New Red Dragon Mission?

kbd512 · 2016-02-10 12:47:08

GW Johnson wrote:

To answer Kbd512's question:
Sure, you can always test in a wind tunnel. Highly recommended to start there. They did with Viking. You can determine aerodynamic coefficients in the tunnel at convenient density and scale for bodies and for airfoils and for all sorts of aerodecelerators. These are forces-measured that are normalized for size with a reference area, and normalized for wind pressure by a simple-to-calculate item called the dynamic pressure.

So sub-scale testing is possible.

GW Johnson wrote:

To use those coefficients in design calculations, the thin air effects get into it when you calculate the expected in-flight dynamic pressure q as either 0.5*density*velocity-squared or 0.5*specific heat ratio*Mach number-squared. The density or the pressure reflects the thin air, drastically reducing your calculated forces. You do need to match the trends of each coefficient with Mach number, as well as attitude angles. Both are very strong effects.

It would be great to have an actual conversation about this, but I guess Q & A will suffice.

GW Johnson wrote:

What you cannot model properly in a wind tunnel is the dynamics of a complete system, because these things don't all scale the same way, nor do they all respond to speed and density effects the same way. That's why the Viking parachute deployment and opening (not to mention stable flight) was tested full scale (more than once) somewhere above 100,000 feet. (Just one test tells you nothing reliable. It has to be repeatable.)
I've wind tunnel-tested ribbon chute and mesh sleeve drogue stabilizers and their deployment subsonic and transonic. The dynamics seen in the tunnel simply do not match flight test. They can't; it just doesn't scale.

I didn't figure it would be possible to simply put the lifting body in a wind tunnel and determine how it would behave under the varying atmospheric conditions on Mars, but I thought we'd at least be in the right ballpark.

GW Johnson wrote:

Here's my question: what exactly is this X-foil you described? I don't understand exactly what it does. Is this steering fins, drag spoilers, a paper helicopter spin system, or is it any or all of the above? It's an intriguing idea.

Look at the rotor on NASA's Sikorsky S-72 X foil demonstrator. Imagine a non-rotating version of that rotor with a thicker hub and wider blades/petals/wings that fold down towards the ground.

The nose/hub/body of the X foil is basically like the face of a capsule heat shield and in point of fact is a heat shield. It's a reconfigurable heat shield like ADEPT, but has real wings to produce lift and isn't directly attached to the payload so the nose/body of the heat shield can also provide some lift. The wings wrap over the body of the capsule or payload so that it fits inside a payload fairing or at least doesn't produce an enormous amount of drag during launch.

Edit: The payload is slung by the docking ring because we want the payload to act as a counterweight to assist with rotating the vehicle lower in the atmosphere. In other words, the heavier bottom end of the capsule faces away from the back of the X foil. To counteract the tendency of the payload to rotate the vehicle in flight, during reentry the bottom two foils extend outward to directly face the oncoming flow and the top two foils are swept back. Lower in the atmosphere after significant deceleration and associated heating occurs, the bottom foils sweep back and the top foils extend outward/forward to right the vehicle, respective to the oncoming flow. From that point until landing, the foils behave like normal wings. Just prior to landing, the all four foils rotate up and the vehicle flares up like the Space Shuttle to kill forward velocity and increase lift. The body also uses slats to increase lift during maneuvering and to assist with trimming the vehicle. From an aerodynamic configuration standpoint, it looks exactly like a capsule during reentry, but then resembles a helicopter with a slung load while it glides to its landing.

The device I'm describing is nothing more than a fancy glider with four foldable wings attached to a blunt conic or pancake shaped lifting body.

Perhaps we can get the thing to fly slowly enough to pop an enormous forced inflation parachute or maybe we skip the parachute idea entirely and just skid land the payload on a relatively smooth surface and then have the rover drive to wherever it needs to collect samples from.

GW Johnson wrote:

Oops! Sorry, Spacenut. We are getting off-topic here. The origin of this thread was whether the news item Louis found was a new Red Dragon mission, or just a re-reporting of something old.

We're not off-topic. We're discussing how to dramatically improve the landed payload mass of a capsule or other payload using a real wing to do what real wings do best. I think this device could be attached to virtually any capsule or payload. I presume that the Dragon capsule is sufficiently durable to receive a decent tug on the docking ring, especially after the mass of the retro-propulsion and heat shield systems have been removed.

