Global Flyer

Rich S. wrote:
"Robert Bonomi" wrote in message
...

Moon-quake, Solar flare, "Deck is fouled", I can think of a bunch of
reasons
that 'divert to alternate' might be required.


Controllers on strike, Aliens on runway, Gotcha.


No, no. That's a *Mars* bar. This is Luna. And it should be *obvious*
that "Almond Joy" is the appropriate one -- "Sometimes you feel like a
nut"
*DEFINITELY* describes this 'food for thought'.

(Don't blame me if you don't like the answer. It was _your_ question,
after
all.


:O)


But, yeah, "glider" -- for lack of a better term. At the landing site,
a *BIG* ramp -- with the _upper_ part conforming to the ballistic
trajectory
you launched into. You have on-board 'maneuvering' thrusters, to tweak
you path to the _exact_ ramp trajectory -- a GCA "glide slope" with a
*vengeance*. You touch down on the ramp, and roll out, possible friction
brakes, possible aircraft-carrier type snubbing cable.


You been watching old Evel Knievel tapes I'll bet.


You can *try*, but I suggest that -first- you calculate the energy-density
of that system. then contemplate the mass requirements, _just_ to power
your "forty watt plasma rifle" -- let alone any on-board flight controls,
instrumentation, life-support system, etc.


Improvements in battery design have been ramping up so quickly in the past
few years that I fully expect to see a pink, drum-beating bunny on the Moon!

Rich S.


Hey, when that happens are ya gonna share what you are drinking?

Dan, U.S. Air Force, retired

Rich S. wrote:

"Dan, U.S. Air Force, retired" wrote in message
news:rGsWd.24184$Sn6.22376@lakeread03...


Hey, they didn't do it that way in "2001 a Space Odyssey" when they
cruised across the surface ofthe moon in the moon bus.


Wasn't that a monorail or cable-suspended car?

Rich "running low on memory" S.


No, it had 6 (?) rocket engines aimed downwards. I had the model whan I
was in highschool.

Dan, U.S. Air Force, retired

On Sun, 06 Mar 2005 14:03:42 +0800, Stealth Pilot wrote:

On Sat, 05 Mar 2005 19:11:22 GMT, Ron Wanttaja
wrote:



Let's assume an open-cockpit single-seater. Call it 200 lbs for the pilot,
another 100 lbs for his suit, 500 pounds of airframe, 20 pounds of avionics, and
50 pounds for batteries and life support supplied. Let's assume our rocket fuel
has a specific impulse of 250 seconds. That's a dry weight of about 870 pounds.

forgive my iggorance.
are we talking earth pounds, moon pounds or mass?
and if we are talking mass is it roman catholic, anglican or
engineering?

Now stop that. :-)

what is actually needed is for someone to do a Wright Brothers on
gravity.
aviation would go another quantum leap forward if we could just negate
the aircraft weight without all that drag.
it is amazing that with all our progress we havent made one single
inroad into understanding or controlling gravity.

You've hit the nail right on the head. Right now, space travel is at the
equivalent level of the Montgolfier brothers. Chemical rockets are a dead end;
the moral equivalent of de Rozier's combination hot air/hydrogen balloon.

Heavier than air flight wasn't possible until the invention of the internal
combustion engine. Similarly, the true exploitation of space is waiting for a
system that will produce good acceleration without the need of tons of fuel.

It's sort of in our grasp, now. Chemical fueled engines have Specific Impulses
(Isp) in the range of 200-300 seconds. Modern electric propulsion units see
ISPs up to about 3000 seconds.

What does that mean? Well, I used an Isp of 250 for the thrust-hovering moon
buggy. If you recall, it needed 25 million pounds of fuel for Rich's
cross-country.

With an ISP of 3000, the fuel requirement drops from 25,000,000 pounds...to a
bit over 1,000. Yes, about four orders of magnitude. These units are
operational *now*...they're used on communications satellites.

