Conceptual Design and Analysis of a Small and Low Cost Launch Vehicle
Georgia Tech, May 2005
http://www.ssdl.gatech.edu/papers/mastersProjects/TayaK-8900.pdf
In this publication, the authors "treat [Microcosm's] Sprite launch vehicle as an example of small and low-cost launch vehicle. The goal of project is to analyze its design concept, confirm performance, and refine its design."
Wednesday, December 28, 2011
Sunday, December 25, 2011
Online: How Small Can a Launch Vehicle Be?
How Small Can a Launch Vehicle Be?
Lawrence Livermore, 10 July 2005
https://e-reports-ext.llnl.gov/pdf/321763.pdf [PDF, 183K]
This classic document reviews the background requirements of launching a vehicle to low Earth orbit, focusing on the issue of lower bounds on the size of the vehicle.
ABSTRACT
Trajectory simulations from Earth to orbit indicate comparative velocity requirements depending on vehicle size, for several propellant options. Smaller vehicles are more affected by drag, resulting in steeper trajectories that require more total velocity. Although they are technically challenging, launch vehicles smaller than 1 ton are not ruled out by the nature of ascent trajectories.
Lawrence Livermore, 10 July 2005
https://e-reports-ext.llnl.gov/pdf/321763.pdf [PDF, 183K]
This classic document reviews the background requirements of launching a vehicle to low Earth orbit, focusing on the issue of lower bounds on the size of the vehicle.
ABSTRACT
Trajectory simulations from Earth to orbit indicate comparative velocity requirements depending on vehicle size, for several propellant options. Smaller vehicles are more affected by drag, resulting in steeper trajectories that require more total velocity. Although they are technically challenging, launch vehicles smaller than 1 ton are not ruled out by the nature of ascent trajectories.
Saturday, December 24, 2011
Online: NASA SPACE VEHICLE DESIGN CRITERIA SP-8000
NASA SPACE VEHICLE DESIGN CRITERIA SP-8000
arocketry.net, 24 December 2011
http://www.arocketry.net/sp-8000.html
If you weren't already aware of them, Nasa produced a whole series of technical tutorials on different aspects of rocket design. If you haven't checked them out, I highly recommend doing so. You'll find everything from propulsion design, propellant feed system design, and a number of other highly-practical tutorials.
arocketry.net, 24 December 2011
http://www.arocketry.net/sp-8000.html
If you weren't already aware of them, Nasa produced a whole series of technical tutorials on different aspects of rocket design. If you haven't checked them out, I highly recommend doing so. You'll find everything from propulsion design, propellant feed system design, and a number of other highly-practical tutorials.
Thursday, December 22, 2011
Book: Design of liquid propellant rocket engines
Design of Liquid Propellant Rocket Engines, 2nd Edition
NASA NTRS, 19 December 2011
http://hdl.handle.net/2060/19710019929 [ PDF, 45M ]
This is the classic Huzel and Huang "Design of Liquid Propellant Rocket Engines". It covers rocket theory and has good design examples.
NASA NTRS, 19 December 2011
http://hdl.handle.net/2060/19710019929 [ PDF, 45M ]
This is the classic Huzel and Huang "Design of Liquid Propellant Rocket Engines". It covers rocket theory and has good design examples.
Wednesday, December 21, 2011
Monday, December 19, 2011
News: Build a DIY Spacecraft is a Daunting Task
To Build a DIY Spacecraft is a Daunting Task and, Not Surprisingly, Getting It Up Where It Belongs, in Space, Is No Less of a Problem
Wired, 19 December 2011
http://www.wired.com/wiredscience/2011/12/to-build-a-diy-spacecraft-is-a-daunting-task/
A ballistic missile is suddenly a simpler, much more affordable, single-stage solution to flying out of Earth’s atmosphere. The performance can be increased far beyond that of a winged space plane. And that’s it.
Wired, 19 December 2011
http://www.wired.com/wiredscience/2011/12/to-build-a-diy-spacecraft-is-a-daunting-task/
A ballistic missile is suddenly a simpler, much more affordable, single-stage solution to flying out of Earth’s atmosphere. The performance can be increased far beyond that of a winged space plane. And that’s it.
Sunday, December 18, 2011
Specific Impulse
Specific Impulse is one of the two key method of measuring the performance of a rocket system (the other being mass ratio). Understanding Specific Impulse is one of the most important things to know to understand orbital rockets.
