Mike Griffin had to make a decision that incorporated more than just technical stuff.<br /><br />His decision had to include ISP, Thrust to weight calculations and all of that stuff that us rocket nerds think about.<br /><br />But his decision also had to include all of the political considerations of not pissing off the wrong people and/or senators and congressman and losing his funding.<br /><br />It's a delicate balancing act requiring vision, leadership, and politcal skill, as well as engineering understanding of what works and what doesn't work.<br /><br />He made a engineering / political gamble. As for the engineering part of it. It wasn't much of a gamble. It will work. As for the political part, well the coming years will determine the wisdom of it.<br /><br />I believe that he has the vision and leadership capability to pull this off and it's a lot better plan than anything of seen for years. Given the political landscape it may be optimal. I'm sure that he wanted a much more ambitious plan than what he proposed, but that was tempered by the fact that if he asked for too much or for the wrong things, he would get nothing.<br /><br />Godspeed Mike Griffin!!!!<br /><br />
Having worked as an Electrical Engineer for almost 20 years and been around a few others. It's been my experience that if you take all of the people with great technical expertise, they will have less "people skills" as an average than the general population.<br /><br />I for one am at the extreme end of the spectrum in that I'm a true nerd.... But one with good technical skills.<br /><br />I have seen some people with great technical skills and great people skills. So, I know it's possible.<br /><br />Benjamin Franklin comes to mind as the best historical example I can think of.
I'm with spacefire on this.<br /><br />Far be it from me to second guess a guy with several degrees, including a Ph.D. and an MBA! <img src="/images/icons/wink.gif" /> And I think given the mandate to go back to the moon with the existing budget, he has come up with the best possible plan. I just think that the direction he is being given is wrong. <br /><br />I believe this is a failure of space policy just as great as that which gave us a compromised space shuttle. I believe that this nation needs to commit to a NASP or VentureStar type of program. I'm not saying that it has to be specifically a scramjet propelled vehicle or SSTO space plane, but that the goal must be to make access to space far cheaper and more routine before we start thinking about sending humans beyond Low Earth Orbit.
I do believe that within 25 at the longest we will have one or more fully functional space elevators. At that point, chemical rockets as launch vehicles will be pointless. Thermal Management systems for re-entry will also be meaningless.<br /><br />I don't know, how do space elevators work on the moon? The gravity is lower, but the rotation rate of the moon is much lower than earth. Maybe tethers might be the way to go there. Just enough rocket power to reach an altitude of a mile or two and then tether on up.<br /><br />As for Mars, again, I know the gravity is less, but I don't know what the rotation rate is off hand.<br /><br />Once your in orbit, it's all about ISP baby. Thrust is almost meaningless. That means that we can throw out most considerations of fuel density.<br /><br />In orbit, LH2/LOX would be the low end of the scale in terms of ISP.<br /><br />Lifting bodies and SSTO are a meaningless concept in a world with a space elevator.<br /><br />So, given that, what R&D path should we proceed down knowing that chemical rocket launch vehicles won't be launching anymore in 25 years?<br />
You lift the modules up past the geostationary point on the elevator and some distance towards the end of it. You then wait until the right time and release them from the tether, giving them at least a large fraction of the velocity needed to intercept the moon.<br /><br />Braking into lunar orbit and landing would probably be done with a conventional rocket but it wouldn't need to be a very big one.
Well, the principle is pretty sound but it relies on a form of semi-unobtanium with very high tensile strength. Carbon nanotubes, theoretically, have just about almost enough strength to do the job. But a lot more work needs to be done; current nanotubes aren't much more than an inch long and they'll need to be on the order of 50000km, the strength of actual lab-produced ones isn't as good as predicted and required, they need to be made in large numbers, need to be woven into a rope/ribbon etc. The technical challenges of deploying the elevator and building the climber "elevator cars" are considerable too but I think the ribbon itself is the limiting factor.<br /><br />Personally I wouldn't say it's straight-out rubbish. I think the concept is more likely to be feasible than, for example, an SSTO chemical reusable cargo-carrying spacecraft. But it is a long way off at the moment and I for one will wait until a suspension bridge is built from nanotubes before getting too excited about a space elevator.
