rocket question

I accidently posted this in the wrong group (was looking at one group
thinking i was looking at another) so I'll repost it he

Its my understanding that you need a 3 stage rocket to get to orbit. How
small can a rocket be and still be able to accomplish inserting a small
object (say, a 1 pound object for arguments sake) into earth orbit.
Do all orbits eventually decay? Or is there some magic sped/alt where it
becomes a permanent orbit?
Thanks
Eric

The Shuttle is going to orbit with a single stage system so why do you think
that it takes 3 stages to get to orbit? How long do you consider that it
takes to consider an orbit to be non-degrading? The moon's orbit is
degrading so consider the time scale.

--
Why do penguins walk so far to get to their nesting grounds?

Bob May wrote:

The Shuttle is going to orbit with a single stage system so why do you
think
that it takes 3 stages to get to orbit? How long do you consider that it
takes to consider an orbit to be non-degrading? The moon's orbit is
degrading so consider the time scale.

--
Why do penguins walk so far to get to their nesting grounds?

The shuttle only looks like a single stage - the boosters are stage 1
and 2, the liquid fuel engine is stage 3. It needs to shed that weight
in order to reach orbit if it hopes to bring any kind of a payload with it.
At least thats the way I understand it.
As for my orbit question - you have a good point about the moon. So let me
modify my question and ask instead that the orbit be good for several
years. I'm just real curious how big of a system it would take to put a
small light-weight science package in orbit for a few years - just for
grins.
Eric

Eric wrote in news:vvudna_6yNoSX8
:

Bob May wrote:

The Shuttle is going to orbit with a single stage system so why do you
think
that it takes 3 stages to get to orbit? How long do you consider that it
takes to consider an orbit to be non-degrading? The moon's orbit is
degrading so consider the time scale.

--
Why do penguins walk so far to get to their nesting grounds?

The shuttle only looks like a single stage - the boosters are stage 1
and 2, the liquid fuel engine is stage 3. It needs to shed that weight
in order to reach orbit if it hopes to bring any kind of a payload with it.
At least thats the way I understand it.

You're misunderstanding the use of the word "stage".

The shuttle is a single stage to orbit with solid boosters assist
during initial ascent. The external tank is used from ignition to
MECO (main engine cut off).

Some launchers also use two sets of solids, one set that ignites on
the ground at launch, and another set of "air start" boosters that
ignite when the first set of boosters fall off. But those are not
considered "stages".

A stage is a section of the booster that contains engines and fuel.
When the fuel is used up, this section is discarded so that the
next "stage", or section with engines and fuel, can be used. The
second stage cannot be used until jettison of the previous "stage".

Think Saturn V. The movie Apollo 13 illustrates is well enough.



As for my orbit question - you have a good point about the moon. So let me
modify my question and ask instead that the orbit be good for several
years. I'm just real curious how big of a system it would take to put a
small light-weight science package in orbit for a few years - just for
grins.
Eric

Based on current designs, even if the launcher had no payload many
systems leave the final stage in orbit for some time. The payload
seperates from the booster and uses it's own small engine to put it
into it's final orbit. Many rocket bodies stay in orbit for years,
depending on the mission, for example geosynchronous satellites.

Theoritically, you could use a slightly modified Minuteman III.
Those already can achieve high velocities (24,000 kmh - ISS orbits
at 18,000 kmh) to deliver their payloads (nukes) on suborbital
arcs to targets on the other side of the planet. However, these
systems don't go for low altitudes. They use ballistic trajectories
that go way up (1120km ceiling, ISS orbits at about 350+ km) so the
reentry warhead comes more or less straight down. That is, they use
more energy to go up where as to acheive orbit you need to use more
energy to across, to acheive orbital velocity. I don't know the
specifics, but if the flight path is changed they should be able to
acheive orbital velocity and only require a small additional final
stage. The point being that these missiles aren't all that big and
their payloads aren't vey big, and the unit cost isn't all that high,
which seemed to be the crux of your question.

http://en.wikipedia.org/wiki/Minuteman_missile

The Russians are doing something similar now with modified sub
launched missiles with mixed success.

http://www.space.com/adastra/adastra...ry_050907.html

You might try sci.astro.satellites.visual-observe. Folks more
knowledgeable than I may be able to give a more concrete answer.

