Red Dragon Discussion Thread (1)

[simonbp]

Understood. How much of a difference, though? And what about climatic fluctuations in atmospheric density, which I believe are also very significant?

The variation of the surface atmospheric density over the course of a day is about a factor of two, and is larger than the seasonal variation. So, as long as you land in full sunlight, it's about as good as you're going to get. Also, you want to be in full sunlight as the relay sats are all in noon-ish polar orbits.

[charliem]

According Mars-GRAM-2005 data the atmospheric density at MOLA can vary from 0.01 kg/m3 to 0.02 kg/m3, even a bit more.

8 km below MOLA from 0.015 kg/m3 to more than 0.04 kg/m3.

But there are few places than low.

[Kaputnik]

So, what would be the ideal Red Dragon landing site?
Somewhere very low, but with a large flat plain that minimises the need for hazard avoidance on final approach.
Does anywhere satisfy these requirements?

[Dalhousie]

So, what would be the ideal Red Dragon landing site?
Somewhere very low, but with a large flat plain that minimises the need for hazard avoidance on final approach.
Does anywhere satisfy these requirements?

Most of the northern plains, in fact.

[charliem]

One of the places they'd like to land Red Dragon on is Green Valley, where Phoenix has already found signs of water ice.

Phoenix landed 4.1 km below MOLA ref. and the terrain there looks quite level. Here is a high-res circular, composite, panoramic around Phoenix: http://www.nasa.gov/images/content/297717main_polar_AGU.jpg

No big boulders in sight.

Another interesting place is the Hellas Basin in the south hemisphere. About 2,000 km wide, most of it is 7 km under MOLA ref. and no lander has paid it a visit yet: http://upload.wikimedia.org/wikipedia/commons/f/f0/False_color_of_Hellas_Planitia.jpeg

If there ever was liquid water on Mars Hellas's huge depression is a likely candidate for a dried seabed, and data from MRO's SHARAD radar sounder suggest that there could be glaciers in its eastern region, just covered by a few inches of dirt.

And there are many more places. Most of Mars between the 50 deg north and 80 deg north parallels is under the -3 km MOLA level.

Here is a map with altitudes: http://pubs.usgs.gov/imap/i2782/i2782_sh1.pdf

One more thing. I think this JPL analysis of the Phoenix lander performance during EDL is very interesting, and relevant to the discussion: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20080034645_2008033759.pdf

[simonbp]

According Mars-GRAM-2005 data the atmospheric density at MOLA can vary from 0.01 kg/m3 to 0.02 kg/m3, even a bit more.

8 km below MOLA from 0.015 kg/m3 to more than 0.04 kg/m3.

But there are few places than low.

Be careful with MarsGRAM. It gives a rough idea of of temp and pressure, but does not cover atmospheric opacity very well at all. Hellas, for example, looks great in pressure, in reality is a giant dust bowl that would be hard just to land in, and pointless for a solar powered lander.

Red Dragon would go to the high northern plains, in a spot that MRO has cleared of boulders. The site itself will be very similar to where Phoenix is, and the Phoenix backup sites should give you an idea what the particular sites are.

[charliem]

If indeed Red Dragon can land 1mT of payload on Mars, an ISRU small scale demo plant would make an interesting second mission.

Weight allowing it could even include a small rocket to prove the feasibility of launching from Mars with the obtained propellants.

[sittingduck]

Since Red Dragon is doing propulsive landing I assume it will be visually (at least on the exterior) very similar to the Dragonrider.  Would the new Super Draco fairings and the asymmetrical docking mechanism most likely be present?

I ask because I'm working on a 3-5 min CG animation for the mission and am currently fleshing out all the hardware and environments.  Does anyone think that there would be any substantial modifications to the exterior for Red Dragon? The subject most open to interpretation still appears to be the power source on the surface (solar? and would it deploy Surveyor or Phoenix style, through the hatch or the top?), whether the drill would go straight through the heat-shield, and whether any other instruments would be pushed out of that hatch or perhaps elsewhere?

