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<font color="yellow">"I think you may be interested in this...."</font><br /><br />Yes I am. So interested in fact that it was the report in the first URL link of the post you're replying to. <img src="/images/icons/smile.gif" />
<font color="yellow">"When two APAS-89s dock one is usually active and the other one passive, but physically they are the same."</font><br /><br />As with many things about the technologies I'm dealing with -- I'm working with reference material that I cannot physically confirm to be correct. I have never seen/touched/used an APAS-89 or seen extremely detailed notes on the limits of its operation. My assumption has always been what you indicate -- namely that two 'active' APAS-89 docking assemblies could dock in the fashion you described. In the patent documentation, however, is a statement from NASA engineers explicitly stating this is not the case. Since these engineers are presumably talking about a field which they know a great deal more than I do regarding the capabilities of the APAS-89 -- I have to make the assumption that they are making a valid statement. For the record, I also have to make the assumption (absent any evidence to the contrary) that they know more than *you* do. This is not an implied slur on your knowledge. However, I have evidence of the credentials of the people involved in the patent, while I have no such information about yours. If you have a link to documentation about the functionality of the APAS-89 that confirms the behavior you describe -- I would be very interested in seeing it. Absent that, I have to continue working under the assumption that two active APAS-89's cannot dock.<br /><br /><font color="yellow">"...while both docking rings are extended..."</font><br /><br />I don't know if we're both looking at the same picture. The one I posted seems to have one ring extended and the other retracted. That would seem to imply one active, one passive.<br /><br /><font color="yellow">"...but electrical glitch and your high-end docking system...</font><br /><br />That's OK. The same electrical glitch you speak of probably turned the G-X3 into an unguided derelict that's about to smash into the station
<font color="yellow">"I'd leave the LIDS for GX3 Block 2"</font><br /><br />I would (and might). The main reason I jumped to it is because Bigelow seems to have bought the rights to it. It's entirely 'conceivable' (although I doubt 'probable') that this will be the *required* mechanism for a craft docking with CSS Skywalker. More importantly than that, however, is that I have some confidence in Bigelow's methods. If he has the rights to this technology -- then he's liable to build (or contract to have built) the most economical and efficient docking system available. A LIDS then might be the cheapest option to use, and the easiest for an ASP competitor to obtain.
<font color="yellow">"If you have a link to documentation about the functionality of the APAS-89 that confirms the behavior you describe -- I would be very interested in seeing it."</font><br /><br />Unfortunately nothing with awe-factor of a patent but something:<br /><br />From Russian Aerospace Guide:<br /><br /><i>In December, the passive docking apparatus (#8001) for PMA-2 arrived from Russia and was to be tested with APAS-89 #3002. The passive mechanisms are simpler versions in which the docking ring is not extendable. A active APAS-89 may be used to dock to a passive or active mechanism, 2 passive's can't be used to dock together. (Russian Space Review 1996, Dennis Newkirk, 1997)</i><br /><br />Here's some kind of NASA manifest that concurs with the deliverance part of previous link.<br /><br />I don't know much about Newkirk but he runs Russian Aerospace Guide and ISS Guide sites. Maybe you should ask him for more information about APAS (and where he gets his info!).<br /><br /><font color="yellow">I don't know if we're both looking at the same picture.</font><br /><br />I actually tried reading the patent. From claim 14 forward got the impression they describe a totally symmetrical system where both units are extended and actively seek alignment while docking, maybe this impression is wrong. Patent language is <i>so</i> clear <img src="/images/icons/wink.gif" /><br /><br /><font color="yellow">"electrical glitch you speak of probably turned the G-X3 into an unguided derelict that's about to smash into the station"</font>
<blockquote><font class="small">In reply to:</font><hr /><p>"I think you may be interested in this...." <br /><br />Yes I am. So interested in fact that it was the report in the first URL link of the post you're replying to. <p><hr /></p></p></blockquote><br />D'oh! <div class="Discussion_UserSignature"> </div>
