ESAS draft report is out!

[gunsandrockets]

"Figures 16, 17, and 33 all show the BNTR with the "ECRV"."<br /><br />Figures 16, 17 and 33 all refer to the old Mars architecture plan except as modified by use of BNTR. The description of one of the vehicles as "piloted lander" should have made that obvious. The piloted lander carries the crew from Earth to Mars in the old architecture.<br /><br />The vehicle I refered to in Figure 29 is for the new architecture where the 'piloted transfer vehicle' carries the crew both to Mars and then back to Earth. This vehicle is also shown in greater detail in Figure 30 on page 39. A detailed breakdown of the mass carried by this architecture is show in table A-5 on page 47 of the report. There is only one ECRV and it is part of the unpiloted 'cargo lander' vehicle, the 'piloted transfer vehicle' does not have an ECRV.<br /><br />"It is not clear from the ESAS summary whether the CEV the crew returns in is one that they dock with the MTV in, or whether the DAV also has a CEV as the crew module."<br /><br />Actually it is clear, and I would think detailed enough to satisfy anybody.<br /><br />http://www.spaceref.com/news/viewsr.html?pid=19067<br /><br />"The ESAS reference Mars mission utilizes a Block 3 CEV to transfer a crew of six between Earth and an MTV at the beginning and end of the Mars exploration mission. A Block 3 CEV CM and SM is launched by the CLV into an orbit matching the inclination of the awaiting MTV. The CEV is first injected into a 55x296-km altitude orbit while the MTV loiters in a circular orbit of 800- to 1,200-km altitude. It then takes the CEV up to 2 days to perform orbit-raising maneuvers to close on the MTV, conducting a standard ISS-type rendezvous and docking approach to the MTV. After docking, the CEV crew performs a leak check, equalizes pressure with the MTV, and opens hatches. Once crew and cargo transfer activities are complete, the CEV is configured to a quiescent stat

 

[gunsandrockets]

"Refrigeration is only possible when the reactor is hot enough to run the Brayton generator. This only happens at the TNI burn "<br /><br />The reason it's called bi-modal is because the BNTR can run in idle mode for the Brayton generator as well as high power mode for rocket propulsion. The description of BNTR operation beginning on page 7 of the Borowski report makes this very clear. The idle mode is not dependant upon the high power mode.<br /><br />"...the ERV [piloted transfer vehicle] must be pruned. There are several ways this can be done. Eliminating the reserve consumables is one simple way of saving 7.3 tonnes immediately. The fact that you have the CEV launched separately saves another 11-12 tonnes as well."<br /><br />Since the Borowski 'piloted transfer vehicle' does not carry an ECRV to Mars, sadly no HLV launch capacity is saved by MTV linking with a CEV in orbit. In fact the MTV will be even more massive than the Borowski vehicle since the MTV will propel the added mass of a CEV to Mars. <br /><br />According to krrr, the HLV has a payload of 113 tonnes to a 1200 km orbit (and maybe 119 tonnes to 800 km?). The MTV will likely mass more than 140 tonnes, exceeding the HLV payload capacity by at least 18%.<br /><br />And besides, if the goal is to orbit a crewed MTV via a single HLV launch, won't the real development issue be 'man-rating' the HLV?<br />(Actually I think the whole 'man-rating' business is a crock, employed as an phony-excuse to reject alternative launch vehicles, I just find ironic humor in turning the same issue back against the HLV)

 

[JonClarke]

"Absence of evidence is not evidence of absence. "<br /><br />Indeed it is not. But nor is it evidence of presence. All the evidence points towards non refrigeration of the propellant prior to the TMI burn.<br /><br />The disposeable NTR has ~1.5 tonnes of fuel cells to provide 1.5 kW of electrical power. This power is largely for the 32 days before TMI<br /><br />A similar mass is provided by the reusable BNTR stage.<br /><br />Because the Brayton generator provides power after the burn the only purpose the cells can serve is to provide the same amount of power for the same period beforehand. <br /><br />The fact that fuel cells provide this power shows that the Brayton generator does not operate prior to TMI, even with a BNTR.<br /><br />Refrigeration requires 15 kW. There is no way the fuel cells can supply this.<br /><br />Therefore there is no and can be no refrigeration until after TMI.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[JonClarke]

