Blue Origin Thread (merged)

[Northstar1989]

4 hours ago, Northstar1989 said:

Seriously, I think this is a really good idea.  Is there anybody here who is good at formal/business/technical writing who would be willing to double-check the assumptions here a bit, and kindly write to SpaceX to inform them that the version of Interplanetary Transport Ship that Elon Musk presented on this month actually meets all the technical requirements  (Delta-V budget, crew accommodations, navigational systems, refueling ability, etc.) for use as a Cycler Ship- with the sole exception that when it docks with another ship it needs to have the capability to transfer over crew and basic supplies as well as fuel?

 

Regards,

Northstar

So anyone, this?

It could and probably should be pitched as the "launch two identical ITS's and use one as a Cycler" version of explaining this, and leave Elon Musk and the engineers at SpaceX to figure out what additional refinements to the design will or will not improve the cost-efficiency further than that.  But it's obvious that it's a workable plan that will cut costs, and it's relatively simple and easy-to-understand.

So, would anyone have an interest in writing up an idea proposal on this and mailing it to SpaceX?

 

Regards,

Northstar

Edited September 30, 2016 by Northstar1989

[Nibb31]

11 minutes ago, Northstar1989 said:

The shorter launch-window is worth the hassle, and doesn't increase costs at all if you do it right.  And did you not catch the point about cramming twice as many colonists into the Interceptor ITS since you will have twice the habitable space for most of the journey?

Yes, and you didn't catch the point that you can double the habitable space by launching 50 pax instead on 100, because there is no need to send 100 pax anytime soon.

You also missed Musk mentioning that a future version of the ITS could have an extended crew section that could accomodate 200 pax, which could also be 100 with double crew-space if you want. We haven't even see a proper study of how much volume would be necessary anyway.

The thing is, there won't be a need for sending hundreds of people to Mars before several decades, because no matter how much money Musk spends on this, the rest of the plan isn't ready. So let's see how the base plan of actually launching this thing and getting it to work. Then we can talk about cyclers and colonial fleets with hundreds of passengers.

The shorter launch window is a huge risk. You miss it, you lose the synod. A normal Mars transfer window lasts weeks, which allows you to reschedule. A cycler RV window is hours.

2 minutes ago, Northstar1989 said:

So, would anyone have an interest in writing up an idea proposal on this and mailing it to SpaceX?

You really think he hasn't considered it already ?

Edited September 30, 2016 by Nibb31

[Northstar1989]

18 minutes ago, Nibb31 said:

Yes, and you didn't catch the point that you can double the habitable space by launching 50 pax instead on 100, because there is no need to send 100 pax anytime soon.

You also missed Musk mentioning that a future version of the ITS could have an extended crew section that could accomodate 200 pax, or 100 with double crew-space if you want.

The thing is, there won't be a need for sending hundreds of people to Mars before several decades, because no matter how much money Musk spends on this, the rest of the plan isn't ready. So let's see how the base plan of actually launching this thing and getting it to work. Then we can talk about cyclers and colonial fleets with hundreds of passengers.

The shorter launch window is a huge risk. You miss it, you lose the synod. A normal Mars transfer window lasts weeks, which allows you to reschedule. A cycler RV window is hours.

Getting twice the people to Mars for the same cost is a boon, no matter how you look at it.  If you don't need 200 people, and 100 will do, you could always cut the baseline capacity of each Cycler to 50 people, and shrink the booster and tanker designs to match.  If you only need 50, you could cut crew capacity to 25, and still do it cheaper with a Cycler Ship than without.

There is literally no limit to how far you can cut crew capacity to reduce surplus capacity, up until the point where your target crew to Mars is two people and each ship only has space for one.  Although, past a certain point you start to lose sharply in terms of cost-effectiveness because larger spacecraft are more cost-effective than smaller ones below a certain size, and over time, more people WILL want and be able to pay for a trip to Mars.  You and I may disagree about where the demand will initially fall (I happen to believe that SpaceX would have no problem finding 200 people willing to pay for a seat to Mars on the first transfer-window, and surveys of the population about how many would be willing to go to Mars if they could afford it have backed me up for many, many years on this conclusion).  Your criticism doesn't make logical sense Nibb.

