Gemini: We can rebuild it, we have the technology

[taralon]

Yes, actually I was referring to that poster. I post somewhat infrequently on nearing three dozen forums and it gets a little hard to keep track of where I have and where I have not posted information. I did manage to find at least one reference to my posting of Falcon V/'Gemini type' mix at http://www.rocketmanblog.com/2004/06/operational_cos.html which went up on July 31, 2004. (Notice that the 'posted by' email link is the same as I gave earlier).<br /><br />I've got to question though if using a design based off of Gemini or Apollo would be 'legal' in the terms of the wording of the prize rules. By using NASA determined specifications for LS capability, DO capability, navigational and communication, and even certain design elements, one could argue that in essence you are using 'government funding or grants' in order to build the craft. It cages in on the same 'gray area' that all reverse engineering does. IE that if you have any sort of specification at all, outside of mass, size, and general outputs, one hasn't really reverse engineered at all, but used prior art. <br /><br />

 

[mrmorris]

<font color="yellow">"...one could argue that in essence you are using 'government funding or grants' ...</font><br /><br />One would be very wrong. There's no way that such could be stretched to consider it government funding. The documents I'm using are all public domain. In the sense that you refer to 'government funding', making use of a spacecraft design book borrowed from a state university would disqualify the craft.<br /><br />It isn't a grey area at all. Funding means actual cash was received by the government specificaly for use in this project.

 

[mrmorris]

Tap_Sa:<br /><br />Do you have any desires to work some torque calculations out to further your moment of inertia post? <img src="/images/icons/smile.gif" /> I found a paper with the various calculations here (pp 26-41), but all those greek characters make me dizzy just to look at them. <br /><br />I ask because I found a couple of largish COTS reaction wheels, and I'm wondering what kind of performance their torque would impart to G-X3. While they are <b>much</b> smaller than what I've shown in my diagrams earlier, that means they're less likely to provide adequate turning speeds. The largest reaction wheels I found were:<br /><br />Honeywell Constellation Series<br />TELDIX HT-RSI High Torque Reaction Wheel<br /><br />They can provide torques levels between .1N and .3N. I don't think this will be good enough, but I can't say for positive, and I *certainly* can't say what level of torque <b>would</b> be sufficient.

 

[nacnud]

It's only some matrix equations get a grip! They are really simple, now do you want the red pill or the blue one?

 

[ve7rkt]

If we use the RWCS (pat. pending <img src="/images/icons/wink.gif" /> ), what will maneuver the G-X3 clear of the station before the DO burn, lest we torch or punch a hole in a solar panel or something?<br /><br />We still don't know if the Falcon V upper stage can be kept around for the ~6months required and still be useful afterwards. We don't know what propellant the upper stage's RCS uses, so we don't know if it's going to boil off. So, we're back to the earlier question of flightplan: ditch the upper stage and fly to the station on your own engines, ditch the upper stage on the station's doorstep, or hang on to the upper stage until deorbit time.

 

[mrmorris]

<font color="yellow">"...what will maneuver the G-X3 clear of the station before the DO burn..."</font><br /><br />At best -- the RWCS will provide only attitude control. G-X3 will need to have a DO module and it still needs thrusters to provide forward/reverse dv. I stated the following about 20 posts back:<br /><br /><i>"Since the RWCS can provide all of the orientation changes for GX-3 (in particular -- the oversize RW at the rear should be great for rolling on re-entry) -- let's eliminate the thrusters from the CM entirely.The strap-on de-orbit module will be enhanced with tanks and thrusters to provide forward/reverse dv for the CM. The degree of dv needed is dependant on exactly when the second stage of Falcon-V exits the scene -- as described in an earlier post. Depending on when it separates -- G-X3 might need no thrusters at all, or a minimal cold-gas system, or a very capable OMS. One of the great things about the OMS being on the strap-on DO frame is that all of these are possible. G-X3 need not be saddled with a single system that has to be everything and a bag of chips. The OMS system can be mission-dependent. In particular -- this means that the early version can use a hydrazine system -- then upgrade to a better technology at a later date. "</i>

 

[mrmorris]

