Author Topic: SpaceX Crewed Circumlunar Mission - 2018  (Read 268604 times)

Offline MATTBLAK

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Re: SpaceX Crewed Circumlunar Mission - 2018
« Reply #1300 on: 11/19/2017 06:24 AM »
BEAM has proven itself to be a viable future option. Though on ISS; they tend to keep the hatch to it shut most times and only go in there a few times per year. Future versions will need to be open a lot longer than that to be viable for regular and long term crewed space operations. I remember the 'Inspiration Mars' guys looked at BEAM derivative to have extra Habitation space for the 500 day Mars flyby mission. For such a Mars mission, other options include having the Dragon docked to either an enhanced Cygnus as a habitat, or a refurbished and used Dragon 1.0 pressure vessel. Another idea of mine is to have the Dragon docked to 2x inline Soyuz Orbital modules. One would be the Habitat and the other could be a storm shelter lined with polyethylene sheeting and water tanks.

But I digress...
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Online AncientU

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Re: SpaceX Crewed Circumlunar Mission - 2018
« Reply #1301 on: 11/19/2017 11:42 AM »
Yes - or a reused Dragon 1.0 module. Or even base a Bigelow with a basic propulsion bus out at DRO or L-2. The idea is increased habitable volume for living, supply storage and experiments. It would have to be 'Beam 2.0' version. But even that wouldn't launch prefabricated with all the needed equipment. The Beam could be packed on top of the Falcon upper stage and after the TLI burn; it inflates and the crew docks with it and extracts it from the upper stage. The Dragon with crew of 2 could be packed to the eyeballs with supplies and equipment, which the crew could transfer to the Beam to free up lots of room in the capsule. The Beam - filled with water and food supplies - could then become the solar storm shelter for the crew. At the end of the mission, the Dragon burns back towards Earth. Filled with trash and uneeded equipment; the Beam is then jettisoned to burn up on re-entry.

Try this approach without destroying hardware on each trip... only way it will be repeatable at any significant cadence.  Maybe leave the Beam or Beam derivative with station-keeping capability in Lunar orbit (suggest EML-1 or 2 better than DRO), either bring back the trash(like good backpackers do) or temporarily stow it in an expendable 'trash bag' which is sent on course to burn up in atmosphere.
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Online nacnud

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Re: SpaceX Crewed Circumlunar Mission - 2018
« Reply #1302 on: 11/19/2017 12:23 PM »
Well the trunk is thrown away each trip, and BEAM only cost $18 million and is nothing more than empty space. Given this is a commercial trip and assuming that the mission is possible with the extra weight the trade is whether this vehicle could be more profitable than just the Dragon 2.

The only way to do that is to add people to the trip each paying less than the current price but cumulatively the profit is more. There is also a time limit on this as once BFS is available it would be significantly cheaper.

Online gongora

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Re: SpaceX Crewed Circumlunar Mission - 2018
« Reply #1303 on: 11/19/2017 02:31 PM »
This really is digressing.  This thread is for the lunar flyby mission that SpaceX announced.  Possible alternate architectures using conglomerations of habitats to fly varying amounts of people around the Moon/Mars probably belong in other threads.

Online meekGee

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Re: SpaceX Crewed Circumlunar Mission - 2018
« Reply #1304 on: 11/19/2017 04:43 PM »
Why go to the expense of two dragons, take a BEAM instead. Add an extended duration pallet to the trunk too, if needed... Could make for some interesting stories.
Because then they'll be dependent on Bigelow, and I don't think they want that.  Plus, Dragons are reusable.
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Offline guckyfan

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Re: SpaceX Crewed Circumlunar Mission - 2018
« Reply #1305 on: 11/19/2017 05:31 PM »
I don't think SpaceX would spend major engineering capacity to expand Dragon capabilities when Dragon as it is can secure a valuable revenue stream until BFS becomes operational.

Online Space Ghost 1962

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Re: SpaceX Crewed Circumlunar Mission - 2018
« Reply #1306 on: 11/19/2017 07:02 PM »
The art of pulling off this mission is in narrow/no scope creep.

The same FH configuration flown. The same Dragon 2 + consumables + deep space comm. Nothing else added. Because then it leverages (and it in turn is leveraging) the CC program, both in proven new capabilities as well as scope of operation/mission profiles.

Remember that they're not taking Dragon past this point. NASA has no belly for it. So forget ambitions for Dragon, as long as there are no other "NASA class customers" asking for them. All serviceable market for Dragon is spoken for. BFS is next end of story. Just accept that. It'll be an amazing accomplishment just one free return mission.

Now to address "+ consumables + deep space comm". Propellant+ congingency is likely covered by existing launch abort capacity, ECLSS capacity is likely an addition/prove/qualification. Additional crew needs as well.

Deep space comm likely an addition under the docking adapter cap. Using a derivative of the MER/MSL HGA integrated into the avionics and software systems is what I'd start with. This is likely the "long pole".

