Author Topic: MCT Speculation and Discussion Thread 4  (Read 621820 times)

Offline guckyfan

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Re: MCT Speculation and Discussion Thread 4
« Reply #380 on: 08/17/2015 05:51 PM »
Minimum consumables requirements are something like:
–Water: 2 kg/person/day drinking + 0.2 kg/person/day for minimal washing. Probably more on long trips for better hygiene
–Oxygen: 0.8 kg/person/day for metabolic consumption (assumes exercise) + leaks + repressurization
–Nitrogen: mostly driven by leak rates, repressurization (e.g. for airlocks)
–Food: 1.8 kg/person/day (includes meal-level packaging) at ~380 kg/m3 density
–Be sure to account for both mass and volume

That's great. Sounds like my estimate of 2kg/person/day was very generous. Getting water and nitrogen from ISRU on Mars is a safe assumption. Also meal-level packaging would add a lot of unnecessary weight. For a long stay under gravity food can be stored in bulk. Maybe I should adjust my estimate from 2 kg to 1 kg for the duration of the surface stay.


Offline nadreck

Re: MCT Speculation and Discussion Thread 4
« Reply #381 on: 08/17/2015 06:16 PM »
Minimum consumables requirements are something like:
–Water: 2 kg/person/day drinking + 0.2 kg/person/day for minimal washing. Probably more on long trips for better hygiene
–Oxygen: 0.8 kg/person/day for metabolic consumption (assumes exercise) + leaks + repressurization
–Nitrogen: mostly driven by leak rates, repressurization (e.g. for airlocks)
–Food: 1.8 kg/person/day (includes meal-level packaging) at ~380 kg/m3 density
–Be sure to account for both mass and volume

That's great. Sounds like my estimate of 2kg/person/day was very generous. Getting water and nitrogen from ISRU on Mars is a safe assumption. Also meal-level packaging would add a lot of unnecessary weight. For a long stay under gravity food can be stored in bulk. Maybe I should adjust my estimate from 2 kg to 1 kg for the duration of the surface stay.

The question is what provisions for systems failures do you make?

I think it is credible to have a large water, oxygen and food store in the early settlement stages, and plenty of margin on any exploratory expeditions to remote locations the evacuation might be delayed in the case of some sort of system failure. However, at an early settlement, I believe if there were 3 sources of water (ISRU, recycled from air from what we exhale, recycled waste) and that each of those systems was redundant and repairable then water supply storage does not need to stretch beyond a safety margin for the settlement and whatever stores need to be sent with a return craft, stock the evacuation craft, go out on missions, and feed propellant manufacture and agricultural activity.

Oxygen, very similar, there will need to be a couple of processes to generate it anyway (there will be excess from propellant manufacture for example) so as long as there is redundant capacity to generate, the margins needed for potential systems outages and flushing/rebooting the habitats a couple of times and of course any ammounts needed to be sent with exploration craft, return craft or maintaining the stock on evacuation craft.

Nitrogen would definitely need to have some storage, and needs to be produced as a supplement to agricultural activity, so here I would suggest a substantial reserve based on the need to reboot agriculture after a disaster as well as whatever atmospheric needs are in the habitats.  Nitrogen will probably only have one type of system for ISRU based on the small percentage in the atmosphere and this might actually be a more vulnerable commodity than any of the others mentioned so far to an outage. However less of it needs to be stored for a return craft, expedition or evacuation craft.