GW Johnson wrote:

I don't think there's anything new about the mission or the Falcon-Heavy/modified-Dragon vehicle. The new thing is some interest finally spreading around within NASA to do the mission.
GW

I think a lot more landed payload mass could be achieved with a reconfigurable reentry system versus sphere/cone heat shield and supersonic retro-propulsion.

I understand that propulsive landing systems are attractive in terms of predictability and experience with using them. However, propulsive landings are decidedly unattractive in terms of landed payload mass. Mars has an atmosphere and it's thick enough to use wings, even if those wings have to be designed differently than the wings we use here on Earth to contend with reentry heating and the much lower atmospheric density.

Last edited by kbd512 (2016-02-10 13:54:50)

SpaceNut · 2016-02-10 14:03:08

Like kbd512 says we are "not off topic" as a little drift from using the capsule in a none steady state is welcomed. As we know there must be a way to reduce the amounts of propulsive landing time and mass. The image of the capsules shell wings using for additional L/D is what the hypercone, adept and other such inflatable do but they all carry the extra mass penaly of adding it on. Picture the legs of Space x first stage but using the aero shell in between the retro rockets instead for the added surface especially once the heat shield is jetisoned.

kbd512 · 2016-02-10 14:54:25

SpaceNut wrote:

Like kbd512 says we are "not off topic" as a little drift from using the capsule in a none steady state is welcomed. As we know there must be a way to reduce the amounts of propulsive landing time and mass. The image of the capsules shell wings using for additional L/D is what the hypercone, adept and other such inflatable do but they all carry the extra mass penaly of adding it on. Picture the legs of Space x first stage but using the aero shell in between the retro rockets instead for the added surface especially once the heat shield is jetisoned.

Capsules have aerodynamics roughly comparable to bricks. With enough lift, even a brick can glide. I'm not trying to make the brick fly incredibly efficiently, I'm just trying to get it to the ground without severely damaging it. My contention is that the mass penalty for a lifting body attached to the top of the payload is not nearly as high as the mass penalty for a propulsive landing.

Although the X foil is a heat shield replacement that weighs significantly more than the PICA-X heat shield, the capsule should still be a lot lighter without the retro-rockets and propellants.

Maybe RCC is not the correct material to use. Maybe a PICA X coating covering some sort aluminum or carbon fiber structure is the way to go. RCC was an initial idea to contend with the heating associated with aerobraking.

NASA thinks their ADEPT equipped payloads will have a 50/50 payload/EDL hardware mass distribution when combined with propulsive landings. I seriously doubt a lifting body would have comparable mass. Is a gliding landing a significantly higher technological hurdle to clear than sky cranes and supersonic retro-propulsion?

Last edited by kbd512 (2016-02-10 14:55:11)

GW Johnson · 2016-02-10 16:27:56

That X-wing thing is an intriguing idea. It's way beyond what obsolete old me is familiar with. That just might help quite a bit during descent. If built as a heat shield and very stout, you could deploy it at one fold-back angle or another, right after peak deceleration gees, while still hypersonic.

I have a hunch such a thing might work all the way to landing here. Not so sure about Mars, where your wing loading (weight per unit planform area) has to be feather-light because of the ridiculously-low density. "Feather-light" is quite incompatible with "stout" in any sense of that word. At least, that would be my first concern on the list.

GW

Last edited by GW Johnson (2016-02-10 16:28:37)

SpaceNut · 2016-02-10 16:38:56

http://www.gizmag.com/nasa-cloth-heat-s … ept/39729/

Dock this on the top where the nose cone opens

adept-test-6.jpg?auto=format&fit=crop&h=200&q=60&w=200&s=f6d716421f58fdf8f83c2a27eff2a183

Now nothing is in the way of the retro rockets firing

kbd512 · 2016-02-10 17:13:26

Maybe the wings can be made of the same fabric that ADEPT uses. The wings would be stowed in the nose cone of the capsule and inflated like HIAD. ADEPT would be connected to the base of the capsule. After peak heating, the docking ring cover is pyrotechnically separated. The wings unfurl and inflate. After the wings inflate and go through a quick test program, ADEPT is pyrotechnically separated to shed mass. You could have relatively large wings that don't weigh very much. It's a one-time use system. It should weigh as little as possible.

Maybe a more durable RCC version of the system could protect capsules that reenter Earth's atmosphere or maybe it's better to use inexpensive disposable carbon fabrics and reuse the actuators inside the wing. It's not like we're going to run out of carbon. There are various materials options with this technology.

