Re: Improved lunar landing architecture

On Fri, 12 Aug 2005 11:21:21 -0700, Hop David
<hopspageHATESSPAaMmM@xxxxxxxxxxxxxxxxxxxxx> wrote:

>With the smaller Martian gravity, Mars' atmosphere thins more gradually.

Well I do know that 27km up it is only 2% the surface level. So
launching from on top Mount Olympus seems to make a lot of sense. I
think that you could well come close to removing this need to go up
before aiming to achieve orbit.

Sounds like a good plan to me.

>On earth the mesosphere is where meteors (and sometimes spacecraft) burn
>up. This is about 80 to 100 km up. I believe the altitude is comparable
>on Mars.

Well you can remove about 1/3rd of that then. And by the time you
start picking up a high velocity, then you are already most of the way
there.

>> The only difference is that all your fuel, cargo, and people, have to
>> be launched directly from Mars surface. And only the additional fuel
>> (and a few extras) is additional to your method.
>
>You think "the additional fuel (and a few extras)" is trivial?

All about having an efficient launch programme.

>The rocket equation:
>Mf/Mp = e^(dV/Ve) - 1
>
>Mf = mass fuel
>Mp = mass payload
>e = approximately 2.72
>dV = delta vee
>Ve = Velocity exhaust.
>
>In short your fuel requirements go up _exponentially_ with delta vee
>increases. And with more fuel, large fuel tanks must be added to the
>payload.
>
>Zubrin advocates methane and oxygen rocket fuel made from Martian in
>situ resources.

Methane seems questionable. There is not that much in the Martian
atmosphere. Only 10 ppb it seems. And Hydrogen would seem like a much
better option.

>Exhaust velocity of Methane and oxygen IIRC is about 3
>km/sec.
>
>Launching from Mars: e^(6.6/3) - 1 = about 8.

Well let me recalculate that using Hydrogen instead of Methane, where
I know that the SSMEs can do about 4.5 km/s. So this calculation would
be...

e^(6.6/4.5) - 1 = 3.34

Quite efficient I would say. Still, thinking about this more does make
me question your delta vee value.

First is that I know that escape velocity from Mount Olympus is 5.0027
km/sec, but then you have to go into a Hohmann transfer orbit from
that. I guess that works out around 5.5 km/s. However, I expect that
the big saving from launching from Mount Olympus is in removing a lot
of your need to go up before going for orbit.

Starting with a very low atmospheric pressure tends to help your could
say.

This may be crude, but I expect that a delta vee of about 6 is a lot
more close to reality. So let me see how this one works out...

e^(6/4.5) - 1 = 2.8

So based on these sizable increases in fuel efficiency, then your
calculation seem to be running some kind of worst possible situation
option.

>You'd need eight times the fuel mass of your interplanetary hab & large
>fuel tank.

Well I make it 2.8, where that does not seem bad when fuel is easy
enough to come by. And since you have to launch from Mars anyway, then
you just turn your inefficient launch system into a more efficient
launch system.

>Launching from Deimos: e^(2.4/3) - 1 = about 1.2
>
>Launching from Phobos: e^(1.8/3) - 1 = about .82.

For some reason I highly doubt that these two moons contain much
methane. So let me rework these calculations for hydrogen...

Deimos = e^(2.4/4.5) - 1 = 0.7
Phobos = e^(1.8/4.5) - 1 = 0.49

>Also much of your payload: oxygen, water, radiation shielding, etc.
>could come from the Martian Moon.

Radiation shielding? I see no reason why your interplanetary craft
would not come well shielded as it finished construction.

Yes, oxygen, fuel and water would need to be done as extra launches
from Mars under my plan. However, you still need to add in your Mars
launches of people, cargo and no doubt food.

>> Local fuel at the expense of time, money, and infrastructure.
>
>It will also take a lot of time and money to set up rocket fuel making
>infrastructure on Mars.

Well NASA seems to want to do that in the one craft that you land on
the surface and just wait until it fills up. I do not see why it would
be that hard though, and where you also have to make fuel in orbit
under your plan.

>Plus launching through an atmosphere subjects the ship to vibration,
>high temperatures and other stress. It would be better to launch
>interplanetary ships from a more benign vacuum environment.

