Author Topic: What is the cheapest and fastest way to go to the moon or mars  (Read 71308 times)

Offline 93143

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Jim has shown that a 10m heat shield can be folded in half to fit a 5m EELV.

Only if it's a disk.  The DRM 5.0 aeroshells were biconics and 10 m across.

Offline Robotbeat

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Jim has shown that a 10m heat shield can be folded in half to fit a 5m EELV.

Only if it's a disk.  The DRM 5.0 aeroshells were biconics and 10 m across.
And those aeroshells have never been tested on Mars. As long as we're doing that, why not a ballute?
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Offline mmeijeri

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So air braking might be just as costly as propulsive braking or landing? 

To answer that question you have to be very careful about which costs you include: development costs, fixed costs, variable costs? Another question is how this affects commercial launch prices. Once we have RLVs (or ISRU) propulsive solutions will become much more interesting. Conversely, starting with propulsive solutions can jump start development of RLVs through demand-pull or as Musk calls it, by providing a forcing function.
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Offline Kaputnik

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IMO, the cheapest and fastest way to Mars would be a simple (as in pretty much fully propulsive), reusable (cheaper since it can be used over and over again), all chemical (faster than SEP), architecture that was evolved from previous spacecraft a la the ULA Lunar plan.

Zegler et al. say their DTAL lander could easily be evolved for use on Mars. My own BOTE calculations suggest that a stretched tank DTAL lander (i.e, an ACES-71) equipped with a heat resistant titanium hull (so it could withstand the full 1 W/cm2) could land fully propulsively--no ballutes, parachutes, or heat shields required.

Then the ULA MTV has a crew capacity of 16 and a nominal delta v of 11 km/sec. If there was refueling capability in Mars orbit, the ULA MTV could cut the 1-way transit times by over half compared to the Hohman transfer; if refueling was deemed impractical (probably the case for the initial missions), it would have enough delta v to do a round trip taking Hohman transfers. Again, this would all be fully propulsive--no heat shields required.

The 7 hundred tonnes of propellant would only cost about $350 million, if refueled at L2 (with Lunar derived LH2/LO2).

See, so the whole thing would be faster and cheaper, since it would be a simple evolution from the ULA Lunar architecture, which is itself a simple evolution from the Centaur 3rd-stage architecture.



Any links to the ULA Mars architecture?
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Offline Warren Platts

http://www.ulalaunch.com/site/docs/publications/AffordableExplorationArchitecture2009.pdf

http://www.ulalaunch.com/site/docs/publications/DepotBasedTransportationArchitecture2010.pdf (this one has a cool picture of their proposed MTV)

http://www.ulalaunch.com/site/docs/publications/DualThrustAxisLander(DTAL)2009.pdf

These mostly describe ideas about how to do a Lunar program, but they say the Lunar architecture would be relatively easily evolved for use on Mars missions. It would be distinguishable from more conventional proposals in that the architecture would mostly  be reusable, and would probably take advantage of Lunar ISRU propellant (although they don't say this, Lunar propellant would be the only way to affordably fill up that MTV they propose).
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Offline constantius

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Personally, I feel like the cheapest and most efficient way to go to mars has to make maximum use of ISRU capabilities. I am also skeptical of the idea that a mars mission needs to bring much scientific hardware. I am not as enthusiastic about martian life as I am about, say, finding mineral ores or other industrial materials that humans can use. We must make as our goal the settlement of mars. That is also why I favor a 1-way mission (which would also free up a lot of mass).

Offline Warren Platts

Personally, I feel like the cheapest and most efficient way to go to mars has to make maximum use of ISRU capabilities.

Are you talking about the Moon or Mars or both?

Quote
I am also skeptical of the idea that a mars mission needs to bring much scientific hardware. I am not as enthusiastic about martian life as I am about, say, finding mineral ores or other industrial materials that humans can use.

Find life or evidence of former life might be as easy as walking out and picking up the right rock. I would recommend trying to find an active geyser or fumarole. Or it might take some drilling to try and find a deposit of liquid water. Life on Earth exists miles down underground. If it's Mars, that's probably where it is. But drilling more than a few feet is going to be relatively mass intensive. Another reason for using Lunar ISRU; that way you're not mass starved.

Quote
We must make as our goal the settlement of mars. That is also why I favor a 1-way mission (which would also free up a lot of mass).