SpaceNut · 2016-02-10 18:06:07

The proposed wings would be simaular to the ones in Airplanes on Mars which once they are inflated an epoxy that was UV ativated would make the wings more rigid to the force of the mars atmospher pushing against them.

Yup got more homework as the topic shows the artifacts and shifting within it, time to make it readable once more.

kbd512 · 2016-02-10 20:12:33

GW Johnson wrote:

That X-wing thing is an intriguing idea. It's way beyond what obsolete old me is familiar with. That just might help quite a bit during descent. If built as a heat shield and very stout, you could deploy it at one fold-back angle or another, right after peak deceleration gees, while still hypersonic.

What type of wing loading can we achieve on the red planet?

Maybe solid TPS is too heavy, but what about fabric TPS?

My knowledge of fabrics is even more limited than my pedestrian knowledge of STS/SLS TPS, but what little I do know indicates that the types of fabrics we'd use are lighter than solid TPS. This is a throw-away item, so cost is an issue. That kills the idea of using RCC for TPS.

If we just wanted to be ruthlessly efficient in terms of cost and weight, how would we design a complete TPS solution for a capsule we want to land on Mars?

As light as PICA X is, could we simply wrap the capsule in a fabric TPS and delete the heat shield?

If we use an inflatable like HIAD or deployable like ADEPT, is there any reason why we couldn't modify the same device to produce lift by reconfiguring itself after peak heating?

For example, if we attached something like ADEPT to the capsule, could we vary its geometry by including longer ribs on the side to generate lift, sandwich an inflatable between two ribs, and then inflate it after reentry to create or unfurl a wing? Basically, could we combine some elements of HIAD and ADEPT to arrive at the ultimate solution to the problem?

Edit:

Since this is way back Wednesday, what are your thoughts on a biplane? For example, an X foil attached to the top of the capsule and an X foil attached to the bottom of the capsule folded up on top of HIAD. The wings could remain short, stiff, and externally actuated. We could use control rods attached directly to the exterior of the capsule to move the foils up/down and adjust AoA. We need four rods pushing down on the tips of the bottom foils and four rods pulling down on the tips of the top foils. A biplane isn't exactly cutting edge technology, but shorter foils should be easier to deploy than longer foils and allow for more rigidity.

Any ballpark estimate on how much weight could be removed from Red Dragon if we didn't need its heat shield or retro-rockets?

GW Johnson wrote:

I have a hunch such a thing might work all the way to landing here. Not so sure about Mars, where your wing loading (weight per unit planform area) has to be feather-light because of the ridiculously-low density. "Feather-light" is quite incompatible with "stout" in any sense of that word. At least, that would be my first concern on the list.
GW

It's useless if it doesn't work on Mars. We already have good methods for landing here.

Last edited by kbd512 (2016-02-10 21:36:25)

GW Johnson · 2016-02-11 11:32:08

OK, here's the scoop on wing loading. It's slippery, there's not one value.

I simply don’t know the answer to the question of whether lifting airplane-like flight is really practical on Mars. But, any sort of steady flight system has to obey these basic physics:

L = W = m g lift = weight for steady level flight. On Mars, g would be 38.4% of what we have here.
L = CL q S lift = lift coefficient (values 0 to near 1-ish) x dynamic pressure x planform area

Put those two together and rearrange slightly:

W/S = CL q = mg/S = (m/S) g

Now put in whichever format is convenient for q:

q = 0.5 x density x velocity squared = 0.5 x specific heat ratio x pressure x Mach number squared
for W/S = (m/S) g = CL 0.5 density velocity-squared = CL 0.5 pressure Mach number-squared

On Mars, whether you look at surface density or pressure, either is about 0.006 or 0.007 times the corresponding values here, which far more than overwhelms your 38% advantage due to reduced g. At higher altitudes, the densities and pressures are even smaller.

Expressed in terms of mass instead of weight, your “mass wing loading” m/S will be a very low number, around .38/.006 = 63 times lower than anything you are used to in terms of aircraft design here, to fly at the same speeds we use here, right at the surface.

We do not know how to build wings that lightweight except maybe for the fragile gossamer things used in human powered aircraft. And those are far beyond the practical sizes of inflatables (which date back to the small one or two-place 1950’s Inflate-A-Plane craft from Goodyear), which are not really as lightweight as you might want. Neither would be robust enough for use at high speeds.

Alternatively, for the same kinds of wings loaded with the same concentrations of mass as we usually use here, you have to fly about 8 times faster on Mars. And that’s in the lowlands. And it’s still true as you try to land! How hard can you hit and still expect to survive?