Reading through the article on Guidance, Navigation, and Control referenced eariler, I realized that G-X3 is deficient in high-accuracy attitude sensors. quikely had noted this some time ago -- but at the time, I thought the magnetometer would suffice for this. It might, but it's not as accurate as I'd like for this purpose. Gemini used two redundant Horizon Sensors to update the Inertial Guidance System. Modern horizon sensors are lighter, more accurate, and consume less power -- so G-X3 should include one. I didn't realize that star sensors provided such a high degree of attitude accuracy though. Despite being (relatively) heavy and power-hungry, I think G-X3 should include a star sensor as well. After all, we're insterested in it being able to autonomously rendezvous and dock with a space station. The greater the accuracy of the instruments -- the more efficient the orbital transfer burns will be. I see the star sensor being the primary system with the horizon sensor used as redundant backup. Using my friend Google, I came up with the following instrument candidates:<br /><br />Horizon Sensor: Mini Dual Earth Sensor (MiDES)<br />Accuracy: .04 degrees<br />Mass: 1.5 kg<br />Power: 800 mW<br /><br />Star Sensor: Ball Aerospace CT-633<br />Accuracy: ~6 arcsec<br />Mass: ~3 kg<br />Power: 9W<br /><br />An image from the article on the common sensors and their attributes (slightly dated):<br />

 

[gunsandrockets]

"It's conceivable to size up the Soyuz/D2 'shape' and put more of the equipment on-board. However, I don't care as much for this shape because it has a very low l/d ratio: between .2 and .3 (as opposed to Gemini's .4-something, and Apollo's .52). While I don't believe in paying for the mass of wings to increase l/d -- a slightly less efficient shape is a much lower price to pay for extra maneuverability. "<br /><br />That's very ironic. Because the only version of Apollo that had an l/d of 0.52 was not a capsule, it was the Convair M-1 Apollo proposal which was a lifting body.<br /><br />http://www.astronautix.com/craft/apollom1.htm<br /><br />The various configurations studied for the Apollo make for fascinating reading.<br /><br />http://www.astronautix.com/craftfam/apollo.htm<br /><br />My favorite version though is the Martin W-1, a lifting body with an l/d of 0.75 and rotating seats.<br /><br />http://www.astronautix.com/craft/apollow1.htm<br /><br />The winning Apollo capsule made by North American only had an l/d of 0.3, not really much better than the Soyuz re-entry module.<br /><br />http://www.astronautix.com/craft/apolocsm.htm<br /><br />For that matter the Gemini re-entry capsule had an l/d of only 0.16, worse than the Soyuz.<br /><br />http://www.astronautix.com/craft/gemini.htm<br /><br />Now Big Gemini did improve on that, having an l/d of 0.3.<br /><br />http://www.astronautix.com/craft/bigemini.htm<br /><br />At least you got the Soyuz l/d right. The Soyuz TM descent module has an l/d of 0.26.<br /><br />http://www.</safety_wrapper

 

[mrmorris]

<font color="yellow">"You shouldn't let your enthusiam for Gemini/Apollo capsules run away with you, at least not to the point of exaggerating their true l/d ratios. "</font><br /><br />I'll see if I can locate the reference where I saw the .5 figure for Apollo. I may have misread, or misremembered -- but there's no point to me deliberately exaggerating. I'm doing everything I can to make this thread as practical as possible. If the Soyuz shape has an l/d ratio very close to Apollo's -- that is <b>great</b> news -- it won't ruin my day. That shape gives great volumetric efficiency, so it will simply make the concept even more practical.

 

[spacefire]

come on, say it with me MrMorris.<br /><br /><br />|<br />|<br />|<br />V <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[mrmorris]

I can't locate a reference showing Apollo with an l/d of .52 and the reference I *thought* it might have been is showing .28, so we'll put it down to me misremembering. The closest I found was the Assessment of Use of Apollo Systems for ISS CRV which stated the l/d ratio was .4. If I run across a document with the .52 figure, I'll try to remember to post it. In any event -- the document I re-located is one that I consider to be authoritative -- a NASA doc from 1969 (i.e. it has actual flight data for all of Gemini, and much of Apollo to work with): NASA SP-8028: Entry Vehicle Control. Ergo -- even if I find such a source document -- *it* may well be incorrect.<br /><br />In any event -- the entry vehicle control doc puts the ratios at:<br /><br />Gemini .19<br />Apollo: .28<br /><br />On the plus side -- in searching for this document -- I found a couple of others that I hadn't seen before. Notably there's a cool one that has all of the Apollo Re-Entry logic: Apollo Reentry Guidance and Navigation Equations and Flow Logic. That'd provide a nice leg-up for developing the reentry logic for a new capsule. <img src="/images/icons/smile.gif" />

 

