Author Topic: Taking the BFR Beyond Mars  (Read 16838 times)

Online rakaydos

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Re: Taking the BFR Beyond Mars
« Reply #40 on: 11/04/2017 09:21 PM »
The slide for using the BFS to land on the Moon and return has the BFS 'parked' in a HEEO while it tanks up. With a top delta-vee of ~6.4 km/s for the BFS, storing launch momentum in such an orbit allows a very effective Oberth Maneuver for Outer Planet missions.
(Snip)
Ceres, from Earth orbit, is a real pain. But it'd be pretty simple from Mars. Thus Mars will be the Gateway to Ceres and the Asteroids.

From LEO, perhaps. Way easier to go to Ceres/asteroids from EML1 than Mars though.

Maybe this goes without saying but I am assuming you mean easier from EML1 than Mars surface. I forget who did a nice post with delta-V calculations a ways back showing how Mars orbit is a very attractive staging point for destinations further out.

Also, just to re-iterate, the largest factor making Ceres a difficult target is not the orbital inclination but rather the absence of aerocapture, requiring a large delta-V at the destination. That changes once there is enough infrastructure on Ceres to fill tankers locally and send them out to meet incoming ships part way to supply propellant for the arrival delta-V.
Sending out takers to rendevous with INBOUND ships? that's just...

Whatever the velocity the inbound rocket is at. The tanker needs to get BACK to the rocket, CANCEL it's backward velocity, MATCH velocity with the rocket, and still have enough fuel to slow the tanker AND rocket the required velocity. Basically 4 and a half times the DV requirement.

Offline KelvinZero

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Re: Taking the BFR Beyond Mars
« Reply #41 on: 11/04/2017 11:59 PM »
Sending out takers to rendevous with INBOUND ships? that's just...

Whatever the velocity the inbound rocket is at. The tanker needs to get BACK to the rocket, CANCEL it's backward velocity, MATCH velocity with the rocket, and still have enough fuel to slow the tanker AND rocket the required velocity. Basically 4 and a half times the DV requirement.
I think the trajectory to do this would be similar to designing a cycler trajectory, even if a cycler is not practical between earth and Ceres. You wouldn't send the tanker/depot towards the ship, but in the opposite direction. You are giving it the velocity a BFS would have as it shot on by. This trajectory has to encounter earth and return to Ceres.

Given the years this fuel would be travelling I suspect it would not end up looking like a BFS tanker.

The similarity of the problem to a cycler might make similar orbital inclination very appealing. There are an estimated 200 asteroids above 100km in size so there are probably very good candidates.

IDEA:
The cycler itself could become a more central destination than a specific world like Ceres. Maybe the next target after Mars could be a cycler well designed to revisit Mars regularly that dips deep into the asteroid belt.

Rather than being concerned with any specific target, which requires large varying delta-v, instead this cycler has a fleet of unmanned ARM-like asteroid grabbers that keep grabbing the low hanging fruit of low delta-v and high value asteroids, in "small" 1000 ton bites.. assuming we stuck with the tiny ARM sized variants.

You could end up with multiple of these cyclers visiting mars regularly, perhaps named after the constellation that is in conjunction when they return.

You would still have permanent colonies on places like Ceres, but they are not hubs. They have varying windows to reach mars, made possible by these cyclers. So the Cyclers become the hubs that connect Mars to the outer solar system.

In this analogy, specific asteroid colonies that produce materials but are not centers of trade are sort of like the "fly over states" :)

Im taking this too far off topic. Im really interested in this but it goes way beyond missions with a few BFR Tanker rendezvous.  I vaguely remember someone had a thread about the best targets within the asteroid belt.

Offline Spacer Dan

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Re: Taking the BFR Beyond Mars
« Reply #42 on: 11/05/2017 02:21 AM »
Station modules seem to by geared towards as large a volume as possible, constrained by the cargo capabilities of the BFF. I suggest, after the cargo, tanker, passenger stages are operational that a semi-expendable second stage would be built. Spacex has demonstrated a 12m fuel tank. A semi-expendible stage would be 12m in diameter with the propulsion engines in a 8m open truss at the bottom of the state. The 'power pack' would be detachable and 2-3 of then stored into a freighter to be brought back to earth. All you would leave in orbit would be the tanks. Payload could be 12m by 20 meter long station segments, massing up to 200+ tons.