Then again, this isn't a personal attack, but you *never* do anything but spread doom and gloom and talk about how any given proposal to increase our space capabilities, no matter how well-designed, won't work, Nibb.  You've been doing it on these forums for years, so you'll have to excuse me if I respectfully take your criticism with the appropriate grain of sand.

Once again, that's not meant as a personal attack.  Some of your criticisms are, at times, highly valid and very well thought-out. The problem is that your conclusions are always, I mean always, the same- that we'll never do anything in space greater than what we've done already, all facts about the march of human progress to the contrary.

 

Respectful Regards,

Northstar

Edited September 30, 2016 by Northstar1989

[Northstar1989]

9 hours ago, Northstar1989 said:

There are a number of ways SpaceX could improve the efficiency of their plan:

(1)  Use a dedicated, reusable lander instead of taking the ITS all the way from LEO to the surface of Mars, and back again, each mission.  This way the ITS won't need to carry enough fuel to both make it to Low Mars Orbit from the surface AND return to Earth in a single stage (the lander should carry crew down to the surface on each trip, and fuel back up to the ITS.  Possibly these two functions could be seperated into different specialized landers for each task to obtain greater efficiency.)  The lander or landers would transfer fuel to the ITS after each ascent, in a similar manner to the tanker refueling the ITS in LEO.

Aside from reducing the Delta-V the ITS needs to carry and allowing the ITS to avoid the need to carry as much heatshielding  (the presentation by Musk shows that the most difficult re-entry with the most maximum G's will actually be on Mars, not Earth) this also benefits from the fact that smaller vessels have lower ballistic coefficients due to the Square-Cube Law (so the lander should experience fewer maximum G's during Mars re-entry), and avoids the need to accelerate any empty tank-mass (originally used to hold the fuel for Mars ascent) from Low Mars Orbit back to Earth.

(2)  Send the cargo seperately from the crew.  This will allow them to to shrink the MCT and use a smaller booster instead of a 42-engine behemoth, thus increasing their launch-volume.  The closer you get to mass-producing your rockets and keeping your launchpads in constant use, the better your economics...

(3)  Send the cargo a transfer-window ahead of the crew, on a slower trajectory.

We know the ITS is already capable of a minimum of 5.4 km/s in order to finish its orbital insertion after booster separation, and most estimates put the transfer trajectory at about 6 km/s based on the 3-5 month table in Elon's presentation, plus they must have additional Delta-V for orbital circularization after aerocapture ,and landing...

So the determining factor on the size of the spacecraft fuel tanks is the Delta-V needed for Mars insertion, capture, and landing- not for initial LEO insertion...  This means that if you developed a cargo-only variant of the ITS you could increase its payload, and send it on a slower transfer (we already know the launch stage is capable of handling a heavier upper stage than the crewed ITS, since the tanker variant weighs about 25 tons more on the launchpad...) since you wouldn't need as much Delta-V for TMI.

The slowest Mars transfers possible take about 16-18 months and 3.1 km/s (minus gravity-assists from the Moon), so there's certainly room in the Delta-V budget for extra cargo, especially if you're willing to not return the cargo-only ITS to Earth for reloading until the NEXT transfer-window (transfer windows come every 26 months,  so otherwise you probably wouldn't want to take longer than about 7-8 months getting to Mars so you'd have plenty of time to unload cargo, head back to Earth a good bit past the transfer-window, and load more cargo before the next transfer window...)

For newcomers to conversation, the first 3 items of my running list of possible improvements to SpaceX's recently-proposed Mars mission architecture can be found above.

