On Jul 10, 12:04 pm, Willie.Moo...@
gmail.com wrote:
> On Jul 9, 4:50 pm, BradGuth
gmail.com> wrote:
>
>
>>> On Jul 9, 2:56 am, Willie.Moo...@
gmail.com wrote:
>
>>> An inclined surface was used by Galileo to reduce the effect of
>>> gravity. How this works is obvious. Hard balls rolling along a
>>> perfectly level hard surface is unaffected by gravity. The same
>>> surface tilted at some angle, is affected by gravity depending on the
>>> angle of the tilt - based on the cosine of the angle. Obviously, if
>>> we have a vertical surface surrounding a circular region, that grows
>>> increasingly flat with radius - by 1/r^2 - we have a model of how
>>> gravity works around the Earth. Rolling a steel marble on a steel
>>> surface shaped like this, provides a means to model orbits.
>
>>> Everything moves along conic sections. Minimum energy orbits from
>>> Earth to Mars depart and arrive tangential to the motion of the
>>> planets, and the effect of the sun is greatest. It takes 8.5 months
>>> to travel between worlds this way, and you have to wait until they're
>>> lined up properly - which occurs every 2.15 years for Earth and Mars.
>>> The sun imparts about 125 km/sec delta vee to the bodies as they orbit
>>> the sun between worlds. The trajectory requires 0.6 km/sec be added
>>> in the right direction at the right time - to the hyperbolic excess
>>> velocity - that is, to the escape velocity of the payload. That is,
>>> you'll need a ship that can impart about 14 km/sec to your payload -
>>> to travel from the surface of the Earth to Mars along such a
>>> trajectory - counting air drag and gravity losses.
>
>>> Now, we've got that covered, we can talk about improvements.
>
>>> Improvements that come with speed.
>
>>> Adding something like 60 km/sec to the speed of a vehicle, makes the
>>> vehicles' input to the veocity smaller than the sun's. The
>>> hyperbolic curve grows in radius and begins to look pretty straight.
>>> Boost times increase as well.
>
>>> The limit is a constant boost rocket that boosts at 1 gee from Earth
>>> to Mars - reaches 700 km/sec.midjourney - on the shortest trip - 1,800
>>> km/sec on the longest trip between the worlds. These take a few days
>>> in transit. Everything else is longer.
>
>>> So, at one extreme, we have 8.5 months - and 0.6 km/sec -
>>> At the other extreme we have 1 to 2 days and 700 to 1,800 km/sec.
>
>>> Something boosted radially from the sun at Earth orbit, would have to
>>> cancel the Earth's orbital motion of about 29.8 km/sec - after leaving
>>> Earth's sphere of influence - that is achieveing escape velocity. To
>>> reach the orbit of Mars, it would have to have a minimum velocity - to
>>> follow this radial trajectory. If mars were there, the velocity of
>>> mars would have to be added to its speed to come to rest on Mars'
>>> surface. If mars were not there, the vehicle would fall radially into
>>> the sun. This would follow a straight line. Its also a very
>>> inefficient use of delta vee. A 30 km/sec hyperbolic excess velocity
>>> could get you to mars in a week or so - depending on where Mars was -
>>> with no danger of falling into the sun, and far lower approach
>>> speeds.
>
>>> Is such performance with rockets possible? Not with chemical
>>> rockets. Not with nuclear thermal rockets - solid core. Gas core
>>> nuclear rockets, high temperature nuclear pulse rockets, laser pulse
>>> rockets, laser light sails, these can attain the velocities we're
>>> talking about here. I've discussed this before in other venues.
>
>>> High exhaust speeds require less propellant fracton, and if far higher
>>> than the delta vee of the rocket, higher energies.
>
>>> For a mars flight, with refueling at Mars, an exhaust speed of 3,000
>>> km/sec (300,000 sec Isp) is adequate to maintain a constant boost
>>> trajectory between Earth and Mars - at 1 gee. Reducing this to 1/3
>>> gee throughout the trip - allows boost to Mars and return without
>>> refueling on the red planet.
>
>>> Another aspect once you have the basic astrogation and propulsion
>>> worked out, is logistics and economics. What sized ship do you
>>> want? A handy sized cargo ship - about 20,000 tons of payload -
>>> 67,000 tons over all mass - appears to be the minimum sized ship for
>>> any real development off world.
>
>>> 20,000 tons payload
>>> 43,000 tons propellant
>>> 4,000 tons empty structure
>
>>> At $600,000 per ton construction cost each ship is $2.4 billion. A
>>> fleet of 10 is the minimum if we're serious about developing the red
>>> planet. $24 billion.
>
>>> Of course, thie ships will carry 20,000 tons per day to the Red planet
>>> - assuming a 5 day cycle time and 5 days refurb. Each of those tons
>>> is likely to cost $100,000 - and so, that's $2 billion per day - in
>>> support costs -to keep this fleet busy.
>
>>> Even at 10x the $600,000 figure above, the $240 billion fleet cost is
>>> small compared to the $720 billion per year payload costs.
>
>>> Some think avoiding this sort of commitment to payloads is one reason
>>> we don't develop this capacity.
>
>>> Of course we could go deeply into the details of why things are so
>>> costly for aerospace - and not so costly for aeronautics, or shipping
>>> businesses. But that gets deep into nonproliferation issues - which
>>> is a reason given for avoiding this part of the containment box.
