Red Dragon Discussion Thread (1)

[NotGncDude]

I have a few questions:
Are Dragon's legs rated for unleveled terrain?

As the paper plays with the numbers and features of the enhanced crew version of Dragon (with propulsive landing), your questions can only be answered from one inside Dragon development. But about autonomous landing capability, there should be enough systems around now which can be used for this.

Even the robotic Dragon with full return and pin point landing capability, will make use of GPS and will land on a cement landing pad. Here we are talking about flying by inertia, recognizing the terrain, and deciding, with no external aid whatsoever (save the MRO maps), where there's a patch of terrain clean and leveled enough to actually land.
We are talking about 3D terrain recognition on real time. That's stuff that even the Google car is not ready for. There's a reason that Curiosity uses those huge wheels and suspension, and the Sky Crane works the way it does. Its to land on very unfriendly terrain.

The main issue with the Google car is dealing with other cars, moving stuff etc. 3D terrain recognition (and cars driving in it) in real time was demonstrated with the DARPA challenge many years ago, a more accurate comparison. As other people point out, ALHAT's been working on this for a while. I expect SpaceX to do better. But who knows, anything can be made to look good on paper.

At which speed did the DARPA challenge cars run on the most difficult terrain? How far ahead did they had to plan ahead? What sort of data amount had to process, and how much time did they had?
Because it's not the same to analyze a couple of HD feeds a few meters ahead while you can stop an think a bit, against analyzing radar/lidar data plus some stereo images while literally falling down like a rock. The timing and the sort of decision making you have is very different.
In particular, at what height can you rally know that the terrain is smooth? I would guess you'd need at least 0.1m of resolution. That's a lot of data when you're falling like a rock. And once you've committed to a patch you're done.
Again, it's not that's not doable. It's that it might well be a couple of orders of magnitude more difficult than the DARPA challenge, and it would need some serious development. This is Mars we are talking about. Flying is not an option, just a soft crash landing.

Hazard estimation and avoidance while landing is not orders of magnitude more difficult than the DARPA challenge. It's easier! (Disclaimer: I work on this stuff, albeit not directly) Technically easier, that is. Of course it is way riskier, since as you say, you can't stop and think about it, plus it's slightly more expensive if it doesn't work.  Hehe.

Let's see. Advantages of the landing problem:
- you only have to solve the problem once (maybe 2 or 3 times, but unlikely), instead of *all the time* while driving
- you're looking from above
- you're flying! you are moving in 3D so quite a bit of flexibility there (with constraints, sure)
- You're further away? Use a better sensor, the sensor is not the issue.

There are disadvantages of course.

Having been exposed to both aerospace GNC and robotics I tell you, aerospace GNC is still in the 70's (and rightly so), while robotics is using stuff from last week. It's market driven.

[baldusi]

Well, will you still say its easier if you want to have a reliability of 99.99%? I'm asking. 
I have a couple of questions about what you wrote. I always assumed that being very high and falling very fast is a problem for two reasons.
The first, is that I'm assuming that the 0.3m data of the HiRise cam is not enough to decide where to fall. I'm assuming that you need at least 0.1m resolution. If that is true (please correct me if I'm wrong), you'd need a very high resolution system. Which is not a problem in itself, but you'd have a very small sample size for the terrain to analyze. So you'd have to take a lot of samples.
I'm going to say the sort of numbers that I have in my head, so please correct me since I expect to be wrong.
From the Page 10 of the Red Dragon presentation (KARCZ-Red_Dragon-NAC-2011-10-29.pdf), I've taken the attached image of the Entry Profile. I've calculated each dash as 12.5km. Thus, on the final vertical bar it would be approximately 75km high and 38km up range. I'm assuming this is a reasonable point to start looking where are you going to touch down, right?
If you used a sensor like the Kodak KAF-50100 or the Dalsa FTF6080C, you'd have a 8k x 6k image on a 48mm x 36mm sensor (that's medium format for the photographic guys). You'd be 84km away from your landing spot. If you wanted a 0.1m resolution, you'd need a lens with a focal distance of 7.7m. You could get that with an aperture of 385mm and an f/20. That's a 15" telescope with an f-number of 20. That gives you 0.1m of resolution. The problem is that you have sampled a 0.8km by 0.6km square.
I've always assumed a falling ellipse of 20km major axis. And the fps is 1! So you have very little time to actually cover a lot of ground. And I don't think you can use a push-broom camera for this application. And I understand that LIDAR has even less resolution and slower swath. Each second that passes, your ellipse of possible landing points get reduced considerably.
The other problem I see, is that you're falling pretty vertically. This makes it more difficult to estimate the vertical component of the terrain by imaging systems. It does help with direct measure systems (like LIDAR). But LIDAR is slow and sort of low resolution (at 84km).
I'm not counting the computing resources that you'll need to process all this information, in a radiation hard and power limited situation.
This are the sort of difficulties that I'm seeing. If those are not realistic parameters, or I'm worrying about solved problems, please tell me. I'm not very knowledgeable in the state of the art.