There’s a lot of different kinds of wings and wing loadings used here, for different types of aircraft. A small plane might carry around 20-30-40 pounds per square foot, but is restricted to very subsonic speeds. Two men can physically pick up and carry one of those wings.

A fighter aircraft might have a wing loading in the 100 pounds/sq.ft range, and be robust enough for pulling 9 gees in supersonic flight. But the weight of a single wing like that is better measured in tons than pounds.

Neither type can fly fast dead broadside to the air, either. They break up very quickly if the vehicle should tumble (which is what happened to shuttle Challenger when its center tank came apart).

Somewhere between those extremes (60-ish times lower wing loading and 8-ish times higher speeds) will lie any possible aircraft designs that would work on Mars. You’ll need enough propulsion to fly fast, and also with which to land without a high-speed crash. It’ll likely be rather fragile. At least, that what it looks like to me.

But I know-for-sure nothing.

GW

Last edited by GW Johnson (2016-02-11 11:33:25)

kbd512 · 2016-02-11 14:52:12

Thanks, GW.

That pretty much rules out use of solid TPS. It probably rules out inflatables, but it would depend on how stiff we can make the inflatable.

That basically means we need huge helicopter blades driven to some ridiculous velocity that no lightweight material will withstand. Contra-rotating LOX/LCH4 turboprop?

I have no idea how much that'd weigh, but I'm guessing it would eat into our mass savings quite a bit.

Edit: Even worse, you'd have to figure out some way to cool the turboprop. I suppose you could use some sort of liquid coolant, but at this point this looks more complicated than using rocket engines.

The Martian atmosphere really is a PITA, isn't it? It makes us use TPS for reentry and then doesn't give us enough pressure to use proper wings.

Last edited by kbd512 (2016-02-11 15:04:41)

GW Johnson · 2016-02-11 15:54:09

Hi Kbd512:

I'm guessing "PITA" stands for "poke in the ass". If so, that's just about right. It's been "too much to ignore, too little to use for much" ever since Viking, back before those landed in 1976. Still is today.

Now I honestly don't know if there are aerodynamic solutions for either real flight or aero-deceleration on Mars for things over about a ton at entry (where we've been, before Curiosity). I don't think the JPL guys are any better off over 1 ton at entry based on what they have written, and they're the ones that have landed all the US probes on Mars that have ever gone there.

If you need data, the basic reference Martian atmosphere model was published by two JPL guys named Justus and Braun, several years ago. They did it for Mars, Venus, Titan, and more, in that one report. I've got summaries of that data for Mars posted on my "exrocketman" site: http://exrocketman.blogspot.com. I would have to go look up dates and titles. It was at least 2 years ago.

The JPL guys are now using something called "Marsgram", with more reliable data, but it is strongly dependent upon latitude and longitude, and time of year. Those properties can vary by over a factor of 2 from the reference atmosphere in the original Justus and Braun model. That's completely unlike Earth. I'm not sure, but I think both Justus and Braun are still involved in this kind of atmosphere modeling, and in entry/descent/landing work at JPL.

Everything these JPL guys have ever sent to Mars uses the same sphere-cone heat shield shape and drag, and pretty much the same conical backshell. There are other geometries, perhaps with even better characteristics, but not the pedigree. They've pretty well locked themselves into using the ringsail chute (a Mach 2.5 max update to the Mach 1.5-2 to subsonic ribbon chute) for their EDL sequences, which I think is a mistake.

Looks like Musk agrees with me: his Red Dragon proposal (that was never submitted) uses retro-propulsion, no chutes at all, to land on Mars a capsule that is near 7 tons at entry, and from direct interplanetary transfer trajectories, just restricted to very shallow entry angles. A different version of that same capsule is supposed to bring crews home here on Earth from Earth orbit without any chutes, except as a backup.

GW

Last edited by GW Johnson (2016-02-11 15:58:51)

kbd512 · 2016-02-11 18:13:54

GW Johnson wrote:

Hi Kbd512:
I'm guessing "PITA" stands for "poke in the ass". If so, that's just about right. It's been "too much to ignore, too little to use for much" ever since Viking, back before those landed in 1976. Still is today.

That's about right.

GW Johnson wrote:

Now I honestly don't know if there are aerodynamic solutions for either real flight or aero-deceleration on Mars for things over about a ton at entry (where we've been, before Curiosity). I don't think the JPL guys are any better off over 1 ton at entry based on what they have written, and they're the ones that have landed all the US probes on Mars that have ever gone there.

