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#220
by
MickQ
on 07 Feb, 2013 10:39
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I've been thinking of landing cargo. There is the problem of getting multiple landers to drop in a relatively close proximity to each other. Apart from the usual "All eggs in one basket" argument , why not join all together in Mars orbit and use some serious thrust ( RD-180 style ) to land it all together ?
Hab, lab, rover/s, power, ISRU plant, supplies, tools everything together in the one selected LZ. Why not
Mick.
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#221
by
Jim
on 07 Feb, 2013 11:18
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I've been thinking of landing cargo. There is the problem of getting multiple landers to drop in a relatively close proximity to each other. Apart from the usual "All eggs in one basket" argument , why not join all together in Mars orbit and use some serious thrust ( RD-180 style ) to land it all together ?
Hab, lab, rover/s, power, ISRU plant, supplies, tools everything together in the one selected LZ. Why not
Mick.
meeting in orbit takes alot of DV.
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#222
by
truth is life
on 07 Feb, 2013 12:42
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meeting in orbit takes alot of DV.
It also makes the landing problem much more serious, eg. if you're using aerodynamic landing you need a much, much larger aerobrake (which imposes all sorts of packaging problems on launch, nevermind robotically managing it in Mars orbit...) and if you're using propulsive landing...well, the mass ratios *should* be the only important thing there, so I suppose it wouldn't actually affect things that much supposing you have the same mass ratio for the same payload as independent and combined pieces.
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#223
by
MickQ
on 08 Feb, 2013 07:15
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Ok. Say all items to be landed are combined together in one big lander before Earth departure and then sent to LMO as one unit by whatever means is most suitable at the time. Could it be propulsively landed with current chemical engines as a complete base ? If so, what engines would be best ?
Mick.
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#224
by
Kaputnik
on 08 Feb, 2013 15:44
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'Best' can be interpreted differently for different purposes.
FWIW I would go with a pump-fed hypergolic engine of some sort. Arguments can be made for cryogenic propellants instead.
The real issue is mass. An entirely propulsive landing will need a fair bit of propellant- about three quarters of the total mass of the vehicle. In theory there would be no difference in mass whatsoever if you landed one big lander, or several smaller ones.
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#225
by
MickQ
on 09 Feb, 2013 05:31
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I don't know much about engine and propellant tech so could you use, as an example, RD-180's with kero/lox brought from Earth for a one off powered landing of a single base unit containing everything needed for the ground phase of the mission
Once safely down the crew would land separately in the ML/MAV and occupy the Base for the duration.
Mick.
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#226
by
Kaputnik
on 09 Feb, 2013 09:23
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I don't know much about engine and propellant tech so could you use, as an example, RD-180's with kero/lox brought from Earth for a one off powered landing of a single base unit containing everything needed for the ground phase of the mission Once safely down the crew would land separately in the ML/MAV and occupy the Base for the duration.
Mick.
Suggest you do a little research
The RD-180 would be a really lousy choice.
- it is ground lit
- is is optimised for Earth sea-level operation
- the LOX would need to be kept from boiling off during months of storage
As I said, pump-fed hypergolics would be more sensible. Similar isp but much better reliability and operability.
Once you have decided what mass you want to land on Mars, look up the delta-v required and plug some numbers into
http://www.strout.net/info/science/delta-v/ then see how big your mission is when it leaves Earth...
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#227
by
ClaytonBirchenough
on 07 Apr, 2013 02:43
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Anyone know/can do simulations to find how much payload can be landed at - 7km MOLA? The Red Dragon is said to be able to land 1000 kg at -1.3km MOLA. So basically, I'm wondering how much payload can be landed in the Hellas Basin (Hellas Planitia).
In addition, attached is a document that may help and provide more insight into the Red Dragon Mars Mission and give specifications needed to calculate, if anyone tries/decides to.
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#228
by
kurniadia
on 23 Apr, 2013 09:05
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Does any one think that terraforming Mars through greenhouse effect is boring? I wonder of possibility of igniting the sleeping volcanos in Mars,
Mars is chilling, it's atmosphere is too cold, can't sustain plants that could transform it's CO2 into O2, so it needs heat, what if NASA detonate some dinamites to give the planet the needed CPR? reactivate it's volcanos ring , temperature rise, ice will melt? plants will tan and drink no? or hurl an asteroid to Mars to expose the core a little, very easy no?
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#229
by
deltaV
on 24 Apr, 2013 04:34
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Anyone know/can do simulations to find how much payload can be landed at - 7km MOLA? The Red Dragon is said to be able to land 1000 kg at -1.3km MOLA. So basically, I'm wondering how much payload can be landed in the Hellas Basin (Hellas Planitia).
In addition, attached is a document that may help and provide more insight into the Red Dragon Mars Mission and give specifications needed to calculate, if anyone tries/decides to.