As I said -- I freely admit ignorance beyond what I read of the APAS in the patent and elsewhere. I don't know of any occurrance of two active APAS installations docking -- so can't look for empirical evidence. Right now -- the best I can say is that it's a question mark. I don't know about Newkirk's credentials -- he may simply be making the same assumption that I did until reading the patent. Before reading that, I would not have hesitated to state with great conviction that two active APAS' could dock.<br /><br /><font color="yellow">"...sometimes just a spring with gas/liquid shock absorber seems much more robust."</font><br /><br />No argument there. You've seen how I have done my best to make everything on G-X3 as simple and robust as possible. However, sometimes it's simply not feasible to do. I've tried envisioning failsafes for nearly everything that might go wrong (batteries die, computer croaks, RCS croaks, etc.). Unfortunately, there's just some things for which the answer is: "If this goes wrong -- it's all over." All that is possible is to design as best as possible with failsafes in place wherever feasible.<br /><br />There are some serious shortcomings with the APAS-89 which LIDS tries to resolve. In particular -- the amount of force required to dock using the mechanical system is a problem. This will be particularly true with CSS Skywalker, as Bigelow will be trying to sell it to commercial renters for its micro-G environment. Docking with the APAS may well disturb experiments and/or manufacturing processes. For this reason, I'm going to do a 180 on my previous statement and say that the LIDS being a docking requirement is indeed quite probable.<br /><br /><font color="yellow">"Don't know if you meant this more as a joke..."</font><br /><br />Lighthearted, but no joke. Video feeds are what capture the public's interest. What captures the public's interest captures the interest of marketing firms, filmmakers, corporate spon
mrmorris, here is what I've been working on lately. Very Soyuz-like shape, but all propulsion and systems are contained in the capsule. <br />I've done some parametric estimations of the weight using data from apollo, gemini, mercury, and soyuz, and the weight can be under 6000 kg using standard practices and materials. The capsule is sized to 11ft diameter to fit on the Falcon V booster.<br /><br />Baseline propellant is LOX/methanol or N204/hydrazine. The main thrusters are in the nose, underneath some sort of door. Same with the docking system. <br /><br />Main heat shield is ablative, I don't yet know what to use on the sides. Maybe titanium like Gemini, or composite with spray-on ablative. <br /><br />Recovery is by a 4-chute cluster to water or land using airbags.<br /><br />The yellow in the picture is the pressure vessel, light brown is the outer mold line, and blue are the tanks.
<br />It's a cool-looking CAD drawing for sure. I don't have enough specifics to say much more than that. However, at 6,000 kg it's too heavy for the FalconV to get to a 400km orbit. Presumably the onboard propulsion is robust enough to perform the burns to make up the remaining distance, dock, and perform the DO burn. Is there a launch-escape system included in that mass figure?<br /><br />For heat shielding on the sides -- I really like the advanced blanket insulations, TABI or DuraFRSI, over an Aluminum-Lithium fairing. I don't know about their availability to private enterprise, though.<br /><br />I like working with modernizing 60's designs because it automagically puts the craft several steps into the design process of a system that's known to work. Also -- weight estimation is a bit less of a black art -- take existing figures and swap original mass figures for new ones every time a new technology is substituted. In addition, since I'm not an aerospace engineer -- it's pretty much required that I take the easy road. <img src="/images/icons/smile.gif" /><br /><br />However -- this also means that I can concentrate on the subsystems more than the capsule shape itself. I don't think that the structure is going to be a sticking point in a private company building such a craft. The 'gotcha', IMO is going to be for a private firm to develop/purchase all of the electronics, software, and sundry other hardware (ECS, RCS, APAS/LIDS). That's why I spend so much time searching for modern COTS systems that can be used to replace Gemini/Apollo equipment. Where reasonable COTS systems are unavailable and development is required (like an ECS system for a capsule this size) -- starting from an existing design means that the firm can reverse-engineer (or get declassified plans for) systems from the original craft.
I used the trial Version of Rhino3D. It only gives you 25 saves though, so I have to use my time gingerly.<br /><br />To my knowledge, there are no decent FOSS CAD programs, but there are some modeling/animation programs like Blender, and the free version of 3D Studio called "gmax". Neither are geared towards engineering though and don't have capabilities like that of Rhino or a real CAD program. But for just sketching out ideas they are probably OK.