DEFINITION
Just like one of the measures of the efficiency of a car is miles per hour, rockets have their own measure of efficiency, Specific Impulse (or Isp), measured in seconds.
Specific Impulse (or Isp) is the number of seconds that one unit weight of propellant will produce one unit force of thrust. The equation for calculating Isp derived from its definition is:
Since there is a unit of force in both the numerator and denominator, they cancel out to leave just seconds.
In both American Standard and Metric, the same formula applies. In metric, you can
just put the thrust force in Newtons and convert the mass of the propellant into its
weight by multiplying by the gravitational acceleration (g = 9.80665 m/s^2) because
Force = mass * acceleration:
Knowing that a propellant can provide 200 seconds of 1 pound of thrust with one
pound of propellant, one can also determine that the propellant will produce
400 seconds of 1/2 pound of thrust with one pound of propellant.
Sometimes, Metric users will just use Mass instead of Weight and so the
value of Metric Specific Impulse is off by a constant factor of 9.8. You'll
see that value used in the literature as well.
ISP EQUATION
The rocket force equation is:
Where:
Where:
EXAMPLES AND REASONABLE RANGES FOR ISP
The following table shows some representative values for different propellant combinations and their vacuum Isp.
But, a rocket motor behaves differently, having different Isp at different altitudes and ambient pressures. The following graph shows the Isp characteristic of a rocket through different atmospheric conditions. It is for a LOX-Isopropyl Alchohol motor with a 1.65:1 mixture ratio, a 3.12:1 expansion ratio and a chamber pressure of 250 PSI (with 90% combustion efficiency).
As can be seen, the Isp varies greatly throughout the flight regime. At sea level, the Isp is about 213 seconds, but by the time it is at 25,000 feet, the Isp has gone up to about 253 seconds. This is with no change of propellant flow characteristics or change of combustion pressure. This is solely due to the effect of the nozzle throughout its flight regime.
Therefore, since a rocket in flight spends more of its flight time at higher altitude, it will see a higher average Isp throughout its flight than its sea level value. This is an important thing to understand and exploit in designing rocket boosters.
DEFINITION
Just like one of the measures of the efficiency of a car is miles per hour, rockets have their own measure of efficiency, Specific Impulse (or Isp), measured in seconds.
Specific Impulse (or Isp) is the number of seconds that one unit weight of propellant will produce one unit force of thrust. The equation for calculating Isp derived from its definition is:
In both American Standard and Metric, the same formula applies. In metric, you can
just put the thrust force in Newtons and convert the mass of the propellant into its
weight by multiplying by the gravitational acceleration (g = 9.80665 m/s^2) because
Force = mass * acceleration:
pound of propellant, one can also determine that the propellant will produce
400 seconds of 1/2 pound of thrust with one pound of propellant.
Sometimes, Metric users will just use Mass instead of Weight and so the
value of Metric Specific Impulse is off by a constant factor of 9.8. You'll
see that value used in the literature as well.
ISP EQUATION
The rocket force equation is:
Force = the thrust of the rocket mdot = the mass flow rate through the rocket Ve = the exhaust velocity out of the nozzle exit Pe = the pressure at the nozzle exit po = the ambient operating pressure Ae = the area at the nozzle exitSince Force is part of the Isp equation, we can subsitute this force equation into the Isp equation to show some important relationships between the factors that produce the thrust of a rocket and its Isp:
Isp = the specific impulse mdot = the mass flow rate Ve = the exhaust velocity Pe = the pressure at the nozzle exit po = the ambient operating pressure Ae = the area of the nozzle exit g = the acceleration of gravityAs can be seen, the pressure of the ambient operating environment affects the Isp of the rocket.
EXAMPLES AND REASONABLE RANGES FOR ISP
The following table shows some representative values for different propellant combinations and their vacuum Isp.
As can be seen, the Isp varies greatly throughout the flight regime. At sea level, the Isp is about 213 seconds, but by the time it is at 25,000 feet, the Isp has gone up to about 253 seconds. This is with no change of propellant flow characteristics or change of combustion pressure. This is solely due to the effect of the nozzle throughout its flight regime.
Therefore, since a rocket in flight spends more of its flight time at higher altitude, it will see a higher average Isp throughout its flight than its sea level value. This is an important thing to understand and exploit in designing rocket boosters.
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