Help - Search - Members - Calendar
Full Version: Unaffordable and Unsustainable
Unmanned Spaceflight.com > EVA > Exploration Strategy
Pages: 1, 2
Jim from NSF.com
QUOTE (Analyst @ Aug 2 2006, 02:50 PM) *
If you launch from the equator you are never worse off (for any inclination) than launching from another place north or south. You are better or the same, but never worse.

Analyst


Not true. It takes more energy to fly at 90 degrees inclination at the equator than at a pole. A launch from the equator due south (180 degree azimuth) would not be become 90 degrees inclination due to the earth rotatation. The azimuth has to be slightly retrograde to cancel out this velocity. The further north, the less velocity to cancel out.
Analyst
Interesting, Jim. I should be more careful with absolute statements. What does this tell us about efficiency in gerneral? Is there a different optimal launch site for any given inclination, e.g. 57 degress inclination best from x degrees latitude, 28 degrees inclination best from y degree latitude?

Analyst
The Messenger
QUOTE (Analyst @ Aug 3 2006, 12:30 AM) *
Interesting, Jim. I should be more careful with absolute statements. What does this tell us about efficiency in gerneral? Is there a different optimal launch site for any given inclination, e.g. 57 degress inclination best from x degrees latitude, 28 degrees inclination best from y degree latitude?

Analyst

There are many logistics: High altitudes are great for launching, but windy and very cold. How many people want to become rocket scientist and live in a miserable climate? What about the effects of rust and corrosion? The probability of tropical storms tearing up the place? Bugs and storms making flights in and out of the launch area risky? Where do you want your workforce located? how secure is a jungle location, where do you plug in the airconditioner...
Jim from NSF.com
QUOTE (Analyst @ Aug 3 2006, 02:30 AM) *
Interesting, Jim. I should be more careful with absolute statements. What does this tell us about efficiency in gerneral? Is there a different optimal launch site for any given inclination, e.g. 57 degress inclination best from x degrees latitude, 28 degrees inclination best from y degree latitude?

Analyst


It works out that you want to launch at the same latitude as the desired inclination
Analyst
QUOTE (The Messenger @ Aug 3 2006, 08:51 PM) *
There are many logistics: [...]


I am well aware of logistics. But this has not been the point in my (theoretical) question if there is an ideal launch site latitude for a given inclination if all you worry about is the most efficient trajectory.

Jim, after your answer I have to rethink this completely. Are you sure you are correct? DonPMitchell, if Jim is right I stand corrected.

Analyst
Jim from NSF.com
By default, a launch going due east (90 degrees azimuth) will be at the inclination equal to the latitude
DonPMitchell
The perigee of the orbit will be approximately where the launch site was (where engine burnout occured actually). Consider the velocity vector at that point on the orbit. The magnitude of that vector must be 7.9 km/sec to sustain orbit. At the equator, the Earth gives you a free eastward component of 0.49 km/sec, and the rest of the velocity vector has to be supplied by the rocket.

So I believe as long as the inclination is less than Arccos(0.49/7.9), then it is most efficient to launch from the equator. That's about 86 degrees. To get a true polar orbit (90 degree inclination) then you have to fight the Earth's motion by launching the rocket somewhat westward. So I think Analyst was right, except for the case of an orbit that is greater than 86 degrees of inclination.

The oldest equatorial launch site is the Kwajalein Missile Range, a complex of island radar, telemetry and launch facilities operated by the US Army. SpaceX is planning to launch their Falcon rockets from there. Like Kourou and the island Sea Launch site, there are no logistic constraints on the direction of launch, from east to north.
tty
The ideal launch site should be:

1. On the Equator
2. As high as possible
3. Have ocean or sparsely inhabited territory to the east

So, disregarding logistics, Mount Kenya, Chimborazo or Sangay would seem to be the best places.

tty
DonPMitchell
Some of these effects are more important than others. At sea level on the equator, you get a tangential velocity of 0.464 km/sec from the Earth's rotation. If you started on a mountain 8 kilometers high, you would only get 0.5 m/sec more velocity. So altitude is irrelevant. Also, google reveals that Sangay is a very active volcano, which I think we would catagorize as a "logistic concern". :-)

Cape Canaveral is at 28 degrees latitude, so it gets 0.410 km/sec of velocity boost. Only 50 m/sec less than the Equator, which isn't really very important. What is important is that you cannot launch into an initial orbit with an inclination less than 28 degrees.