Please don't take this sideways about expendable stages, I'm just saying that large station construction may require a more specialized vehicle if you want to put a 'Space Vegas' into low Earth orbit.  The tanks could be turned into large zero-G habitation at the station. The stages, refueled, would be massive tugs.

Offline Ludus

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Re: Taking the BFR Beyond Mars
« Reply #43 on: 11/07/2017 03:01 AM »
I assumed 150 tons, though most will be the life-support etc for the 10 crew. A cargo vehicle would need to be sent with it for setting up the base and ISRU. Personally I think the power should be sourced from in situ energy flows,
 rather than a reactor we've hauled across the solar system, though that will probably be needed initially. Wind power from high altitude seems more feasible on Titan than on Earth. Superconducting cables to floating wind-turbines seem perfectly suited to the job.

This also connects with BFR and science instruments thread. How much payload can a standard BFS cargo land on Titan?

This approach suggests that a BFS cargo could be sent on an expendable mission on land on an ice moon with over 100 tons of payload for less money than a conventional flyby probe massing a few tons. It could carry several 10 kW reactors. It would be interesting to see what different labs could come up with to include if the money was tight by typical standards but mass and energy requirements that liberal.

Offline DLR

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Re: Taking the BFR Beyond Mars
« Reply #44 on: 11/07/2017 07:40 AM »
The slide for using the BFS to land on the Moon and return has the BFS 'parked' in a HEEO while it tanks up. With a top delta-vee of ~6.4 km/s for the BFS, storing launch momentum in such an orbit allows a very effective Oberth Maneuver for Outer Planet missions.

I've analysed using this technique to fly to Titan (all on a single tank!) with a reasonable aerobrake entry speed of ~7.7 km/s, to land on the surface. It's the easiest Outer System target to reach, but takes ~3 years, so it's an endurance mission. Launching there in a Parabolic solar orbit takes 2.5 years, but means a re-entry speed of ~10.5 km/s. That *might* be doable with a Magnetoshell braking system.

To get to Callisto requires using two BFS Tankers which then transfer propellant to the BFS after all three boost into a Trans-Jupiter Insertion orbit. The Tankers can then return to Earth after a long loop. The BFS needs to aerocapture into Jupiter, then do a bi-elliptical transfer to Callisto. Shaving off ~1.5 km/s in the aerocapture from an entry speed of 60.7 km/s (it's a 500 day solar orbit, not a 1,000 day Hohmann) is the *hard* part. I feel it'll require some tricky tweaking of the TPS. Or a working Magnetoshell braking system. The BFS ends up in low Callisto orbit, so a pre-emplaced Tanker will be needed to land.

Ceres, from Earth orbit, is a real pain. But it'd be pretty simple from Mars. Thus Mars will be the Gateway to Ceres and the Asteroids.

What about skipping the aerobraking and capturing directly into Callisto orbit? If you time the encounter right, Callisto will be moving parallel to the spacecraft on its orbit around Jupiter, so you can deduct Callisto's orbital velocity when calculating orbital capture delta v.

This is from NASA'S HOPE study (2003):

L1 Departure: 0.58 km/s
TJI: 4.55 km/s
Callisto direct OI: 3.75 km/s

Time: 851 Days

Offline tchernik

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Re: Taking the BFR Beyond Mars
« Reply #45 on: 11/07/2017 05:36 PM »
I assumed 150 tons, though most will be the life-support etc for the 10 crew. A cargo vehicle would need to be sent with it for setting up the base and ISRU. Personally I think the power should be sourced from in situ energy flows,
 rather than a reactor we've hauled across the solar system, though that will probably be needed initially. Wind power from high altitude seems more feasible on Titan than on Earth. Superconducting cables to floating wind-turbines seem perfectly suited to the job.