Mass is the nut to crack. Getting it there cheaply will entail reusable vessels as much as possible. If you've got reusable MTV's, there's no reason astronauts can't be rotated out IMO.
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Offline neutrino78x

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Personally, I feel like the cheapest and most efficient way to go to mars has to make maximum use of ISRU capabilities.

Are you talking about the Moon or Mars or both?

Personally I think ISRU should be a big part of both!! Also, to the greatest extent possible, I would want hardware that can be used on both Mars and the Moon. :)

Offline colbourne

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The cheapest and probably the first  way to go to Mars is a one way mission, and will probably be carried out by Musk as he has the will and potentially the means to achieve such  a feat.

For a long term large base requiring a high mass to be transferred  from Earth the ideal candidate would be the rotorvator. This would provide the cheapest cost per unit of mass but would be expensive to construct. A second rotorvator at Mars could be useful for landing and returning from Mars.

Offline Andrew_W

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Without going through the thread, can I just point out that the Apollo spacecraft could have gone to Mars, so any future Lunar hardware can probably be modified to being Mars capable hardware. So who's in in the best position to get men back to the Moon? Probably SpaceX.
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Offline Kaputnik

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Without going through the thread, can I just point out that the Apollo spacecraft could have gone to Mars, so any future Lunar hardware can probably be modified to being Mars capable hardware. So who's in in the best position to get men back to the Moon? Probably SpaceX.
I don't quite get what you are saying. Apollo lacked the delta-v, mission duration capability, and would have been far outside its thermal/environmental design range. In no practical sense could it have 'gone to Mars'. The CM could perhaps have made a re-entry at Mars-return speeds but that's not the same as saying you could go to Mars and back.

Secondly, there is, of necessity, a fundamental difference in design between a Mars lander and a moon lander (and, for that matter, an Earth lander). On the moon, with no atmosphere, you have only way of landing, using propulsion all the way; fortunately the relatively low gravity makes this feasible without a ridiculously large spacecraft. On Earth, the thick atmosphere makes it feasible to use aerodynamic landing instead. Mars occupies an awkward middle ground with the disadvantages of both environments- just enough atmosphere to complicate an all-propulsive landing, enough gravity to really push up the delta-v requirement, but not enough atmosphere to really accomplish as much braking as you would like.
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Offline MATTBLAK

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The Apollo Command Module would have been docked to a Skylab-type Habitation Module, along with a Mars Excursion Module and a cluster of propulsion stages and propellant tanks. The CSM probably would have been a "Block IV" without fuel cells, modified to remain dormant for very long periods of time, if need be. Improved hypergolic propulsion systems would have allowed the CSM's RCS and SPS engines to withstand radiation and long, deep thermal cycles and variances. Without fuel cells, the CSM would have had to rely on an array of batteries capable of being charged from the Mars Mothership's solar arrays.

It certainly wouldn't have had to fly to Mars and back on its own. Any future involvement by Orion or Dragon in such a mission would be similar. I recommend anyone reading this to seek out Stephen Baxter's excellent alternate-history novel "Voyage" that portrays just such a mission.

http://en.wikipedia.org/wiki/Voyage_%28Stephen_Baxter_novel%29
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Offline 93143

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Secondly, there is, of necessity, a fundamental difference in design between a Mars lander and a moon lander...

You may be overstating things.  IIRC, a reusable lunar lander capable of making a two-way trip between a lunar pole and L2 would require around 5.5 km/s of delta-V, and this sort of lander has been proposed before.  According to my calculations, it should be possible to do a fully-propulsive landing on Mars for well under 5 km/s, even with the trajectory shaped to get the lander slow before it gets low.

Early missions will probably use heat shields.  But if we get a base going, with established ISRU infrastructure, a reusable architecture might be more attractive, just as with the moon.  The required landing delta-V is not too much higher than the launch delta-V; if you refuel the lander on the surface you can use it for that, instead of bringing a dedicated ascender.  Then, if you refuel it on orbit, you can use it to land again.  So instead of throwing away a heat shield and lander, as well as a one-shot ascender and its ISRU equipment, that got there via another heat shield and lander, which in DRM 5.0 adds up to 173.6 tonnes of mostly dry hardware (not counting the surface hab), you're throwing away maybe 200 tonnes of hydrolox propellant, or <300 tonnes of methalox, a significant fraction of which can be locally sourced at the base.  And that's assuming the same ~40 tonne landed payload; if there's already a base, you might be fine with less...

You know, the difference in gravity between the moon and Mars is roughly equivalent to the difference in thrust between the RL-10 and the RL-60...

...