Brian
--
http://www.skywise711.com - Lasers, Seismology, Astronomy, Skepticism
Seismic FAQ: http://www.skywise711.com/SeismicFAQ/SeismicFAQ.html
Sed quis custodiet ipsos Custodes? Supernews Sucks!

Eric wrote:

snip

As for my orbit question - you have a good point about the moon. So let me
modify my question and ask instead that the orbit be good for several
years. I'm just real curious how big of a system it would take to put a
small light-weight science package in orbit for a few years - just for
grins.

I don't know what it takes in practical terms (although it's easy
enough to estimate the theoretical minimum energy requirements) but
all that's required to achieve a reasonably stable Earth orbit is to
keep out of the atmosphere. It's hard to be precise about where that
is, because there's no sharp upper boundary to the atmosphere, and
because the altitude of the highest parts varies according to solar
activity and so on. However, what's called LEO (Low Earth Orbit), at
somewhat over 300 km altitude, where the shuttle and ISS spend most
of their time, is feasible without 'boosting' for a period of months
to perhaps several years, thousands of passes at least. (The ISS
occasionally has to rise somewhat higher, for safety and fuel
conservation, when the atmosphere is particularly 'swollen'.) At
altitudes on the order of 1000 km I think atmospheric drag would
become pretty well negligible.

--
Odysseus

On Sun, 16 Oct 2005 13:13:52 -0700, Eric wrote:

I accidently posted this in the wrong group (was looking at one group
thinking i was looking at another) so I'll repost it he

Its my understanding that you need a 3 stage rocket to get to orbit. How
small can a rocket be and still be able to accomplish inserting a small
object (say, a 1 pound object for arguments sake) into earth orbit.
Do all orbits eventually decay? Or is there some magic sped/alt where it
becomes a permanent orbit?
Thanks
Eric


It's all based on the amount of thrust you get from the fuel compared to the
weight of the fuel and it's container and systems...

Right now, we don't have a fuel that can weigh so little that it can get to
space, but we do have systems capable of 2-stage operation.

Don't forget that payload weight, and height of orbit, is a big part of this as
well... since you only want 1 pound at minimal height, you might even break the
1 stage boundary!

I don't have the formulas here, but you basically want to get a fuel
package/motor to 18,000 mph, maybe you could figure it out... gravity will
remain about the same up to the 250 miles you need... dropping to about 97% or
so... so you need to know the motor thrust and fuel weight!

I'd guess with today's tech. it would be the size of a V2...

As for your orbit questions - define permanent? All orbits decay, when depends
on friction of space particles, sunlight pressure, and tide effects.

There is no 'magic speed', speed simply determines the diameter of the orbit.

Try posting this in Rec.Models.Rockets



--

The Lone Sidewalk Astronomer of Rosamond
Telescope Buyers FAQ
http://home.inreach.com/starlord
Astronomy Net Online Gift Shop
http://www.cafepress.com/astronomy_net



"Eric" wrote in message
...
I accidently posted this in the wrong group (was looking at one group
thinking i was looking at another) so I'll repost it he

Its my understanding that you need a 3 stage rocket to get to orbit. How
small can a rocket be and still be able to accomplish inserting a small
object (say, a 1 pound object for arguments sake) into earth orbit.
Do all orbits eventually decay? Or is there some magic sped/alt where it
becomes a permanent orbit?
Thanks
Eric

Actually the moon's orbit is getting larger and not decaying due to
angular momentum conservation. This is due to the fact that the earth's
rotation is slowing slightly because of the moon's gravity and this
loss in angular momentum is gained by the moon. I'm sure someone else
that posts here can elaborate.