This also connects with BFR and science instruments thread. How much payload can a standard BFS cargo land on Titan?

This approach suggests that a BFS cargo could be sent on an expendable mission on land on an ice moon with over 100 tons of payload for less money than a conventional flyby probe massing a few tons. It could carry several 10 kW reactors. It would be interesting to see what different labs could come up with to include if the money was tight by typical standards but mass and energy requirements that liberal.

What I find exciting about these latest developments of rocketry, is precisely their power just by having a single one of them (for the mission, not for the preliminaries).

As qraal describes, they would enable truly incredible possibilities for exploration of the Solar System at large, just by having one or two from time to time.

But the real transformation comes from what they can achieve in groups, with several of them per year coming out of the rocket factories, with both reusable and expendable modes of operation available.

There is no reason why several pieces of that nice payload you say couldn't be taken to Ceres,  Titan or Callisto beforehand, enabling any manned  missions to have plenty of supplies and machinery in place when they arrive, including spare return ships.

And that's an actual human expansion and settlement of space scenario. Not just landing, but with permanent manned facilities with scheduled crew rotations on these amazing places.
« Last Edit: 11/07/2017 06:32 PM by tchernik »

Offline DrRobin

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Re: Taking the BFR Beyond Mars
« Reply #46 on: 11/07/2017 06:36 PM »
The slide for using the BFS to land on the Moon and return has the BFS 'parked' in a HEEO while it tanks up. With a top delta-vee of ~6.4 km/s for the BFS, storing launch momentum in such an orbit allows a very effective Oberth Maneuver for Outer Planet missions.

[...]

To get to Callisto requires using two BFS Tankers which then transfer propellant to the BFS after all three boost into a Trans-Jupiter Insertion orbit. The Tankers can then return to Earth after a long loop. The BFS needs to aerocapture into Jupiter, then do a bi-elliptical transfer to Callisto. Shaving off ~1.5 km/s in the aerocapture from an entry speed of 60.7 km/s (it's a 500 day solar orbit, not a 1,000 day Hohmann) is the *hard* part. I feel it'll require some tricky tweaking of the TPS. Or a working Magnetoshell braking system. The BFS ends up in low Callisto orbit, so a pre-emplaced Tanker will be needed to land.
[...]

What about skipping the aerobraking and capturing directly into Callisto orbit? If you time the encounter right, Callisto will be moving parallel to the spacecraft on its orbit around Jupiter, so you can deduct Callisto's orbital velocity when calculating orbital capture delta v.

This is from NASA'S HOPE study (2003):

L1 Departure: 0.58 km/s
TJI: 4.55 km/s
Callisto direct OI: 3.75 km/s

Time: 851 Days

I think it's a good idea, and I'll bet you can do even better with a multi-moon bank-shot to decrease the delta-V needed at the destination, a la the "Interplanetary Transport Netork" idea (https://en.wikipedia.org/wiki/Interplanetary_Transport_Network), but I don't think it totally obviates the need/benefit for aerobraking. The numbers you cite get you 8.83 km/sec to get to Callisto Orbit, but you'd still need another 1.7 km/sec or so to  land, and 10.5 km/sec total delta-V is more than the nominal BFS can do (though a tanker can).

Offline speedevil

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Re: Taking the BFR Beyond Mars
« Reply #47 on: 11/07/2017 11:39 PM »
The numbers you cite get you 8.83 km/sec to get to Callisto Orbit, but you'd still need another 1.7 km/sec or so to  land, and 10.5 km/sec total delta-V is more than the nominal BFS can do (though a tanker can).

On very beyond Mars (Saturn).

ISRU production is going to be annoying unless you get reactors, as solar is a percent or so of earth.
Getting reactors is going to be politically annoying.

Titan is unfortunately likely to not have well mapped available water ice even if you do get reactors.

Neglecting for the moment the difficulty of extracting this, and rendevous, and ...