Food, well there is one that is more of an issue. Going from zero to hero in the self-supporting food department, will take a long time for a settlement, and must as an ultimate goal be aimed to produce packaged, preserved food that can be used on expeditions, return craft, evacuation craft. So reliance on some imported food elements will exist for many synods even if the basics are provided locally. Agricultural systems will need to be redundant and as they are power intense there is the most potential for downtime from a disaster, needing reboot after a plant disease related flushing so food production and storage will only offset needs from stored imported foods partially and therefore it will be relatively easy to see large stores of food that could keep the incumbent population alive for several years always present in the major settlements even as the populations and safety levels go beyond the strict need for it.
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Offline RonM

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Re: MCT Speculation and Discussion Thread 4
« Reply #382 on: 08/17/2015 06:19 PM »
Minimum consumables requirements are something like:
–Water: 2 kg/person/day drinking + 0.2 kg/person/day for minimal washing. Probably more on long trips for better hygiene
–Oxygen: 0.8 kg/person/day for metabolic consumption (assumes exercise) + leaks + repressurization
–Nitrogen: mostly driven by leak rates, repressurization (e.g. for airlocks)
–Food: 1.8 kg/person/day (includes meal-level packaging) at ~380 kg/m3 density
–Be sure to account for both mass and volume

That's great. Sounds like my estimate of 2kg/person/day was very generous. Getting water and nitrogen from ISRU on Mars is a safe assumption. Also meal-level packaging would add a lot of unnecessary weight. For a long stay under gravity food can be stored in bulk. Maybe I should adjust my estimate from 2 kg to 1 kg for the duration of the surface stay.

That sounds reasonable. If water isn't a concern, many long-term food storage items are highly dehydrated. That plus the reduced packaging due to bulk storage should make it take up less mass. Some freeze-dried foods have a 25 year shelf life.

A single serving of a freeze-dried entree is about 53g, without packaging.

If you have ever had a LRP or freeze-dried meals for hiking, you know they make an MRE look like a gourmet meal. However, it beats starving. But you have to a reliable water supply or it's like eating salty sand and gravel.

Hopefully, the crew wouldn't have to resort to the emergency rations.

Offline nadreck

Re: MCT Speculation and Discussion Thread 4
« Reply #383 on: 08/17/2015 07:41 PM »

If you have ever had a LRP or freeze-dried meals for hiking, you know they make an MRE look like a gourmet meal. However, it beats starving. But you have to a reliable water supply or it's like eating salty sand and gravel.

Hopefully, the crew wouldn't have to resort to the emergency rations.

Actually, I am a back packer and a couple of times on longer trips I dehydrated a few ingredients to make better meals (my friends and I often do a 'meal plan' where each person is assigned a set number of meals to provide for all so that we can benefit from economies of scale at each meal) and I would make soups and pasta sauces that way. After a couple of trips with things like linguine with clam sauce and chicken mushroom soup, my friends pitched in and bought me a dehydrator and I managed to make a lot more variety of really good meals.

My points are that: dehydrated foods don't have to be terrible even if the packaged stuff made for back packers is less than ideal; given the cost of shipping foods from the emergency stores should be eaten before they deteriorate and replaced with new; locally produced food should as soon as possible be packaged for long term storage and eventually even exported.

Note one of the non edible products that early Mars agriculture needs to address is growing feed stocks for cellophane and the coating to make it non permeable to water vapor.
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Offline Impaler

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Re: MCT Speculation and Discussion Thread 4
« Reply #384 on: 08/17/2015 08:34 PM »
ISRU dose almost nothing to reduce consumables because our consumable budget is dominated by PROCESSED FOOD AND SPARE EQUIPMENT.  Not water, nitrogen or any simple elements that could be collected from Mars air or soil.


If you people would read the literature on the current state of the art ECLSS (http://sites.nationalacademies.org/cs/groups/depssite/documents/webpage/deps_063596.pdf) before shooting from the hip you would see that water needs are only 0.25 kg per person day.  The water closure problem is almost a solved problem (the new Pyrolysis process being added now to the ISS to combine methane and CO2 will likely give us the last bit of closure needed).  Some of you are talking about stored OXYGEN like you were reading  Buck Rogers pulp-sci-fi paperbacks from the 50's, we haven't used stored oxygen for breathing since Apollo, all oxygen has been provided by electrolysis of condensed water vapor for decades now, please get with the times.