They produce a lot of thrust for very little fuel, but the actual amount of
thrust they produce is minuscule. The commsats use them to compensate for the
north-south wobble their orbits get from the uneven distribution of mass within
the earth. They need 150 FPS of delta-V per year, and they run the electric
propulsion nearly constantly.

As you might expect, they require a lot of power. But a dozen miles from Rich's
house, a number of airtight spacecraft hulls complete with operational nuclear
power plants lie in storage. The Navy calls them, "mothballed submarines."
Back when a tsunami hit Hawaii forty or so years ago, they powered Honolulu with
the output of *one* of these subs.

Cooling them in space, where you don't have access to billions of tons of cold
sea water, is left to the good offices of your local thermal engineer.

Ron Wanttaja

On Sat, 5 Mar 2005 23:50:23 -0800, "Rich S."
wrote:

"Ron Wanttaja" wrote in message
.. .

"Moon Zero Two", 1969, starring James Olson.

Ooh - I'll look that one up!

It's known as the first space western.... :-)

With a weight increase, the amount of fuel needed increases
disproportionately.
Also, if you add a second seat, you're always going to have to have a body
or
ballast in the spot to keep the beast in balance.

We'll just make the ship expandable. When you've got a passenger, just
unlatch it in the middle and pull the ends out - like you do with the dining
table when Grandma's coming.

You might be able to do something along those lines...depending on how much
acceleration you plan on. Airplanes can tolerate CG shifts because they have
horizontal stabilizers at the end of a longish moment arm. Spacecraft don't.
However, with a fly by wire control system, you could compensate for weight
offsets so the vehicle flies about the same.

You could also handle the problem with something Heinlein referred to as "A
Space Suit Built for Two."

You're not going to be able to work a keyboard, and if you have buttons
and whatnot to push, they're going to have to be well separated to ensure you
don't punch the wrong one. It's gonna be tough to fly without a pressurized
cabin.

Who sez the spacesuit can't have a keyboard- or even a joystick? Pull your
arms inside and start typing. 'Course the chest area would look like Jayne
Mansfield's.

Or just make the suit something like the Jim suits used for diving...

http://www.divingheritage.com/jimkern.htm

Assuming you're not fixed on a Buck Rogers style ship (or even a Space 1999
style ship...) you could make your buggy from a hard-shell space suit. You
probably won't look like Jayne, more like Robbie the Robot ("Danger, Rich
Shankland!").

Like Robert said, though, we could use a mass driver or other ground-based
system to throw the vehicle, and just rely on onboard fuel to land. This
drops
the required onboard fuel to about 750 pounds. Not too bad.

Naw - can't go for the ground based system. What if you want to stop for a
picnic on the shore of the Mare?

Ohhhh, now you want *floats*.... :-)

Well, maybe we *do* have antigravity. After looking at your figures (not
that I understand them), did you say that 5,000 fps is orbital velocity at
10 NM MSL? If so, then what speed is orbital velocity at 1,000' MSL (Moon
Surface Level)? Cruising at that speed would obviate the need for constant
vertical thrust. Half that speed would require less constant vertical thrust
than a hover. If you could find a happy medium, perhaps a small fuel cell,
plutonium reactor, cold fusion motor, or bag of rocks and Hernadez's 98 mph
fast ball would do it.

The problem is, the required orbital velocity is based on the spacecraft's
distance *from the center of the orbital body*, not its distance above the
surface. So the difference is just 30 FPS between orbits 10 NM high and 1000
feet high.

And, in fact, the orbital velocity decreases with increased altitude...but, of
course, you have to burn fuel to get to the altitude.

The 5000 FPS was for a ballistic case, not an orbit. I brute-forced this one to
determine the velocity needed...I used an orbit with a 10 nm apogee and pushed
the perigee below the surface until I had an orbit where the above-ground
portion was approximately 2,000 NM long (it really, REALLY helps to write your
own orbit analysis programs).