6 hours ago, Northstar1989 said:

(4)  Instead of designing the ITS as a Mars transit vehicle that is responsible for supporting the crew all the way to the surface of Mars (or LMO if a dedicated lander were utilized instead of the plan Musk presented), design it as an interceptor-ship to meet up with an Aldrin Cycler Ship to Mars.

The design for a good interceptor is basically the same- a big spacecraft with a lot of Delta-V and a large crew capacity, which you can get to LEO by using it as its own upper-stage stage and refueling it in LEO before proceeding further.   But instead of carrying lots of living space for each crew member sufficient to last months, it should pack the crew in like sardines and only have enough life support for a few days.

When the Cycler ship swings by Earth, the interceptor ship would speed up to match velocity, and should easily be able to rendezvous within a few hours (although stretching that out to closer to 24 might reduce fuel consumption).

The crew would then transfer over to the Cycler Ship (which would be about the mass of the current ITS on the launchpad, but with slightly more of that mass dedicated to crew accommodations and life support, since it wouldn't need a heatshield or landing equipment, and it takes about the same mass to reach a Cycler Orbit as it does to make a 3-5 month transfer to Mars.  In fact, Musk may have selected the current trajectory-time for the ITS since it is almost exactly right to turn into a Cycler Orbit with a small course-correction and make a free return to Earth as a possible emergency abort-option...) and remain on the Cycler until shortly before passing by Mars.  At this point, they would board the interceptor again, and make a course-correction to aerocapture at Mars...

An interceptor-ship version of the ITS would obviously be a lot lighter than the current ITS due to its much more draconian crew accommodations.  The extra mass freed up that the booster is capable of lifting could be used in a variety of ways, but the most useful to me would seem to be launching with full, somewhat larger fuel tanks (in its current form, the ITS launches with only a partial fuel-load, since it would be too heavy for the booster if it launched fully-fueled).

This would mean the ITS would reach orbit with fuel to spare, and reduce the number of tanker launches necessary to fully refuel it for its Mars injection- thus saving money.  I would advocate shrinking the booster and fuel tanks and sticking with the current strategy of partially-loading and completely refueling instead, but the booster ought to be kept its current size to allow for the Cycler Ship to launch atop it the same way the ITS would (as the Cycler Ship would require about the same booster nominal capacity as the current ITS, though the redesigned ITS would have a lower dry mass...)

The transit-time to Mars on a Cycler Orbit is 146 days- almost *exactly* the same voyage and Delta-V as the 3-5 month journey the ITS is designed for.  In fact, when the Earth-Mars distance is such that the current ITS would make a 5-month journey, the only real difference between the current ITS trajectory and that of a Cycler Ship is that you intentionally miss Mars by a bit, so that its gravity doesn't change your orbital period too much...

Similarly, a Cycler Ship only needs to support crew for 5 months (the short leg of its orbit).  So the necessary crew accommodations would be almost identical to the current ITS- except that not needing a heatshield or to carry any fuel aboard for a Mars capture or surface landing would give you a bit more mass to play around with for things like better radiation-shielding, a small greenhouse to reduce the demands on the life-support system and provide fresh food to improve crew morale, solar sails to reduce fuel consumption needed for station-keeping and small course-corrections, and even MORE crew living-space than you find in Musk's current ITS design.

 

 

Realizing that the Delta-V needed to establish a Cycler Orbit, and the Delta-V needed for a 5 month Mars journey like in Musk's current plan are almost IDENTICAL kind of struck me dumb.  It's like finding a Christmas gift you missed opening- in June.

It basically means that if Elon Musk wanted to switch to a Cycler Ship type mission-plan, he wouldn't even have to throw out the ITS design he is presumably already working on at SpaceX.  The company could just use THAT design, with its luxurious crew accommodations, as the Cycler Ship (ideally they'd still shrink the fuel tanks a bit, remove the heatshield, lughten the structural reinforcement needed for re-entry and landing, and rededicate that mass to other things- but they wouldn't have to), and design another version of the ITS as an interceptor-ship with greatly reduced crew accommodations and slightly larger fuel tanks.