The total for physiological maintenance of crew comes out to 2.2 kg per person day and while it might be possible to greatly reduce this it would involve things like a completely closed loop agriculture system, clothing that can be worn for weeks without washing, human waste incineration and recycling, the ability to both manufacture and recycle all paper and packaging materials.  In other words very advanced stuff that might be part of a permanent base but that you won't see on the very first manned landing of 4-6 people which is the context in which Vultur proposed just sending 'more supplies' rather then actually having a safe return option.

And again SPARE PARTS are the killer because you have to maintain the machines as well as the people, MIT estimated the need at 3.5 - 4.6 kg per person day (depending on if the food system is open or closed respectively)  for the Mars One concept which is based current state of the art.  So again I reiterate 5 kg is optimistic when you look at the total picture.  Thus trying to simply bring masses of supplies for a crew to say an additional synod or two if they can't return to Earth is a terrible misallocation, the mass would be much better spent on the systems to ensure they actually get back to Earth on time.
« Last Edit: 08/17/2015 08:47 PM by Impaler »

Offline nadreck

Re: MCT Speculation and Discussion Thread 4
« Reply #385 on: 08/17/2015 09:02 PM »
Why do you dismiss 3D printing as a primary source of spare parts?
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Offline guckyfan

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Re: MCT Speculation and Discussion Thread 4
« Reply #386 on: 08/17/2015 09:12 PM »
Why do you dismiss 3D printing as a primary source of spare parts?

To be honest I would dismiss it for the moment too. However the food assumed by Impaler does not take into account bulk packing as we did. Also I don't see it as a valid assumption that an ECLSS completely new designed for MCT with all knowledge and experience available will need the same amount of spare parts as the present ISS systems do. It will be designed to be more robust and needing less spares. ECLSS on Mars is another item again. It is not part of what we discuss as consumables. It will be designed for Mars with completely different methods, mostly biological. More volume, more initial weight but more efficient to run for a long time.

Offline nadreck

Re: MCT Speculation and Discussion Thread 4
« Reply #387 on: 08/17/2015 09:52 PM »
Why do you dismiss 3D printing as a primary source of spare parts?

To be honest I would dismiss it for the moment too. However the food assumed by Impaler does not take into account bulk packing as we did. Also I don't see it as a valid assumption that an ECLSS completely new designed for MCT with all knowledge and experience available will need the same amount of spare parts as the present ISS systems do. It will be designed to be more robust and needing less spares. ECLSS on Mars is another item again. It is not part of what we discuss as consumables. It will be designed for Mars with completely different methods, mostly biological. More volume, more initial weight but more efficient to run for a long time.

Well if it is designed between now and when they start launching, I think it will be designed with 3D printable spares in mind.

One thing we haven't discussed is CO2 scrubbing and parts/consumables there.

Oh and as important as food is going to be, I think growing fiber for clothing and other non-edible things will be important too.
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Offline Impaler

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Re: MCT Speculation and Discussion Thread 4
« Reply #388 on: 08/17/2015 11:46 PM »
Why do you dismiss 3D printing as a primary source of spare parts?

Because I come from a family that has been in the tool-and-die, plastic injection molding and quality control industries for 3 generations, we know that these additive processes complement but do not replace traditional manufacturing processes.

Furthermore the reactions happening in most ECLSS equipment are high temperature and energy chemistry, that means metal and ceramic vessels, valves and catalysts, they can not be replaced with plastic widgets.

While their is some limited potential for packaging materials to be a source of plastic feed-stocks as soon as you start talking about metallic part printing your looking at bring large amounts of metallic feed-stock, and large amounts of secondary equipment for finishing, measuring and testing the parts created.

In summary 3D printing is not a Star Trek Replicator.

Offline nadreck

Re: MCT Speculation and Discussion Thread 4
« Reply #389 on: 08/18/2015 12:02 AM »
Why do you dismiss 3D printing as a primary source of spare parts?

Because I come from a family that has been in the tool-and-die, plastic injection molding and quality control industries for 3 generations, we know that these additive processes complement but do not replace traditional manufacturing processes.