Ron Wanttaja

"Ron Wanttaja" wrote in message
...

The problem is, the required orbital velocity is based on the spacecraft's
distance *from the center of the orbital body*, not its distance above the
surface. So the difference is just 30 FPS between orbits 10 NM high and
1000
feet high.

And, in fact, the orbital velocity decreases with increased
altitude...but, of
course, you have to burn fuel to get to the altitude.

The 5000 FPS was for a ballistic case, not an orbit. I brute-forced this
one to
determine the velocity needed...I used an orbit with a 10 nm apogee and
pushed
the perigee below the surface until I had an orbit where the above-ground
portion was approximately 2,000 NM long (it really, REALLY helps to write
your
own orbit analysis programs).

When I took physics out at the 'Dub, orbits hadn't even been invented yet. I
can barely remember attending, much less any of the course content. I'll
leave the calculations to the specialists.

From a layman's point of view, it appears as though powered flight on our
Moon should require *less* power than on Earth. If your linen bag of termite
chow can fly in a one-G field on forty horsepower while beating aside air,
smog, clouds, bugs and rain, then our moonflitter should be able to paddle
along in one-sixth G under a lot less power. If you can carry fuel to go for
your hamburger on Earth, then what's the problem out there (other than a
scarcity of Mickey D's)? Absence of air should be an advantage in some ways.

Riddle me that, O Caped Crusader!

On Sun, 6 Mar 2005 09:17:30 -0800, "Rich S."
wrote:

When I took physics out at the 'Dub, orbits hadn't even been invented yet. I
can barely remember attending, much less any of the course content.

Heck, Rich, you were playing "Rock, Rock, Rock," before paper and scissors had
been invented....

From a layman's point of view, it appears as though powered flight on our
Moon should require *less* power than on Earth. If your linen bag of termite
chow can fly in a one-G field on forty horsepower while beating aside air,
smog, clouds, bugs and rain, then our moonflitter should be able to paddle
along in one-sixth G under a lot less power. If you can carry fuel to go for
your hamburger on Earth, then what's the problem out there (other than a
scarcity of Mickey D's)? Absence of air should be an advantage in some ways.

Well, vacuum DOES eliminate drag, but as far as everything else is concerned,
it, well....sucks.

Look at is this way: All aircraft engines are rocket engines. They work by
expelling mass, with the amount of thrust depending upon the amount of mass and
the speed at which its expelled. "Jet" engines use burning gasses to increase
the velocity of the flow, while us poor ol' Fly Baby jockeys have to make do
with carving out a piece of air and throwing it backwards.

Down here in the soup, the mass to expel backwards is free. On the moon,
though, you have to bring that mass with you.

So...how much air, in mass, are we talking about?

Let's take a look at my Fly Baby. It's got a prop 72 inches in diameter. The
pitch is 48 inches...in an ideal world, every turn of the prop blade would shove
a chunk of air 72 inches in diameter backwards a distance of 48 inches.

How much air is that? Almost 200,000 cubic inches. But of course, that prop
isn't 100% efficient. Let's say it's only 1% efficient...that's 2000 cubic
inches of air being pushed backwards to provide thrust.

How much does that air weigh? About 1.2 kg per cubic meter. That's about
0.000043 lbs/cu-inch. Which is about 0.1 lb of air per prop rev.

And...the prop is revolving at about 40 turns per second, so that's about 4
pounds of "propellant" used per second. An hour flight in my airplane uses over
14,000 pounds of "rocket fuel"! Geeze, maybe I better review those Sport Pilot
regs again.... :-)

Ron "Hypergolic" Wanttaja

"Ron Wanttaja" wrote in message
...
On Sun, 6 Mar 2005 09:17:30 -0800, "Rich S."
wrote:

When I took physics out at the 'Dub, orbits hadn't even been invented yet.
I
can barely remember attending, much less any of the course content.