Both could launch atop the current behemoth booster design, and the only real change to their launch cycle would be an extra launch in the second transfer-window for the Cycler Ship (the current launch schedule calls for the launch of a cargo-only ITS a window ahead ofvthe first frewed mission to land the ISRU and test the design for safety/reliability).  The first time around they send crew to Mars they could even dock the interceptor and cycler-ship together BEFORE their Mars injection in order to save fuel vs. a rendezvous is solar orbit... (they'd even be able to fire their engines together with a bit of differential throttling between the two, since they'd have very similar masses and probably even shapes when both fully-fueled).

 

Regards,

Northstar

And here is #4, which is currently being debated.

Note that due to the ability to basically (or even literally) re-use the same ITS design as both a Cycler and Interceptor, I have suggested that somebody write up #4 and submit it to SpaceX as a serious idea proposal.

 

Regards,

Northstar

Edited September 30, 2016 by Northstar1989

[Nibb31]

3 minutes ago, Northstar1989 said:

Getting twice the people to Mars for the same cost is a boon, no matter how you look at it.  If you don't need 200 people, and 100 will do, you could always cut the baseline capacity of each Cycler to 50 people, and shrink the booster and tanker designs to match.  Your criticism doesn't make logical sense Nibb.

Because there is nothing that makes any logical sense in designing a ship to transport 100 people to Mars when you don't even have a clue what to do with those 100 people, or how to keep them alive, once you get there.

From the volume that was presented to us, I don't think you could actually even fit 100 people comfortably in there for 4 months however you look at it.

If SpaceX ever manages to build it and gets someone to pay for it, then maybe we will see a couple of chartered expeditions of 10 or 20 people. Once that phase is done, then we can start thinking about settlement. Since we have no idea what a Martian settlement would be like, the requirements for an actual colonial transport spaceship are likely to have changed entirely by then.

3 minutes ago, Northstar1989 said:

Then again, this isn't a personal attack, but you *never* do anything but spread doom and gloom and talk about how any given proposal to increase our space capabilities, no matter how well-designed, won't work, Nibb.  You've been doing it on these forums for years, so you'll have to excuse me if I respectfully take your criticism with the appropriate grain of sand.

Well, I respectfully take Elon Musk's vision with a grain of perchlorate salt myself, so I think we can call ourselves quit. I'm sorry if I don't drink the SpaceX kool-aid.

 

[Brotoro]

I think I'd prefer to launch a TANKER ship into orbit as step one. Then send up other tankers as needed to fill up the tanks of the first tanker. And THEN send up the crewed spaceship to take on all that fuel and head off to Mars. Less time having the crew waiting around in Earth orbit.

I'd also prefer to send the spacecraft out in pairs so that they can be tethered together and spun for artificial gravity enroute.  

[Motokid600]

People can be wrong. People can be corrected. Von Braun was wrong to dismiss lunar orbit rendezvous and look where that ended up. If you think this design/plan wont receive significant changes whether it'd be this direct transfer or a cycler in its final rendition then... c'mon.

[Nibb31]

13 minutes ago, Northstar1989 said:

Note that due to the ability to basically (or even literally) re-use the same ITS design as both a Cycler and Interceptor, I have suggested that somebody write up #4 and submit it to SpaceX as a serious idea proposal.

He was already asked about the cycler idea at press conference after the IAC presentation and dismissed it as not efficient. Believe me, he's already done the math.

Edited September 30, 2016 by Nibb31

[Northstar1989]

4 minutes ago, Nibb31 said:

He was already asked about the cycler idea at press conference after the IAC presentation and dismissed it as not efficient. Believe me, he's already done the math.

