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#51 Re: Interplanetary transportation » Orbital mechanics » 2004-12-03 16:35:42
Mars is ~ 1.5 AU, you can substitute this with a more accurate number if you like.
The first two tables look at transfer ellipses with Apehelion from 1 to 8 while the lower two tables look at ellipses from 1 to 3. The only reason this was done was to get a better idea of what changes in energy did to the energy requirement.
When looking at energy for departing and arrive from earth/mars systems, just used a hyperbolic trajectory for the analysis. From there you should be able to size a launch vehicle for earth departure.
FYI, the deltaV requirement for escaping the earth Sphere of Influence is about 11k m/s.
If you want to share you work w/ others (especially for these 'back of the envelope problems' just use a spreadsheet program. When your equations become more envolved use Matlab. You don't want to waste time learning a new language when the tools are alread available to you. Also, most '*.m' files can be run in Octave, so that's always an option for folks you would like to share your work with.
#52 Re: Interplanetary transportation » Orbital mechanics » 2004-12-02 18:40:17
Here is an excel file made a couple years ago comparing the specific impulse/mass fraction/transfer time for a hohmann transfer to mars.
http://homepage.mac.com/dbjwright/FileS … .html]mars to earth spreadsheet
Be patient if you have any questions, it's been a while since I last took a look at this. 
#53 Re: Human missions » What Kind of Manned Program Should We Push For? - A Time to choose » 2004-12-02 13:17:52
SpaceNut,
You get no agrument from me. The only thing I'm trying to illustrate (guess I'm not doing that good of a job ) is that is improbable that a small private coorporation will be able to generate the resources to support the development of exploration program. The small guys will come of w/ some innovative ideas that the big guys will impliment to reduce launch cost and thus have more money for R&D, profits, etc. By their nature the small guys will not produce the margins necessary to fund the rapid development of a robust launch system.
This, however, is what many of the Altspace folks are arguing; make a rocket on the cheap and and pull necessary revenue from the big guys. SpaceX and Microcosm are hoping to carve out a niche for institutional/military/medium industry launches and drive up launch frequency. If they can't do that they're sunk.
#54 Re: Human missions » What Kind of Manned Program Should We Push For? - A Time to choose » 2004-12-02 11:50:04
Indeed, the triple-barrel DeltaIV isn't the most robust solution to our heavy lift needs, but it leverages what we already have. A5 isn't going to happen though (if anyone is curious it can be discussed further).
Each SRB produces 2.7M lbs of thrust (5.4M lb total) at an Isp of 280s while the SSME produce about 450K lbs each (total of 1.41M lbs) at an Isp of 426s. The Orbital Maneuvering System is used to achieve orbital insertion w/ about 12k lbs of thrust delivered at an Isp of 313s. The SRBs provide a significant amount of the initial kick to get the thing off the ground. This is part of the problem with the SSMEs, they're a bit *too* efficient to be used deep in the gravity well. This is why many are going back to using Jet-A/RP-1 based propellents for their systems. Theoretically, you would want to have a RP-1 based lower stage and LOX/LH2 upper stage(s) (Saturn V), but cost increases w/ complexity.
Comstar,
You still haven't said anything yet. You have not shown how you plan to reduce launch cost using either current methods or something completely new. The energy sector is a half trillion dollar industry... big deal. What does that have to do w/ aerospace? Fact of the matter is that we are looking at a < 50 unit launch year and their is currently no demand for a heavy launcher outside the needs of government agencies. Where are these resources going to come from? What potential markets have been overlooked that can possibly fund such an intensive R&D program?
This is why I continually bring up Microcosm and SpaceX; these are privately held companies trying develop vehicles that will drasically reduce to orbit cost. Guess what, it ain't easy. They are coming up w/ innovative solutions to a couple problems, but they don't have the resources to be a serious threat to the big guns. It's hard. Damn hard.
#55 Re: Human missions » What Kind of Manned Program Should We Push For? - A Time to choose » 2004-12-02 01:48:09
GCNRevenger , Answer - G3 Mobile telephone Licensing rights in european countries. problem is newer technology at the same time called 802.11a/b/g wireless LAN systems are more preferred throughout the world higher bandwidth for communication and video links clashing technologies like the Beta Max and VHS recording, So don't dismiss technology or ideas that might make your ideas obsolete.
comstar,
You really should research your topics more.