[go4mars]

How much would it cost to include one of these and a little ISRU unit inside Red Dragon for after the drilling and related tests are done? 
It wouldn't have to be used for anything.  Just a little demonstrator since there seems to be excess mass-to-surface capacity.

http://www.youtube.com/watch?feature=endscreen&v=UUtx1EXmtT0&NR=1

[Blackstar]

How much would it cost to include one of these and a little ISRU unit inside Red Dragon for after the drilling and related tests are done? 

I don't know. How much would it cost?

Why not consult some engineering textbooks, then some engineering management and cost estimation textbooks, and then some systems engineering textbooks. You should then be able to easily calculate the answer. Then give us that answer.

[baldusi]

How much would it cost to include one of these and a little ISRU unit inside Red Dragon for after the drilling and related tests are done? 

I don't know. How much would it cost?

Why not consult some engineering textbooks, then some engineering management and cost estimation textbooks, and then some systems engineering textbooks. You should then be able to easily calculate the answer. Then give us that answer.

[sarcasm]That was uncalled for! This is the Internet, nobody is supposed to actually understand the technical/operative/economic requirements and limitations of their questions![/sarcasm]

[go4mars]

Why not consult some engineering textbooks, then some engineering management and cost estimation textbooks, and then some systems engineering textbooks. You should then be able to easily calculate the answer. Then give us that answer.

Time.  Someone out there may have a rough idea of what the ISRU demonstrators on earth have cost, and I've never built a teensy methane rocket.  Others have and know the cost. 

I'm curious whether this could be done for a few million bucks or less.  If transportation to the surface of Mars was free, what might it cost?  I didn't mean to offend you. 

If you have any questions about costs related to oil and gas in Canada I'll be happy to fast-track you to a ball-park estimate which would be a lot more useful and accurate than what you could come up with from textbooks. 

[Comga]

Why not consult some engineering textbooks, then some engineering management and cost estimation textbooks, and then some systems engineering textbooks. You should then be able to easily calculate the answer. Then give us that answer.

Time.  Someone out there may have a rough idea of what the ISRU demonstrators on earth have cost, and I've never built a teensy methane rocket.  Others have and know the cost. 

I'm curious whether this could be done for a few million bucks or less.  If transportation to the surface of Mars was free, what might it cost?   

You might get a good idea of what Earth-bound ISRU systems cost, specifically oxygen and methane Sabatier generator, by looking for Robert Zubrin's projects from a decade or two ago. 

[Blackstar]

[sarcasm]That was uncalled for! This is the Internet, nobody is supposed to actually understand the technical/operative/economic requirements and limitations of their questions![/sarcasm]

Sarcasm? No. Not at all.

Like many people, I enjoy it when, say, a computer programmer for an insurance company in Norway develops an elaborate architecture for building a lunar colony and thereby demonstrates that they should be NASA administrator (rather than that dummy Mike Griffin). I also believe that it is important for people to constantly expand their knowledge and skills base. So I encourage that computer programmer to acquire an aerospace engineering degree, work their way up to become proficient at systems engineering, manage a multi-million (or billion) dollar contract, and then apply for the job of NASA administrator that they so rightfully aspire to and deserve. Yeah, it's a bit of work, and it might require a few years, but per ardua ad astra and all that, right?

Sarcasm would be pointing out that technology demonstrators are not included in Discovery class science missions, or pointing out that when a proposed mission already requires fairy dust and unicorn gas to work, it's probably not a good idea to add an experimental leprechaun catcher to the project as well.

Then again, we can all dream...

[Comga]

Sarcasm would be pointing out that technology demonstrators are not included in Discovery class science missions, ...

It doesn't have to be a Discovery mission.  There is a class of technology development missions.  Mars Pathfinder was one of them.  The rules are different, including allowing the incorporation of existing hardware from previous missions and tech development projects.  Like the airbag buffered landing demonstration on Pathfinder, the first fully propulsive landing on Mars would fit.

However, it is hard to imagine NASA contracting out a full mission like this.  What I have seen over and over is they issue AOIs, RFPs, or study contracts, and then "bring the program in-house", cutting out the contractors.  What is more likely is that a group at JPL will say that they can replicate the Dragon, maybe subbing out the pressure shell, and do it "better" with full JPL protocols including planetary protection.

I can't see "Red Dragon" as a NASA project, if I can see it at all.

[go4mars]

when a proposed mission already requires fairy dust and unicorn gas to work, it's probably not a good idea to add an experimental leprechaun catcher to the project as well.

LOL! 

Do you recommend a different thread to ask about the cost of leprechaun catchers?  The fairy dust and unicorn gas thread seemed a good one to me. 

If the components of a leprechaun-breath converter are laying around already, why not toss them into the belly of a travelling dragon as well, as a low cost, low risk add-on? 

Serious aerospace engineers have suggested that this red dragon mission is a possible contender.  We don't know if the nuts and bolts include a ballute in the trunk, drop tanks, interesting aerocapture trajectories, or other things.  Reputable people have presumably come up with a way that they think dragon can land with several tons of bric-a-brac.  Small methane engines exist, and so do demonstrator units for ISRU rocket juice. 

Why is two birds with one stone so bothersome? 