How rich can you run a raptor before adding more methane is a bad thing for total impulse.
Would adding nitrogen ever be beneficial?
Wondering if this lets you stretch expensive imported oxygen.

Offline Ludus

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Re: Taking the BFR Beyond Mars
« Reply #48 on: 11/10/2017 02:05 AM »



Getting reactors is going to be politically annoying.

Titan is unfortunately likely to not have well mapped available water ice even if you do get reactors.


Reactors are going to be as necessary for humans being seriously spacefaring as reusable rockets so itís gonna have to be addressed.

I had the impression that it was about half water in different mixes and pressures and the ground surface was often water ice rather than rock, though water ice is much like rock at those temperatures. Iíd thought that insulating so waste heat doesnít melt the ground under you was a bigger issue than finding ice.

Online DigitalMan

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Re: Taking the BFR Beyond Mars
« Reply #49 on: 11/10/2017 02:17 AM »

Reactors are going to be as necessary for humans being seriously spacefaring as reusable rockets so itís gonna have to be addressed.

I had the impression that it was about half water in different mixes and pressures and the ground surface was often water ice rather than rock, though water ice is much like rock at those temperatures. Iíd thought that insulating so waste heat doesnít melt the ground under you was a bigger issue than finding ice.

Perhaps in the future reactors can be fueled with off-world nuclear material
« Last Edit: 11/10/2017 02:18 AM by DigitalMan »

Offline Patchouli

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Re: Taking the BFR Beyond Mars
« Reply #50 on: 11/10/2017 02:23 AM »
The numbers you cite get you 8.83 km/sec to get to Callisto Orbit, but you'd still need another 1.7 km/sec or so to  land, and 10.5 km/sec total delta-V is more than the nominal BFS can do (though a tanker can).

On very beyond Mars (Saturn).

ISRU production is going to be annoying unless you get reactors, as solar is a percent or so of earth.
Getting reactors is going to be politically annoying.

Titan is unfortunately likely to not have well mapped available water ice even if you do get reactors.

Neglecting for the moment the difficulty of extracting this, and rendevous, and ...

How rich can you run a raptor before adding more methane is a bad thing for total impulse.
Would adding nitrogen ever be beneficial?
Wondering if this lets you stretch expensive imported oxygen.


BFS would need some kind of solar independent heat source such as RHUs to keep itself from freezing at distances beyond the asteroid belt.
It might even need them for Mars surface ops at higher latitudes so the nuclear politics thing is going have to tackled any way.
« Last Edit: 11/10/2017 02:30 AM by Patchouli »

Offline KelvinZero

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Re: Taking the BFR Beyond Mars
« Reply #51 on: 11/10/2017 03:25 AM »
They have found ice mountains on Titan.

BTW, rather than worrying about waste heat melting the ground out beneath you, engineer to exploit it. There is a whole list of arguments for melting down and creating a small ocean around you. Pretty much every icy body in the solar system could be terraformed this way, into an ocean world under an eggshell of ice.. and you can also start very small: Landers far far simpler than those speculated for Europa ocean missions could just melt down a few tens of meters and begin melting a body of water and provide an airlock into that cavity.

It is one of my hobby horses.

Offline Kaputnik

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Re: Taking the BFR Beyond Mars
« Reply #52 on: 11/10/2017 06:53 AM »
The numbers you cite get you 8.83 km/sec to get to Callisto Orbit, but you'd still need another 1.7 km/sec or so to  land, and 10.5 km/sec total delta-V is more than the nominal BFS can do (though a tanker can).

On very beyond Mars (Saturn).

ISRU production is going to be annoying unless you get reactors, as solar is a percent or so of earth.
Getting reactors is going to be politically annoying.

Titan is unfortunately likely to not have well mapped available water ice even if you do get reactors.

Neglecting for the moment the difficulty of extracting this, and rendevous, and ...

How rich can you run a raptor before adding more methane is a bad thing for total impulse.
Would adding nitrogen ever be beneficial?
Wondering if this lets you stretch expensive imported oxygen.


