Unguided orbital insertion (cheap upper stages)

On Feb 25 2002 John Carmack started a thread by this name. Google
won't let me reply to that thread so I am starting another by the
same name.

John Carmack:
It seems to me like it is possible to put something into a 200km (or
whatever) circular orbit with a simple unguided, spin-stabilized
second stage, even when launched from an straight up/straight down
booster with a 100km apogee.

The idea would be that the X-Prize vehicle would have the passenger
cabin replaced with a fairing over a 300kg, non-streamlined second
stage mounted on a platform that could spin up and precisely aim it
(nearly horizontally) before firing it while the booster still has
significant upwards velocity. The complex stuff comes back down to
be reused, and the second stage is basically a piece of ammunition.

This is an interesting and fun problem, so I played with it a bit
in my simulator. With a high G spin stabilized rocket I can get
an orbit with a 90 km perigee. Depending on how high the apogee
is, the mass, and the drag, this can last for a bit (just over a
day in one sample I did). With a small thruster (Hall thruster
/ion-drive/arcjet) on the payload it can easily raise the perigee
and circularize the orbit.

I don't think that with a spin stabilized rocket aimed at one point
alone you can get into a 200+km circular orbit starting from a
minimal X-prize vehicle (i.e. goes to just over 100 km). If you
aim below horizontal by much you just hit too much air. If you
aim above then as you start to go around the Earth the angle seems
higher and higher relative to your velocity, which is not what you
want. It makes it as if your orbit came from inside the atmosphere,
and so after you get most of the way around that is where you will
be.

One trick (from Henry Cate) is that you could have your apogee
kick motor in front of the payload aimed the opposite way so
that when your spin stabilized vehicle got to the other side of
the Earth it would be aimed the right way. I did this in one
sample below. If spin stabilizing something can last for 40
minutes this could work.

You want high G thrust, so you may need to go to solids. And if
you go to solids you probably need 2 stages. But it seems like
2 spin stabilized solids and a small motor aimed backwards, or
an electric thruster on your payload, and you could get to a stable
orbit from an X-prize vehicle. This could be very cheap, and so
seems like good idea.

See samples 78 to 81 named "X-prize to orbit ..." in Java applet at:

http://spacetethers.com/spacetethers.html

-- Vince

In article ,
Vincent Cate wrote:
One trick (from Henry Cate) is that you could have your apogee
kick motor in front of the payload aimed the opposite way so
that when your spin stabilized vehicle got to the other side of
the Earth it would be aimed the right way. I did this in one
sample below. If spin stabilizing something can last for 40
minutes this could work.

Spin stabilization can last much more than 40 minutes, if the thing is
balanced properly and is spinning around the right axis. Trying to spin a
long skinny stack of hardware around its long axis, in particular, is a
disaster. This may be a problem with two solids underneath the payload
and an apogee motor on top.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |

Henry Spencer:
Vincent Cate wrote:
One trick (from Henry Cate) is that you could have your apogee
kick motor in front of the payload aimed the opposite way so
that when your spin stabilized vehicle got to the other side of
the Earth it would be aimed the right way. I did this in one
sample below. If spin stabilizing something can last for 40
minutes this could work.

Spin stabilization can last much more than 40 minutes, if the thing
is balanced properly and is spinning around the right axis. Trying
to spin a long skinny stack of hardware around its long axis, in
particular, is a disaster. This may be a problem with two solids
underneath the payload and an apogee motor on top.

Since we are start high up (like 90 to 100 km maybe), we don't
need to be long and skinny. A short fat stack would not hit too
much air. How short and fat can small (like 150 kg) solids get?

This method can have lots of margin for directional error by
having extra delta-V in the stages. The alternative of spin
stabilized and then electric thruster will not have as much
margin for directional error.

So this method might be the easiest way to send something into
orbit from an X-prize vehicle?

-- Vince

Vincent Cate wrote:
One trick (from Henry Cate) is that you could have your apogee
kick motor in front of the payload aimed the opposite way so
that when your spin stabilized vehicle got to the other side of
the Earth it would be aimed the right way. BRBR


This is exactly what the Navy guys from China Lake tried in the NOTSNIK
launches of 1958. Looking only at the one or possibly two rockets that ever
got to orbital altitude out of six launches (four tore apart or blew up) the
problem was that there was no way for the satellite to know if it had the right
orientation. Once the third and fourth stages were fired, the assumption was
that the spin stabilization would keep it oriented correctly so that, when the
kick motor fired halfway around the world, the thing would go into a circular
orbit. But you had four staging events, each with a chance to impart a bit of
unwanted motion. It may well be that on the most intriguing launch, when the
New Zealand trakcing station detected the first-pass signal but never one from
a second orbit, the satellite may worked, but have been pointing in the wrong
direction. It may have burned directly into the atmosphere or launched itself
into a higher parabola that still ended up in the atmosphere before a full
orbit was complete. Or it may have expended the fuel on an unintended plane
change, in which case it still ended up re-entering. I've always thought the
audacious engineers and physicists behind this unique effort should have
given up some altitude capability (they were aiming for a 1400 nm circular
orbit) in exchange for a slightly heavier payload with a couple of photocells
that might have made sure the kick motor fired in a useful direction.