If Pioneer astronautics can make an ISRU demonstrator for 6 figures or less (presumably), and little methane engines are laying around already too (definately), it seems to me that a low cost add-on might be worthwhile. 

Yes this assumes that Red Dragon can do as claimed.  Would you have preferred me to make a new thread titled "In the imaginary event that spare capacity is possible on a future Mars mission then..."

[Jim]

Sarcasm would be pointing out that technology demonstrators are not included in Discovery class science missions, ...

It doesn't have to be a Discovery mission.  There is a class of technology development missions.  Mars Pathfinder was one of them.  The rules are different, including allowing the incorporation of existing hardware from previous missions and tech development projects.  Like the airbag buffered landing demonstration on Pathfinder, the first fully propulsive landing on Mars would fit.

That class doesn't exist any more

[Comga]

Sarcasm would be pointing out that technology demonstrators are not included in Discovery class science missions, ...

It doesn't have to be a Discovery mission.  There is a class of technology development missions.  Mars Pathfinder was one of them.  The rules are different, including allowing the incorporation of existing hardware from previous missions and tech development projects.  Like the airbag buffered landing demonstration on Pathfinder, the first fully propulsive landing on Mars would fit.

That class doesn't exist any more

It's getting OT, but the New Frontiers program didn't exist before New Horizons was well underway, IIRC. If NASA wanted to fly Red Dragon, a very big if, they could organize for it.  I know a certain ex-AA-SMD who was very interested in advancing towards Mars Sample Return. He has spoken with Musk, and if he thought this was realistic and was still AA he would find a way.

But the discussion was what kind of things could be added to a hypothetical Red Dragon mission. Your "pixie dust" comment was more to the point than your organizational objection, Jim. 

[simonbp]

Discovery is considered the technology development class for planetary missions, while Explorer covers that for Astrophysics, Helioscience, and Earth Science.

The whole crux of this proposal is that you can launch a Dragon on a Falcon Heavy with a Discovery budget. If they manage to make it to Phase A, we'll know that that is not a ridiculous claim (given enough Non-Disclosure Agreements).

[go4mars]

http://forum.nasaspaceflight.com/index.php?topic=24979.msg858970#msg858970

If there are assumed to be almost no cosine losses, does this Red Dragon mission seem to "work" with just a parachute?   

[Robotbeat]

http://forum.nasaspaceflight.com/index.php?topic=24979.msg858970#msg858970

If there are assumed to be almost no cosine losses, does this Red Dragon mission seem to "work" with just a parachute?   

Proportedly, it "works" even with cosine launches and without a parachute, but the payload is not incredibly impressive (as originally supposed) and would probably need to land at low altitude sites like parts of the Northern Hemisphere and Hellas Basin.

[marsman2020]

How much would it cost to include one of these and a little ISRU unit inside Red Dragon for after the drilling and related tests are done? 
It wouldn't have to be used for anything.  Just a little demonstrator since there seems to be excess mass-to-surface capacity.

An experiment of this type was already developed for the cancelled 2001 Mars Surveyor Lander mission.  When the lander was re-purposed as Phoenix, it was not flown.  I haven't seen any reference as to if the flight hardware still exists.

http://www.lpi.usra.edu/meetings/marsmiss99/pdf/2503.pdf

[Kaputnik]

http://forum.nasaspaceflight.com/index.php?topic=24979.msg858970#msg858970

If there are assumed to be almost no cosine losses, does this Red Dragon mission seem to "work" with just a parachute?   

If you go from firing eight SDT to firing one, you are trading cosine losses for gravity losses
In addition, a key aspect of the supposed capabilities of 'Red Dragon' relies on high speed retropropulsion- as I understand it, the only way you have a chance of firing a thruster succesfully into a high speed/temp airflow is by doing so at an angle.

In case you haven't guessed, I remain very sceptical of the claims made by those behind Red Dragon. AMES involvment notwithstanding, I would lump them in with Elon's claims showing that Falcon would be unprecedentedly reliable, his initial claims on schedule and cost, and his studies showing that they would be reusing first stages using nothing but parachutes and water landing.

[Robotbeat]

...
In addition, a key aspect of the supposed capabilities of 'Red Dragon' relies on high speed retropropulsion- as I understand it, the only way you have a chance of firing a thruster succesfully into a high speed/temp airflow is by doing so at an angle.
...

That's not actually true.

The problem with hypersonic retropropulsion is that putting just one big rocket in the center of the heatshield reduces drag, not that it doesn't work at all. If you had more vertical rockets but that were around the perimeter of the heatshield, you wouldn't have that problem. The cosine losses aren't a strict necessity,

[starsilk]

http://forum.nasaspaceflight.com/index.php?topic=24979.msg858970#msg858970

If there are assumed to be almost no cosine losses, does this Red Dragon mission seem to "work" with just a parachute?   

If you go from firing eight SDT to firing one, you are trading cosine losses for gravity losses

minor nit-pick. you'd be firing two SDT, not one, since they're arranged in four groups of two.

[Robotbeat]

I'm doing some modeling in MATLAB. What is a typical velocity vector (speed and direction) for Mars entry at, say, 200km?