[extropy-chat] Huygens: First visitor to Titan

[Eugen Leitl]

On Fri, Jan 14, 2005 at 04:06:11PM -0800, Stephen Van_Sickle wrote:

> > There's no science to be done in suborbital flights.
> > It's all been done in
> > 1960s with Laika et al.
> 
> Really?  Then why did Nasa alone launch 87 sounding
> rockets in the last 4 years?
> 
> http://www.wff.nasa.gov/~code810/SRBlueBook.htm
> 
> ESA seems to have an active suborbital program as
> well.
> 
> http://spaceflight.esa.int/users/file.cfm?filename=facsrockets

Allright, I scale this back a bit. There's no *major* science to be done in
suborbital flights. 

There's some good science to be done in prolonged microgravity.

There's some serious science and *industry* to be done on lunar surface.
  
> > SpaceShipOne isn't even a suborbital flight. 
> 
> It wasn't?  Guess they fooled me.  Sure looked like
> it.
> 
> Seemed that it fooled some other people, too, who
> wanted to book it for science flights.

I see you've omitted the "suborbital flight" qualifier.
 
> http://www.spacetoday.net/weblog/entry.php?id=260
> http://news.bbc.co.uk/1/hi/sci/tech/3722596.stml

Last one is a 404, but you're absolutely accurate. People don't understand
what 32 MJ/kg difference (between 100 km orbit, and 100 km of what
SpaceShipOne did, zero velocity at 100 km height) means.

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

...

Space does not equal orbit

A common misunderstanding about the boundary to space is that orbit occurs by
reaching this altitude. Orbit, however, requires orbital speed and can
theoretically occur at any altitude. Atmospheric drag precludes an orbit that
is too low.

Minimal altitudes for a stable orbit begin at around 350 km (220 miles) above
mean sea level, so to actually perform an orbital spaceflight, a spacecraft
would need to go higher and (more importantly) faster than what would be
required for a sub-orbital spaceflight.

Reaching orbit requires tremendous speed. A craft has not reached orbit until
it is circling Earth so quickly that the upward centrifugal "force" cancels
the downward gravitational force on the craft. Having climbed up out of the
atmosphere, a craft entering orbit must then turn sideways and continue
firing its rockets to reach the necessary speed; for low Earth orbit, the
speed is about 7.9km per second (18,000 mph). Thus, achieving the necessary
altitude is only the first step in reaching orbit.

The energy required to reach velocity for low earth orbit (32 MJ/kg) is about
twenty times the energy to reach the corresponding altitude (10 kJ/km/kg).
[edit]
 
> Which is all moot, since "per minute" is a very silly
> figure of merit for science.

Given that the amount of available .gov funds is very limited 
(and shrinking) questions of ROI is very relevant.

-- 
Eugen* Leitl <a href="http://leitl.org">leitl</a>
______________________________________________________________
ICBM: 48.07078, 11.61144            http://www.leitl.org
8B29F6BE: 099D 78BA 2FD3 B014 B08A  7779 75B0 2443 8B29 F6BE
http://moleculardevices.org         http://nanomachines.net
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 198 bytes
Desc: not available
URL: <http://lists.extropy.org/pipermail/extropy-chat/attachments/20050116/82428ea1/attachment.bin>