Red Dragon Discussion Thread (1)

[starsilk]

A.  shuttle APU's run on the order of minutes and not weeks.
B.  APU's are mono prop

copy on point B. But you can still carry a lot of mono prop in a derived Dragon.

on point A, was thinking of about several hours of power just for the drill rig. Presume  solar arrays with storage  batteries for other operations.

@go4mars
How deep is the test drill rig aiming for? My guess about 20 meters with 2 meter drill-pipe sections. Could several hours of drill rig operating time be enough?

You would saturate the area with combustion products.

you could capture the APU exhaust. at least long enough to do your sampling.

although it's a good point about contamination - a powered touchdown presumably contaminates the whole area with exhaust products (and maybe kills off any 'life' they're looking for)

[starsilk]

a thought: how much fuel reserve would it take to do short 'boosted hops' on the surface so you could drill in two (three, four..) locations?

drilling in one spot gives you only one chance of 'hitting the jackpot'. if you could jump around a few km in either direction, you should be able to get a whole lot more bang for the buck...

[deltaV]

a thought: how much fuel reserve would it take to do short 'boosted hops' on the surface so you could drill in two (three, four..) locations?

drilling in one spot gives you only one chance of 'hitting the jackpot'. if you could jump around a few km in either direction, you should be able to get a whole lot more bang for the buck...

Mars surface gravity is 0.376 gee so each 1% of mass spent as fuel gives on the order of 0.01 * 300 / 0.376 = 8 seconds of flight time at an ISP of 300 seconds. So on the order of 10% of landed mass as fuel would be needed to move to another location a km away.

[go4mars]

You would saturate the area with combustion products.

Directly below dragon, it would be the surface layer only (if you came straight down) because the propulsive landing system is around the outside, and partially facing outward.  Even if the thrust did pollute deeper right on the drilling location, that would be part of the reason for drilling deeper than a fence-post hole (though truly not ideal). 

Depending on the scientific/geological goals, I agree it would likely be problematic.  Another reason for a large human-run drill rig, on rigs or tracks, for multiple complete cores from numerous holes going down several kilometers. 

http://www.lpi.usra.edu/meetings/geomars2001/pdf/7044.pdf 

[simonbp]

That was my point, where do the solar arrays go?

Could be deployed out of either the instrument hatch (comms hatch on ISS Dragon) or the main hatch. Heck, they could pop the top hatch and raise a "solar umbrella", like Surveyor.

Any unmanned Mars Dragon would have considerable modifications from the LEO Crew Dragon. The key is that EDL is the most expensive and complex part of a Mars landing, and so any commonality with the Crew Dragon helps lower the cost to put a large payload on Mars.

As far as what that payload would be, a "super-Viking" lander with a more advanced version of the MSL wet lab would be a good baseline. Drills are complex and prone to jam (ask Dave Scott), and so a likely lower priority.

[baldusi]

If you had enough torque, could you simply friction weld each drill pipe section to the drilling one? Or does it need to pump fluids?

[Patchouli]

You would saturate the area with combustion products.

That was my point, where do the solar arrays go?

You could place the solar arrays in the nose where the docking hardware normally goes.

[go4mars]

If you had enough torque, could you simply friction weld each drill pipe section to the drilling one? Or does it need to pump fluids?

If you had enough torque, could you simply friction weld each drill pipe section to the drilling one? Or does it need to pump fluids?

Yes.  But threading lengths of drill-pipe is simpler and well established.

As to drilling fluid, if you want to go deep, it is a good idea to have fluid for chip sample removal, cooling, and lubrication.  This usually would flow down the pipe, and back up the annulus.  Unless you are wanting to core.  Then the approach is different.  Atmospheric compressors could do air drilling too (compressed martian atmosphere as the drilling fluid).  That's the typical drilling method in underpressurized basins like the San Juan for drilling the Lewis shale.

[starsilk]

As to drilling fluid, if you want to go deep, it is a good idea to have fluid for chip sample removal, cooling, and lubrication.  This usually would flow down the pipe, and back up the annulus.  Unless you are wanting to core.  Then the approach is different.  Atmospheric compressors could do air drilling too (compressed martian atmosphere as the drilling fluid).  That's the typical drilling method in underpressurized basins like the San Juan for drilling the Lewis shale.

that seems like it would introduce far less 'foreign' contaminants in the cores (Martian atmosphere, not Earthly drilling fluid).. but then I guess you have to worry about 'unknown' contaminants (whatever's in the compressed atmosphere) as opposed to known (and possibly very pure) contaminants.