Haven't had a chance to do much with this the past couple of weeks. However, figured I'd post a couple of the other solutions to the problems posed in Apollo MDAP document.<br /><br />Guidance and Navigation:<br /><br />The original Apollo (and therefore MODAP) used mechanical gyros as their primary means of G&N. Since these have a high rate of drift, and the MODAP was designed for long-term storage at the station (6 months) -- they had to be recalibrated prior to re-entry. The Apollo used a display panel in the lower equipment bay to use star observations to re-orient the gyro. With the addition of the three crew couches -- this bay is not accessible in MODAP. The gyros also required 12 hours to spin up from rest -- meaning the gyros either had to be kept running constantly while the ship was docked to the station or they would not be available if an emergency forced an unscheduled exit from the station.<br /><br />Two things resolve this issue using modern equipment. First -- ring-laser gyros have a much lower degree of drift that mechanical ones. More importantly, though, is that they can use a GPS to re-orient automagically, without requiring the use of stellar sightings. In addition, the spin-up times for a RLG are negligible.<br /><br />TPS:<br /><br />The Apollo TPS was designed for a re-entry at much higher velocities than will be seen by a craft re-entering from LEO. The MODAP doc discusses two methods of reducing the mass of the ablative from Apollo levels -- thinner coatings of ablative on the entire craft or the use of Rene-41 shingles (what Gemini used) on the forward and center sections and ablative in the rear. They conclude that the Rene-41 combination would actually be lighter, but went with the ablative instead due to development time issues (and NASA had stated that they make the minimum alterations to Apollo).<br /><br />A modern craft could use a variant of the Rene-41 option -- using DuraFRSI or TABI blanket insulation on the front and cente
GPS will only provide position information, you still need to determine roll/pitch/yaw angles every so often to keep the inertial system from drifting. <br />Data can come from star tracker, magnetometer, sun sensor, horizon sensor,...<br />Ball Aerospace and SSTL make star trackers, they only weigh a couple of kilos.
<font color="yellow">"GPS will only provide position information"</font><br /><br />You can get attitude using multiple GPS antennas, carrier phase interferometry and number crunching. Google TANS GPS for more information.
Well thats great until your spacecraft spins arround, losing line of sight from one or more antennas, and taking a big drop in accuracy when you needed it the most. I'll take the proven, solid-state, works-at-any-speed, any orientation, inertial system.
I must admit, maybe it's my old-fashioned check-it-three-times-then-check-it-again-and-it-better-be-redundant nature, but I like the idea of the ship being able to figure out where it is, by itself. GPS assistance is nice, but a ring-gyro just can't be beat.
I didn't imply using GPS as only mean of figuring out orientation. Just confirmed that it is doable and how, which btw was new information for me too. These gadgets weigh so little that you could probably have all methods on board, gyro, GPS/NATS, star tracking, and as a last resort, manual star tracking consisting of crosshair sights and astronaut's eyeball.
<font color="yellow">"GPS will only provide position information, you still need to determine roll/pitch/yaw ..."</font><br /><br />As I stated in my post -- the GPS was being used <b>to re-orient the Ring-Laser Gyro</b>. Presumably then, that would mean that the craft also contains a RLG. As Tap-Sa stated -- GPS can also be used to determine orientation, even though that's not what I see as its primary role. I see the craft having ~5 GPS antennas. One at the nose (that would be the bit furthest from the heat shield <img src="/images/icons/smile.gif" /> ), and four more at compas points around the body of the craft a foot or two forward of the heat-shield. I might note -- another shortcoming of using a GPS system as the <b>sole</b> means of G&N is the fact that updates don't come fast enough (generally only about 1-5/second). Even if everything else were perfect about them, there still needs to be something to provide data at a shorter interval than that. However, for determining point-in-time position, they beat what existed in the late 60s hands down.<br /><br />I also see additional G&N equipment beyond the GPS/INS system. <br /><br />Kionix KXP74 high-performance tri-axis accelerometer.<br /> -- At 5x5x1.2mm, I envision having several of these scattered about the hull. They can provide both impact data (like the acceleromaters that have been added to the shuttle orbiters), and also provide auxiliary guidance data.<br /><br />TFM100G2-S Ultra-miniature Triaxial Fluxgate Magnetometer<br /> -- At 3.51 cm x 3.23 cm x 8.26 cm and 117 grams, this will add one more redundant means of determining position and attitude for a minimal mass and volume. JP Aerospace uses this (or a similar model) on their flights.<br /><br />Both Apollo and Gemini had separate Guidance & Navigation and Stablization & Control systames. Each was largely (but not 100%) redundant to the other. With modern electronics, the two systems can contain equipment that makes ea
<font color="yellow">"...MIDG II ..."</font><br /><br />Ayup. Found that a coupla months back and really liked it. Downside, of course, is that it's not space-rated. It's also using MEMS devices, so the gyro won't be as accurate as a RLG or IFOG device.<br /><br />However, as a tertiary backup -- it would likely only be used on a re-entry. As such -- there's much less concern about radiation-induced changes. Also -- while it's not as asccurate as the RLG/IFOG -- since it only gets used *after* they've failed, it's a heckuva lot better than the Mark I Eyeball for determining position and velocity.