The idea may never have been pitched to him as literally just "launch two ITS's and leave one in a Cycler Orbit for re-use the next time it swings by Earth" before.  

People aren't perfect.  And *sometimes* (wink, wink) they dismiss perfectly good ideas when they really ought not to.  It's likely Musk didn't receive a very good pitch of the idea at a press conference, and definitely didn't have much time to think about the version being presented to him then and there.

I stand by use of a Cycler design being a good idea, and think somebody really ought to create a formal write-up of it and pitch it to SpaceX in writing...

 

Regards,

Northstar

[Nibb31]

Listen, he knows about cyclers, he has voiced his opinion on them several times, dating back to this article in 2012 at least:

http://www.space.com/18596-mars-colony-spacex-elon-musk.html

He knows what a cycler is. He's done the math. He is surrounded by a lot of smart people who have come up with a lot of smart plans. Cyclers are not part of those plans.

I don't know what else to tell you at this point. Take up the argument with him. I hear he's on Twitter a lot.

Edited September 30, 2016 by Nibb31

[tater]

Why would someone else write it up? Do the math and write it up yourself if you think it's reasonable. I honesty think it defeats the purpose (edit: of the ITS design).

The only thing it really adds is habitable volume. One craft has to rendezvous anyway, and it only takes what it can take (the crew, and the cargo it can deliver to Mars). So the end result on the surface is the same. A cycler only makes sense if the transit hab is a net mass savings, using the same craft is just a waste.  Ie: tiny crew delivery vehicle, large hab.

Instead of just requoting the same text wall, do the math and demonstrate the benefit. 

Edited October 1, 2016 by tater

[Northstar1989]

17 minutes ago, Nibb31 said:

Listen, he knows about cyclers, he has voiced his opinion on them several times, dating back to this article in 2012 at least:

http://www.space.com/18596-mars-colony-spacex-elon-musk.html

He knows what a cycler is. He's done the math. He is surrounded by a lot of smart people who have come up with a lot of smart plans. Cyclers are not part of those plans.

I don't know what else to tell you at this point. Take up the argument with him. I hear he's on Twitter a lot.

Fair enough.  It looks like Musk HAS seriously considered the idea of Cyclers.  Back in 2012 at least.  And he is correct that you need to make small changes in the orbital plane each cycler, or have roughly 18 different Cyclers at different inclinations and positions relative to the sun (with each reusable only about once every 30 years).  Obviously the plane-changes are the only feasible option early on...

I still think he might not be adequately accounting for the fact that you can roughly halve the per-seat cost to Mars with Cyclers.  A bit less if you need to reduce the capacity of the ITS design to add more fuel-tanks to provide Delta-V for plane-changes, but if you can re-use a Cycler even five times, and keep anything over 60% of the crew-capacity on the redesigned ITS, then you'll still end up with a lower cost-per-seat to Mars by the time you retire the Cycler...

 

Regards,

Northstar

Edited October 1, 2016 by Northstar1989

[Motokid600]

Question. The plan for radiation protection in transit is to just point the engines to the sun to put as much material as possible between the crew and the CME. I wish to confirm something I read talking with another fellow elsewhere. This guy was so adamant in saying that's NOT good enough he actually DID write to Musk. That the radiation from a CME essentially ricochets around the solar system. Planets get hit even if it isn't directly. That the radiation from a CME will come from ALL directions making a proper rad shelter a must have instead of just orienting the ship. Whats the deal here exactly?    Because this factors into and imo favors that cycler design where you COULD have that omni direction shelter.

Edited October 1, 2016 by Motokid600

[tater]

Solar radiation actually tends to spiral out in such an event, so it can certainly hit in a more complex way that direct LOS to the sun (conservation of angular momentum, basically, it's given a strong basically radial component, but it has a tangential velocity as well).

The general suggestion, even for something like the NASA DRA is to have a central location with stores around it. This is considerably more complex for 100 people than 6, however. 