Would the trunk be substantially modified for the interplanetary journey (stretched?  highly visible coms antenna?  modifications or additions to the solar panels?)?

Any educated guesses would be appreciated.

[Robotbeat]

Since Red Dragon is doing propulsive landing I assume it will be visually (at least on the exterior) very similar to the Dragonrider.  Would the new Super Draco fairings and the asymmetrical docking mechanism most likely be present?

I ask because I'm working on a 3-5 min CG animation for the mission and am currently fleshing out all the hardware and environments.  Does anyone think that there would be any substantial modifications to the exterior for Red Dragon? The subject most open to interpretation still appears to be the power source on the surface (solar? and would it deploy Surveyor or Phoenix style, through the hatch or the top?), whether the drill would go straight through the heat-shield, and whether any other instruments would be pushed out of that hatch or perhaps elsewhere?

Would the trunk be substantially modified for the interplanetary journey (stretched?  highly visible coms antenna?  modifications or additions to the solar panels?)?

Any educated guesses would be appreciated.

Are you doing it for NASA and/or one of the NASA centers or a University?

(BTW, make sure to make the plumes really large/spread-out on the surface of Mars because of the low pressure...)

I would highly suspect that instruments would be deployed from the instrument bay on the Dragon spacecraft.

It's possible that (for surface power) a small fairing would protect a solar array on top, like some of the early Dragon concepts.

[Kaputnik]

I'm going to make an assumption/prediction that a Red Dragon would have much reduced thrusters (size and/or number of) because the requirement to slow to a hover in 0.38g is completely different to aborting at 6g on Earth.

So in other words, it would probably have smaller 'noses'.

[Garrett]

I'm going to make an assumption/prediction that a Red Dragon would have much reduced thrusters (size and/or number of) because the requirement to slow to a hover in 0.38g is completely different to aborting at 6g on Earth.

So in other words, it would probably have smaller 'noses'.

Atmospheric braking is orders of magnitude less on Mars than on Earth, so Red Dragon will need a lot of rocket power to slow down.
And why should it need to hover? Why not do what Apollo did: cut off the engines and drop like a stone for the last couple of meters. Let the landing legs buckle and absorb the damage. It's only a one-way mission.

[Garrett]

(BTW, make sure to make the plumes really large/spread-out on the surface of Mars because of the low pressure...)

+1
I love the way you made sure to get that nit-pick a mention 
If only somebody had mentioned it to the Apollo artists, then maybe we could have avoided the conspiracy theorists wondering where the rocket plume is ... 

[Kaputnik]

I'm going to make an assumption/prediction that a Red Dragon would have much reduced thrusters (size and/or number of) because the requirement to slow to a hover in 0.38g is completely different to aborting at 6g on Earth.

So in other words, it would probably have smaller 'noses'.

Atmospheric braking is orders of magnitude less on Mars than on Earth, so Red Dragon will need a lot of rocket power to slow down.
And why should it need to hover? Why not do what Apollo did: cut off the engines and drop like a stone for the last couple of meters. Let the landing legs buckle and absorb the damage. It's only a one-way mission.

'Power' in this case equates to propellant mass, not thrust.

Apollo did hover- there was, IIRC, a 60s allowance for that, and memorably Eagle used up almost all of it before finding a safe spot to touch down.

[sittingduck]

Are you doing it for NASA and/or one of the NASA centers or a University?

(BTW, make sure to make the plumes really large/spread-out on the surface of Mars because of the low pressure...)

I would highly suspect that instruments would be deployed from the instrument bay on the Dragon spacecraft.

It's possible that (for surface power) a small fairing would protect a solar array on top, like some of the early Dragon concepts.

I'm not doing it for NASA or Ames, I'm working on it as an addition to my portfolio (and to get people informed about the mission) but I care passionately about the accuracy of the simulation.

I will use the existing SpaceX CG clips of a Dragon landing propulsively on Mars for exhaust plume reference, hopefully they made it accurate!