Agreed it's not ready for use as a prime system, but - wow! Bury it as deep as possible in the equipment bay, don't power it on unless one of the primary systems fails and it will make a great backup device - and smaller than a Grisham novel at that! <img src="/images/icons/smile.gif" />
<font color="yellow">"Bury it as deep as possible in the equipment bay..."</font><br /><br />Actually what I keep bouncing around in my head is ideas/options for a 'shielded' equipment section in the ship for electronics like this. Namely, non-space-rated devices which are act in either a backup or non-critical capacity. The NSR hardware tends to be cheaper, smaller, and use less power than SR-equivalents.<br /><br />One of the ideas I had recently was to use water as the shielding substance. The MODAP ECS used a glycol loop to pull heat from the cabin and equipment and a water boiler to remove heat from the glycol. If GX-3 were to use a similar system, and the container(s) storing the water for the ECS designed to surround this NSR bay, it would significantly cut down on the possibility of rad-induced problems.
Hi.<br /><br />Sorry to break your train of thought here.<br /><br />I'm working on an "Official History" of SDC. There's a thread in "Free Space" called, simply enough, "Official History."<br /><br />When you get a chance, please post your basic information there (there's no obligation, and you can post as little or as much as you wish, or nothing at all).<br /><br />Basic Info. sought:<br /><br />1. Username(s) used on SDC<br />2. When you joined.<br />3. Any long-term absences (so a chronology of when you were and weren't an active member can be determined).<br />4. Your age (not a requirement).<br />5. Geographic location.<br />6. Profession.<br /><br />Hopefully, somewhere down the road, I will have an "official, free history," replete with a chronology, names, significant events, and so on.<br /><br />As well, any odd, curious, funny, or interesting stories about SDC are appreciated.<br /><br />Thanks!<br /><br />*We now return you to your regularly scheduled thread, already in progress* <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis: </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>
SpaceDev Begins Development of its Small Launch Vehicle SpaceDev Streaker<br /><br />Click here to see downloadable versions<br />The SpaceDev Streaker(TM) Hybrid Upper Stage is shown with blue nozzles. (Graphic: Business Wire)<br /><br /> <br />POWAY, Calif.--(BUSINESS WIRE)--April 4, 2005--SpaceDev (OTCBB: SPDV) has signed a lease to expand its fabrication and test facilities and to begin constructing portable, high tech rocket motor test support equipment in anticipation of test firing new rocket motors that SpaceDev is developing for its low-cost expendable small launch vehicle called SpaceDev Streaker(TM).<br /><br />Under an Air Force Research Laboratory contract announced last October, SpaceDev has designed and will begin development of the SpaceDev Streaker(TM) Hybrid Upper Stage rocket motor. This motor is expected to produce approximately 20,000 pounds of thrust, in contrast to the 15,000 pounds of thrust produced by SpaceDev's hybrid rocket motor technology for Paul Allen's SpaceShipOne. In addition, the Company plans to boost overall performance of this upper stage motor using new techniques and refining current techniques that go beyond that of traditional hybrid motors.<br /><br />"This additional SpaceDev facility will also be located in Poway, California. It will add approximately 11,000 square feet of fabrication space in which we will construct rocket motor development equipment that will be highly adaptable and mobile. This equipment is being built on several large flatbed trailers to maximize mobility and system test flexibility," said Jim Benson, founding chairman and Chief Executive Officer. "This new rocket motor test equipment should be applicable to a wide variety of future hybrid rocket motor developments."<br /><br />SpaceDev is planning to construct its rocket motor test stand with the capability of handling up to 250,000 pounds of thrust. The test stand will be designed to support the 20,000 pounds of thrust produced by the Hybrid Upper Stage motor,