BFS would need some kind of solar independent heat source such as RHUs to keep itself from freezing at distances beyond the asteroid belt.
It might even need them for Mars surface ops at higher latitudes so the nuclear politics thing is going have to tackled any way.

I don't think RHUs are the answer for something the size of BFS. Perhaps useful for some small systems located away from the main cabin, but even then electrical heaters powered by the main power source might be easier.

On Mars, you can do everything with solar, unless you want to work at high latitudes in winter.
Waiting for joy and raptor

Offline jpo234

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Re: Taking the BFR Beyond Mars
« Reply #53 on: 11/10/2017 07:12 AM »
Titan is unfortunately likely to not have well mapped available water ice even if you do get reactors.

The solar system is soggy. Basically everywhere we have looked there is or was an abundance of water. The NASA article "The Solar System and Beyond is Awash in Water" says:

Quote
Perhaps the most surprising water worlds are the five icy moons of Jupiter and Saturn that show strong evidence of oceans beneath their surfaces: Ganymede, Europa and Callisto at Jupiter, and Enceladus and Titan at Saturn.

This puts Titan into the Ocean World category. More details found in "Titan's Underground Ocean":

Quote
The search for water is an important goal in solar system exploration, and now we've spotted another place where it is abundant.
« Last Edit: 11/10/2017 07:19 AM by jpo234 »
You want to be inspired by things. You want to wake up in the morning and think the future is going to be great. That's what being a spacefaring civilization is all about. It's about believing in the future and believing the future will be better than the past. And I can't think of anything more exciting than being out there among the stars.

Offline qraal

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Re: Taking the BFR Beyond Mars
« Reply #54 on: 11/11/2017 03:19 AM »
Hi DLR

Oddly enough a Facebook friend suggested this very same thing to me...

As I envisaged it, the TJI would involve 3 vehicles, two of which are Tankers to top up the BFS. They'd have enough left to stage back to Earth for reuse.

Did the HOPE study quote the C3 value of that orbit?



What about skipping the aerobraking and capturing directly into Callisto orbit? If you time the encounter right, Callisto will be moving parallel to the spacecraft on its orbit around Jupiter, so you can deduct Callisto's orbital velocity when calculating orbital capture delta v.

This is from NASA'S HOPE study (2003):

L1 Departure: 0.58 km/s
TJI: 4.55 km/s
Callisto direct OI: 3.75 km/s

Time: 851 Days

The slide for using the BFS to land on the Moon and return has the BFS 'parked' in a HEEO while it tanks up. With a top delta-vee of ~6.4 km/s for the BFS, storing launch momentum in such an orbit allows a very effective Oberth Maneuver for Outer Planet missions.

I've analysed using this technique to fly to Titan (all on a single tank!) with a reasonable aerobrake entry speed of ~7.7 km/s, to land on the surface. It's the easiest Outer System target to reach, but takes ~3 years, so it's an endurance mission. Launching there in a Parabolic solar orbit takes 2.5 years, but means a re-entry speed of ~10.5 km/s. That *might* be doable with a Magnetoshell braking system.

To get to Callisto requires using two BFS Tankers which then transfer propellant to the BFS after all three boost into a Trans-Jupiter Insertion orbit. The Tankers can then return to Earth after a long loop. The BFS needs to aerocapture into Jupiter, then do a bi-elliptical transfer to Callisto. Shaving off ~1.5 km/s in the aerocapture from an entry speed of 60.7 km/s (it's a 500 day solar orbit, not a 1,000 day Hohmann) is the *hard* part. I feel it'll require some tricky tweaking of the TPS. Or a working Magnetoshell braking system. The BFS ends up in low Callisto orbit, so a pre-emplaced Tanker will be needed to land.



Offline mikelepage

Re: Taking the BFR Beyond Mars
« Reply #55 on: 11/11/2017 06:13 AM »
Ceres, from Earth orbit, is a real pain. But it'd be pretty simple from Mars. Thus Mars will be the Gateway to Ceres and the Asteroids.

From LEO, perhaps. Way easier to go to Ceres/asteroids from EML1 than Mars though.

