbyist level analysis that you might read on someone's blog *cough*.
Why do we have to rush to send a man, if we can just send better robots that could learn the same stuff more cheaply?
Quote from: QuantumG on 05/15/2011 08:54 amDon't be too disappointed if the "details" are nothing more than hobbyist level analysis that you might read on someone's blog *cough*.NASA can't even get to that level. I have a great deal of respect for the man and his passion for the cause.