Mars 9 tons at a time.

[keermalec]

Good point ThereIwas. I believe there is no ressearch on this at the moment but a simple aerodynamic shape, with a mildly heat resistant surface (steel) and some insulation should allow significantly better aerobraking than the MRO. <br /><br />Another (probably better) option is to use a ballute. Temperature can be calculated from atmspheric density and velocity. Mass for a steel shield and insulation can also be estimated. However we need temperature resistance and mass data for ballutes.<br /><br />Slow-down time could maybe be reduced from 6 months to several weeks by reducing the number of passes through the upper atmosphere, so this is certainly very promising. <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

 

[gunsandrockets]

<** Total propulsive delta-v: 10.5 km/s, 1'200 days or 40 months **><br /><br />Aww heck, I was afraid of that. I thought 24 months sounded too good to be true. Damn. <br /><br />Even so, the actual 40 months travel time isn't as bad as I orginally feared. And the payload penalty for reducing travel time to 29 months isn't too bad either.<br /><br />Good job working out the other acceleration times, your list is very handy for quick reference of other options.<br /><br />I'm wondering if there is some kind of sweet spot for electric propulsion in combination with some high thrust propulsion. As this link suggests...<br /><br />http://research.hq.nasa.gov/code_s/nra/current/NRA-02-OSS-01-ISPT2/winners.html<br /><br /><br />... perhaps by carefully balancing the different propulsion elements (maybe also including lunar gravity assists), most of the payload benefits of electric propulsion can be preserved while reducing some of the worst travel times.<br /><br />I can't help but think the modest delta-V added from lunar gravity assist might have a dramatic effect on SEP acceleration times.

 

[keermalec]

<blockquote><font class="small">In reply to:</font><hr /><p>I can't help but think the modest delta-V added from lunar gravity assist might have a dramatic effect on SEP acceleration times. <br /><p><hr /></p></p></blockquote><br />Yes, it probably would. The calculations do get very complicated though, the phasing would be something like:<br /><br />1. Raise Earth orbit by multiple burns at periapsis (assume burn duration = 1/3 of orbital period).<br />2. To get to Lunar L1, total delta-v is 3.11 + gravity losses (lets assume a total of 3.4 km/s).<br />3. The vehicle enters the moon's sphere of influence at 0.89 km/s relative to the moon (retrograde).<br />4. The vehicle does a slingshot maneuver passing 50 km above the lunar surface and turns by 93° (this is good: we leave the moon along its orbital direction, thus benefitting entirely from its orbital velocity)<br />5. Vehicle leaves moon sphere of influence at 1.91 km/s (1.02 = lunar orbital velocity + 0.89 = entry velocity)<br />6. vehicle leaves Earth sphere of influence at 1.4 km/s<br /><br />At first estimate, we shave off about 100 days by raising orbit only to L1 and not all the way to Earth sphere of influence at 955'000 km.<br /><br />Then we enter the interplanetary leg with a 1.4 km/s boost, instead of zero as in the original plan. It is not clear to me how this works with continuous thrust to Mars but it seems the interplanetary delta-v can be reduced from 5.6 to 4.2 km/s, thus increasing the payload (and reducing the time of flight by 20%?).<br /><br />Total delta-v using lunar gravity assist is 8.6 km/s (3.4 + 4.2 + 1) instead of 10.5, thus payload should increase from 50% to 55% for the 40-month, 0.00002 G version, or from 43% to 46% for the 29-month, 0.00003 G version. <br /><br />Total time of flight reduction using lunar gravity assist may be around 13%. ie 35 months instead of 40, and 25 months instead of 29... <br /><br />It seems using lunar gravity assist with SEP can get a payload mass fraction of 46% to LMO in 25 month <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

 

[gunsandrockets]

<It seems using lunar gravity assist with SEP can get a payload mass fraction of 46% to LMO in 25 months! (to be verified)><br /><br />Heh. Now we are (almost) back to the 24 month trip time after all!<br /><br />This is sounding more and more like a very promising method to pre-position cargo at Mars as part of a manned mission.