[Motokid600]

6 minutes ago, tater said:

 

The general suggestion, even for something like the NASA DRA is to have a central location with stores around it. This is considerably more complex for 100 people than 6, however. 

And even more so with the currently designed ship. A cycler ship could essentially be one big shelter. Or be built in a fashion where 100 people could huddle in a central point.

 

 

 

Edited October 1, 2016 by Motokid600

[tater]

A cycler would not be all shelter, it would have to be massive for that. I think it's a risk/benefit analysis in the end.You try and mitigate what you can, but if nature decides to kill you it's like sailing into a hurricane back in the day.

[Nothalogh]

Arguing Cycler vs Interceptor is silly, each one is ideally suited for an entirely different task.

Cycler = High Volume, Low Priority cargo

Interceptor = High Priority, Low Volume cargo

 

It's Rail Freight vs FedEx

[Motokid600]

20 minutes ago, tater said:

A cycler would not be all shelter, it would have to be massive for that. I think it's a risk/benefit analysis in the end.You try and mitigate what you can, but if nature decides to kill you it's like sailing into a hurricane back in the day.

A cycler can be massive to an extent without the need of a giant propulsion system ( post-ejection that is ). The living quarters could be in the center and during emergencies people can retreat inward.  

15 minutes ago, Nothalogh said:

Arguing Cycler vs Interceptor is silly, each one is ideally suited for an entirely different task.

Cycler = High Volume, Low Priority cargo

Interceptor = High Priority, Low Volume cargo

 

It's Rail Freight vs FedEx

"Cycler = High Volume, Low Priority cargo" Is this not what's necessary for long term colonization?

Edited October 1, 2016 by Motokid600

[Northstar1989]

1 hour ago, tater said:

Why would someone else write it up? Do the math and write it up yourself if you think it's reasonable. I honesty think it defeats the purpose.

The only thing it really adds is habitable volume. One craft has to rendezvous anyway, and it only takes what it can take (the crew, and the cargo it can deliver to Mars). So the end result on the surface is the same. A cycler only makes sense if the transit hab is a net mass savings, using the same craft is just a waste.  Ie: tiny crew delivery vehicle, large hab.

Instead of just requoting the same text wall, do the math and demonstrate the benefit. 

Fair enough, let's run the numbers in greater detail, more explicitly, and this time with the assumption that you entirely remove the cargo capacity in order to provide the extra fuel tanks for the Cycler's plane-changes, but increase the crew complement a single Cycler ITS can sustain to 450 (each person requires about a ton of payload capacity) by greatly enlarging the crew quarters, removing the heatshield and landing legs from the Cycler variant, and the crew capacity of the Interceptor to 350 (you also remove all 350 tons of cargo from it), and can only re-use each Cycler and Interceptor 12 times.  Let's also say the marginal cost of each new ITS is $640 million, roughly based on Musk's presented figure of $140,000 a ton with 12 re-uses of the 450-ton payload capacity, 100-man, 350 tons cargo ITS he proposed, and it costs $10 million to refuel and refurbish the ITS each time it lands back on Earth, and refuel it again in LEO before TMI (the actual costs are lower, due to accounting for capital costs in the $140,000/ton figure, but I'll ignore that for now).

 

Ok, so launch-schedule with two ITS's, using one as a Cycler and the other as an Interceptor (and launching the Interceptor with double its sustainable crew-capacity) would look like this:

Transfer Window #1:

- Launch two ITS's, with 800 total people aboard (450 on Cycler, 350 on Interceptor).  Cost = $1280 million.  Payload = 800 people.

Transfer Windows #2-12

- Refurbish and refuel Interceptor.  Launch with 800 people (450 will be transferred to the Cycler after rendezvous with it) each launch.  Cost = $110 million.  Payload = 8800 people.

So, the total cost ends up being $1390 million to transport 9600 people to Mars.