The Russians and Americans do multiple-burn maneuvers to get into less inclined orbits. Evidently the most efficent maneuver is to increase the apogee, then at apogee fire perpendicular to the orbital plane to change its angle, and then reduce the apogee.
djellison
QUOTE (DonPMitchell @ Aug 5 2006, 10:06 AM) *
So altitude is irrelevant.


So why didn't the fire Space Ship One from the ground then wink.gif

Doug
tty
QUOTE (DonPMitchell @ Aug 5 2006, 11:06 AM) *
Some of these effects are more important than others. At sea level on the equator, you get a tangential velocity of 0.464 km/sec from the Earth's rotation. If you started on a mountain 8 kilometers high, you would only get 0.5 m/sec more velocity. So altitude is irrelevant. Also, google reveals that Sangay is a very active volcano, which I think we would catagorize as a "logistic concern". :-)


I was not considering the extra rotation speed which is indeed minimal. However the take-off altitude is
not at all irrelevant, for a number of reasons:

1. You save the energy needed to lift the vehicle those x kilometers

2. Air resistance is much less

3. Rocket engine efficiency is better in thinner air

4. Max Q will be appreciably lower, permitting a lighter structure

As a matter of fact I'm a bit surprised that nobody has ever built a high altitude launch site. The reason is probably mostly logistic, and also due to the problem with discarded stages impacting potentially inhabited areas. Still, the Cinese don't seem to worry about this.

tty
RNeuhaus
QUOTE (tty @ Aug 5 2006, 01:57 PM) *
I was not considering the extra rotation speed which is indeed minimal. However the take-off altitude is
not at all irrelevant, for a number of reasons:

1. You save the energy needed to lift the vehicle those x kilometers

2. Air resistance is much less

3. Rocket engine efficiency is better in thinner air

4. Max Q will be appreciably lower, permitting a lighter structure

As a matter of fact I'm a bit surprised that nobody has ever built a high altitude launch site. The reason is probably mostly logistic, and also due to the problem with discarded stages impacting potentially inhabited areas. Still, the Cinese don't seem to worry about this.

tty

What about does with less gravity per kilometer of altitude as Doug has said previously influence the velocity escape? The gravity is around 9.8 m/secē at the sea level but I don't know about what would be the acceleration if the launch platform is on the highland of equadoran Andean territory (above than 3,000 msnm). The Earth gravity variation effect up to 13,000 msnm (airplane intercontinental flights) would be very subttle or not?

Rodolfo
DonPMitchell
Ah, right you are tty, lower air pressure is an advantage.

The Chinese don't seem to worry about impacting their territory, nor do they seem to worry about using horribly toxic non-cryogenic fuel. The controversy about using NDMH and N2O4 goes back to the old feuds between Korolev and Glushko.

When the second M-69 launch exploded near the launchpad, a kiloton of this toxic mixture went off -- the yield of a tactical nuclear weapon! When people saw the poisonous orange cloud, there was pandemonium as they rushed to their cars to escape. I'm amazed that anyone would use this for manned launches.

Oh dear, this thread is really meandering. But I think the original white-paper discussion was beaten to death.
dilo
QUOTE (RNeuhaus @ Aug 5 2006, 07:56 PM) *
The Earth gravity variation effect up to 13,000 msnm (airplane intercontinental flights) would be very subttle or not?

Rodolfo, 13000m is a 0.2% distance variation from Earth center; due to inverse square dependency of gravity force from distance, the acceleration reduction at this height is 0.4% or 4cm/s2.
The reduction on top of a (virtual) mountain with the same heght is lower, due to gravity ot the mountain itself...
dvandorn
QUOTE (DonPMitchell @ Aug 5 2006, 03:41 PM) *
Ah, right you are tty, lower air pressure is an advantage.

The Chinese don't seem to worry about impacting their territory, nor do they seem to worry about using horribly toxic non-cryogenic fuel. The controversy about using NDMH and N2O4 goes back to the old feuds between Korolev and Glushko.