Mars does not have that much of an atmosphere. Like where Earth is 100
kPa then Mars is about 0.8 kPa. And launching from Mount Olympus at
only 2% this pressure would be 0.016 kPa.

Almost like a vacuum before you even launch, which is why I believe
that you can take a much more direct route to orbit. After all that is
only 1/6250th of Earth atmospheric pressure at sea level.

>> Yes, where it sounds like a nice refuel point. The problem is that it
>> is a lot of extra time and infrastructure for this little gain.
>
>Little gain? please see above paragraphs discussing the rocket equation.

I have seen them. Nothing like a good efficient rocket launch business
to get you into orbit.

Your case makes a lot more sense for the more fuel that you intend to
use for your interplanetary craft, but these plans do not really use
that much fuel. More about efficiency.

Also I am sure that such a craft could make use of large ion engines
to get that extra zip between planets. I can say that Mars has Xenon
at 80 ppb in the atmosphere. Sounds like a better fuel system to me,
but that nuclear generator could be a bit dodgy.

How does your two rocks do for Xenon? None at all I would presume,
where this is the one likely fuel that could give your people and
cargo a more faster ride between planets. That would cut down their
radiation exposure.

So your fuel dump business would not be useful if it could not provide
the best fuel to use. Sure they can use your normal fuel for orbital
work, but that long travel time can sure benefit from a powerful ion
engine.

NASA should have the technology mastered when it comes to Mars time.

>Not a refuel point. The ship from Mars to Deimos would be small, only
>needing to accomodate passengers for a few hours.

Not to forget the cargo and maybe food.

>The interplanetary craft parked at Phobos would be fully fueled from
>Phobos resources.

You would be surprise when you come to fill up and it reads "Xenon
Only" on the tank. :-]

>How many decades and trillions would it take to create a self sufficient
>Martian colony? This investment could be sustained through several
>administrations and winds of public opinion?

Well this NASA Moon and beyond plan seems to have got a lot of support
from both the population and congress. So I would believe that a real
attempt to double the number of planets that us humans live on would
also get a lot of support.

>And with no return on investment?

I have yet to see your idea return a profit. And you have all this
extra infrastructure to support. I have not even heard your mention
what happens when your widget breaks.

My plan is more direct. And once this colony becomes self-supporting,
then further investment is all related to how fast you want expansion
to go.

>Sounds like a good fantasy.

All space plans seem like that. I mean like NASA is really going to
get any return from their Moon Base. Nothing that you could make some
$$$ from at least.

>Achieving a return on investment from more accessable resources, though
>difficult, is much more plausible than getting an ROI on Martian products.

And how do you intend to do that? I have already wrote off the space
solar power plan, when nuclear is already more cost efficient.

>Once there is return on investment, expanding into space becomes self
>sustaining.

It seems more about achieving an internal market I would say. And then
all these Earth folk can profit from stocks and bonds. So there does
seem like a good way to profit from space.

>So you would be spending trillions on your cow and never getting any
>real meat beyond several flags and lots of footprints.

And humans living on Mars with a profitable Martian economy.

The Xenon market should be a good one for Mars, when not even the Moon
has Xenon.

>> So I directly state that the more infrastructure that you have the
>> more NASA's support costs will go up and up. And by maintaining this
>> infrastructure they will cripple themselves from further expansion.
>
>And with Martian infrastructure NASA's support costs will go down and down?

I would call it a more focused approach. Under whatever scheme you
would still need infrastructure on Mars.

>> As the one thing that your Phobos and Deimos plan most overlooks is
>> that this is yet one more location to support with additional food,
>> hardware, repairs and other required resources.
>
>I believe it would be substantially easier to establish a base on Phobos
>or Deimos than Mars.

I am doubtful. Mars has a complete wealth of resources. So I am sure
that your needs from the Mars surface would increase over time.

>> So in the end it makes a lot of sense to stop assing about and to run
>> a Mars Colony Direct plan ASAP.
>
>Is ROI in your vocabulary?

It does not seem in any space based scheme at this time. Still, as I
said the Martian stock market is an idea.

>Perhaps civilizations could invest huge
>amounts over decades and centuries with no ROI in Pharoah's time. That
>time has passed.

This is all well and nice, but I have yet to hear a plan that can
really make some profit.

Cardman.
.

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