Alternative fuel systems for aero-space

[kausikram k sayee]

all the space vehicles today depend on combustion tech for launching
purposes . this technology which depends on an oxidiser and a fuel
gives just enough thrust to take a space vehicle from the earth surface
to the space against the gravity. now the speed and fuel capacityof
these vehicles will not be enough for long space missions ....so is
there a way by which we can use an alternate technology to launch space
vehicles without using combustion technology ...is there a way to over
come or anull the gravitational forces and make a body levitate ....?

[Victor]

kausikram k sayee wrote:
> all the space vehicles today depend on combustion tech for launching
> purposes . this technology which depends on an oxidiser and a fuel
> gives just enough thrust to take a space vehicle from the earth surface
> to the space against the gravity. now the speed and fuel capacityof
> these vehicles will not be enough for long space missions ....so is
> there a way by which we can use an alternate technology to launch space
> vehicles without using combustion technology ...is there a way to over
> come or anull the gravitational forces and make a body levitate ....?
>

That's an interesting question. There has been some talk about using
carbon nanotubes (CNTs) to create a space elevator, but unless the cost
of production for CNTs decreases a great deal, this will not be a
feasable option. I believe CNTs costs are on the order of $1000/kg.

If you are concerned with fuel depletion over a long duration, electric
propulsion (EP) is the way to go as it makes efficent use of propellant.
Though it is not very powerful, EP powering a spacecraft would be an
ideal choice for exploration missions or missions to the outer solar
system (Deep Space 1 and JIMO, for example). EP only operates in a
vacuum environment, so it will require a two-stage launch, most
likely the combustion engine you mention.

-Victor

[Mirco Romanato]

Victor wrote:

> That's an interesting question. There has been some talk about using
> carbon nanotubes (CNTs) to create a space elevator, but unless the cost
> of production for CNTs decreases a great deal, this will not be a
> feasable option. I believe CNTs costs are on the order of $1000/kg.

last time I look for this was 100$/g probably now they are around to 50$/g.

$1000/kg would be a very good (for now) price tag for industries and
enought to start build the SE.

Mirco

[quasarstrider]

(Bill Kno) wrote in message >...
> CNTs will become less expensive to make. The space elevator will
> become the "cheap" way to get, not only into space, but also as far as
> Mars and the astroid belt.

Assuming they can make them strong enough that is.

[Victor]

quasarstrider wrote:
> (Bill Kno) wrote in message >...
>
>>CNTs will become less expensive to make. The space elevator will
>>become the "cheap" way to get, not only into space, but also as far as
>>Mars and the astroid belt.
>
>
> Assuming they can make them strong enough that is.
>

I do not believe strength will be an issue. I cannot recall exact number
off the top of my head, but Wikipedia puts the strongest CNT specimen
around 63 GPa tensile stength,
(http://en.wikipedia.org/wiki/Carbon_nanotube). With advances in the
field of CNT alignment and growth methods, I believe 63 GPa will soon
become the norm, only to be surpassed by stronger "recipes" of CNTs.

As for the cost of CNTs, I agree they will become cheaper manufacture.
Right now, I believe it is a question of material science engineering
and growth methods. Once a cheap, reliable method is discovered, the
"CNT door" will open into many other realms, not just the space elevator.

[David Summers]

(quasarstrider) wrote in message >...
> (Bill Kno) wrote in message >...
> > CNTs will become less expensive to make. The space elevator will
> > become the "cheap" way to get, not only into space, but also as far as
> > Mars and the astroid belt.
>
> Assuming they can make them strong enough that is.

Actually, I believe the final limit on Space Elevators will be
maintainence. Repair and upkeep on an object 50,000 km long in a
hostile environment (with asteriods coming in at 20 km per second)
will end up being more expensive then launching a high-tech rocket.
The other problem I see with an elevator is throughput. Realistic
elevator technology will make the time to orbit about a week, while a
rocket gets there much faster.

It may be more reasonable for bulk cargo, like modern trains, but it
probably will not be as cheap as other methods (using the same
materials) because of the maintenence problem.