Maybe this goes without saying but I am assuming you mean easier from EML1 than Mars surface. I forget who did a nice post with delta-V calculations a ways back showing how Mars orbit is a very attractive staging point for destinations further out.

Would be interested if you can find that.  I can imagine an argument that, from a dV perspective, Mars orbit is an attractive staging point... once Mars is already a thriving colony/hub and is generating whole tanker loads of propellent in excess to their needs, but logistically, I can't see how EML1 and the Deep Space Gateway are not going to be the most efficient staging points for decades to come.

(snip)
You would still have permanent colonies on places like Ceres, but they are not hubs. They have varying windows to reach mars, made possible by these cyclers. So the Cyclers become the hubs that connect Mars to the outer solar system.

In this analogy, specific asteroid colonies that produce materials but are not centers of trade are sort of like the "fly over states" :)

Im taking this too far off topic. Im really interested in this but it goes way beyond missions with a few BFR Tanker rendezvous.  I vaguely remember someone had a thread about the best targets within the asteroid belt.

That was me, and this thread here (although I was really focussing on NEOs):
https://forum.nasaspaceflight.com/index.php?topic=38820.msg1445943#msg1445943

What I think will happen now - and I'm writing a novel to depict this - is a "hub and spoke model" centred around cis-lunar space.  Of course the Mars colony will be the "fattest" spoke, but I think it will only be one of hundreds or more.  The rest will require the placement of "stepping-stone" colonies at Apollo asteroids which have the same/similar inclination & ascending node as desirable "anchor" locations, plus rendezvous opportunities with them.

I was originally using Ceres as my story's "anchor location" and the NEO Apollo asteroid 1999 JT6 as my "stepping stone colony".  Because of the inclination/distance factor, I've switched to 16 Psyche as the anchor location, and another Apollo as the stepping stone: 2008 EQ is a nothing rock, barely 50m across, but it's big enough to mine, and provide for a storm shelter/radiation protection, and most importantly flies by Earth every 7 years for the next century or more.

Offline DrRobin

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Re: Taking the BFR Beyond Mars
« Reply #56 on: 11/15/2017 11:56 PM »
Ceres, from Earth orbit, is a real pain. But it'd be pretty simple from Mars. Thus Mars will be the Gateway to Ceres and the Asteroids.

From LEO, perhaps. Way easier to go to Ceres/asteroids from EML1 than Mars though.

Maybe this goes without saying but I am assuming you mean easier from EML1 than Mars surface. I forget who did a nice post with delta-V calculations a ways back showing how Mars orbit is a very attractive staging point for destinations further out.

Would be interested if you can find that.  I can imagine an argument that, from a dV perspective, Mars orbit is an attractive staging point... once Mars is already a thriving colony/hub and is generating whole tanker loads of propellent in excess to their needs, but logistically, I can't see how EML1 and the Deep Space Gateway are not going to be the most efficient staging points for decades to come.


Found it:
It was by metaphor
https://forum.nasaspaceflight.com/index.php?topic=41306.msg1597199#msg1597199
the file is its.ods

Offline DrRobin

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Re: Taking the BFR Beyond Mars
« Reply #57 on: 11/16/2017 12:37 AM »
Ceres, from Earth orbit, is a real pain. But it'd be pretty simple from Mars. Thus Mars will be the Gateway to Ceres and the Asteroids.

From LEO, perhaps. Way easier to go to Ceres/asteroids from EML1 than Mars though.

Maybe this goes without saying but I am assuming you mean easier from EML1 than Mars surface. I forget who did a nice post with delta-V calculations a ways back showing how Mars orbit is a very attractive staging point for destinations further out.

Would be interested if you can find that.  I can imagine an argument that, from a dV perspective, Mars orbit is an attractive staging point... once Mars is already a thriving colony/hub and is generating whole tanker loads of propellent in excess to their needs, but logistically, I can't see how EML1 and the Deep Space Gateway are not going to be the most efficient staging points for decades to come.