You really should research your examples more.
You really need a better understanding technology, its applications, its limitations.
You really need to do a better job of supporting your arguments. The question your getting here are nothing compared to those you'll get in the industry.
A. Stanley,
Thanks, in my heart of hearts, I still dream of interstellar travel :-D. I'll concede on hypersonics vehicles a bit, just brings back memories of "Reaganonics", "Space Station Freedom" and "Star Wars". Oh, the chills...
#56 Re: Human missions » What Kind of Manned Program Should We Push For? - A Time to choose » 2004-12-02 00:48:14
It seems to me that Microcosm has logical disadvantages compared with most other launch ideas, rather than the other way around. They try and use all low-cost parts on a small rocket, despite the fact that such an approach would be better suited to a large rocket which could absorb the extra structural weight without decreasing the payload mass fraction as much.
I meant logistical... still doesn't help me at all . I agree with your assessment (and I have said the same to a friend working there), an additional issue is that the reliability of system is going to attrocious until they are able to launch a significant volume of these things... not sure how long that is going to take.
What I'm more interested in are the differences philosophy between the companies and the legitimacy of each. What is the happy medium between efficiency and economy? Hell, what are chances of someone other than LM or Boeing getting meaningful payloads into orbit!?! Those are the question begin addressed by these guys, I don't think a moonshot is in the radar .
One thing I've been wondering about for an inital Mars mission is what I call a "Blaze of Glory" mission where the Shuttles are chopped to necessary systems and used to launch the 2-3 massive loads required for the mission. Not very robust and definitely not the most favorable option, but if the administration determines it just wants to go and collect rocks it might be the most economical.
#57 Re: Human missions » What Kind of Manned Program Should We Push For? - A Time to choose » 2004-12-02 00:15:13
fltwright,
I love a laugh, especially your first statement. I will tell you why that is funny; in the last two years a single geographic region of this world charge for licensing rights equivalent of US$350 Billion (1/3 of a trillion dollars ) in a new technology to private enterprise.
That's fine and dandy, if you have a product/service. What product/service are you proposing that would recoup the cost of developing a robust spaceflight infrastructure?
That would mean the consumers would need to pay a running cost and license recoup fee and a profit margin for this new technology. The individual enterprises then come together to reduce and eliminate duplication costs thus making the process more economic, so they could sell the technology.
I don't know what industry your talking about, but the contemporary aerospace industry does not share IP, especially when it would benefit the launch capabilities of their competitors (case in point - read up on Pintle injectors and try to figure who is actually allowed to use them).
That is why I think your statement is laughable and extremely funny and any person that thinks the same way, not understanding the way business environment will provide a solution to all issues / problems / including government issues.
Private enterprise does not what to invest the massive amounts of resources required to develop the systems to facilitate this sort of exploratory mission. The only thing we can get to now is vacuum, what sort of commerce can you base upon that?
GCNR,
W.R.T. hypersonic vehicles, I haven't seen anything that would indicate that it would be functional outside of *instantly* deliverying small payloads to orbit quickly. The materials I've seen w.r.t. manned orbital hypersonic vehicles aren't too favorable. You still need traditional traditional rockets for maneuvering and orbital transfer events. Hypersonic vehicles are getting to orbit on some trim mass budgets, just having a hard time seeing it. Any resources you have on the subject would be welcome.
Kliper/OSP - Hehe. Hang over from the expendable vs. reuseable crew transfer vehicle argument. Personally, I'm still up in the air on this issue...
SpaceX - I want them to be successful so that LM and Boeing will cut some of the fat. Any ideas regarding manned space flight w/ this system are nothing more than illusions of grandeur.
#58 Re: Interplanetary transportation » Space Elevators and Pipelines » 2004-12-01 23:20:55
Won't work. The pipeline idea is based upon the premise that you can completely isolate the gas/fluid on the inside from the pipes external environment, i.e. a perfectly rigid volume. This is impossible. Keep in mind that must of the strength in carbon-carbon chains are coupled between their stress-strain directions. If you take away their flexibility, they won't be strong enough to endure the induced tension. There are many other reasons you need these things to be flexible.