Frank

wrote in news:1129519142.129570.86390
@o13g2000cwo.googlegroups.com:

Actually the moon's orbit is getting larger and not decaying due to
angular momentum conservation. This is due to the fact that the earth's
rotation is slowing slightly because of the moon's gravity and this
loss in angular momentum is gained by the moon. I'm sure someone else
that posts here can elaborate.

Frank

I can elaborate, with two words: tidal friction.

Brian
--
http://www.skywise711.com - Lasers, Seismology, Astronomy, Skepticism
Seismic FAQ: http://www.skywise711.com/SeismicFAQ/SeismicFAQ.html
Sed quis custodiet ipsos Custodes? Supernews Sucks!

Skywise wrote in
:

Eric wrote in news:vvudna_6yNoSX8
:

Bob May wrote:

The Shuttle is going to orbit with a single stage system so why do you
think
that it takes 3 stages to get to orbit? How long do you consider that
it takes to consider an orbit to be non-degrading? The moon's orbit
is degrading so consider the time scale.

--
Why do penguins walk so far to get to their nesting grounds?

The shuttle only looks like a single stage - the boosters are stage 1
and 2, the liquid fuel engine is stage 3. It needs to shed that weight
in order to reach orbit if it hopes to bring any kind of a payload with
it. At least thats the way I understand it.

You're misunderstanding the use of the word "stage".

The shuttle is a single stage to orbit with solid boosters assist
during initial ascent. The external tank is used from ignition to
MECO (main engine cut off).

Some launchers also use two sets of solids, one set that ignites on
the ground at launch, and another set of "air start" boosters that
ignite when the first set of boosters fall off. But those are not
considered "stages".

A stage is a section of the booster that contains engines and fuel.
When the fuel is used up, this section is discarded so that the
next "stage", or section with engines and fuel, can be used. The
second stage cannot be used until jettison of the previous "stage".

Think Saturn V. The movie Apollo 13 illustrates is well enough.



As for my orbit question - you have a good point about the moon. So
let me
modify my question and ask instead that the orbit be good for several
years. I'm just real curious how big of a system it would take to put a
small light-weight science package in orbit for a few years - just for
grins.
Eric

Based on current designs, even if the launcher had no payload many
systems leave the final stage in orbit for some time. The payload
seperates from the booster and uses it's own small engine to put it
into it's final orbit. Many rocket bodies stay in orbit for years,
depending on the mission, for example geosynchronous satellites.

Theoritically, you could use a slightly modified Minuteman III.
Those already can achieve high velocities (24,000 kmh - ISS orbits
at 18,000 kmh)

ARGH...can't believe I made that mistake....the 18,000 number oft
quoted is for mph, not kph. A figure I found for the ISS is given
as about 27,600 kmh. Since that's faster than the max speed of a
Minuteman III, it would need an additional stage to reach orbit.
And that's exactly what they do. Come to find out the Minotaur
launcher uses a Minuteman III first stage - a solid motor.


to deliver their payloads (nukes) on suborbital
arcs to targets on the other side of the planet. However, these
systems don't go for low altitudes. They use ballistic trajectories
that go way up (1120km ceiling, ISS orbits at about 350+ km) so the
reentry warhead comes more or less straight down. That is, they use
more energy to go up where as to acheive orbit you need to use more
energy to across, to acheive orbital velocity. I don't know the
specifics, but if the flight path is changed they should be able to
acheive orbital velocity and only require a small additional final
stage. The point being that these missiles aren't all that big and
their payloads aren't vey big, and the unit cost isn't all that high,
which seemed to be the crux of your question.

http://en.wikipedia.org/wiki/Minuteman_missile

The Russians are doing something similar now with modified sub
launched missiles with mixed success.

http://www.space.com/adastra/adastra...ry_050907.html

You might try sci.astro.satellites.visual-observe. Folks more
knowledgeable than I may be able to give a more concrete answer.

Brian



--
http://www.skywise711.com - Lasers, Seismology, Astronomy, Skepticism
Seismic FAQ: http://www.skywise711.com/SeismicFAQ/SeismicFAQ.html
Sed quis custodiet ipsos Custodes? Supernews Sucks!