Found it:
It was by metaphor
https://forum.nasaspaceflight.com/index.php?topic=41306.msg1597199#msg1597199
the file is its.ods

In particular, for Ceres, metaphor's #'s are that from LEO it takes 5.5 km/sec dV to get to the right point in space but another 6 km/sec to match velocities and land -and 11.5 km/sec total is more than BFS can do. It's the same total dV from Mars surface but "only" 7.5 km/sec from Mars orbit, which would let BFS deliver a significant payload.

(I tried to re-do these calculations myself and I get somewhat different numbers: a bit lower for the transfer orbit but 1.2 km/sec higher for the dV at the destination, but then again, I am an orbital mechanics noob, so I'd be curious to know what more knowledgeable folks think.)

Offline tdperk

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Re: Taking the BFR Beyond Mars
« Reply #58 on: 11/16/2017 10:14 AM »
logistically, I can't see how EML1 and the Deep Space Gateway are not going to be the most efficient staging points for decades to come.

I believe there is no rational reason to believe the first SpaceX Mars landing will not have sufficient excess ISRU fuel capacity, for the sake of a safety margin in dispatching the next synods's vessels with the expectation of return, that it will not be generating available fuel from the get go.  Within one decade or less of that landing, agree with them on a price and you can fill your tanks there.

A staging orbit around the Moon looks good if the departure vessel is O2/H2 fueled, or when a CC asteroid is emplaced there as a feedstock for MethaLox.  It would be to SpaceX's long term advantage to do so if liquid fuels are not eclipsed by better tech by then.

Offline qraal

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Re: Taking the BFR Beyond Mars
« Reply #59 on: 11/17/2017 10:30 PM »
Hi

From my own calculations, the trip time quoted below is *nearly* Hohmann - a tiny bit of extra delta-vee is enough to shave off ~150-200 days. The delta-vee assumes a low orbit, rather than direct touch down.

A 1,000 day Hohmann would need ~5.4 km/s delta-vee for a direct touch down trajectory. A full tank delta-vee of 6.4 km/s would reduce the trip time to ~685 days. A bit quicker if the Isp gets as high as 385 seconds - I'm assuming a Block 1 Vacuum Raptor performance of 375 seconds.

Once on Callisto the first task would be ISRU acquisition. There's definitely H2O and CO2 ices, but I wonder if there's not trapped O2 from radiolysis of the ice? We know there's very likely such on Europa, probably Ganymede's poles, but confirmation on Callisto would ease the power requirements. Instead of electrolysis for making oxygen, it'd be just hydrogen feedstock for making CH4. Merely melting the ice would give us the O2 - though the energy cost-effectiveness would depend on its volumetric abundance.

Hi DLR

Oddly enough a Facebook friend suggested this very same thing to me...

As I envisaged it, the TJI would involve 3 vehicles, two of which are Tankers to top up the BFS. They'd have enough left to stage back to Earth for reuse.

Did the HOPE study quote the C3 value of that orbit?



What about skipping the aerobraking and capturing directly into Callisto orbit? If you time the encounter right, Callisto will be moving parallel to the spacecraft on its orbit around Jupiter, so you can deduct Callisto's orbital velocity when calculating orbital capture delta v.

This is from NASA'S HOPE study (2003):

L1 Departure: 0.58 km/s
TJI: 4.55 km/s
Callisto direct OI: 3.75 km/s

Time: 851 Days

[..]

To get to Callisto requires using two BFS Tankers which then transfer propellant to the BFS after all three boost into a Trans-Jupiter Insertion orbit. The Tankers can then return to Earth after a long loop. The BFS needs to aerocapture into Jupiter, then do a bi-elliptical transfer to Callisto. Shaving off ~1.5 km/s in the aerocapture from an entry speed of 60.7 km/s (it's a 500 day solar orbit, not a 1,000 day Hohmann) is the *hard* part. I feel it'll require some tricky tweaking of the TPS. Or a working Magnetoshell braking system. The BFS ends up in low Callisto orbit, so a pre-emplaced Tanker will be needed to land.



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