[Tom Kent]

(David Summers) wrote in
om:

> (quasarstrider) wrote in message
> >...
>> (Bill Kno) wrote in message
>> >...
>> > CNTs will become less expensive to make. The space elevator will
>> > become the "cheap" way to get, not only into space, but also as far
>> > as Mars and the astroid belt.
>>
>> Assuming they can make them strong enough that is.
>
> Actually, I believe the final limit on Space Elevators will be
> maintainence. Repair and upkeep on an object 50,000 km long in a
> hostile environment (with asteriods coming in at 20 km per second)
> will end up being more expensive then launching a high-tech rocket.
> The other problem I see with an elevator is throughput. Realistic
> elevator technology will make the time to orbit about a week, while a
> rocket gets there much faster.
>
> It may be more reasonable for bulk cargo, like modern trains, but it
> probably will not be as cheap as other methods (using the same
> materials) because of the maintenence problem.
>

You're not kidding hostile environment. The elevator has to be on the
equator and go all the way up. Since the orbit of EVERY satellite MUST
cross the equator, any satellite below geosynchronous orbit will be a
potential collision hazard...and at great speed to...in LEO its like 7km/s.
Plus its not like you're just going to be able to move this flimsy cable
out of the way, unless you put thrusters in the middle or something.

Tom

[Jim Kingdon]

> Plus its not like you're just going to be able to move this flimsy cable
> out of the way, unless you put thrusters in the middle or something.

Well, at http://www.isr.us/Downloads/niac_pdf/chapter10.html#objects
they propose moving the space elevator by moving the anchor point
(which they have on a Sea Launch style floating platform, largely so
that they can move it).

In fact, that site (in particular
http://www.isr.us/Downloads/niac_pdf/contents.html and in general
http://www.isr.us/SEHome.asp?m=1 ) makes a pretty good stab at
answering the obvious objections to space elevators. They answer the
usual questions of the form "oh but it will never work because of X"
for a variety of values of X.

[David Summers]

Jim Kingdon > wrote in message >...
> > Plus its not like you're just going to be able to move this flimsy cable
> > out of the way, unless you put thrusters in the middle or something.
>
> Well, at http://www.isr.us/Downloads/niac_pdf/chapter10.html#objects
> they propose moving the space elevator by moving the anchor point
> (which they have on a Sea Launch style floating platform, largely so
> that they can move it).
>
> In fact, that site (in particular
> http://www.isr.us/Downloads/niac_pdf/contents.html and in general
> http://www.isr.us/SEHome.asp?m=1 ) makes a pretty good stab at
> answering the obvious objections to space elevators. They answer the
> usual questions of the form "oh but it will never work because of X"
> for a variety of values of X.

What I was referring to was not a killer impact, which has been
addressed as you say. I was talking about the buildup of non-lethal
impacts. For example from the data on the site you gave, a one micron
object will strike the cable in a given section length 200 times per
day (the linked article was unclear about the length in question, but
the width is 10 cm). Each of those collisions very slightly, almost
unmeasurably, decrease the strength of the cable.

My point is merely that this means constant maintenence will be
required to replace worn cables, on a very large object. From a
business point of veiw, this makes owning a cable a very expensive
proposition. Not impossible to do mind you, just expensive. I
believe that the same advances that the cable requires, when applied
to an RLV will be more cost effective (smaller object, less
maintenence). (Basically, we are finally getting our pre-orders of
unobtainium!)

-David

[Abrigon Gusiq]

Can Microwaves be used to heat the air around it or something else? To
use a field effect and no longer need to use old style combustion?

Mike


kausikram k sayee wrote:
>
> all the space vehicles today depend on combustion tech for launching
> purposes . this technology which depends on an oxidiser and a fuel
> gives just enough thrust to take a space vehicle from the earth surface
> to the space against the gravity. now the speed and fuel capacityof
> these vehicles will not be enough for long space missions ....so is
> there a way by which we can use an alternate technology to launch space
> vehicles without using combustion technology ...is there a way to over
> come or anull the gravitational forces and make a body levitate ....?

[Jim Kingdon]

> Can Microwaves be used to heat the air around it or something else?

Sure, see "laser launcher" at, say,
http://www.asi.org/adb/02/10/launch-method-comparison.html

or
http://www.space.com/businesstechnology/technology/beamed_propulsion_021105.html (especially the "lightcraft" section).