henry, the reports I've seen from people working in the field.<br /><br />http://www.spectrum.ieee.org/aug05/1690<br /><br />seem to be saying 10 years is possible but 15 years is very do-able to build a space elevator.<br /><br />I simply added another 10 years pushing it out to 25 years. That's just because I'm a pessemist sometimes.<br /><br />The current articles don't mention taper factor.<br /><br />Taper factor was introduced before the invention of the carbon nanotube.<br /><br />The idea was that the maximum tension on the elevator was at Geo-sync orbit. The further away you go from geo-sync orbit the lower the tension, because you have less length of cable to support. The tension reaches it's minimum at the ends.<br /><br />If you made the cable thicker and therefore stronger at geo-sycn orbit and thinner near the ends. You could build an elevator out of weaker/heavier materials.<br /><br />I don't remember the exact formula but a do remember that it was a 5th power polynomial. In other words, double the strength to weight ratio of the material and the taper factor was reduced by a factor of 32.<br /><br />It is possible to build a space elevator out of simple steel, but the taper ratio become astronomical. I think for kevlar it was on the order of about 1000 to 1, but i'm probably wrong... It's been at least 15 years since I read that particular article.<br /><br />Any case with CNT technology I haven't heard anybody mention a taper ratio. But then this stuff is pretty strong.<br /><br />I don't know what the ideal taper ratio is for optimal payload, but I know that it isn't unity.<br /><br />The point i'm trying to make is that if the strength/weight ratio isn't quite high enough, there is a way around that, by introducing a taper.
You could build a space elevator on the moon a fair amount easier than on earth, however it'd be radically different since the lunar 'day' is so long. <br /><br />The cable would form a loop, attached to a tower at each of the moon's poles and spin around like a jumprope with a counterweight. You'd have to climb the tower, then the cable, but otherwise it'd work like a traditional space elevator. The moon's gravity being so low, I doubt you'd need 'unobtanium' or complex tapers to do the job either.
Looking beyond just Nasa, I'd like to see the main space industrys (I'll leave China out for now as it raises more questions than answers) work closer together, having said that it can cause a lot of politcal and funding problems so I'd like to see less duplicity. <br /><br />So Nasa can concentrate on getting manned spaceflight beyond LEO, I'd like to see ESA take over more of the science workload (they are already offering exciting earth observation and interplanetary programs) and share findings with NASA in exchange for places onboard ISS and future moon missions, Russia and ESA look to be working closer together now anyway (Kippler) So together they can cut down on duplicitous work. <div class="Discussion_UserSignature"> <font color="#800080">"All God does is watch us and kill us when we get boring. We must never, ever be boring" - <strong>Chuck Palahniuk</strong>.</font> </div>
>>Mike Griffin had to make a decision that incorporated more than just technical stuff. ETC...<<<br /><br />Good post, BarryKirk, couldn't have said it better myself. <div class="Discussion_UserSignature"> <p> </p><p>One Percent of Federal Funding For Space: America <strong><em><u>CAN</u></em></strong> Afford it!! LEO is a <strong><em>Prison</em></strong> -- It's time for a <em><strong>JAILBREAK</strong></em>!!</p> </div>
Here's my vision in more words, and this time it does not focus on a certain technology: <br />Cheap access to LEO is of paramount importance. The government should set up competions similar to the Bigelow prize, in three categories:<br />Small payload to LEO;<br />Heavy Payload to LEO;<br />Human payload to LEO;<br />A great portion NASA's budget should be used for the prizes. NASA will regain the advisory role NACA had, but this time it would include space research, bidding on rockets from private companies to launch its probes.<br />As cheap access to LEO is developed by the private industry, NASA can expand its capabilities by purchasing hardware or rides from the prize winners. <br />More ambitious missions-Moon, Mars and beyond, will be orchestrated by an assembly of government agencies, foreign government agencies, universities and commercial entities.<br />Since we have cheap access to LEO, these missions would be tens of times less expensive than our current quotes.<br />Many companies will be able to exploit LEO by themselves, leading eventually to mining bases on the Moon or in the asteroid belt and a bunch of colonies on Mars. <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>