FWIW, here's work on the Iris cubesat DSN transponder at JPL. This a a low gain, low bandwidth application, but it gives one an example of scope of this activity.

Online TrevorMonty

Re: SpaceX Crewed Circumlunar Mission - 2018
« Reply #1307 on: 11/19/2017 09:48 PM »
Dragon doesn't have DV to enter and return from any lunar orbit. Flyby is all it is capable of.
To add extra DV would require service module, which needs between trunk and US. Can't be in trunk as is that is mass limited by LAS requirements.

Offline MATTBLAK

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Re: SpaceX Crewed Circumlunar Mission - 2018
« Reply #1308 on: 11/19/2017 10:11 PM »
Any 'propulsion pallet' in the trunk could be made ejectable at moment of abort by explosive bolts if need be. But that's only an idea and would require an additional, costly re-design. Which would be worth it in the context of other missions and further uses...
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Online Space Ghost 1962

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Re: SpaceX Crewed Circumlunar Mission - 2018
« Reply #1309 on: 11/20/2017 12:45 AM »
Stay on thread topic. "Crewed Circumlunar Mission". Goes around and comes back - free return.

Props are solely required for midcourse/entry corrections. There's already excess. Likewise, FH has excess delta V for this mission.

So lets say the vehicles are fixed, all the equipment (per my post above) is set no changes. What else might you do?
(Also lets assume DSN/Stargate/commercial supplement comm/tracking operations).

You're going to fly from 39A - the only pad with crew access. 39A/40 have been used to prep Dragon. West coast recovery and Hawthorne refit. Dragon mission outfitting local to pad. Every 3-6 months a CRS/CC mission, 2-6 slots for free return missions, so 6-10 annual mission rate for Dragon. 8-16 F9 reuse boosters, 2-6 FH core boosters, 6-10 F9US in total per year. That's a very healthy amount of operations for a HSF side of the business (nor counting recovery/reprocessing costs).

This would exceed Soyuz/Progress and only be surpassed by Shuttle in the past. Past a singular mission, reaching this kind of activity level would be a remarkable follow-on achievement. Cost of operations would drop significantly.

If all of this were to happen, well before EM1, you'd have a cost per seat of a lunar capable mission architecture in common use by NASA. The excess delta V in the capsule, LV, excess payload capacity, and vehicle flight rates/history ... would leave a lot of room for NASA/others to address mission planning shortfalls/contingencies with.

Anything that might result as HSF "follow on" for Dragon would come from that capability, refreshed by successive Dragon flights.

Even after Apollo flew, Gemini was constantly "resurrected".  The cost basis alone made it too easy to do, even though it hadn't flown missions for a fair portion of a decade, unlike this case. A lot can happen in the in-determinant future.

But it's not SX or space cadet ideas that would arrive at such. Just the cold, hard realities of need. Like that of avoiding LOM/LOC.

add:
One other thing I forgot to add. It is possible for lunar and high C3 missions with certain orientations to fly an extremely lofted trajectory. This would be more difficult to track/navigate/guide than "normal", but it would allow vehicle recovery while imparting more delta-V to the payload, since its the downrange boost back and the horizontal velocity that increase stress on the booster recovery, not the vertical velocity as much.

So the vehicle doesn't rotate until after staging, you have certain concerns about trajectory and guidance, so this is far from an easy choice. It would mean longer entry burns for all three boosters, higher vertical decelleration/heating. But net/net more propellant into a delta-v into a highly elliptical orbit that would have to coincide with the TLI burn's ascending/descending node opposite the planet from launch. (And, if it were done from a higher latitiude like at Vandenberg, one could gain an interesting "advantage" from the lunar trajectory. One could also as a side effect bring along a geosynch payload that could "rideshare" after separation.)
« Last Edit: 11/20/2017 06:20 PM by Space Ghost 1962 »

Offline guckyfan

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Re: SpaceX Crewed Circumlunar Mission - 2018
« Reply #1310 on: 11/20/2017 05:44 AM »
Dragon doesn't have DV to enter and return from any lunar orbit. Flyby is all it is capable of.
To add extra DV would require service module, which needs between trunk and US. Can't be in trunk as is that is mass limited by LAS requirements.

Is this really true? Sure it can not reach LLO. But the available delta-v without powered landing, should be enough to reach a DRO orbit.

Online envy887

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Re: SpaceX Crewed Circumlunar Mission - 2018
« Reply #1311 on: 11/20/2017 01:02 PM »
Dragon doesn't have DV to enter and return from any lunar orbit. Flyby is all it is capable of.

Very high lunar orbits only require about 300 m/s to enter and leave, and L2 NRHOs require about 650 to 700 m/s to enter and leave with a lunar flyby. Both are likely within reach of a stock D2, although cargo mass, flight time, and orbit utility and stability may vary.

DROs tend to be about 1200 to 1400 m/s to enter and leave, so only Orion can reach and return from those without upgrades.
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