 

[nuaetius]

I have looked around on the internet and in the forums here and I have never seen any numbers on this. If Russia where to launch 2 Progress resupply ships to the ISS at the same time, could they transfer fuel between themselves either while connected to the ISS or in orbit. IF they can do this how much Delta-v can be generated by a refueled Progress module? <br /><br />The reason I ask is this. If you refueled a Progress module with just enough fuel to put it into a cycler orbit between Earth and Mars it would be the 1st man made object to go to Mars and then return, which is a technological stepping stone to the 9 ton and cycler ideas that would be nice to knock out with a trash truck instead of a dedicated mission.<br />

 

[scottb50]

A cycling orbit between Earth and Mars wold not be a continuous no energy required loop, with the changing locations of the planets you would need to enter an orbit at both ends and depart at an appropriate time for the return.<br /><br />To do it with a Progress module would be feasible, but would only be proving a point that is already understood.<br />It would be like proving we can put men on the moon when we have already put men on the moon. <br /><br />It seems like every excuse is used to not do something that could easily be done. <div class="Discussion_UserSignature"> </div>

 

[keermalec]

The Progress module is only designed for a delta-v of 200 m/s. Therefore refuelling it would not give it the velocity needed to get to Mars.<br /><br />However, refuelling is probably the key to launching a Trans-Mars vehicle on existing rockets. <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

 

[j05h]

<i>> The Progress module is only designed for a delta-v of 200 m/s. Therefore refuelling it would not give it the velocity needed to get to Mars.<br />However, refuelling is probably the key to launching a Trans-Mars vehicle on existing rockets.</i><br /><br />We have been discussing direct-throw, and it seems to work for getting there. For a Progress module, it would be thrown by Proton or Delta IV-H. It is possible but not optimal, and probably wouldn't make it. It would also need larger solar panels. Purpose-built Mars transit modules make more sense. <br /><br />I really like the idea of starting sooner with less payload then later with maybe more payload. <br /><br />Keer- what are your further thoughts on throwing several Dragon capsules and SunDancers together with resource modules and docking them in transit? Is it feasible for getting people to Mars? It satisfies the "flotilla" concept while offering half-crew returns to Earth in an emergency. Those craft (and the proposed pressurized and palette cargo pods) will all be roughly within Delta IV H throw-weight for Mars insertion. That means, if it works, that Mars projects can start today.<br /><br />The small-package method also allows relatively large rover/probe/beacon precursors to be launched. It could feature MER sized rovers, weather, balloons and radio/laser positioning and comm hardware. This would be able to guide other landers in while exploring the local area using current technology. The two assets missing are the lander (which we have roughed out in this thread) and a reliable Mars Balloon (which the Planetary Society designed in the 80s). Importantly the rocket(s) already exist, as does the rover and parts of the EDL and cruise hardware. What is the best way to get there sooner than other approaches and stay in a sustainable/increasing manner? <br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[keermalec]

Hi Josh, I suppose you mean Dragon-type capsules and SunDancer-type modules. Remember these vehicles are not designed for Mars but for Earth orbit. Specifications will be quite different.<br /><br />A dragon-capsule-type entry vehicle is necessary for Mars atmospheric entry and a sundancer-type habitat may do the trick for the trans-Mars trip. <br /><br />However, on Earth parachutes can slow the dragon-type entry vehicle to landing velocities (2-3 m/s) but on Mars only 630 m/s will be attained. This is way too fast for landing (unless you want a splattered crew) and so landing rockets and legs need to be integrated with a (presumably) jettisonable aeroshell.<br /><br />Concerning the sundancer habitat module, it will probably need better cosmic ray shielding (as the trip is longer and the Earth's mass no longer blocs out half the harmful rays), more solar panels (Mars is further away from the sun) and a very very reliable air and water recycling system, which is not at the moment test-proven.<br /><br />I don't really like the idea of doing a rendez-vous during Mars transit because that means simultaneous Delta-IV Heavy launches from the same latitude (the modules need to have the same trajectories and the same orbital planes). I prefer the idea of rendez-vous in LEO. This also allows much greater mass (23.8 tons vs 8 tons) per launched element and boils down to almost exactly the same mass to Mars. The Earth departure Stage is simply combined with the payload in LEO. <br /><br />Concerning staying there in a sustainable/increasing manner, the NASA DRM-3 goes into a lot of detail on a tentative Mars base. <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

 

[paul_klinkman]

If you don't know about our team, we're expecting to have orbit-gathered oxygen refueling capabilities soon. We can be up in 5 years if NASA pushes the effort and in 10 years if NASA doesn't.<br /><br />If you can get 9 tons of cargo into low earth orbit, a refuelable space tug can get it up to near-lunar orbit and can let it slingshot out past the moon. If you can get an empty LOX tank to orbit, we can fill it. If your crew capsule needs an extra 500 tons of water as radiation shielding, please order in advance, but we expect to be able to fill that order.<br /><br />Also available: <br /><br />Nitrogen, an alternative propellant for Hall-Effect ion engines, and part of Nitrogen Tetroxide monopropellant.<br /><br />Helium, a ballast gas in LOX tanks, kind of hard to store and liquefy but the Hubble Telescope uses it.<br /><br />Probably hydrogen. Gathering hydrogen is at a slight extra cost, still cheaper than launches, hard to liquefy, but easily stored as water.<br /><br />NASA's current launch costs for propellant are $10,000/kilogram. We could see some rocket company slashing that to $3,000/kilogram. We expect to be a fair piece less than that, including startup costs.