Furthermore the reactions happening in most ECLSS equipment are high temperature and energy chemistry, that means metal and ceramic vessels, valves and catalysts, they can not be replaced with plastic widgets.

While their is some limited potential for packaging materials to be a source of plastic feed-stocks as soon as you start talking about metallic part printing your looking at bring large amounts of metallic feed-stock, and large amounts of secondary equipment for finishing, measuring and testing the parts created.

In summary 3D printing is not a Star Trek Replicator.

I believe rather than plastic it will be a material that can be produced on Mars (there are some cellulose additive manufacturing efforts going on right now) and definitely metal, and probably ceramic. If you design the equipment with the intent for having the vast majority of replaceable parts with what can be produced with relative ease then there is a small subset of parts that require unique materials or production techniques that can't be made locally and those will have to have spares on hand to last until replacements can be ordered and delivered from Earth.  Metal is not impossible today, nor is ceramic, the possibilities in the next 5 years are immense considering how far additive manufacturing has come so far. For the first wave though the cut off is likely going to be where additive manufacturing is by 2020 to have ECLSS equipment designed and built by the 2025 launch window. But it isn't just ECLSS, it is every system that will be used in a settlement that needs to be optimized for locally sourced spares.
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Offline Vultur

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Re: MCT Speculation and Discussion Thread 4
« Reply #390 on: 08/18/2015 02:13 AM »
I don't think food production via agriculture need be either complex/difficult or especially fragile.

Agricultural systems will need to be redundant and as they are power intense there is the most potential for downtime from a disaster, needing reboot after a plant disease related flushing

Why power intense? Mars gets sufficient sunlight for plant growth -- probably more than, say, the Pacific Northwest temperate rainforests or England (due to clouds) which are both rather lush.

It should be rather simple to eliminate all plant diseases by not bringing them from Earth. Even if this fails, plant disease doesn't usually mean complete collapse of the system, as you'd have multiple species.

Offline Impaler

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Re: MCT Speculation and Discussion Thread 4
« Reply #391 on: 08/18/2015 02:14 AM »
Your saying an entire mining industry needs to be established to support manufacturing of spare parts, to keep the ECLSS running to keep the FIRST LANDING of 4-6 astronauts alive for multiple synods so we can postpone having to figure out how to do a return trip???

Did you not pay attention to the original premise of this tangent?  I have been talking this ENTIRE time about initial landings of small numbers for exploratory purposes, you seem to be talking about Blue Mars level end-state total self sufficiency a century from now.  Your scale and time range are so out of step with what I'm talking about it's like talking about how the James town settlers will will generate electricity.

Offline Vultur

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Re: MCT Speculation and Discussion Thread 4
« Reply #392 on: 08/18/2015 02:20 AM »
MCT is not part of some MarsOne no-return suicide pact,

-MCT will definitely return (Musk said to reuse the spacecraft if nothing else) but given its expected size and payload capacity I see no reason why the first crew wouldn't intend to stay permanently.


(And "Mars to Stay" plans aren't inherently suicidal. Risky, but not insanely so, and they actually make a lot of sense given a limited-per-year budget).


Quote
Even once a base is established people will rotate in and out for a long time before anyone even thinks about settling permanently.  A return option MUST exist at the time the first person sets foot on Mars.

Based upon what?


You have no idea what your talking about.  If you have some notion of canned or frozen food then you've completely blown the mass budget on the food alone as that would be ~75% water, the only practical way to send food is dry and that reduces it's self-life,

What about freeze-dried, vacuum-packed?

Quote
You know nothing about ECLSS is you think 5 kg a day is zero recycling,

5 kg number doesn't include spares or anything else mechanical, it's food+water+oxygen use.

Quote
The MarsOne nonsense got shot down by MIT for exactly the same failure to consider spares.

I wouldn't use that paper as a source, given that it assumed a wheat/soy based agriculture system which is a terrible choice when space is a constraint.

Offline nadreck

Re: MCT Speculation and Discussion Thread 4
« Reply #393 on: 08/18/2015 05:53 AM »
I don't think food production via agriculture need be either complex/difficult or especially fragile.

Agricultural systems will need to be redundant and as they are power intense there is the most potential for downtime from a disaster, needing reboot after a plant disease related flushing

Why power intense? Mars gets sufficient sunlight for plant growth -- probably more than, say, the Pacific Northwest temperate rainforests or England (due to clouds) which are both rather lush.

It should be rather simple to eliminate all plant diseases by not bringing them from Earth. Even if this fails, plant disease doesn't usually mean complete collapse of the system, as you'd have multiple species.

You know microbes and virus mutate, something in human intestinal flora and fauna might mutate and become a pathogen to the plants. Or anything else that gets there.

If you are doing hydro or Aero 'ponics you have a fair bit of energy in the system, artificial light will be more, if you don't want radiation to require potential resets to the growing environment, and if you want to not rely on always going back to unmutated seed stock you need your growing getting its light indirectly being radiation shielded from the light and the incident cosmic rays. So underground, artificially lit, recirculation systems, filters, pumps it is all energy intensive.

Maximum credible disaster is that the growing environment needs to be flushed and reset. Lets provision for it. Not a big deal but pretending it might not be necessary is foolhardy.

Same thing with whatever the largest pressurized area is. Presume you might need to maintain pressure during a leak, presume it might completely depressurize and need to be repressurized.


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Offline nadreck

Re: MCT Speculation and Discussion Thread 4
« Reply #394 on: 08/18/2015 05:59 AM »
Your saying an entire mining industry needs to be established to support manufacturing of spare parts, to keep the ECLSS running to keep the FIRST LANDING of 4-6 astronauts alive for multiple synods so we can postpone having to figure out how to do a return trip???
I am presuming 10 - 20 on the first expedition. I expect human exploration to branch out from the first landing site in the first synod by rover, maybe the 2nd, or 3rd synod will bring secondary settlements, Also by the 3rd synod the equipment to travel to other locations via high inclination orbit to refuel at a depot then land at any point on Mars and take off again to land at one of the settlements with propellant ISRU. At that point real exploration starts to happen, and by then the population is around 50 with maybe 20 or so of the people who had travelled to Mars having returned.

By the 10th synod of human occpuation maybe the population is up over 500 and 100 passenger MCT's start to arrive.
Did you not pay attention to the original premise of this tangent?  I have been talking this ENTIRE time about initial landings of small numbers for exploratory purposes, you seem to be talking about Blue Mars level end-state total self sufficiency a century from now.  Your scale and time range are so out of step with what I'm talking about it's like talking about how the James town settlers will will generate electricity.
And I have been pointing out for almost as long that this is a thread about MCT and that is not about a few boots and flags - it is about settling Mars from the get go.
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Offline Impaler

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Re: MCT Speculation and Discussion Thread 4
« Reply #395 on: 08/18/2015 06:44 AM »
You seem to be throwing your lot in with Vultur and the MarsOne nonsense of immediate colonization from the first footprint.  This is not going to happen, it's like saying that Neil Armstrong should have colonized the moon rather then coming back.

Any logical sequence would consist of first exploratory scouting missions, followed by outposts with personnel cycling in and out and then finally a permanent settlement once lots of infrastructure is built up and optimum sites are found.

Offline guckyfan

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Re: MCT Speculation and Discussion Thread 4
« Reply #396 on: 08/18/2015 06:58 AM »
Any logical sequence would consist of first exploratory scouting missions, followed by outposts with personnel cycling in and out and then finally a permanent settlement once lots of infrastructure is built up and optimum sites are found.

It seems you don't comprehend what the availability of a transport system for 100t payload combined with abundant local resources like water, CO2 and nitrogen means. Especially combined with the aim for colonizing driving development.

I am absolutely convinced that beginning with the first landing there will be a permanent presence. Some will go back after 2 years, some will stay longer, some may stay for the rest of their lives.

Offline nadreck

Re: MCT Speculation and Discussion Thread 4
« Reply #397 on: 08/18/2015 02:36 PM »
You seem to be throwing your lot in with Vultur and the MarsOne nonsense of immediate colonization from the first footprint.  This is not going to happen, it's like saying that Neil Armstrong should have colonized the moon rather then coming back.

No I am saying what I believe is the intent of use of MCT. We have many threads discussing other Mars mission styles, and while I would be very sad if we just did an Apollo style sortie on Mars, that is the context of many of those threads (we also have specific threads to discuss agriculture, aspects of ISRU whose context implies longer term missions).


Any logical sequence would consist of first exploratory scouting missions, followed by outposts with personnel cycling in and out and then finally a permanent settlement once lots of infrastructure is built up and optimum sites are found.

And here we can agree to disagree, my best case scenario for the economics of exploring Mars includes settling Mars.  Some surveying will happen by unmanned probes (and effectively that has already started), and the first settlement may not end up being the epicentre of Martian colonization, but it will provide the base to start really exploring Mars from. The one alternative I can see is if we do ISRU on Phobos or Deimos and supply many manned sorties to the surface of Mars before building the first settlements. This would still involve a permanent presence and the one reason I don't really elaborate on it here is the idea that it doesn't work all that well with the MCT model driving Mars settlement.

As for people cycling in and out, of course they will, but not everyone. A high percentage of the first few hundred people to visit Mars will be scientists and explorers supporting them, some colonists but chosen for their ability to build settlements and the needed infrastructure and not operate it. But of the first few hundred people to go my bet is that some of them would have gone intending to stay but end up returning to Earth, and some will have gone intending to return to Earth but stay instead.
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Offline guckyfan

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Re: MCT Speculation and Discussion Thread 4
« Reply #398 on: 08/18/2015 02:59 PM »
The one alternative I can see is if we do ISRU on Phobos or Deimos and supply many manned sorties to the surface of Mars before building the first settlements. This would still involve a permanent presence and the one reason I don't really elaborate on it here is the idea that it doesn't work all that well with the MCT model driving Mars settlement.

This may or may not warrant an extended discussion. I do like that idea as I was always thinking of fuel ISRU at Phobos or Deimos. Do we know if MCT would be able to land with  enough fuel to lift off again? It probably should not be much heavier than on a normal landing with 100t supplies. So with minimal life support for a small crew and very little cargo to maximise fuel. Still seems not enough with less than 100t to lift off and reach Phobos. Maybe entry from orbit at lower speed allows for some more payload.

Offline Nilof

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Re: MCT Speculation and Discussion Thread 4
« Reply #399 on: 08/18/2015 03:44 PM »
New info from Musk about the Raptor and MCT(and sorry about the crossposting):

Quote from: Elon Musk
Yeah, these are seemingly absurd percentage improvements, however not impossible. The critical elements of the solution are rocket reusability and low cost propellant (CH4 and O2 at an O/F ratio of ~3.8 ). And, of course, making the return propellant on Mars, which has a handy CO2 atmosphere and lots of H2O frozen in the soil.

The design goal is technically 100+ metric tons of useful cargo per flight, so maybe more than 100 people can be taken. Depends on how much support mass is needed per person and the luggage allowable.

Avionics, sensors, communications, aspects of vehicle structure, landing pads and a few other things get better with scale, plus it is more fun to be on a cruise ship than a bus, so I suspect that the 100 people per flight number grows a lot over time, maybe to several hundred. Also, we could subsidize the equivalent of economy by charging a lot more for first class.

Factor in all of the above and getting below $100k/ton or person eventually is conceivable, as the trip cost is then dominated by propellant, which is mostly liquid oxygen at a mere $40/ton (although a lot of it is needed per useful ton of cargo). That would be really awesome!

Looks like the Raptor will run oxidizer rich. That puts its niche even closer to the BE-4.
« Last Edit: 08/18/2015 03:47 PM by Nilof »
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

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