When the second M-69 launch exploded near the launchpad, a kiloton of this toxic mixture went off -- the yield of a tactical nuclear weapon! When people saw the poisonous orange cloud, there was pandemonium as they rushed to their cars to escape. I'm amazed that anyone would use this for manned launches.

Oh dear, this thread is really meandering. But I think the original white-paper discussion was beaten to death.

Well, Don, the U.S. of A. used those horribly toxic fuels to launch 10 manned Gemini capsules on the Titan II booster. And, of course, every lunar orbit insertion, every lunar descent and ascent, and every trans-Earth injection performed during Apollo used these fuels.

And, IIRC, the Shuttle uses these fuels for its reaction control system and its orbital maneuvering system.

And, oh yes, the CEV and LSAM are now planned to use these fuels.

I agree, they're horribly toxic, hard to handle, and even small leaks can have catastrophic effects. But the specific impulse of these fuels, along with their (relatively) easy storage over the course of a long mission, make them still the best choice for many applications...

-the other Doug
The Messenger
"Toxic" fuels do not necessarily yield highly toxic reaction products. Hydrazine reduces to nitrogen and ammonia. The sodium azide burned in early air bags yielded almost pure nitrogen.

Shuttle propellant is not very toxic, although there is evidence exposure to one of the main ingredients (perchlorates) can cantribute to thyroid problems. Shuttle exhaust fumes do contain hydrochloric acid, although direct contact with the exhaust, after it has cooled, will usually only be slightly irritating, unless inhaled.
DonPMitchell
Click to view attachment

UDMH is both toxic and carcinogenic. It's been a big concern in Kazakhstan for some time now, and Russia is developing the Kerosene/LOX Angara first stage as a replacement for the Proton. When spent rocket stages from Baikonur fall to Earth, the local residents rush out and begin cutting them up to sell the titanium scrap metal. Children play in the wreckage, herds of farm animals die mysteriously. You also get considerable contamination around the launch site, because combustion is not perfect during startup.

Click to view attachment Click to view attachment

Titan II was an ICBM developed in 1959, and hastily pressed into service as a manned launcher when the space race first began. The Ariane 1 also used this fuel, but it was developed with extensive Soviet assistance -- they even supplied UDMH to France. But for a country to use this technology for manned flight in 2006 is not very advanced.
DonPMitchell
Looks like NASA has decided to put some serious money into COTS, the program to boost new private-sector space efforts.

MSNBC

It's a gamble, but I would like to see SpaceX succeed with the Falcon series. In interesting feature of Kistler is that they are using Russian engines designed for the N-1 moon rocket -- LOX/Kerosine staged-combustion engines.
Littlebit
http://www.spaceref.com/news/viewsr.nl.html?pid=23230

NASA OIG Report: NASA's Plan for Space Shuttle Transition Could Be Improved by Following Project Management Guidelines

QUOTE
Our evaluation of NASA's "Human Space Flight Transition Plan" found that it did not comprehensively address certain elements that we believe are essential to management and high-level oversight of an activity of the transition's scope and importance.

Specifically, the transition plan did not comprehensively address the following elements:

A work breakdown structure that divides the transition activities into manageable segments.

Detailed cost estimates to support the budget preparation process and facilitate cost control.

Metrics for measuring transition progress and success.

Periodic milestone reviews.

Internal and external communication plans to facilitate an efficient flow of information to the stakeholders.

Asset end-state requirements and security provisions for Space Shuttle Program property.

A centralized data management system to document transition-related recommendations and decisions.

Clearly defined responsibilities for the components of the transition governance structure and designation of the component responsible for post-2010 decisions.

Two comments:

1) It is surprising that this project-level planning is not in place.

2) This assessment is buzzword loaded, and could have been written by any audit of any type of enterprise anywhere. Perhaps technical expertise is not required in the OIG; or they may be taking a first-things-first approach.
peter59
NASA has decided to end its use of the Boeing Delta II rocket.
Delta II will be retired

In my opinion it's very bad decision, Delta II is so cheap and reliable launch vehicle.
What you think about this decision ?
djellison
http://www.unmannedspaceflight.com/index.php?showtopic=4626 is a discussion on that issue
This is a "lo-fi" version of our main content. To view the full version with more information, formatting and images, please click here.
Invision Power Board © 2001-2014 Invision Power Services, Inc.