 

Compare that to the baseline plan Musk recently proposed:

Transfer Window #1:

- Launch 8 ITS's, with 800 people aboard (100 on each ship), and 2800 total tons of cargo (350 on each ship).  Cost = $5120 million, Payload = 800 people, 1400 tons cargo.

Transfer Windows #2-12:

-Refurbish and refuel BOTH spacecraft.  Launch with 800 people, 2800 tons cargo each launch.  Cost = $880 million, Payload = 8800 people, 30800 tons cargo.

 

So, the total cost for the "traditional" plan ends up being $6000 million, to transport 9600 people and 33600 tons of cargo to Mars, vs. $1390 million for the Cycler design, which transports 9600 people and 0 tons of cargo to Mars.  That means you cut $4610 million off the cost, but lose 33600 tons of cargo capacity.  However you should be able to send cargo-only ITS's with a minimum of 450 tons of cargo each launch, and probably about 500 tons if you rely on a slower transfer-trajectory for cargo.

So, let's say you conduct a series of launches of cargo-only ITS's.  This should cost you about $750 million for each 12 launches ($640 million to build each ITS, $110 million to refuel and refurbish it each subsequent transfer-window), but place 6000 tons of cargo on the Martian surface over the 12-reuse lifetime of each ITS with a 500-ton capacity to Mars for each cargo-only mission.

Meaning you need 6 of them to place 36000 tons if cargo on the surface, at an additional cost of $4500 million.  So, you saved about $110 million (1.8%) on the cost of your mission, and sent 2400 (7.14% more) additional tons of cargo to the Martian surface.  These aren't exactly enormous margins vs. the plan Musk proposed, but it's a small improvement.

It does appear, however, that a Cycler ship design variant only makes sense if you strip ALL the cargo from the Interceptor and send it on slower cargo-only ITS's.  This is because the Cycler Ship only benefits the crew you can bring to Mars with each ITS, the cargo doesn't benefit in any way.  So, you will need to develop 3 closely-related variants of the ITS instead of one for a cost of under $110 million.

That's not a lot of money to play with for extra R&D, and less when you consider that over 24 years (the lifetime of each ITS, and time period over which you save $110 million- at a rate of $10 million each transfer-window after the first) any money you spend up front essentially accrues capital costs of around 5% a year- meaning you only ACTUALLY have around $50 million to play around with in extra R&D (compare that to an estimated $10 billion R&D budget for the ITS), and whatever you don't spend constitutes your actual cost-savings for using a Cycler Ship...

I'm starting to see why Musk wasn't interested in Cycler Ships-  apparently the cost-savings are MUCH less than I expected, and you have the extra hassle of needing to develop 3 different closely-related variants of the ITS right at the beginning for the plan to work at all...

 

Regards,

Northstar

Edited October 1, 2016 by Northstar1989

[Nothalogh]

Just now, Motokid600 said:

"Cycler = High Volume, Low Priority cargo" Is this not what's necessary for long term colonization?

Both are necessary

[Motokid600]

Just now, Nothalogh said:

Both are necessary

And the more I think of it both is what we may get. Hell musk said it himself they MAY go to a cycler system eventually. There are still some glaring issues with the design of the ITS though. Radiation protection, thermal management, the lack of gravity. All of which a purpose built cycler ship can cover. I like Northstar's idea of simply using abother ITS and that may be how it ends up, but I firmily believe that eventiually a dedicated ship(s) could be developed for greater capacity and safety.

[softweir]

3 hours ago, CatastrophicFailure said:

You really can't say this definitively, giving that no one has yet tried. 

You missed a point: the regolith is rich in perchlorate salts. We make bleach out of perchlorate salts. So the regolith is like soil soaked with bleach. Nobody needs to try growing potatoes in bleach-soaked-soil because we know it is damned toxic.