I would like to see more development in propulsion (ion drives, solar sails, nuclear drives?...etc) systems and craft sub systems (like a deflector shield of some sort..maybe kevlar or some fantastic fiber, magnetic shield) that will allow for a permanently space based craft that can travel around the solar system being manned or unmanned. Something that can get us from point A to point B inside the solar system so we can explore and bring back to LEO asteroid material. <br /><br />This could be used as a preclude to astroid mining, fuel production, rescue missions, cargo missions...etc. Kinda like an F-150 for our solar neighborhood. <br /><br />I would also like to see the commercial sector to get a hotel up in orbit and fuctional. Then get mining operations up and running.<br /><br />If you think about it the technology for the space F-150 can be applied to a lunar cruise ship for tourism. I'm kinda bothered that we have never went from LEO to moon orbit and back to LEO. So there is no experience with such a maneuver but I think this will be necceary in the future if we keep space stations around the Earth, and want to keep reusable components in space to be maintained in space rather than on Earth and launching them every time. <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>
space elevators are possible once nanotubes can be mass-produced. rotating/"beanstalk" tethers are possible now. I would argue that a full-size space elevator is more practical than spacefire's mega Scramjet - the engineering is simpler.<br /><br />josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>
> <i><font color="yellow">I'd like to know building a structure 36,000km long is simpler and cheaper than building a SSTO</font>/i><br /><br />There are unknowns about the Space Elevator, primarily in building the strong but lightweight ribon. But progress has been made and continues to be made. As progress is made, more people take it more seriously, more researchers tackle parts of the problem, progress accelerates, etc. Is there a fundamental barrier? This is not known yet.<br /><br />But if it does work, the cost to put a given amount of mass in orbit will be incredibly low compared to anything else existing or planned. That would certainly be a transformational event.<br /><br />Wikipedia has an article:<br /> http://en.wikipedia.org/wiki/Space_elevator<br /><br />IEEE Spectrum had a good article on recent progress:<br /> http://www.spectrum.ieee.org/aug05/1690</i>
With the rotating tethers, you don't need to attain orbital velocity, so the design is much simplified. Spaceship 1 could have intercepted a rotating tether and gotten a boost into orbit. Also, no thermal protection system is needed because momentum exchange is used to slow you down instead of friction.<br /><br />Space elevators sound too much like the tower of babel, god knows (literally?) what kind of whackos might come out of the woodwork over it. Best to keep the infrastructure in space, safely out of the reach of luddites, zealots and terrorists.
> <i><font color="yellow">With the rotating tethers, you don't need to attain orbital velocity, so the design is much simplified.</font>/i><br /><br />Thats true. I stand (or sit, actually) corrected.<br /><br />I once saw a design for a pair of rotating tethers, one at the Moon and one at the Earth. Once the system started going, moving mass from Earth orbit to the surface of the Moon and back was incredibly efficient.<br /><br />For those interesting is various uses of tethers for space, see<br />http://www.tethers.com/index.html</i>
Rather than fighting it out between what really are two very deserving projects, why not combine space elevators and an spaceplane-like SSTO into a nearly seamless transport system? An earth orbiting elevator (not rotating as a tether most likely would be), would only need to be on the order of 4000-5000km and would be capable of meshing quite well with a NASP-like SSTO. The bottom end of the EOE would be traveling at far less than orbital velocity at say 150-200km, so an SSTO would only have to achieve something like 15,000mph to meet up with the elevator and dock. Attaching a suborbital SSTO to the bottom of the elevator would admittedly cause a brief inbalance, until some sort of thruster (Ion, Chemical, Plasma, Mass, whatever) could be used to balance the station about it's changed center of mass. Because the SSTO doesn't need to get up to orbital velocity it can carry more payload, and the inevitably higher weight of an atmospherically designed orbiter is lessened because higher ISP engines (those designed to always work in a vacuum) can be used when it imbalances the elevator.<br /><br />http://www.affordablespaceflight.com/<br /><br />The website above basically lays out what I think is a rather rational approach to spaceflight, largely devoid of the propogandist aspects our current effort seems to exude. I'm all for going back to the moon, but we need to develop the infrastructure to go there and return frequently enough with a low enough cost to sustain a base. Low cost to LEO and an efficient way of getting out of earth's gravitational field certainly seem to be near the top of any such infrastructure system. <br /><br />Even if we can't get a space elevator in the next 10-20 years, I'd like to see a LEO to Lunar shuttle capable of docking with a HOTOL SSTO. I won't go so far as to advocate Ion, Plasma, Nuclear or Chemical rockets, but certainly it'd be best if it was optimized for the hig