Looking at Figure 17 of
http://www.ssdl.gatech.edu/papers/conferencePapers/IEEE-2006-0076.pdfand
http://www.lpi.usra.edu/meetings/marsconcepts2012/pdf/4216.pdfI would guess that the lower altiutude would save on the order of 150 m/s of delta vee from additional drag, which should improve payload on the order of (e^(150/2800)-1) * 5180 = ~300 kg. Be wary of my guess however as IANARS.
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#230
by
ClaytonBirchenough
on 25 Apr, 2013 20:51
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Anyone know/can do simulations to find how much payload can be landed at - 7km MOLA? The Red Dragon is said to be able to land 1000 kg at -1.3km MOLA. So basically, I'm wondering how much payload can be landed in the Hellas Basin (Hellas Planitia).
In addition, attached is a document that may help and provide more insight into the Red Dragon Mars Mission and give specifications needed to calculate, if anyone tries/decides to.
Looking at Figure 17 of
http://www.ssdl.gatech.edu/papers/conferencePapers/IEEE-2006-0076.pdf
and
http://www.lpi.usra.edu/meetings/marsconcepts2012/pdf/4216.pdf
I would guess that the lower altiutude would save on the order of 150 m/s of delta vee from additional drag, which should improve payload on the order of (e^(150/2800)-1) * 5180 = ~300 kg. Be wary of my guess however as IANARS.
Thanks a lot. I was also wondering the same for MSL if it were to land at around -7km MOLA. So what would the payload be if MSL were to land at an area that was -7km MOLA?
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#231
by
spectre9
on 04 May, 2013 23:29
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Strange question really.
I assume you could increase the weight of the payload and still slow it down to around mach 2 where the parachute deploys but I speculate the parachute would not be strong enough to deal with the extra mass without a disreef.
I'm no expert but I think MSL is right on the edge of what's possible with parachutes.
For heavier payloads retropropulsion and drag surfaces like flaps on the capsule are required.
Thought I'd have a crack since the question hasn't been answered yet. If anybody has any further insight I'd welcome it.
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#232
by
Patchouli
on 05 May, 2013 03:21
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I don't know much about engine and propellant tech so could you use, as an example, RD-180's with kero/lox brought from Earth for a one off powered landing of a single base unit containing everything needed for the ground phase of the mission Once safely down the crew would land separately in the ML/MAV and occupy the Base for the duration.
Mick.
A couple of NK43s would be a better choice if you want to use a big kerolox engine for landing.
Though a cluster of super Dracos or CECEs might be your best bet for a lander engine.
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#233
by
rayleighscatter
on 07 May, 2013 01:25
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The talk lately about capturing asteroids and carting them about the galactic neighborhood led me to a question.
Could a waylayed asteroid be realistically brought along to Mars as part of a human visit and if so, would positioning it between the sun and the crew act as shield from radiation?
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#234
by
ClaytonBirchenough
on 07 May, 2013 11:04
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The talk lately about capturing asteroids and carting them about the galactic neighborhood led me to a question.
Could a waylayed asteroid be realistically brought along to Mars as part of a human visit and if so, would positioning it between the sun and the crew act as shield from radiation?
Maybe part of the asteroid, but maneuvering the asteroid to and from Mars would cost so much because of all the propellant, that it would be in-feasible. With regolith from the asteroid put into sort of sandbags, maybe it could be used as radiation shielding.
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#235
by
Danderman
on 01 Feb, 2014 14:58
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Is Mars more or less spherical than the Earth?
How about in terms of gravity, does it have a "bulge" like Earth?
Or, is it the case that Mars orbiting spacecraft have to fly so high above the surface that gravitational perturbations don't impact the orbit?
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#236
by
smoliarm
on 01 Feb, 2014 15:48
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Is Mars more or less spherical than the Earth?
How about in terms of gravity, does it have a "bulge" like Earth?
Or, is it the case that Mars orbiting spacecraft have to fly so high above the surface that gravitational perturbations don't impact the orbit?
In terms of shape:
The average geometrical deviation from ideal sphere is higher for Mars;
The max geometrical deviation from ideal sphere is higher for Mars (~4x compared to Earth);
Mars is substantially less symmetrical than Earth;
In terms of gravity field:
Asymmetry of the Earth's lithosphere is partially compensated by oceans.
Asymmetry of the Mars' lithosphere is higher and there is nothing to compensate it.
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#237
by
Danderman
on 01 Feb, 2014 15:50
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How does that asymmetry impact orbital flight of Mars probes? Is it such that spacecraft in low Mars orbits, even those beyond the tangible atmosphere, have lifetime problems, like lunar orbiting craft?
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#238
by
Danderman
on 01 Feb, 2014 20:50
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I am looking at the Elektra radio relay system, which is a de facto standard for Mars missions, and was wondering if Elektra represents a hardware implementation around a frequency, or whether Elektra is also a digital communications protocol?
My end issue is wondering if navigational positioning data could be streamed from a Mars navsat via Elektra transmissions to surface rovers.