"The vehicle I refered to in Figure 29 is for the new architecture where the 'piloted transfer vehicle' carries the crew both to Mars and then back to Earth. This vehicle is also shown in greater detail in Figure 30 on page 39. A detailed breakdown of the mass carried by this architecture is show in table A-5 on page 47 of the report. There is only one ECRV and it is part of the unpiloted 'cargo lander' vehicle, the 'piloted transfer vehicle' does not have an ECRV."<br /><br />Whether or not a ECRV is present is not a key party of the archiecture. Remember it only masses 4.5 tonnes. For example couple of years later the same team produced a new mission profile in which the MTV with transhab MTV (not ERV) also carried spare ECRV top Mars. I have been trying for years to get the original paper, without success, but a summary can be found at Portree's site. http://www.marsinstitute.info/rd/faculty/dportree/rtr/at26.html With respect to MTV assembly it says:<br /><br />"SDHLV launch 6 occurs 30 days after SDHLV launch 5. It places into assembly orbit an 11.6-ton "spinelike" saddle truss with RCS thrusters, a 17-meter-long "in-line" tank holding about 43 tons of LH2 propellant, a 2-meter-long, drum-shaped module containing 6.9 tons of consumables, and a 5.1-ton spare Earth Crew Return Vehicle (ECRV). The LH2 tank and consumables module nest inside the saddle truss. BNTR stage 3 and the saddle truss assembly rendezvous and dock, then propellant lines from the LH2 tank to the BNTR stage link automatically... A Space Shuttle launch carries into assembly orbit the Mars crew and a 20.5-ton deflated Transhab module... A Space Shuttle orbiter performs rendezvous with the BNTR stage/saddle truss one week before departure for Mars. After rendezvous, the spare ECRV flies automatically to a docking unit in the Space Shuttle payload bay and docks. Astronauts use the Shuttle's robot arm to ho <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[JonClarke]

"The reason it's called bi-modal is because the BNTR can run in idle mode for the Brayton generator as well as high power mode for rocket propulsion. The description of BNTR operation beginning on page 7 of the Borowski report makes this very clear. The idle mode is not dependant upon the high power mode. "<br /><br />The Brayton generator runs on waste heat generated by a an idle reactor. This heat is generated by the decay of fission products, by fission. Before the reactor is turned on the heat from the decay of the uranium fuel is miniscule and not enough to run the generator. The only way to avoid this is to launch a hot reactor. There is no evidence of this. Don't say absence of evidence is evidence of absence, launching a hot reactor is such a radical departure from the normal approach to operating reactors in space that it would be mentioned if proposed.<br /><br />"Since the Borowski 'piloted transfer vehicle' does not carry an ECRV to Mars, sadly no HLV launch capacity is saved by MTV linking with a CEV in orbit. In fact the MTV will be even more massive than the Borowski vehicle since the MTV will propel the added mass of a CEV to Mars."<br /><br />Irrelevant, as we both have noted, to some extent functions of the MTV CEV can be unloaded into the CEV, so that the MTV mass can be reduced to some extent.<br /><br />"The MTV will likely mass more than 140 tonnes, exceeding the HLV payload capacity by at least 18%. "<br /><br />I agree. Once again, much much performance improvement can we get out of the SDLV? 2%, 5%, 10%. But unless they can get 15-20% I don't think that it can be done with a single launch. so that means that:<br /><br />1) Such an improvment is possible (unlikely?)<br /><br />2) Major mass savings over Borowski (perhaps)<br /><br />3) We are all barking up the wrong tree and ESAS is not using Borowski at all (possible)<br /><br />On man-rating, the SDLV is composed of components that are manrated already, you would need to man rate the stack only, <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[JonClarke]

Coincidently I was browsing today at the newsagents and found the Astronomy magazine special issue on Mars. In it was a picture that Portree had used to illustrated the Borowski 2001 study. from the credits i was able to track down John Frassanito's artwork. Most of the drawings that were on Portree's site are here, plus some others. http://www.frassanito.com/<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[JonClarke]

Trying to summarise what can be concluded about the discussion on the ESAS architecture so far:<br /><br />1) Based on Drake not the DRM (surprising since I recall Griffin linking DRM 3.0 (which he helped develop) with the VSE Mars mission).<br /><br />2) NTR and probably BNTR, based on development of Boroski's work (which relies heavily on Russian technology)<br /><br />3) The DAV probably does not use ISPP and may resemble the 1967 North American Rockwell lander<br /><br />4) The currently proposed SDLV is too small for the mission (not known whether it will be ugraded or whether, despite the summary, the mission will require in orbit assembly)<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[centsworth_II]

I find it interesting that you see one-way Mars missions as "unrealistic for a long time to come". Many proponents of one way missions see it as a way to get humans on Mars sooner by eliminating the complication and expense of having to devise a way to get them back in a timely manner.<br /> <div class="Discussion_UserSignature"> </div>