#59 Re: Human missions » What Kind of Manned Program Should We Push For? - A Time to choose » 2004-12-01 22:22:10
GCNR has got it right,
Private owned industries simply do not have the resources to pull or a manned space program; there are no worthwhile assets that the company can recoup it resources from in a reasonable time frame (15 - 20 years). Unless there is some pent up demand for bottled vacuum, I don't think we will see any sort of extraplanetary commerce .
If you want to talk about contemporary launch system development you have to follow the hardware:
1a) SpaceX - Thier building a 'micro' launch vehicle to compete with Orbital Space Sciences Pegasus-class launch vehicle, which is mainly a rapid deployment/technology testing platform. I personally think they are bringing some good ideas to the table, but illustrate how difficult it is to get to space.
1b) Microcosm - Are taking a more "russian" inspired approach towards reducing launch cost; instead of spending billions of dollars on small increases in efficiency (i.e. - SSME turbopump redesign) make every part as inexpensively as possible and attain reliability through frequency. I really like the contrast between these two companies and can't wait to see how this pans out. Microcosm has some logitical advantages while SpaceX has managed to assemble a rather talent team in short order.
2) Missile Defense - Recieving the most launch system funding of any other program (not exactly sure why...). The only thing we can hope to get from this is gelled propellants.
3) Triple-barreled AtlasV/DeltaIV - as much as I like the RD-170, the triple barreled A5 scares the crap out of me. LockMart still hasn't fully addressed the 3g lateral kicks consistently observed on the platform and this would just be exasperated on a triple barrel configuration. RS-68 stands a much better chance of being man-rated for space flight. I really, really, really don't like the triple barrel EELVs, but the are likely to be our only option in the 13-17 year time frame.
4) SS1/WhiteKnight - Very cool toy. It's fun and exciting, but keep in mind that they are repeating a feet that was accomplished by the USAF almost 30 years ago (from what I understand Rutan was apart of that project). Scaled simply does not have the resources to develop launch vehicle capable of folks into orbit and back down. They will constantly drive the private space and come up with a couple of good ideas ( the ideas of changing your entry profile - nice), but they won't attain the Holy Grail. Won't hurt their succes as a company.
5) Hypersonic vehicles - will NEVER be used to get people into orbit. Never. Military will have plenty of use for them.
6) Kliper - Addresses the biggest problem with the Shuttle, it's too damn big/complex. The bigger the vehicle is, the more susceptible it will be to problems. Energia's biggest hurdle will be economics rather than technical.
All things said, the all arguments w.r.t to manned space programs return to energy density. The fact that the world's hyper-power can barely manage to get off this rock illustrates that manned spaceflight really, really, really hard; and this is not for a lack of intentions. We are running into true, honest-to-god, physical limitations of these systems. It's going to take a long time, it ain't going to be cheap and mistakes will be made. The question is if we can stomach such an expenditure, not if we can do it any differently.
#60 Re: Human missions » Delta IV Heavy and Beyond » 2004-11-23 07:26:43
Why not beryllium tankage?
Beryllium is really, really nasty stuff. Minimal gain for high cost.
http://http://www.beryllium411.org/?src=googlead]chronic beryllium disease
#61 Re: Space Policy » Space fairing Nations - The ever changing view » 2004-11-23 07:20:31
It probobly wouldn't cost less then building a TSTO "Shuttle-II," more basic research needs to be done.
Indeed, a lot of basic research is stil required. We still do not fully understand the dynamics inside of the combustion chamber and maintaining a flame at supersonics is still extremely difficult.
Also, you will still need convention chemical rockets for maneuvering, docking and deorbiting events. These things are going to have a non-trivial weight penalty associated with them and will not be able to lift massive payloads for a very long time, if ever.
Finally, I fear these things are going to reak havok atmosphere; I would be very interested in any studies folks have on this. Don't get me wrong, I think scramjets are extremely cool, but I think only the military will see any utility in ths.