[mrmorris]

spacefire:<br /><br />I've asked you before -- quite politely, not to post in this thread unless you'd care to contribute to the subject at hand. If you miss the debates about lifting bodies vs. capsules -- then start a thread on it. You'll get plenty of takers. The current discussion with gunsandrockets is *not* an argument for lifting bodies. I'm not suprised that you take it that way -- seeing as you probably think that the fact that today is Wednesday is an argument for lifting bodies. <br /><br />In point of fact -- the lower l/d ratios are an argument *against* the need for the use of a lifting body. My contention has always been that the Gemini and Apollo capsules were able to achieve landing accuracies of ~4 n.m. and ~1 n.m. from their target point. If they were able to do that with l/d ratios of .19 and .28 respectively -- then there's no need for a higher one.<br /><br />Now -- I'll ask again that you please not post in this thread unless you'd like to talk about the design of a capsule using modern technology. Since you have always expressed absolute disinterest in the subject, I don't believe that to be the case. However, if you'd like to start a comparable thread about the design of a lifting body, that would be a great thing and a valuable addition to the SDC forum.

 

[mrmorris]

<font color="yellow">"And you really should give the Soyuz another look since of all the capsule forms it is the best. "</font><br /><br />Of course one of the significant advantages to using the Gemini/Apollo as a starting point would be eliminated if we instead went with the Soyuz as a starting point. There are <b>huge</b> amounts of documentation available on the design and performance of Gemini/Apollo. Keep in mind that this thread isn't intended for the CEV development project. It is targeting a private firm developing a craft to win the ASP. Having the pre-existing documentation as a starting point will almost assuredly amount to millions saved in develpment costs. While amounts in the 'millions' are likely to be a rounding error on the CEV development cost -- they might well be dealbreakers on the ASP-craft development cost.

 

[gunsandrockets]

"I can't locate a reference showing Apollo with an l/d of .52 and the reference I *thought* it might have been is showing .28, so we'll put it down to me misremembering."<br /><br />One possible explanation. If you google with the terms, l/d Apollo spacecraft, the first hit on the google search results page reads as...<br /><br /><br />"Apollo<br />... L-2C design was the basis for the Apollo spacecraft that ultimately emerged.<br />... had a total mass of 2540 kg, and a hypersonic L/D ratio of 0.52. ...<br />www.astronautix.com/craftfam/apollo.htm - 61k - May 18, 2005 - Cached - Similar pages "<br /><br />It only becomes clear after clicking through the link and reading the next page that the 0.52 l/d reference is to the Convair M-1 lifting body proposal for Apollo.

 

[gunsandrockets]

"Of course one of the significant advantages to using the Gemini/Apollo as a starting point would be eliminated if we instead went with the Soyuz as a starting point. There are huge amounts of documentation available on the design and performance of Gemini/Apollo.... Having the pre-existing documentation as a starting point will almost assuredly amount to millions saved in develpment costs."<br /><br />I doubt it. The differences between a vehicle which could win the American Space Prize and the Apollo capsule are so great that any similarity in shape would only reflect a superficial relationship.<br /><br />And it isn't just things like the requirement for five people instead of three that would make the most difference. The real killer factor and the real challenge of the American Space Prize is the 80 percent reusability requirement. The only reusable manned space vehicle that has ever flown is the Space Shuttle Orbiter. The Gemini, Apollo and Soyuz re-entry capsules were designed and flown as expendables. (And no, I don't think that the Gemini 2 capsule flown in an unmanned suborbital test and then rebuilt into a Gemini B for a second unmanned suborbital test flight counts as a reusable manned orbital flyer. )<br /><br />In fact much of the vaunted simplicity and economy of capsules comes from the fact they were designed as one expendable part of a larger spacecraft system of other expendable parts. When as much of the spacecraft is thrown away as possible, a process which the roomy and lightweight Soyuz masters, it's easy to achieve efficiency. But trying to preserve the whole spacecraft mass as much as possible from launch to splashdown, and then reflying it again after the stresses it has undergone is hard.<br /><br />I think Bigelow made a mistake when he set the conditions for the American Space Prize. If a private company had succeeded in recreating just the capabilty of the Soyuz without a government contract, and flown it successfully before 2010 that wou

 

[mrmorris]