[Zed_Noir]

A.  shuttle APU's run on the order of minutes and not weeks.
B.  APU's are mono prop

copy on point B. But you can still carry a lot of mono prop in a derived Dragon.

on point A, was thinking of about several hours of power just for the drill rig. Presume  solar arrays with storage  batteries for other operations.

You would saturate the area with combustion products.

Would use the solution that Inco previously used for their smelters in Canada. A really tall smokestack for the combustion production to drift away from the drill site. Connecting about sixteen 2 meter composite pipes sections should be enough.

That was my point, where do the solar arrays go?

Partially cladding the upper exterior of the Dragon for minor portion of the sunlight collection along with a bigger nosecone during launch. Plus deplorable solar arrays on mobile units

Consider and rejected mounting umbrella like solar array on the top of the Dragon. That's where I would put a robotic arm to support drilling operations, deploying payloads and assembling stuff. Also the robotic arm would be use to clear away the residues from descend motors with a dozerblade like attachment for a separate detached drilling rig. The robotic arm would be stowed during transit like the in-flight refueling probe on modern jet fighters (non-USAF) conformally to the side of the Dragon.

[docmordrid]

Stick an RTG on it.

[Zed_Noir]

Stick an RTG on it.

Even with an ASRG type of RTH you only getting about 110W per generator. It's not enough power. Never mind the shortage of Plutonium  238 isotopes.

[starsilk]

Stick an RTG on it.

then F9-H has to be qualified for nuclear payloads, which by all accounts is extremely difficult.

of course.. Elon was dropping hints about a 'beyond Pluto' NASA mission at the AIAA. that would also require an RTG.

[Zed_Noir]

of course.. Elon was dropping hints about a 'beyond Pluto' NASA mission at the AIAA. that would also require an RTG.

Maybe a FH with a separate Russian Briz-M hypergolic kick stage and an Ion thrusters Interplanetary cruise stage for the beyond Pluto missions. But this is getting off topic.

[Nathan]

There is no reason that there cannot be a larger hatch on the dragon for this mission. Can have payload bay style doors open out instead, to enable a full volume payload to descend to the surface via deployable ramps. Or no descent to surface but have the payload deployed sideways above the surface (for sampling mission)
Dragon derived is probably  correct. Minimal modification but certainly modified.

[starsilk]

of course.. Elon was dropping hints about a 'beyond Pluto' NASA mission at the AIAA. that would also require an RTG.

Maybe a FH with a separate Russian Briz-M hypergolic kick stage and an Ion thrusters Interplanetary cruise stage for the beyond Pluto missions. But this is getting off topic.

hmm? the RTG would replace solar panels, not propulsion. the point is that out that far even huge solar panels won't provide enough power.

[docmordrid]

Start with no enclosed pressure hull, just enough of its bottom and a platform to attach the engineering compartment bits and payload. Also a minimal space frame to set the contour with a disposable aeroshell for re-entry.

[Zed_Noir]

of course.. Elon was dropping hints about a 'beyond Pluto' NASA mission at the AIAA. that would also require an RTG.

Maybe a FH with a separate Russian Briz-M hypergolic kick stage and an Ion thrusters Interplanetary cruise stage for the beyond Pluto missions. But this is getting off topic.

hmm? the RTG would replace solar panels, not propulsion. the point is that out that far even huge solar panels won't provide enough power.

You did notice the part with the Ion thrusters in my response. What else but some sort of RTG to power them beyond the orbit of Jupiter.

[Jim]

That was my point, where do the solar arrays go?

Could be deployed out of either the instrument hatch (comms hatch on ISS Dragon) or the main hatch. Heck, they could pop the top hatch and raise a "solar umbrella", like Surveyor.

Any unmanned Mars Dragon would have considerable modifications from the LEO Crew Dragon. The key is that EDL is the most expensive and complex part of a Mars landing, and so any commonality with the Crew Dragon helps lower the cost to put a large payload on Mars.

The issue is all the previous landers shed their heatshields and aeroshells.  Dragon can't (or then it isn't a Dragon anymore).  Dragon wouldn't put a large payload on Mars, it is going to put a large amount of Dragon structure on Mars.  The Dragon structure is going to be a limiting factor.

[Jim]

There is no reason that there cannot be a larger hatch on the dragon for this mission. Can have payload bay style doors open out instead, to enable a full volume payload to descend to the surface via deployable ramps. Or no descent to surface but have the payload deployed sideways above the surface (for sampling mission)
Dragon derived is probably  correct. Minimal modification but certainly modified.

Yes, there is, it is not that simple just to enlarge the hatch.  There are load paths that must be taken into account.  Payload bay doors?  You got to be joking.
Dragon is a pressure vessel.