>
>>> Of course a constant boost ship that gets us to mars in a few days -
>>> gets us to the moon in a few hours - and by adjusting the thrust level
>>> - provides a nice scout ship to survey the entire solar system - at
>>> very low gee - or periods of zero gee - for outer solar system
>>> exploration. We can get to the Kuiper Belt in a few months - less
>>> time than aminimum energy orbit from Earth to Mars. And with 20,000
>>> ton payload, we have a crew and supplies sufficient to do major
>>> research and activity when we get there.
>
>> Obviously you're talking about lots of serious retro-thrust braking,
>
> Yes, that's what it means when you say you're using a rocket for
> braking at the destination end.
>
>> or are we planning on something along the lines of the lithobraking
>> alternatives?
>
> No, obviously not.
>
>
>
>> Where exactly are we going to come up with the spare trillions of our
>> hard earned loot to blow, so to speak, on what can’t possibly benefit
>> the lower 99.9999%% of humanity, and yet afford another decade of
>> complex R&D in order to pull this Mars thing off?
>
> Nuclear pulse technology is 1950s era technology. Advanced anti-
> proton microfission triggers for clean fusion reactions is 1970s era
> technology. Super advanced laser pulse technology to trigger clean
> fusion reactions is 1990s era technology. Aspects of all of these are
> still highly classified. Likely in part due to the impact they would
> have on our space program and global culture. I mean, 10 people
> walking on the surface of the moon taking a few pics gave rise to the
> environmental movement, and we haven't heard the last of Noetic
> Institute - it just keeps getting stronger. We used to say if we can
> go to the moon why can't we xxx -and you fill in the blank. This puts
> tremendous pressure on the status quo. Its naive to think that
> sending thousands of people throughout the solar system won't have far
> larger consequences to our emerging global culture - its also naive to
> think that the wise guys who think about such things, haven't taken
> steps to maintain some semblance of 'rationality' - of course in
> retrospect their rationality is likely the greatest irrationality of
> our age - akin the rationality of the Spanish Inquisition - we just
> don't see it yet.
>
> Aneutronic reactions carried on pulse fashion inside a hydrogen
> atmosphere, has the potential to create extremely powerful and
> extremely energetic exhausts
>
>
http://en.wikipedia.org/wiki/Aneutronic_fusion
>
> Speeds of 30,000 km/sec are possible. With highly dilute systems,
> 3,000 km/sec are readily achieveable at sizeable thrusts - sufficient
> for terrestrial and planetary launch. Adapting these systems to very
> powerful orbiting fusion power plants, that use laser energy to beam
> energy to users on the ground - is also possible.
>
> One can see emerge the following developmental arc;
>
> 1) terrestrial solar
> 2) space solar - beamed laser energy to terrestrial units
> 3) sun orbiting - deep space solar - interplanetery beaming
> 4) fusion power - beamed laser energy
> 5) fusion thrusters - interplanetary commerce
> 6) laser light sail - interstellar commerce
> 7) 0.3c collision - microscopic black hole research
>
> The cost of power drops with temperature - whether that is achieved by
> concentrating sunlight, moving close to the solar surface, or
> implementing clean fusion power - doesn't matter. The physics of
> large fusion reactors and the physics of obtaining energy from large
> fusion reactors is the same - regardless whether it is the sun or a
> smaller artificial star engineered for a variety of purposes - its the
> same underlying technology.
>
> As the cost of energy and power drops - industrial life grows less
> expensive - and standard of living rises.
>
>> Isn’t Mars pretty much dead to the core, as in frozen solid and
>> possibly even dry-ice cold enough to the core?
>
> That's premature. Basically the development arc is this;
>
> 1) small suborbital payloads
> technology: chemical boosters
> result: ICBM
> outcome - world peace
>
> 2) moderate orbiting payloads
> technology: chemical booster and kick stage
> result: comsat, spysat, navsat, weathersat
> outcome - world information system
>
> 3) large cislunar payloads
> technology: very large chemical boosters
> result: Apollo manned landing on the moon
> outcome - environmental movement, world as one place
>
> ***DEVELOPMENT HALTED 1963***
>
> technology: very large reusable chemical boosters
> result: Power satellite
> outcome -
> ...
>
> read more »
I can agree that nuclear pulse is technically doable, but it's not
likely going to bring that trillion+ $/mission cost down, nor is it
going to pull off all that many of those R&D years required before
safely leaving Earth behind in their nuclear pulse dust, so to speak.
For the unfortunate moment of our energy starved and badly inflated
cost of doing most things, I think we need to keep Mars on the back
burner unless private and thus income taxable investment loot can pick
up at least 50%% of that spendy R&D plus the all-inclusive mission cost
of getting a few brave folks to/from Mars, preferably without their
having to use body bags and w/o our frail environment subsequently
getting infected by some kind of tough Mars spore/microbe that we
can't gamma irradiate, smother via vacuum or much less freeze to
death.
Consider that perhaps what caused Mars to lose it's surface water and
breathable atmosphere was some kind of weird panspermia contributed
spore that converted h2o into h2 and methanes that got blown away once
the planet magnetosphere went south. Are we sure it's a good idea to
bring a few of those Mars spores back to Earth?
- Brad Guth Brad_Guth Brad.Guth BradGuth