<font color="yellow">"The differences between a vehicle which could win the American Space Prize and the Apollo capsule are so great that any similarity in shape would only reflect a superficial relationship. "</font><br /><br />I think you've skipped to the end of the thread and started posting. Either that, or you skimmed the thread -- because this has been discussed before early in the thread. I was using Gemini alone as a model then, but the text was:<br /><br /><i>"Your question however, was what starting with the Gemini buys. Testing isn't it. Even if you tried to duplicate the Gemini exactly to the specs it was built in the mid-60's (impossible to start with), testing done at that time would hold no relevance to copies made 40 years later. <br /><br />However -- it buys a set of documentation on a spacecraft concept that is known to be viable. You can go to this site to get all the familiarization manuals on the Gemini. These explain in detail the various subsystems of the craft, and how everything works together. A craft built using different equipment to achieve the same ends still has an enormous leg up with this head start. For a company building a spacecraft today -- they'd better be able to document every susbsystem, and every procedure -- normal or emergency -- in as much detail as those manuals do. The way that I've been determining weight savings for modern equipment is by looking through these docs -- seeing what was used on Gemini -- then locating a modern equivalent. In most cases -- I'm finding that the modern equipment incorporates the functions of several pieces of Gemini-era equipment, weighs a small fraction thereof, and uses a tiny fraction of the power. "</i><br /><br />The first, and in some ways the hardest part of the task of building a spacecraft from scratch is deciding exactly what's needed to make it functional. The existing Gemini/Apollo documentation provides the vast majority of that job. <br /><br />In addition -- if you've n

 

[gunsandrockets]

"I think you've skipped to the end of the thread and started posting."<br /><br />You sure seem to leap to conclusions. I first started reading this thread when it was less than half it's current size.<br /><br />"Again -- you're demonstrating that you have not read the thread, but feel informed enough to comment on the design. "<br /><br />Lighten up. I wasn't criticizing or even directing a comment towards your precious G-X3 design. I was merely emphasizing the difficulties of cramming all non-reentry module equipment into a Soyuz re-entry capsule.<br /><br />I believe there is a rule of thumb which goes that for every pound not returned from orbit one pound is saved in liftoff mass. The mass savings from having the tiniest possible re-entry capsule add up fast. That's why the Soyuz is the most efficient of all the manned spacecraft in terms of living space vs liftoff weight.<br /><br />The reusability requirement of ASP, by forcing re-entry capsule growth fights against the basic mass efficiency principle of expendable designs.<br /><br />"Since you're talking of the 'simplicity of capsules' -- presumably you're referring to it in the context of 'as opposed to other shapes', "<br /><br />There you go presuming again. Wouldn't it have been easier to accept as my meaning the plain text of my post which hammered on the issue of reusablilty?<br /><br />"...Parachutes can be reused,..."<br /><br />Are you serious? Maybe for a skydiver who always carries a reserve chute a parachute can be reused. But reusing a space capsule parachute?<br /><br />"Must focus on today's task... five people to orbit -- dock -- undock -- five people to ground level. "<br /><br />The most difficult issues, the 80 percent reusability, the 60 day turnaround to flight, haven't received nearly the focus they deserve. I think there are at best a couple of throwaway references to the 60 day requirement, and even then not until halfway through the thread.

 

[mrmorris]

<font color="yellow">" I first started reading this thread when it was less than half it's current size. "</font><br /><br />Then if you feel the need to note that the resemblance to Apollo will only be superficial you haven't understood what I've stated in the thread. I've <b>already</b> indicated that even if G-X3 is based on a Gemini/Apollo starting point, the completely different technologies being used for the subsystems and the different manufacturing processes used in building the structure means that it will be an entirely different vehicle. This is inescapable. The point I'm trying to make is that having an extremely well-documented model as a starting point is a huge leg up. The ASP is so hard from the get-go that having this advantage may well be the difference between winning the contest or failing miserably.<br /><br /><font color="yellow">"I wasn't criticizing or even directing a comment towards your precious G-X3 design."</font><br /><br />Your post repeatedly referred to the difficulties of making the 20% rule using a capsule-based design in a thread specifically about the design of G-X3. This would generally be seen as a pretty good indicattor that you were referring to G-X3, and the fact that several of your points have been covered in regards to the G-X3 design would generally make it appear that you had not read them. Without a statement to the contrary -- there was no way for me to have psychically deduced that you were referring to a hypothetical capsule design that was *not* G-X3.<br /><br />I may well have misread your post, but if so, I believe that the post was written in such a fashion as to make that inevitable.<br /><br /><font color="yellow">"I believe there is a rule of thumb which goes that for every pound not returned from orbit one pound is saved in liftoff mass. The mass savings from having the tiniest possible re-entry capsule add up fast."</font><br /><br />I agree. Completely. Since you've read the t

 

[rancamp]

gunsandrockets quotes mrmorris:<br /> />>"...Parachutes can be reused,..." <br /><br />Then states:<br /> />Are you serious? Maybe for a skydiver who always<br /> />carries a reserve chute a parachute can be reused.<br /> />But reusing a space capsule parachute?<br /><br />And what factors would prevent reuse? Please note that all space capsule parachutes are made out of 'standard' materials and don't have to have any special properties. They open at subsonic speeds unlike many test parachutes, or space probe parachutes that are build for such things as supersonic or hypersonic opening.<br />About the 'only' reason that space capsule parachutes are not reused is because the Russians have never felt the need to 'bother' since each Soyuz capsule is 'new' from top to bottom.<br />The U.S. never resused chutes because they were all designed to be 'cut-away' to preven their sinking from pulling a capsule off balance in the water.<br /><br />So I'm curious as to what 'special' factors you consider a 'capsule' parachute to require?<br /><br />Randy

 

[nacnud]

I think the SRB parachutes are reused.