 

[keermalec]

Amazing outlooks, Paul, if you can deliver. As I said before, I personnally plan only on existing technology, but I would love to persue this conversation with you on your old Atmospheric Gatherer thread, as reminded by gunsandrockets, if you agree. <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

 

[j05h]

<i>> If you can get 9 tons of cargo into low earth orbit, a refuelable space tug can get it up to near-lunar orbit and can let it slingshot out past the moon.</i><br /><br />This thread is about sending 9 tons (closer to 8.25t) on a direct Trans-Mars Injection, using the heaviest existing American rocket, the Delta IV-Heavy. This is using something that exists today. The competing concept that Keermalec is describing is assembly in LEO using same. There are advantages to each. We discussed slingshots past the moon a while ago and it is a lot of trouble for barely any help. <br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[keermalec]

<blockquote><font class="small">In reply to:</font><hr /><p>This thread is about sending 9 tons (closer to 8.25t) on a direct Trans-Mars Injection, using the heaviest existing American rocket, the Delta IV-Heavy. This is using something that exists today. The competing concept that Keermalec is describing is assembly in LEO using same. <p><hr /></p></p></blockquote><br />Josh, the main reason I embarked upon the LEO concept is because the 8-tons to Mars idea, though appealing, is simply too dangerous for manned missions. Amongst the points made earlier we find:<br /><br /><br />1. 8-tons to Mars is the mass sent on a Hohmann transfer (ie 258-day) trajectory to Mars. Most Mars scenarios today believe the trip should be limited to 6 months (180 days) maximum to avoid cosmic ray damage to the crew. Additional shielding means additional mass and that is one thing the 8-ton direct concept does not have. Faster transfer time means more propellant which again means more mass.<br /><br />2. As seen before, an interplanetary habitat for 6 persons will weigh just above 30 tons. Assuming we can scale that down linearly (which is not at all certain) that means 5 tons per person. An aerobrake for an 8-ton vehicle will be about 1.6 tons and propulsive capture will mass even more. Therefore an 8-ton capsule to Mars can only provide a habitat for a single person. Sending a single person on a lonely 9-month trip (not to say 2 1/2 year mission!) raises some serious security issues.<br /><br />3. Lanching several 8-ton modules onto a TMI for in-transit assembly is currently impossible as these must be launched simultaneously from colinear points on Earth intersecting their orbital plane. If launched from Cape Canaveral for example, the second launch site must be on a line inclined at 28° to the equator, and crossing Cape Canaveral. Such a launch site does not currently exist.<br /><br /><br />Launching to, and assembly in, LEO solves all of these problems. To me the LEO concept is not a competing one: it i <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

 

[j05h]

The root to me is doing Mars in relatively small packages. The thing that makes no sense is putting off Mars because of an inability to utilize existing resources. <br /><br />If that means staging everything in LEO, or doing human flights from LEO, that's fine. I think it still makes sense to consider direct-throw for cargo and probes, especially considering the simplicity of the idea. <br /><br />I generally agree with your crew-safety issue but think that could be tested fully if there were a couple of Delta-IV (or F9H) pads that could launch co-planar. <br /><br />I would never suggest sending a single person in a capsule - it's to dangerous, there's to much to be done, there's to much chance of The Crazy setting in.<br /><br /><i>> 2. As seen before, an interplanetary habitat for 6 persons will weigh just above 30 tons.</i><br /><br />Right, which is why I bang my head every time someone tries to insist that the first step is to build a 150t HLV. <br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[gunsandrockets]

<Right, which is why I bang my head every time someone tries to insist that the first step is to build a 150t HLV.><br /><br />An examination of the NASA Design Reference Mission (DRM) 3.0 for Mars is enlightening as to the potential of medium lift boosters such as the EELV.<br /><br />DRM 3.0 was predicated on an 80 tonne LEO payload HLV derived from the Space Shuttle; basically the Shuttle C. DRM 3.0 used 6 HLV flights to assemble 3 rockets in LEO, with a grand total mass of about 450 tonnes. These three rockets used Nuclear Thermal Propulsion TMI, aerocapture at Mars and Mars Semi-Direct architecture to support a long-stay conjunction class manned mission of six crew. The whole mission boils down to six launches from Earth, three EOR, and a total of 75 tonnes of payload per crew member.<br /><br />Now six launches of a Delta IV heavy could place about 143 tonnes of payload into orbit. If propulsion of similar efficiency to DRM 3.0 was used then in theory a similar style mission to DRM 3.0 but with a crew of two is possible using just the Delta IV. I think that is very interesting.