 

[JonClarke]

To quote a character in "From the earth to the moon": "There is no way in God's green earth that we could ever, ever do anything like that!"<br /><br />IMHO it would be immoral, unethical and downright stupid for people to go on a one-day mission to Mars until we know whether or not people can actually live out their lives and raise children there. Those questions are going to require decades of exploration and permanant Mars bases to answer.<br /><br />As I see it, while there may be some individuals and groups who are dedicated (and foolhardy) enough to do it before then. But to do so costs will have to be about a 1/1000th of what they are now and a lot of technology which does not yet exist will have to be available or adaptable off the shelf. By the time this happens I suspect governments and government consortia would have obtained the experience outlined in the paragraph above. Just as by the time Rutan and co made their brief private hops into space (and all power to them), the US and Russian space programs had clocked up nearly 20 years of almost continuous habitation in LEO plus gone to the moon.<br /><br />And why would people go one way anyway? People went on one-day settlement trips on earth in search of wealth, personal or communal freedom, or living room. Mars does not offer any of that. It is cold, airless, barren, drenched in radiation, people can only survive with the age of sophisticated technology and immense personal and communal discipline. People will go for knowledge, adventure, and enlargement of human horizons, Antarctica in the sky if you will. But not looking for a new earth. IMHO of course.<br /><br />That is why I find discussing the first missions and first bases much more interesting (and useful). These identify the hurdles that must be crossed before we can even seriously consider settlements. IMHO of course!<br /><br />Mind you, there are times when I have been wrestling with the masses of MTVs and ERVs that one way missions start <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[gunsandrockets]

"Less than a page of text and three drawings hardly qualifies as detailed."<br /><br />What? As regards the CEV that docks to the MTV and whether it is the same CEV used during Earth return it's extremely detailed. It describes in tedius detail exactly how that particuar CEV is utilized, from launch until return to Earth. <br /><br />"It is not clear whether the CEV they return home in is the same one, although it certainly possible. "<br /><br />It is clear. It is the same CEV.<br /> <br />I already posted this once, I even posted the text and capitalized the relevant sentence it so it would stand out. Maybe if I spoon feed the most important text it may finally sink in. I hate repeating myself.<br /><br />http://www.spaceref.com/news/viewsr.html?pid=19067<br /><br />"The ESAS reference Mars mission utilizes a Block 3 CEV to transfer a crew of six between Earth and an MTV at the beginning and end of the Mars exploration mission....Once crew and cargo transfer activities are complete, the CEV is configured to a quiescent state and remains docked to the MTV for the trip to Mars and back...As the MTV approaches Earth upon completion of the... round-trip mission, the crew...transfers to the CEV...and undocks from the MTV. "<br /><br />Hmmm...the CEV remains docked to the MTV for the trip to Mars and back. To Mars AND back.

 

[JonClarke]

You've convinced me! <img src="/images/icons/smile.gif" /> <br /><br />I must say I do prefer using one CEV for the whole mission. Also the CEV is very large - far larger than is needed for the cabin of a 6-person ascent stage, which needs only to mass 4-5 tonnes.<br /><br />Do have any idea as yet on how much a SDLV performance can be upgraded? I find it curious that there were various statements when ESAS was first announced about SDLV performance being optimised for mars missions when it is too small for single launch approaches and too large of convenient orbital assembly (for which an 80-90 tonne payload capacity as with Shuttle C would have done nicely).<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[gunsandrockets]

"Do have any idea as yet on how much a SDLV performance can be upgraded? I find it curious that there were various statements when ESAS was first announced about SDLV performance being optimised for mars missions when it is too small for single launch approaches and too large of convenient orbital assembly"<br /><br />According to page 10 of the Executive Summary of the final (not draft) ESAS report, EOR of two HLV will be employed for constructing individual Mars ships. That's a total of six HLV plus one CLV launched for each manned mission to Mars.<br /><br />The payload of the HLV (without using the 250 tonne EDS third stage) is about 109 tonnes to LEO. Two HLV should then have enough margin to place enough mass into a 1000 km Earth orbit to assemble one Mars ship of approx. 180 tonnes.

 

[JonClarke]

Excellent! This mades much more sense. I would assume with other studies on launch would carry the payload and one the earth departure stage. It also allows a significant 34%) margin over the magnum. Other than being a good idea it also keeps other propulsive options open.<br /><br />Thanks for finding this.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>