 

[gunsandrockets]

"So I'm curious as to what 'special' factors you consider a 'capsule' parachute to require?" <br /><br />It's a simple question of costs vs. benefits. Re-using the parachutes would be a foolish economy. <br /><br />Sure it's possible to re-use the parachutes, but would you really want to do so? How carefully should the chutes be inspected before re-use? How does that inspection meld with the necessity of a 60 day turn-around time? How many times could the chutes be reused? What is the margin of safety? And how much mass (not much) and money (questionable) is really saved by reusing the chutes?<br /><br />And the consequences if the chutes fail? Five people die. It's too critical a part to waste questionable economies on.<br />

 

[gunsandrockets]

"Since the 80% rule is against the entire launch vehicle ..."<br /><br />"The 80% reusability I've calculated out as best as possible given the lack of figures to work from . Since both the Falcon-V and G-X3 exist only as electrons on a hard drive somewhere -- it's a little difficult to work out mass fractions. Using the weights supplied by SpaceX for the Falcon I and V rockets, plus the mass estimates I have for G-X3 -- the 80% rule seems workable. I don't have any means to improve upon that estimate... so how exactly do you feel that this issue should receive additional focus in this thread? "<br /><br />You are incorrectly intrepreting the ASP requirements.<br /><br />http://www.astronautix.com/craftfam/ameprize.htm<br /><br />The requirements apply only to the manned orbital space vehicle and not the launch vehicle. You can't water down the orbital vehicle reuse requirements by lumping it in with the launch vehicle's mass.<br /><br />And it's a good thing too since no launch vehicle, including the SpaceX vehicles would qualify under the ASP requirements. SpaceX has received government money for it's launch vehicle development. SpaceX isn't even counting on it's 1st stage recovery system working as part of it's economic plan. And even if the recovery system does work, SpaceX isn't counting on complete recovery figuring that just the recovery of engine components make it worth their while. And even if the SpaceX recovery system is completly successful, it's not intended to meet a 60 day turnaround time for reuse.<br /><br /><br /><br />

 

[gunsandrockets]

"As for the 60-day turnaround -- I believe that the shuttle orbiters are seen as the rule rather than the exception. This makes sense from one standpoint -- they're the only semi-reusable spacecraft ever developed. However -- the sheer size of the orbiters is a major contributer to their turnaround time. Let's work this out on a mass basis -- that's arguably a legitimate means of estimating the turnaround time. Endeavor masses 78,000 kg and we'll say has a turnaround time of 365 days (one assumes it can be done faster... SG?). Assuming a linear relationship -- a 6,000 kg RLV would take around 28 days to turnaround. Keep in mind -- this capsule is going to be the size of an SUV!"<br /><br />That's an interesting way to examine the turnaround length but you left out one part of the equation, the army of people working on the turnaround. So your equation may be correct but only while using the same number of people on each spacecraft. Somehow I don't think using such a large number of people and the associated costs is what Bigelow had in mind for the ASP winner<br /><br />I speculate that other factors rather that sheer size of vehicle and sheer number of workers is the key to solving the turnaround issue. Part of it is how user friendly is servicing the vehicle? From what I understand the Shuttle doesn't even have access hatches. Servicing parts is like building a ship in bottle. Another factor is how rough a ride does the vehicle go through before reflight? That might be an issue for a typical capsule design with it's rough touchdown and passive thermal protection system. I think it's noteworthy that t/Space is using an active cooling thermal protection system with a passive system backup for it's reusable capsule.<br />

 

[ve7rkt]

Well, there could be room for misinterpretation if you go by the version of the ASP requirements on the Astronautix site. On the other hand, if you go to Bigelow Aerospace's own website:<br /><br />"6. No more than twenty percent (20%) of the Spacecraft may be composed of expendable hardware (the term 'Spacecraft' encompasses the launch vehicle in its entirety, including but not limited to, any and all fuel tanks, external rockets, carrier craft, and boosters)"

 

[gunsandrockets]

I stand corrected!<br /><br />I am also astonished at Bigelow's stupidity. Forget about the orbital elements. Under these conditions not only does no existing launch vehicle qualify I am not aware of any even in development which could qualify. There must be some mistake.