Heck, Rich, you were playing "Rock, Rock, Rock," before paper and scissors
had
been invented....

As a teacher's assistant, it was my job to keep the candles lit during the
lectures.

Down here in the soup, the mass to expel backwards is free. On the moon,
though, you have to bring that mass with you.

So...how much air, in mass, are we talking about?

Lots free photons floating around, though. Do photons have mass? Even a
little bit? If they do, couldn't we collect them in the front, accelerate
them until their mass becomes ~ infinite, then toss them out the back?

Heck, come to think of it, we don't even need protons. If mass increases as
velocity closes in on C, all we need for reaction mass is a handful of
depleted uranium. If we can toss it away fast enough. I don't suppose that
..50 caliber hawgleg that Ammeter carries would do it. We need a railgun or
two.

Rich "Thinking about lighter-than-vacuum balloons next" S.

P.S. I like that idea about recycling boomers!

In article ,
Rich S. wrote:
"Robert Bonomi" wrote in message
...

No, no. That's a *Mars* bar. This is Luna. And it should be *obvious*
that "Almond Joy" is the appropriate one -- "Sometimes you feel like a
nut"
*DEFINITELY* describes this 'food for thought'.

(Don't blame me if you don't like the answer. It was _your_ question,
after
all.

:O)

[[.. sneck ..]]

You been watching old Evel Knievel tapes I'll bet.

You've never been required to play "catch" with raw eggs, have you?

Seriously, a number of years ago, some engineering school did a variant
on the 'package an egg so it won't break when dropped X feet' contest,
where the contestants had to build something to _catch_ an egg, w/o breaking
it.

You can *try*, but I suggest that -first- you calculate the energy-density
of that system. then contemplate the mass requirements, _just_ to power
your "forty watt plasma rifle" -- let alone any on-board flight controls,
instrumentation, life-support system, etc.

Improvements in battery design have been ramping up so quickly in the past
few years that I fully expect to see a pink, drum-beating bunny on the Moon!

Y'know, you could probably *sell* that idea to the copper-top people for an
ad campaign.

In article ,
Ron Wanttaja wrote:

[snip]
So...we have to burn our downward thrusters for four hours. "G" on the Moon
is
about 5.6 ft/Sec^2. We'd need to burn the same to counter that. Total
acceleration required is 5.6 ft/sec^2 x 4 hours x 3600 seconds/hour... about
80,000 FPS, about sixteen times more than a ballistic S/C using a mass driver
for launch, and, as a point of interest, almost three times what a spacecraft
launch from the *Earth* needs. With the accel/decel Delta-V, our 870-pound
spacecraft requires 24.9 *million* pounds of fuel.

Doesn't the vehicle get lighter as fuel and oxidizer are consumed,
requiring less thrust, lowering the consumption rate...

Dan "and-so-on, and-so-on, and-so-on" Nafe
danATscuba-trainingDOTnet

On Sun, 06 Mar 2005 23:33:48 -0500, Dan Nafe wrote:

In article ,
Ron Wanttaja wrote:

[snip]
So...we have to burn our downward thrusters for four hours. "G" on the Moon
is
about 5.6 ft/Sec^2. We'd need to burn the same to counter that. Total
acceleration required is 5.6 ft/sec^2 x 4 hours x 3600 seconds/hour... about
80,000 FPS, about sixteen times more than a ballistic S/C using a mass driver
for launch, and, as a point of interest, almost three times what a spacecraft
launch from the *Earth* needs. With the accel/decel Delta-V, our 870-pound
spacecraft requires 24.9 *million* pounds of fuel.

Doesn't the vehicle get lighter as fuel and oxidizer are consumed,
requiring less thrust, lowering the consumption rate...

Exactly, but the basic rocket equation takes that into account:

Fuel = Initial Mass * (1 - 1/(e^(Delta-V/(ISP * g)))

Ron Wanttaja