Is the "instrument bay" the panel that flips open under the side-hatch?  Any images on early Dragon concepts for that solar array? 

For the Red Dragon I've currently got a replica of the berthing/docking hatch from the SpaceX CCDev CG video, but I suppose I'll have to switch this out for the newer top hatch visible in the latest Dragonrider demo.  I'm not entirely clear on how where solar panel placement would work out with that.  Any help is appreciated, as I'll be sharing the full animation online when it's done. 

Edit:Grammar

[Jim]

For the Red Dragon I've currently got a replica of the berthing/docking hatch from the SpaceX CCDev CG video, but I suppose I'll have to switch this out for the newer top hatch visible in the latest Dragonrider demo.

why would you do that?  it isn't going to dock with anything and a larger opening would be more beneficial.

[Jim]

  but I care passionately about the accuracy of the simulation.

you are going to fail since there is no real design to copy

[sittingduck]

For the Red Dragon I've currently got a replica of the berthing/docking hatch from the SpaceX CCDev CG video, but I suppose I'll have to switch this out for the newer top hatch visible in the latest Dragonrider demo.

why would you do that?  it isn't going to dock with anything and a larger opening would be more beneficial.

Operating under the assumption they want to change as little as possible from the stock Dragonrider to keep costs down. The CBM on top and the "nose" fairings below would represent some sort of hybrid of the Cargo and manned Dragons, wouldn't it?  Then again, if there is some sort of solar array on top as Robotbeat suggests it will probably be very different again.  I've never seen (and cannot find unfortunately) any reference for the early Dragon concepts which may include this feature.

  but I care passionately about the accuracy of the simulation.

you are going to fail since there is no real design to copy

Perhaps I should have chosen my words more carefully.  Let's just say I care passionately about the plausibility of the simulation.

[adrianwyard]

Unfortunately, it's anybodies guess at this point what the top would look like. Even if the (first) Red Dragon is simply an EDL demo I doubt they'd take a CBM to Mars when mass is at such a premium. Given they'll switch out the CBM for NDS on DragonRider it's my guess they'll switch it for something custom on Red Dragon.

You could go the easy route and show it landing with the nose-cap fairing on. I could see this being left on to protect instruments, camera-masts, antennas, and perhaps solar arrays. It would deploy after landing.

Anyway, good luck. The world needs more CGI artists who are passionate about accuracy! (And failing that, plausibility.)

[adrianwyard]

Here comes some more speculation on how SpaceX might do an early Red Dragon with minimal changes from DragonRider:

1] Take a DragonRider, make the necessary propulsion/tankage changes for Mars EDL.
2] Remove the docking system. In its place, add a 'cup' shaped pressure wall that descends into the stock pressure vessel, freeing up a large unpressurized volume. Keep the nose-cap fairing on through EDL to increase the available volume. Place your payload (e.g. science package) in this space.
3] Once on Mars, deploy the nose cap, and push the unpressurized payload - including solar arrays and high-gain antenna, up out of the top of the spacecraft.

The payload(s) would be entirely self-contained, all SpaceX would do is land it and push it out into the Mars environment to fend for itself. They could be provided by NASA, ESA, anyone.

For surface access you need a similar but more aggressive mod:
1] Remove the side hatch.
2] Behind the hatch add a wall that opens up volume into the pressure vessel large enough to accommodate a small rover, robot arm, etc.
3] Once on Mars, deploy the TPS cover over this area. It hinges down toward the surface with the fulcrum located low down where the grapple fixture is on DragonRider.
4] If the you've brought a rover, mount it to the inner surface of this cover. Once the cover has hinged down to the surface, you release the mounts, and roll off.

+ I worry the new pressure walls could be heavy, but perhaps the Dragon atmosphere could be chosen (lowered) to minimize the strength needed?

[oiorionsbelt]

Is it a requirement that the pressure vessel be pressurized for Red Dragon?