 

[vulture2]

Maybe we should have a station in LEO where the pieces of the spacecraft could be assembled .. hey, that was what von Braun wanted going to do.

 

[keermalec]

<blockquote><font class="small">In reply to:</font><hr /><p>Maybe we should have a station in LEO where the pieces of the spacecraft could be assembled .. hey, that was what von Braun wanted going to do. <br /><br /><p><hr /></p></p></blockquote><br />This was actually discussed in a previous thread. The up-front costs for establishing an orbital assembly facility seem just huge and it is believed quality control cannot be as good as in ground assembly. <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

 

[keermalec]

<blockquote><font class="small">In reply to:</font><hr /><p>Now six launches of a Delta IV heavy could place about 143 tonnes of payload into orbit. If propulsion of similar efficiency to DRM 3.0 was used then in theory a similar style mission to DRM 3.0 but with a crew of two is possible using just the Delta IV. I think that is very interesting. <br /><p><hr /></p></p></blockquote><br />I also believe it is possible to lanch a manned Mars mission using only existing launchers. I have been owrking on it and one big problem is the payload diameter (5.13 m external fairing for the Delta-IV) which does not allow transport of a pressurised rover to the martian surface, for example. <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

 

[gunsandrockets]

<I also believe it is possible to launch a manned Mars mission using only existing launchers. I have been working on it...><br /><br />interesting<br /><br /><... and one big problem is the payload diameter (5.13 m external fairing for the Delta-IV) which does not allow transport of a pressurised rover to the martian surface, for example. /><br /><br />Really? Even if a DRM 3.0 type combined payload fairing/biconic heatshield was employed? What size rover are you talking about?

 

[gunsandrockets]

<Maybe we should have a station in LEO where the pieces of the spacecraft could be assembled .. hey, that was what von Braun wanted going to do.><br /><br />Not neccessary. DRM 3.0 used a very simple system of docking two pieces in LEO for every Mars Rocket, so no LEO assembly is required. One HLV would lift up the NTR propulsion module of the Mars Rocket and a second HLV would lift up the payload module. All told, a total of six HLV to construct three Mars Rockets in LEO.<br /><br />One cargo Mars Rocket prepositions the ERV into low Mars orbit. The second cargo Mars Rocket prepositions the nuclear electric-power system, ISRU plant, and Mars Ascent Vehicle onto the surface of Mars. The third Mars Rocket carries the crew in a habitat-lander which lands on Mars near the prepositioned cargo.

 

[keermalec]

<blockquote><font class="small">In reply to:</font><hr /><p><... and one big problem is the payload diameter (5.13 m external fairing for the Delta-IV) which does not allow transport of a pressurised rover to the martian surface, for example.> <br /><br />Really? Even if a DRM 3.0 type combined payload fairing/biconic heatshield was employed? What size rover are you talking about? <br /><p><hr /></p></p></blockquote><br />The SEI rover is about 3m high, for a pressurised cylinder of 2.2m. This is just measured from the drawings: no numerical indications are given in the report. Its length is not indicated but it must be 6 to 7 meters long.<br /><br />I like the triconic aerobrake idea in DRM 3 rev1 but it has not been tested and I am trying to stick to existing, test-proven technology in this project. My idea is, hopefully, to determine what can be done today with today's technology, to reach Mars.<br /><br />I believe I will stick to unpressurised rovers for the time being, as these can certainly fit in a 5m diameter aeroshell and should allow 90 km exploration radius if we base ourselves on the lunar rover. Adding a fuel and life support cart should conceivable extend the radius much further. Hm.. maybe a cart-drawn pressurised habitat for multiple-day excursions? <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

 

[keermalec]

Hey, I just found this three-man pressurised mini rover design for the Moon!<br /><br />Unfortunately even this rover is too large for a 5.13m diameter conic aeroshell. Maybe I will have to assume the triconic aeroshell works. <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

 

[thereiwas]

There is a type of recreational trailer called a "pop-up", which is essentially a tent mounted on a small base with wheels. So how about an "expandable" habitat on a hard wheeled base? It gets expanded once on the surface.

 

[keermalec]

Very good idea, may I include it in the project? <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

 

[thereiwas]

Sure. Something like this Wienermobile with a shorter wheelbase. A small Bigelow mounted on a powered cart.