Matt Bille
)
OPINIONS IN ALL POSTS ARE SOLELY THOSE OF THE AUTHOR

(MattWriter) wrote in message ...
Vincent Cate wrote:
One trick (from Henry Cate) is that you could have your apogee
kick motor in front of the payload aimed the opposite way so
that when your spin stabilized vehicle got to the other side of
the Earth it would be aimed the right way.

This is exactly what the Navy guys from China Lake tried in the NOTSNIK
launches of 1958.

This is very interesting. A good URL (search for NOTSNIK) is:

http://ftp.seds.org/pub/info/newslet...views.9807.txt

It seems they had 4 months and $300,000 to get something to orbit.
This has got to be one of the shortest times and the lowest budget
for any orbital launch vehicle development.

It was also the first air launch to orbit (or at least attempted).

From URL:
This rocket had a total length of 4.38 meters (14.4 feet), a
fin span of 1.65 meters (5.42 feet) and weighed only 950 kilograms
(2,100 pounds). Even with the mass of the Skyray included,
NOTSNIK is the smallest known system ever built to launch satellites.

Some more info and pictures at:
http://www.ninfinger.org/~sven/models/vault/NOTSNik/

This seems like a general method that a few guys with an X-prize vehicle
would want to think about trying. :-)

-- Vince

Henry Spencer wrote:
In article ,
Vincent Cate wrote:
One trick (from Henry Cate) is that you could have your apogee
kick motor in front of the payload aimed the opposite way so
that when your spin stabilized vehicle got to the other side of
the Earth it would be aimed the right way. I did this in one
sample below. If spin stabilizing something can last for 40
minutes this could work.

Spin stabilization can last much more than 40 minutes, if the thing is
balanced properly and is spinning around the right axis. Trying to spin a
long skinny stack of hardware around its long axis, in particular, is a
disaster. This may be a problem with two solids underneath the payload
and an apogee motor on top.

Liquids are of course a real problem, as liquid filled objects tend
to do odd things when spun.

Diddn't the black arrow series of launches from the UK do essentially
this?

In article ,
Ian Stirling wrote:
Spin stabilization can last much more than 40 minutes, if the thing is
balanced properly and is spinning around the right axis...

Liquids are of course a real problem, as liquid filled objects tend
to do odd things when spun.

While there are problems, they can be tamed with careful design. It's
not a common choice for liquid-fuel systems, but it has been done.

Diddn't the black arrow series of launches from the UK do essentially
this?

No, Black Arrow's liquid first and second stages were three-axis
stabilized. Only the solid third stage was spun.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |

(Henry Spencer) wrote in message ...
Spin stabilization can last much more than 40 minutes, if the thing is
balanced properly and is spinning around the right axis. Trying to spin a
long skinny stack of hardware around its long axis, in particular, is a
disaster. This may be a problem with two solids underneath the payload
and an apogee motor on top.

In NOTSNIK [1] the payload was a 2.3 lb doughnut (8 inch diameter) with
a 1.25 lb apogee kick motor in the middle. So this is the type of
thing you would want to do to for your spin to last half an orbit.
This is an extra payload design requirement, that might bother
customers, but could be ok for some X-prize guys who just want to
get something into orbit.

-- Vince

[1] For info on NOTSNIK see:
http://ftp.seds.org/pub/info/newslet...views.9807.txt

Henry Spencer:
[...]
Finally, most prominently, Explorer 1 was put into orbit by an
unguided three-stage solid cluster lobbed up to orbital altitude
by a stretched Redstone. In all three cases, the launcher was
guided, but the guidance system stayed behind after pointing and
spinning up the upper stage(s).

Nice that 3 stages of spin stabilized solid rocket were demonstrated
45 years ago.

They were spun up to something like 750 rpm. Also they were high
G stages, like X-prize to orbit would probably be. Payloads for
this type of launch would have to be a bit more rugged than normal.

Some time back I called up a company that makes solid rocket engines
for model rockets and they were happy to make reasonably large
engines, big enough for this, using lightweight cases (most model
rocket engine cases are relatively heavy) for a price. Someone who
can make a working X-prize vehicle should be able to purchase a
couple solids (order of 150 Kg and 30 Kg) and make a spin stabilized
2nd and 3rd stage to get a small payload with a thruster into orbit.
Fun fun fun.

-- Vince

In article ,
Vincent Cate wrote:
Finally, most prominently, Explorer 1 was put into orbit by an
unguided three-stage solid cluster...

They were spun up to something like 750 rpm. Also they were high
G stages, like X-prize to orbit would probably be. Payloads for
this type of launch would have to be a bit more rugged than normal.

Likewise the rocket motors. At 700RPM, the centrifugal force on the
Juno I second-stage motors was 180G!
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |