Author Topic: Battle of the architectures- BFR v Mars Cycler  (Read 24870 times)

Offline SteveKelsey

I am sure this has been debated a lot on this site but the topic keeps coming up in replies to another thread so I thought I should start a specific thread on the debate- which architecture is better for mass colonisation- the BFR architecture being built by SpaceX or the Mars cycler approach.

In the Crimson corner is the BFR- reusable spacecraft that launch from Earth and return to Earth repeatedly with an Earth booster stage to cope with the Earths gravity well.

In the Scarlet corner the Mars Cycler, a big zero-G ship assembled in orbit served by shuttles.

My belief, to be challenged and corrected, is that the complexity of the Mars cycler architecture will always lose out to the simplicity of the BFR approach on economic grounds, but that just me.  :)

 
« Last Edit: 11/28/2018 09:35 am by SteveKelsey »
2001 is running a little late, but we are getting there.

Offline Russel

  • Full Member
  • ****
  • Posts: 1083
  • Liked: 122
  • Likes Given: 4
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #1 on: 11/28/2018 09:37 am »
Can it be BFR/BFS v Mars Cycler v Something Altogether More Pragmatic and Sensible

?

:)

Offline SteveKelsey

Re: Battle of the architectures- BFR v Mars Cycler
« Reply #2 on: 11/28/2018 10:01 am »
Help yourself Russel  :)
2001 is running a little late, but we are getting there.

Offline TripleSeven

  • Full Member
  • ****
  • Posts: 1145
  • Istanbul Turkey and Santa Fe TEXAS USA
  • Liked: 588
  • Likes Given: 2095
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #3 on: 11/28/2018 10:27 am »
I am sure this has been debated a lot on this site but the topic keeps coming up in replies to another thread so I thought I should start a specific thread on the debate- which architecture is better for mass colonisation- the BFR architecture being built by SpaceX or the Mars cycler approach.

In the Crimson corner is the BFR- reusable spacecraft that launch from Earth and return to Earth repeatedly with an Earth booster stage to cope with the Earths gravity well.

In the Scarlet corner the Mars Cycler, a big zero-G ship assembled in orbit served by shuttles.

My belief, to be challenged and corrected, is that the complexity of the Mars cycler architecture will always lose out to the simplicity of the BFR approach on economic grounds, but that just me.  :)

Since we are speculating here...in my view the Mars Cycler is the system that eventually in a lot of years that humanity (or the US and western powers) will settle on to do a Mars science program.

Three reasons in no particular order

1.  Its unclear to me that a Mars science program has or will be based on Mars.  Mars has two natural space stations which have enormous advantages in terms of exploring Mars with both Robots and humans.  Its not clear to me that a base on Mars in the early (first twenty years) stages is a good thing in terms of exploring the entire planet.  Particularly if either or both of the moons end up having water on them

2.  Cycler ships will probably have some sort of artificial gravity ...and my belief is that this will be essential for keeping the folks who are going to Mars in usable shape.

3.  Ships that can take off from earth, refuel, go to Mars, land, take off go back to EArth are going to be very complicated...and not have shapes ideal for interplanetary travel...the configs will mostly be governed by the entry phases.
Ones mileage may vary. 

Offline Lampyridae

  • Veteran
  • Senior Member
  • *****
  • Posts: 2641
  • South Africa
  • Liked: 949
  • Likes Given: 2056
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #4 on: 11/28/2018 10:32 am »
Basically to make a cycler passenger service work, you need something that can quickly convey passengers and have some kind of way to get to Mars if something goes wrong. In other words a BFR.

I can see a cycler that's basically a flying hotel resort that merely provides legroom, artificial gravity and radiation shielding for BFR passengers.

But you can get these things with multiple BFRs flying together.
« Last Edit: 11/28/2018 10:33 am by Lampyridae »

Offline TripleSeven

  • Full Member
  • ****
  • Posts: 1145
  • Istanbul Turkey and Santa Fe TEXAS USA
  • Liked: 588
  • Likes Given: 2095
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #5 on: 11/28/2018 10:38 am »
Basically to make a cycler passenger service work, you need something that can quickly convey passengers and have some kind of way to get to Mars if something goes wrong. In other words a BFR.

I can see a cycler that's basically a flying hotel resort that merely provides legroom, artificial gravity and radiation shielding for BFR passengers.

But you can get these things with multiple BFRs flying together.

What you need in my view is redundancy in the Cycler to allow maintenance on it if something breaks or is disabled.  I dont have the exact number of years ISS has been crewed, but for all the talk about assurred return since it was perm crewed there has never been any real talk toward abandoning it for a technical problem...and it's unclear to me that there ever will.  The vehicle has enough (and it should have more but ...) redundancy to allow damaged sections to be closed off and "fixes worked".  A Cycler would certainly have more of all that...and all you really need is a vehicle which can ""jump on" and off...the jump off would mostly be aero braking...and the jump on is just solid propulsion...

But the key points for me at least is that you have gravity to push back the ill effects of no g...a lot of radiation shielding and a lot of power.  At worst in my view you would need two Cyclers...

Offline hkultala

  • Full Member
  • ****
  • Posts: 1199
  • Liked: 748
  • Likes Given: 945
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #6 on: 11/28/2018 10:47 am »
I am sure this has been debated a lot on this site but the topic keeps coming up in replies to another thread so I thought I should start a specific thread on the debate- which architecture is better for mass colonisation- the BFR architecture being built by SpaceX or the Mars cycler approach.

In the Crimson corner is the BFR- reusable spacecraft that launch from Earth and return to Earth repeatedly with an Earth booster stage to cope with the Earths gravity well.

In the Scarlet corner the Mars Cycler, a big zero-G ship assembled in orbit served by shuttles.

My belief, to be challenged and corrected, is that the complexity of the Mars cycler architecture will always lose out to the simplicity of the BFR approach on economic grounds, but that just me.  :)

Since we are speculating here...in my view the Mars Cycler is the system that eventually in a lot of years that humanity (or the US and western powers) will settle on to do a Mars science program.

Three reasons in no particular order

1.  Its unclear to me that a Mars science program has or will be based on Mars.  Mars has two natural space stations which have enormous advantages in terms of exploring Mars with both Robots and humans.  Its not clear to me that a base on Mars in the early (first twenty years) stages is a good thing in terms of exploring the entire planet.  Particularly if either or both of the moons end up having water on them

Even when doing to these moons, atmospheric-capable ship can aerobrake on mars atmosphere while pure vacuum ship cannot.

Quote
2.  Cycler ships will probably have some sort of artificial gravity ...and my belief is that this will be essential for keeping the folks who are going to Mars in usable shape.

Two atmospheric-capable ships can be tethered together for artificial gravity.

Quote
3.  Ships that can take off from earth, refuel, go to Mars, land, take off go back to EArth are going to be very complicated...and not have shapes ideal for interplanetary travel...the configs will mostly be governed by the entry phases.
Ones mileage may vary.

Building a ship from parts in orbit is much more complicated. Look at the "project troy" plans of reaction engines. They first need to build an orbital factory until they can even start building the craft itself.

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.679.3415&rep=rep1&type=pdf


Offline su27k

  • Senior Member
  • *****
  • Posts: 6414
  • Liked: 9100
  • Likes Given: 885
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #7 on: 11/28/2018 10:57 am »
Purdue University AAE 450 Project Destiny basically did this: A comparison of Mars colonization using ITS direct vs cycler (built using Bigelow modules, launched and assembled by cargo ITS, transport to/from cycler is also using specialized ITS ship). The conclusion is cycler is about 3.5x the cost of ITS direct.

Offline TripleSeven

  • Full Member
  • ****
  • Posts: 1145
  • Istanbul Turkey and Santa Fe TEXAS USA
  • Liked: 588
  • Likes Given: 2095
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #8 on: 11/28/2018 11:01 am »
I am sure this has been debated a lot on this site but the topic keeps coming up in replies to another thread so I thought I should start a specific thread on the debate- which architecture is better for mass colonisation- the BFR architecture being built by SpaceX or the Mars cycler approach.

In the Crimson corner is the BFR- reusable spacecraft that launch from Earth and return to Earth repeatedly with an Earth booster stage to cope with the Earths gravity well.

In the Scarlet corner the Mars Cycler, a big zero-G ship assembled in orbit served by shuttles.

My belief, to be challenged and corrected, is that the complexity of the Mars cycler architecture will always lose out to the simplicity of the BFR approach on economic grounds, but that just me.  :)

Since we are speculating here...in my view the Mars Cycler is the system that eventually in a lot of years that humanity (or the US and western powers) will settle on to do a Mars science program.

Three reasons in no particular order

1.  Its unclear to me that a Mars science program has or will be based on Mars.  Mars has two natural space stations which have enormous advantages in terms of exploring Mars with both Robots and humans.  Its not clear to me that a base on Mars in the early (first twenty years) stages is a good thing in terms of exploring the entire planet.  Particularly if either or both of the moons end up having water on them

Even when doing to these moons, atmospheric-capable ship can aerobrake on mars atmosphere while pure vacuum ship cannot.

Quote
2.  Cycler ships will probably have some sort of artificial gravity ...and my belief is that this will be essential for keeping the folks who are going to Mars in usable shape.

Two atmospheric-capable ships can be tethered together for artificial gravity.

Quote
3.  Ships that can take off from earth, refuel, go to Mars, land, take off go back to EArth are going to be very complicated...and not have shapes ideal for interplanetary travel...the configs will mostly be governed by the entry phases.
Ones mileage may vary.

Building a ship from parts in orbit is much more complicated. Look at the "project troy" plans of reaction engines. They first need to build an orbital factory until they can even start building the craft itself.

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.679.3415&rep=rep1&type=pdf

Sorry I am on my I pad so its harder to just do the quote answer thing

I would just say this.  What you said about atmospheric ships is accurate...but in the long run they are far from optimium for sustained inter planetary travel in terms of space, interconnectivity, power etc.  its my view based on the dynamics that I think are likely for "Mars operation" (and this would be true for Venus ops as well ie the sky cloud concepts) that 1) there will be repeated traffic between EArth and X during the launch windows, 2) there will be as many people coming and going and 3) the travel time will prove more limiting in terms of health and "sanity" than the stay time (2-4 years) on the planet or in its atmosphere.  The Cycler system can be "larger" and in my view more functional for that specific task. 

And as I noted I think that the two moons are going to play a large role in the planets (at least Mars) exploration and trying to figure out where to put the first perm base on the planet...ie robots are going to visit a lot of places before the choice is made, and people will visit a lot (but less than the robots) places as well ...all in short duration stays

As for space construction.  ISS has proved that works really well..and robots will in the future make it even easier. 

There is no right or wrong answer to this, its all opinion. 

The Moon in my view is kind of different...travel times are very short...what is going to be interesting there is to see what system evolves for exploring it...both for humans and robots.  A Cycler would not be needed because of the travel time issue.  The question is however in my view...issomekind of station needed as an initial point?  My guess is no.

Offline TripleSeven

  • Full Member
  • ****
  • Posts: 1145
  • Istanbul Turkey and Santa Fe TEXAS USA
  • Liked: 588
  • Likes Given: 2095
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #9 on: 11/28/2018 11:04 am »
Purdue University AAE 450 Project Destiny basically did this: A comparison of Mars colonization using ITS direct vs cycler (built using Bigelow modules, launched and assembled by cargo ITS, transport to/from cycler is also using specialized ITS ship). The conclusion is cycler is about 3.5x the cost of ITS direct.

I might quibble with the number but no doubt it is more expensive.  It is also more robuts inmy view

Offline SteveKelsey

2001 is running a little late, but we are getting there.

Offline Lampyridae

  • Veteran
  • Senior Member
  • *****
  • Posts: 2641
  • South Africa
  • Liked: 949
  • Likes Given: 2056
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #11 on: 11/28/2018 12:22 pm »
https://engineering.purdue.edu/AAECourses/aae450/2017/spring/docs/AAE%20450-Project%20Destiny.pdf


Ah thank you, I had forgotten the link for this. An informative study.

Also, the study found the need for Mars direct flights in order to bring ticket prices down to $200 000pp. This was for the old 12m ITS though, and required huge numbers of flights. But I don't think this is necessarily the right conclusion. For a start, they are assuming one-per-ITS cyclers built with BA-330 and XL modules. Fair enough. But they were using 3 nuclear reactors each, at a cost of $4 billion out of the $18 billion per cycler.

At some point it simply becomes easier to keep your interplanetary habitats interplanetary and just using the BFR's enormous lift capacity to lift people instead of the same habitat space again and again. With 10 000 people per synod, you would wind up with small space-going resort cities.

Heck you could use the return capacity of the BFRs to make a cycler out of Martian resources, seeing as you've also got capacity to make habitats. Cyclers are also literally moveable assets. Brake one into cislunar space to serve as a gateway station / tourist trap, have some regularly visiting Venus (a good candidate), send them to the asteroid belt, Jupiter and so on.
« Last Edit: 11/28/2018 01:05 pm by Lampyridae »

Offline spacenut

  • Senior Member
  • *****
  • Posts: 5181
  • East Alabama
  • Liked: 2587
  • Likes Given: 2895
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #12 on: 11/28/2018 01:46 pm »
Mars cycler will be like a trans-Atlantic cruise ship.  BFS (Starship) will be the 747.  Which one won out over time.  Cyclers will take what?, about 9 months every time.  Starship will transit during the synods when Mars is closest to earth cutting time in transit.  Cycler will require a transport to and from the cycler adding a little more time and complexity. 

Cyclers will be great if they are built large enough to provide artificial gravity in route.  However two starships could dock and spin on the way to Mars and creating some partial gravity. 

Offline SteveKelsey

Re: Battle of the architectures- BFR v Mars Cycler
« Reply #13 on: 11/28/2018 02:42 pm »
I have a number of questions regarding the study as well but must caveat those heavily in that the degree of expertise that went into the study far outstrips mine.

However, we are in the final analysis considering a mass transportation system. It may be a challenging one, but those challenges do not remove the learns from mass transportation where scale and simplicity of operation  reduce costs.

 My concerns regarding the cycler architecture are.

The cycler must maintain a high velocity to avoid the burden of deceleration and acceleration at Earth or Mars orbit. A shuttle therefore has to match this velocity at both ends of the trip not just attain LEO. It seems an extravagant use of fuel and demands a high performance from the shuttle, in fact it demands a BFR like performance and fuel expenditure just to catch up with the cycler and return to Earth or Mars.

If the Cycler solves this problem by decelerating, it needs constant replenishing at both ends of the trip. As we are talking about a very large vehicle it will be expending a large amount of fuel. Refuelling can be sequenced with loading/offloading passengers and cargo but it is an unnecessary additional task.

Accelerating and decelerating the Cycler also puts  significant limitations on its design which makes this an even less attractive option.

So we need BFR like performance form our shuttles, which the study acknowledges. That means we still need an Earth booster stage and we still need in orbit refuelling in order to deliver that performance. It seems odd to me to propose a system that demands an interplanetary capability from its shuttles, but then limit their use to supplying another interplanetary craft.

Assuming the Cycler is bigger than a BFR we then need to handle the in orbit transfer of cargo, passengers and fuel in multiple operations. If you limit the scale of your Cycler to reduce this task your reduce the Cyclers carrying capacity and therefore its earning capacity. If you max out its carrying capacity you increase the complexity and risks involved in multiple docking and loading operations. Remember it's not as 'simple' as docking. Cargo and passengers have to be transferred.

My final point of concern is that with a Cycler architecture you are significantly increasing the  development and production cost of the system. With the BFR architecture you need the ship and the booster and you are done. With the Cycler you need Interplanetary ship and the means of launching the components and assembling the modules in orbit. You still need a BFR style and scale of shuttle at both ends of the trip to intercept the Interplanetary Cycler ship. Thats three times the number of vehicles to achieve the same goal per passenger head. I don't see how that can ever be more cost effective.
« Last Edit: 11/28/2018 02:49 pm by SteveKelsey »
2001 is running a little late, but we are getting there.

Offline TripleSeven

  • Full Member
  • ****
  • Posts: 1145
  • Istanbul Turkey and Santa Fe TEXAS USA
  • Liked: 588
  • Likes Given: 2095
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #14 on: 11/28/2018 04:02 pm »
I have a number of questions regarding the study as well but must caveat those heavily in that the degree of expertise that went into the study far outstrips mine.

However, we are in the final analysis considering a mass transportation system. It may be a challenging one, but those challenges do not remove the learns from mass transportation where scale and simplicity of operation  reduce costs.

 My concerns regarding the cycler architecture are.

The cycler must maintain a high velocity to avoid the burden of deceleration and acceleration at Earth or Mars orbit. A shuttle therefore has to match this velocity at both ends of the trip not just attain LEO. It seems an extravagant use of fuel and demands a high performance from the shuttle, in fact it demands a BFR like performance and fuel expenditure just to catch up with the cycler and return to Earth or Mars.

If the Cycler solves this problem by decelerating, it needs constant replenishing at both ends of the trip. As we are talking about a very large vehicle it will be expending a large amount of fuel. Refuelling can be sequenced with loading/offloading passengers and cargo but it is an unnecessary additional task.

Accelerating and decelerating the Cycler also puts  significant limitations on its design which makes this an even less attractive option.

So we need BFR like performance form our shuttles, which the study acknowledges. That means we still need an Earth booster stage and we still need in orbit refuelling in order to deliver that performance. It seems odd to me to propose a system that demands an interplanetary capability from its shuttles, but then limit their use to supplying another interplanetary craft.

Assuming the Cycler is bigger than a BFR we then need to handle the in orbit transfer of cargo, passengers and fuel in multiple operations. If you limit the scale of your Cycler to reduce this task your reduce the Cyclers carrying capacity and therefore its earning capacity. If you max out its carrying capacity you increase the complexity and risks involved in multiple docking and loading operations. Remember it's not as 'simple' as docking. Cargo and passengers have to be transferred.

My final point of concern is that with a Cycler architecture you are significantly increasing the  development and production cost of the system. With the BFR architecture you need the ship and the booster and you are done. With the Cycler you need Interplanetary ship and the means of launching the components and assembling the modules in orbit. You still need a BFR style and scale of shuttle at both ends of the trip to intercept the Interplanetary Cycler ship. Thats three times the number of vehicles to achieve the same goal per passenger head. I don't see how that can ever be more cost effective.

The only propulsive burns a Cycler would do would be to maintain its "cycle" orbit...there would be some but the fuel use would be "small"

The "shuttles" would have to expend energy to accelerate to rendezvous and dock with the Cycler but the mass that they would have to accelerate would be much much less than a BFR sized vehicle...and most if not all of the cargo transfer could and would be easily automated.  On arrival when it was time to "jump off" most plans use the atmosphere of the destination world to aerobrake into orbit.    Most of that could be done with expandable type heat shields.

If there was propellent on both the EArth and destination planet end...the job gets a lot easier...and then you use specialized entry/take off vehicles to get down to the planet...

The big deal with the cyclers is that you get gravity, lots of power, and mass to protect people...at least in my view

Offline SteveKelsey

Re: Battle of the architectures- BFR v Mars Cycler
« Reply #15 on: 11/28/2018 04:23 pm »
I agree that the shuttles should deal with the velocity transfer. Based on the Aldrin cycler model that means you need a shuttle capable of reaching circa 24,000kph for Earth and 35,000kph for Mars. That is a non-trivial performance, you still need a BFR performance level for the shuttle.

http://buzzaldrin.com/files/pdf/1985.10.28.ALDRIN_SAIC_PAPER.Cyclic_Trajectory_Concepts_0.pdf

On shuttle size you can't just scale down the ship size without addressing the efficiency issue. Sure it's easier to build a smaller ship, but you need more of them or more launches to transport the same passenger and cargo load adding operational complexity, risk and therefore cost.  You might be be able to automate cargo transfer using  cargo modules - a bit like containers for shipping, but you still have to deal with multiple passenger transfers.
« Last Edit: 11/28/2018 04:26 pm by SteveKelsey »
2001 is running a little late, but we are getting there.

Offline SteveKelsey

Re: Battle of the architectures- BFR v Mars Cycler
« Reply #16 on: 11/28/2018 04:32 pm »
I am sorry that last link leads to a very poor pdf copy of the original Aldrin proposal. Here is a better link to a latter paper that looks at a more efficient variation on the concept.

https://www.researchgate.net/publication/267241987_A_Low-Thrust_Version_of_the_Aldrin_Cycler
2001 is running a little late, but we are getting there.

Offline TripleSeven

  • Full Member
  • ****
  • Posts: 1145
  • Istanbul Turkey and Santa Fe TEXAS USA
  • Liked: 588
  • Likes Given: 2095
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #17 on: 11/28/2018 04:47 pm »
I agree that the shuttles should deal with the velocity transfer. Based on the Aldrin cycler model that means you need a shuttle capable of reaching circa 24,000kph for Earth and 35,000kph for Mars. That is a non-trivial performance, you still need a BFR performance level for the shuttle.

http://buzzaldrin.com/files/pdf/1985.10.28.ALDRIN_SAIC_PAPER.Cyclic_Trajectory_Concepts_0.pdf

On shuttle size you can't just scale down the ship size without addressing the efficiency issue. Sure it's easier to build a smaller ship, but you need more of them or more launches to transport the same passenger and cargo load adding operational complexity, risk and therefore cost.  You might be be able to automate cargo transfer using  cargo modules - a bit like containers for shipping, but you still have to deal with multiple passenger transfers.

I suspect we are looking at differences of scale in the effort...I am "considering" 10-20 people at a cycle.


Offline SteveKelsey

Re: Battle of the architectures- BFR v Mars Cycler
« Reply #18 on: 11/28/2018 04:49 pm »
Good point. I am contrasting the BFR approach with an alternative Cycler architecture and therefore had assumed a much larger passenger manifest. Didn't make that clear, sorry.
2001 is running a little late, but we are getting there.

Offline Zed_Noir

  • Senior Member
  • *****
  • Posts: 5490
  • Canada
  • Liked: 1809
  • Likes Given: 1302
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #19 on: 11/29/2018 02:37 am »
My thinking is that the Starship BFS is for moving people between Earth and Mars as rapidly as possible. A jetliner analog.

While the Mars cycler will be much bigger than anyone is thinking right now capable of transporting cargo in the mega tons. A variant of the Starship BFS will be the cargo lighters/shipping containers. Since the Mars Cycler will have limited time to loaded and discharged cargo. It will be much easier to just docked the variant Starship BFS to the Mars Cycler. A large LASH (Lighters Aboard Ship) cargo ship analog. Cargo will be mainly bulk commodities like gases, fluids & raw materials.

There might be a caretaker crew aboard the Mars Cycler. Which would require some sort of artificial gravity.

Offline MikeAtkinson

  • Full Member
  • ****
  • Posts: 1980
  • Bracknell, England
  • Liked: 784
  • Likes Given: 120
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #20 on: 11/29/2018 11:32 am »
There are lots of different versions of cycler architectures, so it is difficult to make general statements, but the advantages are I think as follows.

1. The cycler can be very large, both in terms of volume and mass. This allows relative luxury for the crew, adequate radiation shielding and copious supplies and spare parts for maintenance and emergencies.

2. The cycler and taxi can be designed to play their relevant roles without compromise.

3. The architecture is much more fuel efficient, as the cycler mass only needs to be accelerated once, then can use electric propulsion for minor course corrections.

4. A large cycler could provide artificial gravity, crew can reach Mars in top condition and acclimate back to Earth's gravity on the journey.


These pretty big advantages bu are I think outweighed by the disadvantages when compared to Starship (BFS).

1. Most flights to Mars will be cargo, not crew. Cycler architectures only really work for crew, if there are separate cargo ships there is a loss of commonality, if there aren't separate cargo ships then the disadvantages below apply to cargo as well as crew.

2. Spaceship is one design for both cargo and crew, therefore experience from on carries over to the other.

3. The hard parts of a Mars mission are launch and EDL, and doing those economically for a Mars settlement, solving for those gives the transit virtually for free. There is large cargo volume and mass (large items, mass for a colony) and life support that can last for years (for the first crew on Mars).

4. The Starship can be thoroughly inspected and refurbished if necessary every two (or perhaps four) years. In contrast a Cycler can only be maintained in flight. New technology can be added via re-manufacturing as well as swapping line replaceable units.

5. Loss of a Starship (e.g. due to a fire) only loses that Starship, and might lead to design changes in other Starships. Loss of the Cycler would cut out an inbound or outbound leg until another one was produced and launched (many years). It would be difficult to add improvements to the other cycler.

6. The Cycler is produced in very low numbers (2 or 4 with very limited replacements) and is much bigger than a Starship both leading to high development and manufacturing costs. In contrast Starship would be in serial production with development cost spread over many units and alternative uses (such are moon flights, Starlink launch). Experience from these other uses may lead to improvements in the Starships for journeys to Mars.

7. Using a cycler has several highly critical events that Starship does not have, docking and undocking of the taxi and coming out of hibernation after the long (uncrewed) leg.

8. Starship uses a fleet approach to give mutual aid during the journey, not so for a single clycler.

9. Starship is much more flexible, it is not easy to grow the cycler size so coping with increased traffic demand is difficult.

10. for taxis going to a cycler there is an extremely short launch window (effectively instantaneous) while the launch window for Starship is in the weeks (if single synod reuse is desired) to months when journeys can take between 3 and 9 months.

Online edzieba

  • Virtual Realist
  • Senior Member
  • *****
  • Posts: 6105
  • United Kingdom
  • Liked: 9332
  • Likes Given: 39
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #21 on: 11/29/2018 12:53 pm »
Reposted and expanded from the other thread:

The key advantage of a Cycler is that you have a big chunk of spaceship that does not need to be dragged out of a gravity well at either end. That means all transit shielding mass can be left in orbit, and all coast-phase habitation mass (and volume!) can be left in orbit. Depending on IRSU capability, it also means you can carry far more mass to the Martian surface than could fit on the number of descent stages you bring with you: land the descent stage, collect stockpiled ISRU propellant, launch back to the Cycler for the next cargo load, etc.

If the BFS is used as a shuttle to load a Cycler rather than direct transit then there is another advantage: all your BFSes need  only tool around in cisluner space, so their reuse loop is significantly shortened; and all those BFS you use for the short time of cycler resupply then return to Earth and can be re-used for domestic purposes for the rest of the synod.

Online rakaydos

  • Senior Member
  • *****
  • Posts: 2825
  • Liked: 1869
  • Likes Given: 69
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #22 on: 11/29/2018 05:51 pm »
All the advantages of a cycler depend on the ability for travelers to leverage infrastructure are either end of the journy. (For instance, you save habitable volume and radiation shielding for the trip, because you can use habitable volume and rad shielding on the planet when you get there.)

This implies that cycler is useless for actually building the infrastructure at mars in the first place.

Only once Mars has the infrastructiure of a PTP destination, can a cycler be worthwhile as a PTP parking spot- providing long term living conditions, letting the passangers stretch their legs on the months long trip to mars, before piling back into the packed PTP rocket to arrive at Mars, or back at earth the same way.
« Last Edit: 11/29/2018 09:01 pm by rakaydos »

Offline Lars-J

  • Senior Member
  • *****
  • Posts: 6809
  • California
  • Liked: 8485
  • Likes Given: 5384
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #23 on: 11/30/2018 12:28 am »
Cyclers will always have two crippling disadvantages:
1. No delta-V savings at all. All ships docking with the Cycler need to accelerate to TMI to reach it. (I get the feeling that many subconsciously forget that and think that it will just pick up crafts in LEO - in this case the oceanliner analogue does not apply)
2. A single cycler could not cover every launch window, you would need several. And it would also severely limit Mars windows. A standalone ship going to Mars can tweak the launch window up to a few weeks in either direction. No such thing with a cycler - you have a pretty instant launch window from LEO.

Cyclers will never make sense, IMO. Not for *any* Mars architecture.
« Last Edit: 11/30/2018 12:33 am by Lars-J »

Offline QuantumG

  • Senior Member
  • *****
  • Posts: 9238
  • Australia
  • Liked: 4477
  • Likes Given: 1108
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #24 on: 11/30/2018 12:33 am »
First one, then the other.
Human spaceflight is basically just LARPing now.

Offline KelvinZero

  • Senior Member
  • *****
  • Posts: 4286
  • Liked: 887
  • Likes Given: 201
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #25 on: 11/30/2018 12:50 am »
Cyclers will always have two crippling disadvantages:
1. No delta-V savings at all. All ships docking with the Cycler need to accelerate to TMI to reach it. (I get the feeling that many subconsciously forget that and think that it will just pick up crafts in LEO)
2. A single cycler could not cover every launch window, you would need several. And it would also severely limit Mars windows. A standalone ship going to Mars can tweak the launch window up to a few weeks in either direction. No such thing with a cycler - you have a pretty instant launch window from LEO.

Cyclers will never make sense, IMO. Not for *any* Mars architecture.
I think you also always need significant delta-v to keep encountering both earth and mars. Eg they are not even in exactly the same plane.
A bit off topic, but I see a potential future use for cyclers (non-mars) that only need to match one object. One case is if we have an asteroid civilisation. We could have say twelve cycler trajectories, named for the month or constellation when they encounter earth, that pass through the asteroid belt a year or so later, and needs practically no delta-v to remain on target. They could be very large. They could be towns and universities as well. The craft that accelerates to meet them could be a flimsy tin can, but you only spend a week or so in that.
Another example is heavily shielded cyclers dedicated one to each of the moons of Jupiter and a point outside the dangerous radiation zone and near jupiter escape velocity so they can all be reached from each other with little energy.

Offline Lars-J

  • Senior Member
  • *****
  • Posts: 6809
  • California
  • Liked: 8485
  • Likes Given: 5384
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #26 on: 11/30/2018 02:37 am »
A bit off topic, but I see a potential future use for cyclers (non-mars) that only need to match one object. One case is if we have an asteroid civilisation. We could have say twelve cycler trajectories, named for the month or constellation when they encounter earth, that pass through the asteroid belt a year or so later, and needs practically no delta-v to remain on target. They could be very large. They could be towns and universities as well. The craft that accelerates to meet them could be a flimsy tin can, but you only spend a week or so in that.

But that's the problem... It can't be just that. If your engine shuts down before necessary delta-v to meet the cycler, you are in deep s**t. You need to have a much larger ship to be a safe haven until rescue can be mounted.

Offline KelvinZero

  • Senior Member
  • *****
  • Posts: 4286
  • Liked: 887
  • Likes Given: 201
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #27 on: 11/30/2018 03:41 am »
A bit off topic, but I see a potential future use for cyclers (non-mars) that only need to match one object. One case is if we have an asteroid civilisation. We could have say twelve cycler trajectories, named for the month or constellation when they encounter earth, that pass through the asteroid belt a year or so later, and needs practically no delta-v to remain on target. They could be very large. They could be towns and universities as well. The craft that accelerates to meet them could be a flimsy tin can, but you only spend a week or so in that.

But that's the problem... It can't be just that. If your engine shuts down before necessary delta-v to meet the cycler, you are in deep s**t. You need to have a much larger ship to be a safe haven until rescue can be mounted.
I can think of ways to help that, but that is not the purpose of the cycler. It is to solve another problem.

The purpose of the cycler is to let you travel a year in a town-sized environment instead of a tincan-sized one.. not specifically to address that risk of failure during the departure burn.

Offline alexterrell

  • Full Member
  • ****
  • Posts: 1747
  • Germany
  • Liked: 184
  • Likes Given: 107
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #28 on: 11/30/2018 08:30 am »
Slightly related question? Assuming BFR wins over the cycler...

Would it make sense to have a BFR which only does Earth orbit to Mars? A BFR equipped for Mars and providing space for passengers may not be optimized for Earth Launch.

Would it make sense to have a BFR "shuttle" launch 120 passengers, who then transfer to two BFR "Inter-planetaries"? The former would have no closed cycle life support, sleeping cabins, showers, etc. The latter could even rotate around each other to provide some gravity for the journey.

Of course, the Interplanetary variant still has to land on a planet, so it can't dispense with landing legs, gravity handling equipment and powerful engines (but they'd all be vacuum optimized). It would also have to be "serviced" off Earth, so that might have to wait till we have the infrastructure.

A Phobos - Earth orbit architecture would get over even that problem. This could be a rotating space station, fuelled on Phobos, and going from there to High Earth Orbit. It would be like a cycler, but with a powered stop at each end. However, SpaceX and NASA are both ignoring Phobos/Deimos in their plans.

Offline Russel

  • Full Member
  • ****
  • Posts: 1083
  • Liked: 122
  • Likes Given: 4
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #29 on: 11/30/2018 09:11 am »
On that note I'll simply point out that my ideal architecture involves transport to and from Earth orbit and Mars orbit and then a specialised lander/ascent vehicle on the Mars end.

One can then consider which Mars orbit.

The original problem that Cyclers were meant to solve was avoiding the costs involved in escaping the Earth and Mars gravity wells. But as has been pointed out, the "taxi" needed for a Cycler has to be a fairly capable craft and then you have to consider what can go wrong. Besides I don't think Cyclers as originally proposed were meant to be cruise liner sized things. They were meant to be more modest.

Since then we've proven reusable boosters and this is game changing since we can now afford to use chemical fuel and high energy transits. That partly deals with the radiation issue.

Offline Spaniard

  • Member
  • Posts: 73
  • Liked: 6
  • Likes Given: 1
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #30 on: 11/30/2018 11:48 am »
My opinion.

On first missions, the simpler, the better... So go as direct as possible.

When you have a minimal of continuity and volumen, go to more efficient architecture.

For example... I imagined

Reusable Earth... Earth extreme orbit ( perihelion close to Earth, aphelion close to leave Earth orbit and go to Solar Orbit). Chemical... Fast.

EEO orbit to MEO orbit (Mars equivalent) through ion spaceship. Because ion allows us to accelerate in a long journey that it's dead time in any case, with high ISP.
MEO to Mars surface though reusable chemical rocket.

That's mean fast travel. Space ion ship could be bigger that BFR model and have some limited artificial gravity and better shielding.


With really high volumes of people. Mars colonization level.
Cyclers with emergency spaceship rockets. More focused on comfort than efficiency. We are talking about a lot of regualr people, so more confort is better. But captured spaceships to attach to the cycler could make probably Mars travel by itself, so an accident could be non-fatal if the spaceship loose the cycler.

Offline Russel

  • Full Member
  • ****
  • Posts: 1083
  • Liked: 122
  • Likes Given: 4
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #31 on: 11/30/2018 12:03 pm »
Two things. Whilst you are still in orbit around a planet and if you have lots of time, you can apply ion thrust when you are nearest the planet and thus at highest velocity. This is how to get the Oberth effect even whilst using ion thrust. You don't need a slow spiral. You instead kick yourself into a higher elliptical orbit with each close pass.

Secondly, I'm not bothered by the idea of going from LEO to LMO and back again using entirely chemical thrust. Provided you can deliver fuel cheaply enough to LEO you can effectively brute force it. And this is exactly where we are headed with reusable boosters - and possibly a reusable upper stage.

You can optimise somewhat if your vehicle does have ion thrust capability but a few tens of KW and a few Newtons is about the limit without getting festooned in arrays.

Offline alexterrell

  • Full Member
  • ****
  • Posts: 1747
  • Germany
  • Liked: 184
  • Likes Given: 107
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #32 on: 11/30/2018 02:46 pm »
On that note I'll simply point out that my ideal architecture involves transport to and from Earth orbit and Mars orbit and then a specialised lander/ascent vehicle on the Mars end.

One can then consider which Mars orbit.


Phobos to High Earth Orbit and back again, with aerocapture and orbit circularisation at both ends, requires about 3200m/s delta V, plus reserve. That would be optimum if (and probably only if) Phobos (or Diemos) can be used for fuel, and would have a base to receive passengers and service space craft.

(Fuel usage could be reduced further by using a tug as a "1st stage" and a "last stage". That way the interplanetary ship only needs 2200m/s. But it's more complex that way. And ultimately a Phobos tether could replace most of the fuel).

Earth to High Earth orbit takes a matter of days so can be done with airline-style seating.
Quote

The original problem that Cyclers were meant to solve was avoiding the costs involved in escaping the Earth and Mars gravity wells. But as has been pointed out, the "taxi" needed for a Cycler has to be a fairly capable craft and then you have to consider what can go wrong.

Almost all of the escaping gravity wells efforts is in getting to a high orbit.
Earth to High Orbit: About 12 km/s
Mars to Phobos: About 5.5km/s
Compared with the round trip of 3.2km/s between the High(ish) Orbits.

Quote
Since then we've proven reusable boosters and this is game changing since we can now afford to use chemical fuel and high energy transits. That partly deals with the radiation issue.

I used to think it would even make sense to use electric propulsion to move fuel and cargo from LEO to HEO. However, the promised low cost of BFS launches probably negates that. It also means that the interplanetary craft would come down to LEO, to avoid a duel stage tanker refilling operation. 

Offline Spaniard

  • Member
  • Posts: 73
  • Liked: 6
  • Likes Given: 1
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #33 on: 11/30/2018 02:56 pm »
Secondly, I'm not bothered by the idea of going from LEO to LMO and back again using entirely chemical thrust. Provided you can deliver fuel cheaply enough to LEO you can effectively brute force it. And this is exactly where we are headed with reusable boosters - and possibly a reusable upper stage.
Thats the idea because I separate High Orbit from Transfer Orbit.

Ion is efficient, but acceleration is slow, so leave Earth Orbit takes too much time. Time that means mass for manned in another way. Life support.

So chemical to high orbit is faster. And later, Between Earth and Mars, we could use ion, because we have plenty of time to use the engine.

From mars high orbit to mars low orbit, chemical is better again.

Time mean more mass too on manned missions.

Offline TripleSeven

  • Full Member
  • ****
  • Posts: 1145
  • Istanbul Turkey and Santa Fe TEXAS USA
  • Liked: 588
  • Likes Given: 2095
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #34 on: 11/30/2018 03:10 pm »
the nice part about cyclers

1.  Ion drive handles almost all the planetary maneuvering and that propellent is fairly easy to resupply from earth as the cycler makes its "pass"

2.  the fuel needed to "meet" the cycler and load on crews (from Mars, the Earth and Venus) is less than having to boost theentire space ship carrying all these people into a transfer orbit

3.  the folks can disembark on the same spaceship that they came on...and in the three worlds mentioned above they can aerobrake to a station for transfer to the ground...if that is where the exploration is taking place)

4.  the cycler has a lot of room (or reasonable room anyway), power, sustainability for solar activities and lilkely ways to negate zero G  (see the Nautilus concept)

5.  we have a lot of experience maintaining one (ISS)

US space policy is going that way :)

Offline SteveKelsey

Re: Battle of the architectures- BFR v Mars Cycler
« Reply #35 on: 11/30/2018 06:51 pm »
Triple Seven said the nice part about cyclers is

(lots of interesting stuff and...)

2.  the fuel needed to "meet" the cycler and load on crews (from Mars, the Earth and Venus) is less than having to boost the entire space ship carrying all these people into a transfer orbit

(followed by more interesting stuff)



This is the bit that this numpty doesn't get Tripple7. To meet a cycler you have to match velocities. Unless you decelerate the cycler at each end then your shuttle has to match transfer velocities. Wherever you expend the energy, you have to match velocities so I am so dumb I am not seeing the reduction in fuel. Can you expand on why a cycler means less fuel/energy to help the mentally challenged?
« Last Edit: 11/30/2018 06:52 pm by SteveKelsey »
2001 is running a little late, but we are getting there.

Offline Russel

  • Full Member
  • ****
  • Posts: 1083
  • Liked: 122
  • Likes Given: 4
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #36 on: 12/02/2018 05:58 am »
Secondly, I'm not bothered by the idea of going from LEO to LMO and back again using entirely chemical thrust. Provided you can deliver fuel cheaply enough to LEO you can effectively brute force it. And this is exactly where we are headed with reusable boosters - and possibly a reusable upper stage.
Thats the idea because I separate High Orbit from Transfer Orbit.

Ion is efficient, but acceleration is slow, so leave Earth Orbit takes too much time. Time that means mass for manned in another way. Life support.

So chemical to high orbit is faster. And later, Between Earth and Mars, we could use ion, because we have plenty of time to use the engine.

From mars high orbit to mars low orbit, chemical is better again.

Time mean more mass too on manned missions.

You don't actually have to have the crew on board whilst a vehicle is going from low Earth orbit to high Earth orbit  using ion thrust. So it doesn't matter if this process takes months.

The vehicle kicks itself into a higher orbit on each pass going steadily into a higher and more elliptical orbit. Then when the orbit is high enough, the crew take off, an rendezvous with the vehicle. All going well the vehicle use chemical thrust on its last close approach to achieve Earth escape.

You can achieve the same thing in reverse on Mars approach. Chemical thrust to capture into a high orbit. The crew use a lander to land from there. Then the vehicle may choose to go to a lower orbit whilst the crew is on Mars (or it can remain in a high orbit for that matter).

On return to Earth you could keep the lander and expend the rest of the vehicle. Also one of your options in both cases is the lander doing an aerobraking pass or passes to slow down to a low orbit, and then go in for landing - which reduces g forces and thermal loading.

As I said, I think we now have the capability to brute force a Mars architecture out of chemical thrust. But a modest amount of ion thrust can help.

Offline MikeAtkinson

  • Full Member
  • ****
  • Posts: 1980
  • Bracknell, England
  • Liked: 784
  • Likes Given: 120
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #37 on: 12/02/2018 01:04 pm »
Triple Seven said the nice part about cyclers is

(lots of interesting stuff and...)

2.  the fuel needed to "meet" the cycler and load on crews (from Mars, the Earth and Venus) is less than having to boost the entire space ship carrying all these people into a transfer orbit

(followed by more interesting stuff)



This is the bit that this numpty doesn't get Tripple7. To meet a cycler you have to match velocities. Unless you decelerate the cycler at each end then your shuttle has to match transfer velocities. Wherever you expend the energy, you have to match velocities so I am so dumb I am not seeing the reduction in fuel. Can you expand on why a cycler means less fuel/energy to help the mentally challenged?

The idea is that you use a Taxi that is much smaller than a full fledged BFS. It will still need to carry the supplies for crew on the journey (to supply the cycler) and crew associated payload (personal luggage, etc.). The taxi can be physically smaller and have a simpler life support system that is only good for a few days use. There is no need for the taxi to carry extensive spare parts or tools. In addition a cycler can have more radiation shielding than a BFS sized spaceship and can not having to do entry, descent and landing it can be optimised for transit, containing a hoop for artificial gravity like Nautilus-X for instance.

A taxi can be quite small (Dragon 2 size) and there is not much benefit from going much larger than that, direct flights in contrast benefit from a large spaceship, arguably the current iteration of BFS (the DearMoon Starship) is smaller than optimum.

Cargo has no benefit from using a cycler (except live cargo).

If artificial gravity and high levels of radiation shielding are not provided by the cycler then BFS style direct flights can be better, they can be shorter (3 months instead of 6 months for a cycler), have fewer safety critical events, have commonality between crew and cargo flights and have a longer launch window.

Offline TripleSeven

  • Full Member
  • ****
  • Posts: 1145
  • Istanbul Turkey and Santa Fe TEXAS USA
  • Liked: 588
  • Likes Given: 2095
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #38 on: 12/02/2018 01:45 pm »
Triple Seven said the nice part about cyclers is

(lots of interesting stuff and...)

2.  the fuel needed to "meet" the cycler and load on crews (from Mars, the Earth and Venus) is less than having to boost the entire space ship carrying all these people into a transfer orbit

(followed by more interesting stuff)



This is the bit that this numpty doesn't get Tripple7. To meet a cycler you have to match velocities. Unless you decelerate the cycler at each end then your shuttle has to match transfer velocities. Wherever you expend the energy, you have to match velocities so I am so dumb I am not seeing the reduction in fuel. Can you expand on why a cycler means less fuel/energy to help the mentally challenged?

Mike did a pretty good job...but I would say this

in a cycler we are talking (at least I am) A "big" massive vehicle...lots of power, lots of shielding, "lots" (compared to most) of space, and maybe some artificial gravity.  picture ISS sized vehicle...the vehicle uses Ion propulsion which is long term but quite efficient...

and is in constant "cycler orbit"

the vehicle to get to it and jump off it is MUCH smaller and less massive...really is just a vehicle that has at most a few days of stand alone flight...and since it is less massive it takes less fuel to accelerate. and more or less aerobrakes into the orbit of either Mars or Earth...and then goes to another vehicle (or moon) and the people dispurse from that. 

So in a "cycle" you would have a vehicle coming to the cycler from "earth/mars/venus" while another vehicle leaves the cycler and goes to the planet.  the one leaving aerobrakes into orbit (not much fuel it could even descend directly to the surface if you wanted) the one coming from the planet or a space station all it has to do is accelerate the far less mass to match with the cycler.

Cargo has no real benefit to cycling...(unless its live as Mike points out)  but cargo doesnt worry about zero gee affects, radiation, going nuts because you are in a small space...no power etc.

I have a feeling (and that is all it is really) based on ISS stuff that three things are going to be an issue with TRAVEL in the solar system given our present technologies in propulsion.  the first is solar radiation. I know everyone talks "safe places" but I suspect that is not going to be good enough to stop large affects from it.

the second is no gravity.  after X months in Zero g...I suspect adaption back to gravity is going to be time consuming...

the third is isolation and space. lack of it I think is going to be very difficult mentally

good afternoon

Offline MikeAtkinson

  • Full Member
  • ****
  • Posts: 1980
  • Bracknell, England
  • Liked: 784
  • Likes Given: 120
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #39 on: 12/02/2018 03:33 pm »
I have a feeling (and that is all it is really) based on ISS stuff that three things are going to be an issue with TRAVEL in the solar system given our present technologies in propulsion.  the first is solar radiation. I know everyone talks "safe places" but I suspect that is not going to be good enough to stop large affects from it.

Not a significant problem in my opinion. With a storm shelter solar radiation is not significant even during solar storms. Cosmic rays are significant, but only add a few % to the risk of getting cancer (not necessarily the risk of dying from it), confounding effects like better healthcare for crew make average days of life lost difficult to estimate. Cosmic rays for a 3 month journey are likely to have less effect than things like diet, exercise and pollution all of which will be different for Mars crew and settlers. Cosmic rays for Mars missions are much less dangerous than smoking. The mortality from other dangers during Mars settlement (accidents, etc.) are much higher than cosmic rays.

For longer journeys, say to the moons of Jupiter then cosmic rays start to become a major issue.


the second is no gravity.  after X months in Zero g...I suspect adaption back to gravity is going to be time consuming...

Definitely a major problem. Probably acceptable for 3 month transits and 2 years at Mars gravity, especially with gradual improvements in mitigation methods. Longer missions to Mars and settlement are unknown at present as there has been little research on partial-g living.

Missions to the main belt asteroids and moons of Jupiter almost certainly need artificial gravity.

the third is isolation and space. lack of it I think is going to be very difficult mentally

A real problem with small crews. Up until BFS crew sizes on Mars missions were small (DRM 1,3,4, Mars Direct, etc.) usually had crews of 4 or 6. Sometimes the crew would be split for a month or so, say to investigate the moons of Mars or for a long duration rover traverse. These missions had relatively small amounts of space per crew member. The current plan for Starship seems to be to send two crews of 12 on the first mission and then build up to larger sizes over subsequent synods. Between the crew and cargo Starships there will be relatively large amount volume per person, which will grow as surface structures are constructed.

Isolation from family and society in general will be an issue, and perhaps a problem for some. However most people are pretty strong mentally, even more so those selected for Mars crews; they will also benefit from stimulating work, a diverse intelligent Mars community and free communication with Earth (not real-time because of speed of light delays).

Offline Slarty1080

  • Senior Member
  • *****
  • Posts: 2740
  • UK
  • Liked: 1871
  • Likes Given: 814
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #40 on: 12/02/2018 10:53 pm »
I have a feeling (and that is all it is really) based on ISS stuff that three things are going to be an issue with TRAVEL in the solar system given our present technologies in propulsion.  the first is solar radiation. I know everyone talks "safe places" but I suspect that is not going to be good enough to stop large affects from it.

Not a significant problem in my opinion. With a storm shelter solar radiation is not significant even during solar storms. Cosmic rays are significant, but only add a few % to the risk of getting cancer (not necessarily the risk of dying from it), confounding effects like better healthcare for crew make average days of life lost difficult to estimate. Cosmic rays for a 3 month journey are likely to have less effect than things like diet, exercise and pollution all of which will be different for Mars crew and settlers. Cosmic rays for Mars missions are much less dangerous than smoking. The mortality from other dangers during Mars settlement (accidents, etc.) are much higher than cosmic rays.

For longer journeys, say to the moons of Jupiter then cosmic rays start to become a major issue.


the second is no gravity.  after X months in Zero g...I suspect adaption back to gravity is going to be time consuming...

Definitely a major problem. Probably acceptable for 3 month transits and 2 years at Mars gravity, especially with gradual improvements in mitigation methods. Longer missions to Mars and settlement are unknown at present as there has been little research on partial-g living.

Missions to the main belt asteroids and moons of Jupiter almost certainly need artificial gravity.

the third is isolation and space. lack of it I think is going to be very difficult mentally

A real problem with small crews. Up until BFS crew sizes on Mars missions were small (DRM 1,3,4, Mars Direct, etc.) usually had crews of 4 or 6. Sometimes the crew would be split for a month or so, say to investigate the moons of Mars or for a long duration rover traverse. These missions had relatively small amounts of space per crew member. The current plan for Starship seems to be to send two crews of 12 on the first mission and then build up to larger sizes over subsequent synods. Between the crew and cargo Starships there will be relatively large amount volume per person, which will grow as surface structures are constructed.

Isolation from family and society in general will be an issue, and perhaps a problem for some. However most people are pretty strong mentally, even more so those selected for Mars crews; they will also benefit from stimulating work, a diverse intelligent Mars community and free communication with Earth (not real-time because of speed of light delays).
I doubt very much that the first Mars crew will be 12 strong. Each person carried adds a large overhead of oxygen, water, food, clothes and assorted other items. I would be very surprised if the first mission carried more than 6 people and probably only 4. The first Mars missions will be very difficult mass wise as it is unlikely that ISRU can be used for oxygen and methane production. Oxygen may be produced direct from the atmosphere but finding sufficient water is unlikely to be reliable at first so methane will need to be brought from Earth with subsequent mass penalty.
My optimistic hope is that it will become cool to really think about things... rather than just doing reactive bullsh*t based on no knowledge (Brian Cox)

Offline MikeAtkinson

  • Full Member
  • ****
  • Posts: 1980
  • Bracknell, England
  • Liked: 784
  • Likes Given: 120
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #41 on: 12/03/2018 05:58 am »
I doubt very much that the first Mars crew will be 12 strong. Each person carried adds a large overhead of oxygen, water, food, clothes and assorted other items. I would be very surprised if the first mission carried more than 6 people and probably only 4. The first Mars missions will be very difficult mass wise as it is unlikely that ISRU can be used for oxygen and methane production. Oxygen may be produced direct from the atmosphere but finding sufficient water is unlikely to be reliable at first so methane will need to be brought from Earth with subsequent mass penalty.

Water mining from the Mars atmosphere is possible. It is quite power intensive and probably practical for propellant production, however it is more than good enough for water for crew use. With closed loop water recycling, crew water needs are very low.

I am suggesting a first mission crew of 24, that is two ships of 12. Having a larger first landing crew is important if SpaceX want to sell some or all of the seats, it at least triples the revenue potential. Less crew also means less work done, delaying expansion and hence future revenue potential. Assuming 4 cargo flights of 100 tonnes payload as well, that would be 600 tonnes of payload, or 25 tonnes per crew member. In contrast the NASA Mars DRMs had much less landed payload per crew, under 5 tonnes IIRC.

Bringing methane from earth for the return journey propellant is much harder and more expensive, it would require the landing of several tanker Starships (somewhere between 4 and 6 depending on details), this is more than SpaceX plans to launch in the first synod. So crew could not land on the second synod, which would be more tankers. The tankers are a dead end, not needed after ISRU is working. This at least doubles the cost of the first crew.

All told a doubling of the costs, a lengthening of the timescales and a reduction in revenue potential is not in SpaceX's interests and is inconsistent with what we know of their plans.

Getting back to BFR vs Mars Cycler. The use of BFR allows a much cheaper and faster build up of resources and crew on Mars


Offline Slarty1080

  • Senior Member
  • *****
  • Posts: 2740
  • UK
  • Liked: 1871
  • Likes Given: 814
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #42 on: 12/03/2018 09:58 am »
Trying not to wander here I know the topic is the cycler, but the issue of ready access to Martian water is relevant. If Martian water is not readily available for the first missions the cycler might be delayed. The greater the mass of stores required from Earth (assent methane for instance) the bigger the “taxi” has to be. But I will start a new thread for further discussion of water extraction from the Martian atmosphere.
My optimistic hope is that it will become cool to really think about things... rather than just doing reactive bullsh*t based on no knowledge (Brian Cox)

Offline spaceman100

  • Full Member
  • *
  • Posts: 122
  • NORTH EUROPE
  • Liked: 8
  • Likes Given: 18
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #43 on: 01/04/2019 03:16 pm »
I figure Mars Cycler is too slow.

https://en.wikipedia.org/wiki/Mars_cycler

I think we need new efficient engines from Blue Origin and Space X to build the new ship.

Big enough ship could reach 70 000 km/h speed.

For shielding I would make the lander big enough so that the crew would actually spend 98% of the time there.

You gotta have a separate lander...just like in the moon landing.


Rail launch and ION drive might work too ?



This is moon capable at 76 ft long...Mars system has to be 150-180 ft long.
« Last Edit: 01/04/2019 07:27 pm by spaceman100 »

Offline SteveKelsey

Re: Battle of the architectures- BFR v Mars Cycler
« Reply #44 on: 01/06/2019 02:02 pm »
I think this thread is slipping from its focus. We are not talking about Mars transportation, we are talking about Mass transportation. The purpose of the Starship/Super Heavy is Mars colonisation and that means transportation of people and resources in bulk, not the six man crews suggested earlier in the thread.  SpaceX are targeting 100 colonists per flight so that should provide the benchmark.

A Cycler architecture requires the following

1. An Earth optimised shuttle and associated booster sized to ship 100 colonists out to rendezvous with the Cycler.
2. A Mars optimised shuttle sized to rendezvous with the cycler and land 100 colonists
3. The Cycler suitably sized to transport the 100 colonists between earth and Mars.

The commonalities available to these three systems are limited because the performance requirements of each are radically different.

The Shuttles

Both shuttle designs would need to be optimised to meet their respective operational environments. An Earth shuttle needs to be optimised to manage the Earths high gravity and thick atmosphere. A Mars shuttle needs to be optimised to deal with  Martian gravity and atmosphere. Although both systems may share some components and systems e.g. It is possible to imagine engines can be essentially the same with modifications and avionics and electronics could be shared, however,  the differences are far greater than the commonalities., e.g. the Earth shuttle would be a TSTO design whereas the Martian shuttle could be SSTO.

Note also that the performance requirements of the shuttles are no less arduous than the StarShip/SuperHeavy, if fact, they may be higher depending on the design decisions made. The SS/SH system can reach LEO, but to be able to accelerate to escape velocity the Starship needs refuelling. Is the Cycler shuttle going to adopt the same strategy or will the size of the shuttle and its booster stage be enlarged to to give it enough velocity so that it can reach escape velocity to rendezvous with the Cycler without refuelling? Or is the size of the shuttle to be reduced to make this task easier?  If so how small does it need to be to achieve this and how many flights are required to ship the 100 colonists? Or, is the Cycler going to be decelerated and accelerated at each ’terminus’ to reduce the demands on the shuttles. This has been proposed in several studies, however these studies were based on a crew of 6, not the 100 envisaged by Musk.


The Cycler

The Cycler design is  usually presented as a flying ‘hotel’. Its benefits are the ability to significantly reduce the use of propellent to get to Mars by using gravity assist,  improve the comfort and convenience of the colonists on the flight and the ability to improve safety by increasing redundancy. All very laudable aims and very feasible. The proposals I have read all base the Cycler design on the in-orbit assembly of modules, which is a very practical approach. Habitation modules, power modules, and the structural modules needed for enabling  rotation to provide gravity, a key benefit of the Cycler proposal, have nothing in common with the design of either shuttles. It is probable that the Earth booster required for the Earth shuttle could be employed launching the Cycler components, but as far as I can see, this is the only significant commonality between the Cycler and the Shuttle systems.

But we have to talk about scale. A Cycler sized to transport 100 colonists is a substantial piece of in-flight infrastructure. Its modules would need to be sized to fit the mass and diameter constraints imposed by the Earth booster built for the Earth shuttle. This determines the number of launches and complexity of the inflight assembly. Assuming a sensibly sized shuttle- e.g. sized to take 25 colonists, its conceivable that a Cycler could be assembled from a smaller number of modules as the ISS, as each module would be larger and may employ Bigelow like methods to increase the living space of each module beyond the constraints of the launch vehicle. The Cycler will also have significant mass, and this would argue against decelerating and accelerating the structure to ease the rendezvous task of the Cycler Shuttles/Taxi’s.

IMHO the assumptions made above for a colony scale Cycler are reasonable considering the todays state of the art. There may well be smarter ways of doing it, but anyone suggesting improvements please accept that they have to be capable of supporting 100 colonists per trip- the objective defining the SS/SH architecture.


What does this demand in terms of asset development?


1. An Earth optimised shuttle.
2. An Earth booster stage
3. A Mars optimised shuttle
4. Cycler habitation module
5. Cycler cargo module
6. Cycler propulsion  module/s ( to get the Cycler up to speed)
7. Cycler power supply module
8. Ground infrastructure for 1, 2. and 3.

Additionally the program for the Cycler is involved. A lot has to take place before the first trip can be made.

1. The Mars shuttle/s have to be launched to Mars ( assume two for redundancy)
2. The Cycler has to be launched and assembled over N flights. It took 40 to assemble the ISS bust I am suggesting to will take less than that.  N.B. You might need two Cyclers to optimise the efficiency of the Cycler method, but let’s ignore that for now.

Operationally the Cycler architecture is complex, demanding far more LEO  and LMO operations in terms of docking, passenger and cargo transfer, refuelling and replenishing the Cyclers supplies.

This compares and contrast with the Starship/Super Heavy model

1. One ship
2. One tanker
3. One booster.
4. Ground Infrastructure for 1,2.

Operationally the SS/SH is far simpler.


Now consider cost and timing.

 I can’t see how the Cycler architecture, for all its theoretical advantages, can be cheaper and become operational quicker than the Starship/Super Heavy architecture. It is far more complex in development, delivery and operational terms.  At a minimum you need to develop four vehicles, Earth shuttle, Earth Booster, Mars shuttle, and the complex Cycler, none of which allow much in the way of commonality.  This is the part that breaks the Cycler proposal for me. Any proposal that quadruples the capital investment and increases the operational complexity  per passenger ticket just can’t win out in a mass transportation scenario, which is the comparison this thread needs to address.



http://buzzaldrin.com/files/pdf/2001.12.15.REPORT_FOR_NASA-JPL.Evolutionary_Space_Transportation_Plan_for_Mars_Cycling_Concepts.pdf
2001 is running a little late, but we are getting there.

Offline Cherokee43v6

  • Full Member
  • ****
  • Posts: 1176
  • Garner, NC
  • Liked: 935
  • Likes Given: 236
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #45 on: 01/06/2019 03:35 pm »
I'm curious why this needs to be a battle?

It's like having Columbus hold off his voyages of exploration while he waits for the development of the Clipper Ships. 

The Clippers couldn't be developed until the technology and the economic demand were both in place.  Similarly, Cycler Ships are geared toward high volume, strong economic demand.

An interesting note is that the great liners were often served off-shore from some ports by launches carrying as many (or more) passengers as the early colonization ships.

Personally, I see BFR and Cyclers as having a sequential, followed by symbiotic relationship.  Early on, BFR with 100 passengers flies the route to establish the initial colony.  Later, BFRs are modified to carry 2 or 3 hundred passengers out to meet a cycler and several are sent at once.  (Look at how the airlines have fitted out the demo models of the 747 and A380 compared to how the actual operators have them outfitted.)

They would dock with the cycler which would house the passengers for the trip.  They'd then re-board the Hi-Cap BFR for the descent to Mars.
"I didn't open the can of worms...
        ...I just pointed at it and laughed a little too loudly."

Offline SteveKelsey

Re: Battle of the architectures- BFR v Mars Cycler
« Reply #46 on: 01/06/2019 04:23 pm »
For ‘battle’ in the title read competition :).
If we apply mass transportation economics the Cycler architecture will never compete with the SS/SH architecture. The Cycler system will always be more complex to operate and expanding the Cycler system capacity will never be as simple as just rolling more SS/SH units off the production line.  The cruise ship v airline analogy holds. Today, after decades of competitive development, Cruise ships are for pleasure, to move people en-mass you use aircraft because it’s the cheaper architecture. Don’t get me wrong, I love the idea of an interplanetary cruise liner, I just can’t see it being competitive.

P.S. Typo city using my phone- now corrected
« Last Edit: 01/06/2019 08:27 pm by SteveKelsey »
2001 is running a little late, but we are getting there.

Offline Slarty1080

  • Senior Member
  • *****
  • Posts: 2740
  • UK
  • Liked: 1871
  • Likes Given: 814
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #47 on: 01/06/2019 10:38 pm »
For ‘battle’ in the title read competition :).
If we apply mass transportation economics the Cycler architecture will never compete with the SS/SH architecture. The Cycler system will always be more complex to operate and expanding the Cycler system capacity will never be as simple as just rolling more SS/SH units off the production line.  The cruise ship v airline analogy holds. Today, after decades of competitive development, Cruise ships are for pleasure, to move people en-mass you use aircraft because it’s the cheaper architecture. Don’t get me wrong, I love the idea of an interplanetary cruise liner, I just can’t see it being competitive.

P.S. Typo city using my phone- now corrected
I get the point, although I think the ultimate reason aircraft are used for people is because it is quicker. If time were not such a concern then ships would be cheaper - just cut the luxury and add lots more small cabins, would have thought a big liner could carry tens of thousands like that.
My optimistic hope is that it will become cool to really think about things... rather than just doing reactive bullsh*t based on no knowledge (Brian Cox)

Online rakaydos

  • Senior Member
  • *****
  • Posts: 2825
  • Liked: 1869
  • Likes Given: 69
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #48 on: 01/09/2019 07:35 pm »
A cyler would be designed to handle a full Starship PTP passanger load indefinitely. It would exist so that a BFR doesn't need to operate in mars-cruise loadout, only destination-to-destination, with the cycler as one of the destinations.

Offline spaceman100

  • Full Member
  • *
  • Posts: 122
  • NORTH EUROPE
  • Liked: 8
  • Likes Given: 18
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #49 on: 01/10/2019 08:22 am »
I'm curious why this needs to be a battle?

It's like having Columbus hold off his voyages of exploration while he waits for the development of the Clipper Ships. 

The Clippers couldn't be developed until the technology and the economic demand were both in place.  Similarly, Cycler Ships are geared toward high volume, strong economic demand.

An interesting note is that the great liners were often served off-shore from some ports by launches carrying as many (or more) passengers as the early colonization ships.

Personally, I see BFR and Cyclers as having a sequential, followed by symbiotic relationship.  Early on, BFR with 100 passengers flies the route to establish the initial colony.  Later, BFRs are modified to carry 2 or 3 hundred passengers out to meet a cycler and several are sent at once.  (Look at how the airlines have fitted out the demo models of the 747 and A380 compared to how the actual operators have them outfitted.)

They would dock with the cycler which would house the passengers for the trip.  They'd then re-board the Hi-Cap BFR for the descent to Mars.

Yes and forgetting all about Kontiki and Viking ships !

Offline tyrred

  • Full Member
  • ****
  • Posts: 920
  • Seattle
  • Liked: 750
  • Likes Given: 20640
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #50 on: 01/10/2019 09:27 am »
Propose we need both, competitively, to determine the statistical cost/benefit of using one vs other vs both in cooperation.

Question is who will actually field either, both, or neither.

Gut feeling is cyclers lose in the "responsiveness" category but win in the "economy" category. 

Refueling should become routine, and the economics of refueling events vs mass vs ISP vs capability would *hopefully prove out on a near-even playing field.  In a sci-fi future, of course.

Offline SteveKelsey

Re: Battle of the architectures- BFR v Mars Cycler
« Reply #51 on: 01/14/2019 11:55 am »
Could you expand on your thinking on why the Cycler architecture would be more economical? Every time I look at it it seems the more expensive system due to its greater complexity in operation and need for four completely different vehicle architectures to support it. 
2001 is running a little late, but we are getting there.

Offline Slarty1080

  • Senior Member
  • *****
  • Posts: 2740
  • UK
  • Liked: 1871
  • Likes Given: 814
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #52 on: 01/14/2019 01:29 pm »
Propose we need both, competitively, to determine the statistical cost/benefit of using one vs other vs both in cooperation.

Question is who will actually field either, both, or neither.

Gut feeling is cyclers lose in the "responsiveness" category but win in the "economy" category. 

Refueling should become routine, and the economics of refueling events vs mass vs ISP vs capability would *hopefully prove out on a near-even playing field.  In a sci-fi future, of course.
I think the prime advantage of a cycler is protecting passengers from prolonged periods of zero gravity, radiation and confined spaces. But with the new Starship architecture it will be possible to reduce the transfer time to perhaps as little as 3-4 months so the transfer need not be as prolonged as was once thought and radiation and zero gravity will be lesser issues. In addition the volume available would go a long way to reducing the problem of confined space.

In short transfer of passengers to Mars in a Starship looks like being a very practical proposition. The Starship/SH program is underway and should be producing results in the next few years.

There appears to be very little likelihood of a cycler vehicle appearing before Starship becomes operational due to development costs and lack of a willing operator. And once a Starship based transport system is available the barrier to a cycler will be higher still.
My optimistic hope is that it will become cool to really think about things... rather than just doing reactive bullsh*t based on no knowledge (Brian Cox)

Offline spacenut

  • Senior Member
  • *****
  • Posts: 5181
  • East Alabama
  • Liked: 2587
  • Likes Given: 2895
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #53 on: 01/14/2019 03:18 pm »
I can see where eventually there would be a need for a large fuel depot in LEO so the Starship can refuel quickly with one docking, and get on its way. 

As more cargo and larger crews are needed, a fuel depot near the lunar L2 location, for outbound tank top offs, and in bound tank top offs.  Maybe even a fuel depot at a Mars orbit. 

If 6 tankers are needed to fill up a Starship in LEO, then that is a lot of docking operations needed quickly to keep people from waiting several days in LEO before proceeding to Mars.  Why not use Starship cargo or tankers to fill a fuel depot constantly year round so during the synod when Starships go to Mars, they could refuel much more quickly. 

Online edzieba

  • Virtual Realist
  • Senior Member
  • *****
  • Posts: 6105
  • United Kingdom
  • Liked: 9332
  • Likes Given: 39
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #54 on: 01/14/2019 03:49 pm »
One major economic benefit of a cycler is freeing up resources. Say a cycler can handle 10 BFS' worth of passengers. That's 10 BFS that now immediately fly back to Earth and can be used for revenue generation for the rest of the synod, rather than spending that time coasting to Mars earning zip.

Offline ThinkerX

  • Full Member
  • ***
  • Posts: 341
  • Alaska
  • Liked: 126
  • Likes Given: 63
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #55 on: 01/14/2019 07:58 pm »
maybe use cyclers for bulk cargo (little or no crew) with no pressing time limit?  something you don't care if it takes an extra year or so to get to its destination?

Offline Lars-J

  • Senior Member
  • *****
  • Posts: 6809
  • California
  • Liked: 8485
  • Likes Given: 5384
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #56 on: 01/14/2019 09:45 pm »
One major economic benefit of a cycler is freeing up resources. Say a cycler can handle 10 BFS' worth of passengers. That's 10 BFS that now immediately fly back to Earth and can be used for revenue generation for the rest of the synod, rather than spending that time coasting to Mars earning zip.

That's not how orbital mechanics work! Whatever craft are used to send stuff to the cycler will need to stay with it.

A cycler would swing by Earth at the same speed as a mars injection burn. To rendezvous with a cycler a craft needs to put itself on a Mars intersecting transfer orbit. ZERO propellant is saved.

With a BFS/BFR architecture available, Cyclers make NO sense. Maybe some decades later they could work. But then a bigger and better BFS could be available. And so on.
« Last Edit: 01/14/2019 09:46 pm by Lars-J »

Offline Slarty1080

  • Senior Member
  • *****
  • Posts: 2740
  • UK
  • Liked: 1871
  • Likes Given: 814
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #57 on: 01/14/2019 09:48 pm »
One major economic benefit of a cycler is freeing up resources. Say a cycler can handle 10 BFS' worth of passengers. That's 10 BFS that now immediately fly back to Earth and can be used for revenue generation for the rest of the synod, rather than spending that time coasting to Mars earning zip.
Once the BFS reach the cycler they won'y have sufficient propellant to return to Earth
My optimistic hope is that it will become cool to really think about things... rather than just doing reactive bullsh*t based on no knowledge (Brian Cox)

Offline Slarty1080

  • Senior Member
  • *****
  • Posts: 2740
  • UK
  • Liked: 1871
  • Likes Given: 814
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #58 on: 01/14/2019 09:49 pm »
maybe use cyclers for bulk cargo (little or no crew) with no pressing time limit?  something you don't care if it takes an extra year or so to get to its destination?
There is no point using a cycler for cargo
My optimistic hope is that it will become cool to really think about things... rather than just doing reactive bullsh*t based on no knowledge (Brian Cox)

Offline Zed_Noir

  • Senior Member
  • *****
  • Posts: 5490
  • Canada
  • Liked: 1809
  • Likes Given: 1302
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #59 on: 01/14/2019 10:14 pm »
<snip> 
If 6 tankers are needed to fill up a Starship in LEO, then that is a lot of docking operations needed quickly to keep people from waiting several days in LEO before proceeding to Mars.  Why not use Starship cargo or tankers to fill a fuel depot constantly year round so during the synod when Starships go to Mars, they could refuel much more quickly.

No need for purpose build propellant depots in the near future. You can use a Starship Tanker (that should be StarTanker IMO) as ad hoc orbital mini depot. AIUI the propellant contents of a top off Starship Tanker can filled the Starship Transport's tanks full with propellants to spare.

So that before a Mars bound Starship Transport lifts off from Earth a dedicated receiving tanker in orbit with full tanks is waiting to top off the Starship Transport's tanks.

So you just need to have a large fleet of Starship tankers available for each Mars launch window. Including Starship Transports on propellant delivery runs to the orbit Starship Tanker mini depots.

Online edzieba

  • Virtual Realist
  • Senior Member
  • *****
  • Posts: 6105
  • United Kingdom
  • Liked: 9332
  • Likes Given: 39
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #60 on: 01/15/2019 11:59 am »
One major economic benefit of a cycler is freeing up resources. Say a cycler can handle 10 BFS' worth of passengers. That's 10 BFS that now immediately fly back to Earth and can be used for revenue generation for the rest of the synod, rather than spending that time coasting to Mars earning zip.

That's not how orbital mechanics work! Whatever craft are used to send stuff to the cycler will need to stay with it.

A cycler would swing by Earth at the same speed as a mars injection burn. To rendezvous with a cycler a craft needs to put itself on a Mars intersecting transfer orbit. ZERO propellant is saved.

With a BFS/BFR architecture available, Cyclers make NO sense. Maybe some decades later they could work. But then a bigger and better BFS could be available. And so on.
- 'Chomper' holding a crew transfer module launches
- Tanker fully loads chomper with propellant
- Chomper burns to catch cycler (which has slowed on approach using high-ISP-low-thrust engine such as SEP or NEP)
- Chomper offloads CTM to cycler
- Now empty chomper burns to return to Earth
- Meets tanker in Earth orbit (or prior if needed) to reload propellant for landing

If insufficient propellant remains for the chomper to return to Earth after meeting the cycler, a full tanker can be dispatched along with one or more chompers to re-fill prop at the cycler. The CTM acts as a convenient way to avoid dwell time at the cycler, containerise all life-support systems and avoid trucking them back with the chomper (with said life support acting as distributed backup - or even primary - when attached to the cycler) and acting as a useful hold for personal goods and supplies while attached to the cycler. The CTMs still end up idling during transit, but those have minimal revenue generating potential and would still need to do so even with direct transit integrated into a Starship.

Overall propellant use is rather higher than direct transit, but avoids leaving revenue-generating vehicles to coast in idle. Direct transit would still occur for many years beforehand as it makes so sense for lower flight rates, and allows a collection of vehicles to accumulate at the Mars end for offloading (a mirror of the onloading process).

Offline Slarty1080

  • Senior Member
  • *****
  • Posts: 2740
  • UK
  • Liked: 1871
  • Likes Given: 814
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #61 on: 01/15/2019 11:02 pm »
One major economic benefit of a cycler is freeing up resources. Say a cycler can handle 10 BFS' worth of passengers. That's 10 BFS that now immediately fly back to Earth and can be used for revenue generation for the rest of the synod, rather than spending that time coasting to Mars earning zip.

That's not how orbital mechanics work! Whatever craft are used to send stuff to the cycler will need to stay with it.

A cycler would swing by Earth at the same speed as a mars injection burn. To rendezvous with a cycler a craft needs to put itself on a Mars intersecting transfer orbit. ZERO propellant is saved.

With a BFS/BFR architecture available, Cyclers make NO sense. Maybe some decades later they could work. But then a bigger and better BFS could be available. And so on.
- 'Chomper' holding a crew transfer module launches
- Tanker fully loads chomper with propellant
- Chomper burns to catch cycler (which has slowed on approach using high-ISP-low-thrust engine such as SEP or NEP)
- Chomper offloads CTM to cycler
- Now empty chomper burns to return to Earth
- Meets tanker in Earth orbit (or prior if needed) to reload propellant for landing

If insufficient propellant remains for the chomper to return to Earth after meeting the cycler, a full tanker can be dispatched along with one or more chompers to re-fill prop at the cycler. The CTM acts as a convenient way to avoid dwell time at the cycler, containerise all life-support systems and avoid trucking them back with the chomper (with said life support acting as distributed backup - or even primary - when attached to the cycler) and acting as a useful hold for personal goods and supplies while attached to the cycler. The CTMs still end up idling during transit, but those have minimal revenue generating potential and would still need to do so even with direct transit integrated into a Starship.

Overall propellant use is rather higher than direct transit, but avoids leaving revenue-generating vehicles to coast in idle. Direct transit would still occur for many years beforehand as it makes so sense for lower flight rates, and allows a collection of vehicles to accumulate at the Mars end for offloading (a mirror of the onloading process).
The problem here is that it requires an entirely new engine concept NEP/SEP which is not currently available and not likely to become available in the foreseeable future.

If such an engine were available then it would make sense to use it in the form of a tug rather than a cycler (or your proposal which is (I believe) half tug half cycler). With faster transit times allowed by these sort of engines there would be even less need for a cycler.
My optimistic hope is that it will become cool to really think about things... rather than just doing reactive bullsh*t based on no knowledge (Brian Cox)

Offline Hop_David

  • Full Member
  • ****
  • Posts: 1656
  • Ajo, Arizona
    • Hop's Gallery
  • Liked: 147
  • Likes Given: 60
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #62 on: 01/27/2019 05:41 pm »
I am sure this has been debated a lot on this site but the topic keeps coming up in replies to another thread so I thought I should start a specific thread on the debate- which architecture is better for mass colonisation- the BFR architecture being built by SpaceX or the Mars cycler approach.

Some comments on the Aldrin cycler.

Aphelion is 2.23 A.U., well past Mars' 1.52 A.U. orbit. So the cycler's orbit crosses Mars' orbit at a good angle. That means rendezvous with the cycler would take lots of delta V.

Low Mars Orbit to Cycler: 7.5 km/s.
Mars Surface to Cycler: 11 km/s.

Even if the taxi's hab is a small fraction of the cycler hab, the huge delta V budget makes the Mars to cycler taxi a large, expensive vehicle.

Taxis from earth to cycler also suffer a larger delta V budget. About 5.1 km/s from LEO to cycler.

And the Aldrin cycler calls for rotating the line of apsides around 50º each synodic period. Aldrin called for Earth swing bys to accomplish this turn. But some delta V would need to be provided by reaction mass.

And Mars noticeably eccentric elliptical orbit makes maintaining the cycler orbit a big headache.

I've always regarded Aldrin's cycler scheme as an impractical Rube Goldberg device.

There are less delta V intensive cyclers like the VISIT-1 and VISIT-2 Cyclers. But Earth and Mars fly bys are much less frequent.
« Last Edit: 01/27/2019 05:43 pm by Hop_David »

Offline Hop_David

  • Full Member
  • ****
  • Posts: 1656
  • Ajo, Arizona
    • Hop's Gallery
  • Liked: 147
  • Likes Given: 60
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #63 on: 01/28/2019 03:55 pm »
That said, I believe many Musketeers are overly optimistic on BFR. Large delta V budgets mandate small mass fractions for structure and thermal protection. I do not believe it will be possible to have economic, reusable vehicles going from one planetary surface to another.

I am encouraged to see Musk talking more about propellent depots. If the BFR is refueled, we're no longer talking about 20 km/s delta V budgets.

What I'd like to see is an interplanetary vehicle parked in planetary orbit between trips. Like in Andy Weir's The Martian. James Oberg called this scheme a cycler. Incorrectly, in my opinion.  A cycler as proposed by Oberg and Aldrin would fly by a planet, not stop and park in planetary orbit.

Parking the interplanetary vehicle in Earth or Mars orbit does have some of the advantages of full fledged cycler, though.
1) The vehicle doesn't need the robust structure and thermal protection to survive the extreme conditions of re-entry.
2) It doesn't need a stud hoss thrust to weight ratio of a vehicle ascending from a planetary surface. This allows for fewer rocket engines and higher ISP propellents.
3) It takes less delta V to move between planetary orbits than it does going from surface to surface.

So there is some things in common between Hermes and the cycler scheme Oberg and Aldrin worked on together. I've been reading Oberg's stuff for a lot of years and I am a fan. So I'll cut him some slack and call the Hermes a cycler of a sort.

However there are some things I don't like about The Martian. Between mission the Hermes parks in low earth orbit or low Mars orbit. See this video for The Martian's backstory. If the goal is the reduce the large vehicle's  delta V, why park so deep in a planet's gravity well?

Better places to park a "castle" (to use Oberg & Aldrin's term) would be EML2 and Phobos, in my opinion.

Low Earth Orbit to Low Mars Orbit is about 6 km/s while EML2 to Phobos is about 3 km/s.

With Phobos as a stop, extracting the abundant oxygen from Phobos minerals is a possibility. Thus the "taxi" (to use another Oberg-Aldrin term) from Phobos to Mars surface could have propellent to help shed velocity on reaching Mars' atmosphere. This would make Mars EDL much less challenging.

So I like the notion of Musk's BFR with propellent depots if the depots are at EML2 and Phobos.
« Last Edit: 01/28/2019 03:58 pm by Hop_David »

Offline Lar

  • Fan boy at large
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 13463
  • Saw Gemini live on TV
  • A large LEGO storage facility ... in Michigan
  • Liked: 11864
  • Likes Given: 11086
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #64 on: 01/28/2019 04:37 pm »
I don't see this as much of a battle, TBH. At present, cycler isn't practical. Wait 10 years from start of regular service to Mars and maybe things will be different. But cycler is too early. IMHO.
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline Hop_David

  • Full Member
  • ****
  • Posts: 1656
  • Ajo, Arizona
    • Hop's Gallery
  • Liked: 147
  • Likes Given: 60
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #65 on: 01/29/2019 04:40 pm »
At present, cycler isn't practical.

Neither is BFR. We aren't going to start colonizing Mars any time soon.

Offline Lar

  • Fan boy at large
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 13463
  • Saw Gemini live on TV
  • A large LEGO storage facility ... in Michigan
  • Liked: 11864
  • Likes Given: 11086
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #66 on: 01/30/2019 02:15 am »
At present, cycler isn't practical.

Neither is BFR. We aren't going to start colonizing Mars any time soon.
Both are future. One is just notional. The other is orders of magnitude closer to realization since it's under active development. And thus a lot closer to practical. But your point is taken. Still, I think cycler is easily bested in the race to realization.
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Online rakaydos

  • Senior Member
  • *****
  • Posts: 2825
  • Liked: 1869
  • Likes Given: 69
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #67 on: 02/05/2019 01:30 pm »

What I'd like to see is an interplanetary vehicle parked in planetary orbit between trips. Like in Andy Weir's The Martian.

Without aerocapture, you double your DV costs reaching planetary orbit. Aerocapture needs the same reentry capability as direct entry. As long as your heat shield doesnt cost you half your DV budget (And the stainless steel starship is doing interesting things with counting the heat shield as part of minimal structural mass) it's better to bring all the tanks to the martian gas station, and not rely on shuttle flights.

Offline Lemurion

Re: Battle of the architectures- BFR v Mars Cycler
« Reply #68 on: 02/05/2019 09:36 pm »
My issue with cyclers is where does the propellant come from?

(Simplified) With BFS you only need sufficient propellant for a one-way trip. Aerocapture is used at the other end.

Cycler shuttles (even if they use aerocapture) need to either ride the whole way on the cycler and deposit passengers on the other end or enough propellant both to enter the initial transfer orbit and then boost back to the launch planet.

The first eliminates the savings from specialized vehicles for Earth and Mars and the second greatly increases the shuttle propellant and delta-v requirements. Moreover, if the shuttle tanks from the cycler, where does it get that propellant mass from?

Online rakaydos

  • Senior Member
  • *****
  • Posts: 2825
  • Liked: 1869
  • Likes Given: 69
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #69 on: 02/15/2019 04:55 pm »
My issue with cyclers is where does the propellant come from?

(Simplified) With BFS you only need sufficient propellant for a one-way trip. Aerocapture is used at the other end.

Cycler shuttles (even if they use aerocapture) need to either ride the whole way on the cycler and deposit passengers on the other end or enough propellant both to enter the initial transfer orbit and then boost back to the launch planet.

The first eliminates the savings from specialized vehicles for Earth and Mars and the second greatly increases the shuttle propellant and delta-v requirements. Moreover, if the shuttle tanks from the cycler, where does it get that propellant mass from?
Agreed and brings me back to my point- a cycler needs a Starship to act as a shuttle to be practical. Starship does not need a Cycler to be practical for small loads, but a cycler may be a quality of life improvement

Offline spacenut

  • Senior Member
  • *****
  • Posts: 5181
  • East Alabama
  • Liked: 2587
  • Likes Given: 2895
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #70 on: 02/15/2019 05:30 pm »
Since SS is going to be refueled in LEO, it makes sense to have a large fuel depot in LEO to fill the SS's going to Mars.  Also if there is a potential landing problem with a SS returning from Mars, say a hydraulic problem or a problem with the transpiration system, the SS could use it's landing fuel to slow down and get in orbit near or at the fuel depot.  A SS could be sent up to retrieve the return passengers/cargo for earth landing.  In the meantime the SS might be able to return to Mars but not earth landing, and could still be used as an in space shuttle or for moon sorties to the moon and back to the fuel depot.  No need to scrap the SS. 

Not downing the Cycler concept, but it would have to be huge to have enough fuel to sustain orbit between earth and Mars, bring cargo and people to and from Mars, and since it is in long orbit, may have to have some type of artificial gravity, either centrifuge or rotating.  It would take longer to build the Cycler and infrastructure than doing everything direct with SS and refueling at this time. 

Offline TrevorMonty

Re: Battle of the architectures- BFR v Mars Cycler
« Reply #71 on: 02/16/2019 07:37 am »
SS does need depot just full tanker in LEO. Launch tanker then fill it with X tanker launches, once fill launch SS. First tanker may have better insulation for long term storage.


Online rakaydos

  • Senior Member
  • *****
  • Posts: 2825
  • Liked: 1869
  • Likes Given: 69
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #72 on: 05/06/2019 01:54 am »
Bumping this thread to put a random thought I had on page...

Cyclers are about as future-proof as gas station towns on the American Old Route 66. They are fundamentally dependent on interplanetary transportation being both seasonal (that is, lining up with cycler orbits which are synchronized to the synods) and time consuming (where the extra shielding mass and living space are worthwhile for the duration of a trip)

Fusion has been 20 years away for the last 50 years, but does anyone really believe it will never be solved? A high ISP/high thrust torch drive (fusion, antimatter, unicorn farts, whatever) would turn every cycler built to that point into an isolated backwater, it's only upkeep being historical tourism. People complain about "flyover states" left behind by economic development- Building a cycler network would be setting the stage for another hardship of that sort.

Offline Hop_David

  • Full Member
  • ****
  • Posts: 1656
  • Ajo, Arizona
    • Hop's Gallery
  • Liked: 147
  • Likes Given: 60
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #73 on: 08/05/2019 10:33 pm »
The other is orders of magnitude closer to realization since it's under active development. And thus a lot closer to practical.

Awhile back I was complaining this forum was placing their bets on SLS, Orion and Constellation for beyond low earth orbit human spaceflight. (Looking at the categories...) And nasaspaceflight still seems to think the good ol' boy aerospace gang will be the ones to take humans to Mars or wherever. Even though one of the mods seems a SpaceX fan boy.

A Mars cycler system as proposed by Aldrin is quite impractical.

However the notion of an interplanetary vehicle berthed in planetary orbits is not. An interplanetary vehicle that descends and descends all the way to/from the bottom of planetary gravity well is impractical. If that's what Musk has in mind I'd say he's being optimistic.

Andy Weir's Hermes was an interplanetary ship that would berth in planetary orbits between trips. James Oberg likes to call the Hermes a cycler even though it was a lot different than the cycler Oberg and Aldrin wrote about it Scientific American.

Offline KelvinZero

  • Senior Member
  • *****
  • Posts: 4286
  • Liked: 887
  • Likes Given: 201
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #74 on: 08/06/2019 02:54 am »
Just throwing this old idea out there because it is probably too small for it's own thread. ( I may have posted it before )
I don't see much use for cyclers between two bodies because you always need a fair bit of propulsion keeping them on track so you can never have the real dream of a genuinely comfortable town-sized transport for free.

One place in the far future where perhaps cyclers may become useful is cyclers with only one specific target and another diffuse one. I think this would require far less station keeping. Two examples of this could be
(*) Earth and the asteroid belt.
(*) The moons of Jupiter and a safe high orbit outside Jupiters lethal radiation.

How do you travel to the asteroid belt when you have thousands of colonies? A single hub in the asteroid belt is no solution. Half the belt will be further from it than from earth itself. Ceres is not in a great orbit to begin with. Instead, how about a portion of your asteroid colonies being on petal-like orbits that take it near earth and then pass through the asteroid belt at a decent clip. I think it would be poetic if you had enough that one came near the earth every month. Then we could name their orbits (each containing multiple cyclers, assuming multi-year periods) after constellations. Since trips would still take years perhaps these could be university towns so you can pick up your degree on the way out. They could also do the last phases of manufacturing after the mass-wasting phases such as ore processing. This way your product does not need to be years out of date on arrival.

How do you efficiently dive into jupiter's radiation belt to visit your in-laws on worlds like Europa? How about a heavily shielded cycler for each moon? Perhaps it includes a mass driver to match a shuttle's velocity to the moon as it skims past so you only spend minutes instead of days exposed without maximum shielding. The cycler can also carry you from the moon to a high orbit where it would not take much energy to transfer to the cycler dedicated to another moon. They all intersect pretty much the same circular orbit that could escape jupiter entirely with just a nudge, thus suiting electric propulsion nicely.

Offline Yaotzin

  • Member
  • Posts: 57
  • Liked: 39
  • Likes Given: 0
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #75 on: 08/06/2019 06:15 am »
However the notion of an interplanetary vehicle berthed in planetary orbits is not. An interplanetary vehicle that descends and descends all the way to/from the bottom of planetary gravity well is impractical. If that's what Musk has in mind I'd say he's being optimistic.
Quote from: Hop_David
I am encouraged to see Musk talking more about propellent depots. If the BFR is refueled, we're no longer talking about 20 km/s delta V budgets.
You seem to be unaware that Starship/BFR/ITS/MCT is and always has been intended to be refueled in orbit. It's not some monster 20km/s direct to Mars vehicle.

For a remotely sustainable architecture with an interplanetary vehicle, you still need a reusable launcher, and a reusable lander...like Starship. Why bother with designing a whole new vehicle for the middle?

I can see a cycler making sense later, if you're sending lots of ordinary people. 3 months in a tin can is OK for astronauts but maybe not regular folk. You could make the conditions in a cycler much, much more pleasant.

Offline spacenut

  • Senior Member
  • *****
  • Posts: 5181
  • East Alabama
  • Liked: 2587
  • Likes Given: 2895
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #76 on: 08/06/2019 06:47 am »
The cycler concept would be like an ocean liner.  Long trip would require artificial gravity and a lot of fuel.  It would have to be loaded with orbit adjustment fuel, cargo, and possibly a reusable lander for use at Mars.  It would require traditional rockets with humans to dock and deliver their passengers.  Lots of thing going on.  Humans delivered in capsules (how many flights, how many passengers?).  How many refueling flights during is travel by earth.  Lots of dockings and off loadings just to keep cycler going all the while the cycler is moving by. 

SS/Superheavy would only go when Mars and earth are close in their orbits for a shorter trip.  SS goes up, docks and refuels with a tanker SS, and off she goes with enough fuel to get to and land on Mars, probably 3 month trip.  Then it would have to refuel with a pre-installed fuel depot tanker making fuel for 2 years prior to human return trip.  SS would land refuel, off load people or cargo, then fly back with a full tank to earth and and land with return people and/or cargo.  Seems more simple.  Only one docking and fuel loading at pre-installed SS tanker/fuel depot in earth orbit before departure of large SS vehicle.  One fuel loading on the ground at Mars for return.  Mars SS tanker/fuel depot on the surface would continously be making fuel during the off synods.  SS tanker in orbit could continuously be refueled in LEO during off synods.  Orbital tanker would not have to have return shielding or legs installed just solar panels and refrigeration equipment, maybe some shading.  Engines could be removed by a visiting cargo SS and returned to earth for use on another SS.

Remember there will be three types of SS's.  Cargo, tanker, and passenger.  There maybe a combinatiion passenger/cargo flight or two in the beginning to set things up.  SpaceX is going to have many many SS's built.  Probably fewer reusable  boosters.  Keeping tanking equipment in LEO and on Mars will be simpler for maintenance. 

Trying to catch a flying by cycler with many launches at many different launch times and angles is far more complicated.     

Offline Nilof

  • Full Member
  • ****
  • Posts: 1177
  • Liked: 597
  • Likes Given: 707
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #77 on: 08/06/2019 10:47 am »
The Starship is near-optimal for a pure chemical architecture once you view a fleet of them as a system instead of considering an individual ship, with prop transfer from tankers in the fleet replacing staging whenever staging looks like it would help.

However, there definitely is value to high-power SEP spacecraft down the line, especially considering that a rapidly reusable heavy lifter like Starship makes is a lot easier to develop a SEP system with a hardware-rich approach.

SEP is especially useful if you want to get the ships back in one synodic period, or if you want the capability to send a ship to mars outside of the standard launch windows, since low thrust trajectories are much more flexible. And it also has an easy Mars ISRU refueling option if it can use argon propellant.
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.

Offline FutureSpaceTourist

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 48174
  • UK
    • Plan 28
  • Liked: 81684
  • Likes Given: 36941
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #78 on: 08/08/2021 11:52 pm »
https://twitter.com/xtina_korp/status/1424353282521243651

Quote
About 9 years ago, Buzz Aldrin and I went to meet with @ElonMusk at SpaceX HQ in El Segundo, CA. Buzz had hoped to share his plans of perpetual cycling orbits between Earth and Mars with Elon. (a thread)
📷@RGVAirealphotos

twitter.com/xtina_korp/status/1424353613779017728

Quote
Buzz’s Cycler is a spacecraft and system using the trajectory he devised similar to the spacecraft in the movie “The Martian” even though author Andy Weir didn’t give Buzz credit.

https://twitter.com/xtina_korp/status/1424353777495257093

Quote
Buzz wanted Elon to support his concept and maybe work together on Mars missions. However, during the meeting Elon said he didn’t want to see Buzz’s plans.

Buzz was flabbergasted. He said, “I thought you wanted to get to Mars!”

twitter.com/xtina_korp/status/1424353971515371520

Quote
Elon replied that he did and Buzz asked how he was going to do it. Buzz was convinced his Cycler was the only logical and sustainable way.

Elon said “I’m going to build a big f*cking rocket. It’ll be able land vertically.”

https://twitter.com/xtina_korp/status/1424354336063299592

Quote
Buzz was extremely skeptical. I asked about the timeline and Elon said between 10-12 years.

Lo and behold - here’s that big f-ing rocket. @elonmusk did it!

Offline Dalhousie

  • Senior Member
  • *****
  • Posts: 2766
  • Liked: 780
  • Likes Given: 1132
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #79 on: 08/08/2021 11:57 pm »

Lo and behold - here’s that big f-ing rocket. @elonmusk did it!
[/quote]

Don't count your rockets before they are operational.
Apologies in advance for any lack of civility - it's unintended

Offline Twark_Main

  • Senior Member
  • *****
  • Posts: 3621
  • Technically we ALL live in space
  • Liked: 1878
  • Likes Given: 1187
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #80 on: 08/09/2021 02:37 am »

Lo and behold - here’s that big f-ing rocket. @elonmusk did it!

Don't count your rockets before they are operational.

The bar was

Quote
Elon said “I’m going to build a big f*cking rocket. It’ll be able land vertically.”

He built it. "Operational" is a later milestone.

Doggammit, he hit his stated schedule for a change. Darn impressive long-term timeline estimation right there.


"The best way to predict the future is to create it." -- Alan Kay
« Last Edit: 08/09/2021 02:48 am by Twark_Main »
"The search for a universal design which suits all sites, people, and situations is obviously impossible. What is possible is well designed examples of the application of universal principles." ~~ David Holmgren

Offline eachus

  • Member
  • Posts: 1
  • Nashua, New Hampshire USA
  • Liked: 0
  • Likes Given: 0
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #81 on: 08/12/2021 10:46 pm »
Can it be BFR/BFS v Mars Cycler v Something Altogether More Pragmatic and Sensible?

How about this there are a number of earth orbit crossing asteroids, Apophis in 2026 is a good starting point.  Send a Starship loaded with tools and machinery that digs a large hole and builds several thrusters on the surface.  Most of these thrusters can literally be at the throwing rocks level of sophistication, but cold gas thrusters are easier.  The "main engines" would be an uprated VASMIR engine or some such.  Take an RTG along for power until the Starship is stabilized and robots can be put to work creating solar power assets.  These need not be high-quality photoelectrics. For example, mirrors could be created by refining metal (aluminum?) from the regolith and using the mirrors to increase the light intensity on PE cells brought up from the earth.

While this is going on, you have robots digging a hole toward the center of the asteroid, and hollowing it out.
 The goal is to put Apophis in an orbit that passes close to Earth and then to Mars.  And to have an interior protected by hundreds of meters of rock from cosmic rays and solar radiation.  (Some cosmic rays will be powerful enough to blast all the way through--and have lots of secondary rays in that interior volume.  But no worse than Earth, where the atmosphere does the same thing.)

Does this seem like too much work?  One Starship refueled in orbit should be able to take on the order of a hundred tonnes of cargo to the asteroid.  Getting VASMIR propellant from the asteroid may be too tricky.  So take a few tonnes as cargo.  For that matter, the VASMIR system could be built into the nose of the Starship and operated from there.

Offline QuantumG

  • Senior Member
  • *****
  • Posts: 9238
  • Australia
  • Liked: 4477
  • Likes Given: 1108
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #82 on: 08/12/2021 11:01 pm »
Welcome to the forum!

How about this there are a number of earth orbit crossing asteroids, Apophis in 2026 is a good starting point.  Send a Starship loaded with tools and machinery that digs a large hole and builds several thrusters on the surface. Most of these thrusters can literally be at the throwing rocks level of sophistication...

Most asteroids, we've learnt, are "rubble-piles" like (25143) Itokawa. So it's more like you have to put a big bag around them, and do it very carefully, because multi-body gravity systems are notoriously unpredictable. Doesn't mean this is a bad idea, just that we don't know how to do it - the unknown unknowns are still pretty hefty. On the flip-side, the potential for a breakthrough idea is hiding in all that complexity. Imagine if you were to induce a strong magnetic field that interacts with the gas-like fringe of material that surrounds these bodies... perhaps you could create streamers of magnetic bits, perhaps even sorting them in the process. Ore processing works a whole-lot better when you have separated out the impurities... and so on.

Learning how to process asteroid material is totally worthwhile and inevitable in a robust space economy - but we gotta do it first.


Human spaceflight is basically just LARPing now.

Offline Bryan Hayward

  • Member
  • Posts: 98
  • Madison AL
  • Liked: 213
  • Likes Given: 848
Re: Battle of the architectures- BFR v Mars Cycler
« Reply #83 on: 08/04/2022 02:13 pm »
I wonder if there is a between solution, as in between Starship only for initial missions and Cycler (Weir's version that goes between EML2 and Phobos or equivalent, not to LEO and LMO) for routine commerce in the "sci-fi" future.

Send up two SS at a time, one optimized for Earth operations and one for Mars ops. The interplanetary ship (IPS) is a central hub with two long and wide pylons, with a SS dock on each - a really robust dock that can handle 1g forces or better.  The Starships use chemical to boost nearly to trans-Mars injection (TMI). The IPS has an ion drive, whether it is solar or radioisotope or even fission powered is dependent on TRL at the time it is built. The IPS boosts to final TMI and accelerates nearly continuously, rotating for gravity the whole time.  The IPS has the usual cycler advantages.

1) artificial gravity to varying degrees along the pylons, with full g at each SS for exercise and other activities
2) plenty of room
3) multiple radiation shelters (which are assisted by prop tanks and water tanks)
4) large propellant tanks

IPS will flip midway, probably with the help of the Starships' reaction control systems, and begin deceleration. Pre-placed propellant depots at EML2 and Mars orbit makes sure each SS is topped off to the required level.  The IPS will have spare prop tanks that are heavily shielded thermally and have active cooling.  After docking, the SS will offload the prop so the mass at then ends of the pylons is minimized and the preservation of prop is maximized.

Tags: BFR Mars Cycler 
 

Advertisement NovaTech
Advertisement Northrop Grumman
Advertisement
Advertisement Margaritaville Beach Resort South Padre Island
Advertisement Brady Kenniston
Advertisement NextSpaceflight
Advertisement Nathan Barker Photography
0