Maybe there is a way to extract the perchlorate salts from the regolith, but that would be a very water-consuming and energy-consuming exercise. And even if you succeeded, what is left is so short of everything plants need (nitrates, sulphates, phosphates and all the other nutrients) that you have to add all those, so why not make things easier and leave the regolith out of the equation? Why go to all that effort to import a toxic, caustic material into your base where it will be a serious health hazard?

[tater]

18 minutes ago, Motokid600 said:

A cycler can be massive to an extent without the need of a giant propulsion system ( post-ejection that is ). The living quarters could be in the center and during emergencies people can retreat inward.  

It still needs exactly the same propulsion system to get into its orbit that any other craft of the same mass would.

 

18 minutes ago, Motokid600 said:

"Cycler = High Volume, Low Priority cargo" Is this not what's necessary for long term colonization?

Such cargo doesn't even need people at all, so the cycler is entirely wasted in that case. Use ion propulsion, or a direct cargo variant (no LS at all, ir lands.

[Northstar1989]

25 minutes ago, tater said:

It still needs exactly the same propulsion system to get into its orbit that any other craft of the same mass would.

 

Such cargo doesn't even need people at all, so the cycler is entirely wasted in that case. Use ion propulsion, or a direct cargo variant (no LS at all, ir lands.

The Cycler needs a propulsion system to get into its LEO and its Cycler Orbit, but it doesn't need a very large one to make orbital adjustments (in fact an ion engine would probably work for this purpose).  So it starts to look A LOT more appealing if you developed a seperate reusable tug that could haul the Cycler into its Cycler Orbit and then detach and return to Earth orbit the next time its orbit swings back that way...

With an Interceptor-Cycler system, you only need a fraction of the normal propulsive-capacity for each crew member you carry to Mars.

For instance, if the Cycler and Interceptor were of roughly equal mass (because they were both designed to launch on the same booster), then you could have a single tug deliver the Cycler to its orbit unmanned, then seperate and perform a course-change to arrive back at Earth ahead of the Cycler, where it would refuel, pick up the Interceptor Ship, and bring the Interceptor to the Cycler when it made its Earth flyby.

This would mean that if, between the two of them, the Cycler and Interceptor ships packed twice as much mass as a standard ITS normally could, then you would only need a single tug between the two of them, instead of two tugs for an equivalent number of standard ITS's.

Of course, any proposal to utilize reusable tugs would probably work best if the Interceptor itself did not descend to the Martian surface, but instead relied on specialized landers to carry crew down to Mars.  That way you wouldn't need to worry about performing re-entry and propulsive landing with two craft only attached together via docking- which would pose some structural integrity problems...

It's worth noting that you would basically never have to dock or undock the tug with anything again after docking it with the Interceptor Ship.  So you could basically weld those two craft together if you wanted, even design the RCS system to be self-contained and detachable to save on deadweight on future missions, as the tug could very well remain attached to the Interceptor for the rest of its usable lifespan...

 

Regards,

Northstar

Edited October 1, 2016 by Northstar1989

[tater]

This is getting way OT for a space thread as they've said they are not interested in cyclers. Just throwing some water on this from the Elon POV, he also envisioned 1000 ITS leaving at once in that talk. At once. LOL.

The cycler needs to be identical to the regular vessel other than the small amount of dv needed for EDL at Mars. Assuming that it keeps it for corrections, then what do you get other than doubling the space, but with only the ability to take half of it to Mars?

An ITS needs to deliver 100 people, plus cargo. Sending 200 people and cargo for 100 doesn't cut it, and regardless, only the 1 ship of cargo can land, even if you cram people in for the short EDL part of the mission. So you've used 2 ships to get 2 shiploads of people to Mars. If they both landed, then you'd still get to reuse both of them, just at a different synod than it would be with Musk's plan now. I'm not seeing it as useful when the vehicles have any parity. If it required 5X the volume for an ITS full of people to be happy in transit, then maybe that makes sense, but 2X the people in 2X the volume... nope.