On the other hand, if you could devise a reusable launch vehicle for Mars that had an integrated heat shield and could go up and down on one propellant load, it could be used to fill Mars orbital propellant depots instead of being a drain on them.  It would probably be bigger, though, and/or have less payload, and you'd lose commonality with the lunar lander...

A full-capability reusable lunar lander like that would have enough delta-V for literally any body we might ever want to land on other than Earth and Venus, though surface ISRU would be required on a couple of the bigger ones.  Modifications would probably be required for certain targets...
« Last Edit: 02/21/2012 10:31 am by 93143 »

Offline Warren Platts

If you want to do ISRU on Mars, you might as well go for highest Isp LH2/LO2. In which case, you'll probably want to demonstrate the technology on Lunar ice first. In which case you'll have Lunar ISRU at your disposal. Which in turn means you can take Martian ISRU off the critical path.

I've looked at the ULA Lunar lander that they say can be scaled up to work on Mars. E.g., using an ACES-71 and a titanium or Inconel skin would have enough delta v to land fully propulsively and deposit a 20 to 25 mT dry cargo. A beefed up ascender could be reused, but it would have to be filled up on the surface.

Since you'll be going for Martian ISRU anyways, and to make a big difference, you'll want to make 1,000+ tonnes, then you're going to need a big tank farm to manage the feedstocks and products, so reusability, at least for the first decade or two isn't really advisable, because you'll need to build up the tank farm anyway. The ascender could dock with an ACES-71 lander sent fresh from Earth, and the fully loaded ascender/descender could land with the ascender ready to take off again.
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Offline Robotbeat

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If you want to do ISRU on Mars, you might as well go for highest Isp LH2/LO2. ...
Why? CO/O2 is really easy.
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Offline Warren Platts

If you want to do ISRU on Mars, you might as well go for highest Isp LH2/LO2. ...
Why? CO/O2 is really easy.

A. LH2/LO2 is not hard as long as you have water

B. You can drink it and breathe it and wash with it and grow crops with it

C. You need water anyway, so going with CO/O2 isn't going to get you out of that one

D. LH2/LO2 has a much better Isp than CO/O2

E. You can run RL-10's and RL-60's on LH2/LO2

F. You can run fuel cells on LH2/LO2

G. You'll have a single, common fuel to run your entire cis-Martian architecture on

H. You can take Martian ISRU off the critical path, thus reducing development and time costs

I. LH2/LO2 can be exported for beyond Mars uses--like returning to Earth

J. Hydrogen extracted from water is useful in many ISRU beneficiation processes where a reducing agent is needed

K. Save development costs of CO/O2 ISRU infrastructure (because its unnecessary) and development costs of CO/O2 rocket engines which don't exist now, and wouldn't have proven reliability by the time they're needed in a critical path role on Mars surface
« Last Edit: 02/21/2012 04:38 pm by Warren Platts »
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Offline Robotbeat

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1) It doesn't need to be mined and is always available on every point on the planet in unlimited quantities and requires no hard cryogenic storage. This vastly simplifies the whole project.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline Warren Platts

1) It doesn't need to be mined and is always available on every point on the planet in unlimited quantities and requires no hard cryogenic storage. This vastly simplifies the whole project.

C. You need water anyway, so going with CO/O2 isn't going to get you out of that one. Therefore, you are merely adding an extra, unnecessary layer of duplicated effort that vastly complexifies the whole project.
« Last Edit: 02/21/2012 05:02 pm by Warren Platts »
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return."--Leonardo Da Vinci

Offline Warren Platts

Since the thread is about the cheapest way to get to Mars, if the Mars project came after a vibrant, Lunar propellant station was up and running, if you think about it, the big ticket development costs for a Mars landing would essentially be zero. Even the MTV would simply be an evolved version of the L2 Gateway station (probably be a Bigelow module surrounded by discarded ACES-121/JUS upperstages or their equivalent). Practically everything needed would already be developed; it would just be a matter of saddling up and going.
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Offline Robotbeat

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1) It doesn't need to be mined and is always available on every point on the planet in unlimited quantities and requires no hard cryogenic storage. This vastly simplifies the whole project.

C. You need water anyway, so going with CO/O2 isn't going to get you out of that one. Therefore, you are merely adding an extra, unnecessary layer of duplicated effort that vastly complexifies the whole project.
We need water anyway, so why do we bother breathing air?

If you bold a point, it doesn't make it more important. I read it the first time.

Besides, your main point is Moon development, you barely care about going to Mars.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

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