ISP units

Maybe the unit for isp should be changed to say nanoseconds? So all
isp gets multiplied by 10^9 and everybody anting to see large
isp in their rocket design will be happy...

--
Sander

+++ Out of cheese error +++

In article ,
Sander Vesik wrote:

Maybe the unit for isp should be changed to say nanoseconds? So all
isp gets multiplied by 10^9 and everybody anting to see large
isp in their rocket design will be happy...

Actually, Isp is measured in #force/#mass/sec -- incorrectly referenced
as "seconds".

Orval Fairbairn wrote:
In article ,
Sander Vesik wrote:

Maybe the unit for isp should be changed to say nanoseconds? So all
isp gets multiplied by 10^9 and everybody anting to see large
isp in their rocket design will be happy...

Actually, Isp is measured in #force/#mass/sec -- incorrectly referenced
as "seconds".

Real rocket men measure effective exhaust velocity.

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

4500 m/s is a nice round number.

http://cosmic.lifeform.org

http://spacebombardment.blogspot.com...and-clock.html

Propulsion System ISP (Hours)
AM-Beam MAX..................2,834
H-Fe Fusion MAX.............1,417
H-He Fusion MAX...............850
IC-Fusion MAX ................283
ORION MAX ....................278
NSWR 90% UTB MAX...............133
AIM ..........................17
VASIMR (high gear) .............8
Mini-Mag Orion .................6
ORION Low Altitude ..............4
1959 ORION 2nd Gen...............3
ORION Fusion ...................2
ORION Fission ..................1
1959 ORION 1st Gen...............1
Space Shuttle x3 SSME............0
Saturn-V first stage ............0
Single Saturn-V F-1 .............0
Space Shuttle x2 SRB.............0

In article ,
Thomas Lee Elifritz wrote:

Orval Fairbairn wrote:
In article ,
Sander Vesik wrote:

Maybe the unit for isp should be changed to say nanoseconds? So all
isp gets multiplied by 10^9 and everybody anting to see large
isp in their rocket design will be happy...

Actually, Isp is measured in #force/#mass/sec -- incorrectly referenced
as "seconds".

Real rocket men measure effective exhaust velocity.

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

4500 m/s is a nice round number.

http://cosmic.lifeform.org

Yes -- but Isp is good for measuring propellant consumption and helps
you size turbopumps (liquid fuel), etc.

Exhaust velocity (and exhaust molecular mass) are important, too.

Orval Fairbairn wrote:
In article ,
Thomas Lee Elifritz wrote:

Orval Fairbairn wrote:
In article ,
Sander Vesik wrote:

Maybe the unit for isp should be changed to say nanoseconds? So all
isp gets multiplied by 10^9 and everybody anting to see large
isp in their rocket design will be happy...
Actually, Isp is measured in #force/#mass/sec -- incorrectly referenced
as "seconds".
Real rocket men measure effective exhaust velocity.

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

4500 m/s is a nice round number.


Yes -- but Isp is good for measuring propellant consumption and helps
you size turbopumps (liquid fuel), etc.

Exhaust velocity (and exhaust molecular mass) are important, too.

So is thrust in Newtons. Do the exercise, I have.

For instance, you could linearly accelerate an atom. Exhaust velocity
would be very high, thrust would be very low. The only reason molecular
mass enters is in the length of the accelerator required to accelerate a
given molecular mass to a given velocity.

An extremely efficient but singularly useless propulsion method.

High Isp isn't always the most efficient either :

http://www.neofuel.com/optimum/

http://cosmic.lifeform.org

Orval Fairbairn wrote:
In article ,
Sander Vesik wrote:

Maybe the unit for isp should be changed to say nanoseconds? So all
isp gets multiplied by 10^9 and everybody anting to see large
isp in their rocket design will be happy...

Actually, Isp is measured in #force/#mass/sec -- incorrectly referenced
as "seconds".

Yes. So? You are taking the post altogether too seriously ;-)

http://spacebombardment.blogspot.com...rpt-pg-14.html

"Isp = m/sec / m/sec^2 = sec "