The good news is that an aerodynamic solution doesn't have to be capable of level flight. The bad news is that it still has to land at some reasonable speed. From your last post, I don't think a fixed wing is practical. It might be possible to land using a very high power helicopter, but only internal combustion engines could provide the kind of power required.

GW Johnson wrote:

If you need data, the basic reference Martian atmosphere model was published by two JPL guys named Justus and Braun, several years ago. They did it for Mars, Venus, Titan, and more, in that one report. I've got summaries of that data for Mars posted on my "exrocketman" site: http://exrocketman.blogspot.com. I would have to go look up dates and titles. It was at least 2 years ago.

I read it.

GW Johnson wrote:

The JPL guys are now using something called "Marsgram", with more reliable data, but it is strongly dependent upon latitude and longitude, and time of year. Those properties can vary by over a factor of 2 from the reference atmosphere in the original Justus and Braun model. That's completely unlike Earth. I'm not sure, but I think both Justus and Braun are still involved in this kind of atmosphere modeling, and in entry/descent/landing work at JPL.

That's a major problem.

GW Johnson wrote:

Everything these JPL guys have ever sent to Mars uses the same sphere-cone heat shield shape and drag, and pretty much the same conical backshell. There are other geometries, perhaps with even better characteristics, but not the pedigree. They've pretty well locked themselves into using the ringsail chute (a Mach 2.5 max update to the Mach 1.5-2 to subsonic ribbon chute) for their EDL sequences, which I think is a mistake.

I think it's time to experiment with forced inflation parachutes.

GW Johnson wrote:

Looks like Musk agrees with me: his Red Dragon proposal (that was never submitted) uses retro-propulsion, no chutes at all, to land on Mars a capsule that is near 7 tons at entry, and from direct interplanetary transfer trajectories, just restricted to very shallow entry angles. A different version of that same capsule is supposed to bring crews home here on Earth from Earth orbit without any chutes, except as a backup.
GW

Elon's team is going to use what they have the most experience with. That doesn't mean retro-propulsion is the best solution.

kbd512 · 2016-02-12 12:21:46

GW,

After thinking about this some more, I'm not ready to give up on the X foil yet.

Perlan II Glider:

Weight: 818 kg

Wing Loading: 33.48 kg/m^2.

Wing Span: 25.6M

Intended Operating Altitude: 27000M+

Expected Velocity: 640 km/h

My design would roughly double that wing area. If we use six foils instead of four foils, the wing area could be further increased. I have roughly 11M of usable payload length and 4.5M worth of usable payload width to work with using the current Falcon Heavy payload fairing.

I need to further research mechanical properties of polymer aerogels and bi-layer graphene / graphene papers. If the device can survive the aerodynamic forces and heating associated with reentry, it should substantially improve delivered payload mass by substantially reducing structural mass associated with EDL hardware. It'd be really bulky, but the avionics, actuators, batteries, and payload bridle would likely weigh as much as the entire wing. It should be stupidly light and rigid for its size.

I was thinking that we'd embed multiple graphene ribbons in the aerogel spanning from the actuator to the tip of the wing through the aerogel to improve rigidity. A layer of thin film solar cells could probably also be wrapped onto the surface of the wing. I've no idea whether or not it would survive reentry, but it could potentially provide power for the payload in-transit.

SpaceNut · 2016-02-13 00:02:45

I think in some ways you might be thinking of this old space company startup efforts https://en.wikipedia.org/wiki/Rotary_Rocket

S2000092-Prototype_Roton_rotary_rocket_in_hangar-SPL.jpg

http://www.risacher.org/uton/background.html

http://www.lunar.org/docs/LUNARclips/v6/v6n2/Roton.html

GW Johnson · 2016-02-13 14:17:26

You do know that the key figures from the Rotary Rocket outfit went on to become XCOR Aerospace?

GW

Excelsior · 2016-04-27 14:31:10

NASA and SpaceX seem to have made it official...

SpaceX plans to debut Red Dragon with 2018 Mars mission

SpaceX has entered into an agreement with NASA for a Dragon mission to Mars, set to take place as early as 2018. Known as “Red Dragon”, the variant of the Dragon 2 spacecraft will be launched by the Falcon Heavy rocket, ahead of a soft landing on the surface of Mars. The mission is also part of an agreement with NASA to gain further data on Mars landings.
...
These plans involve the Red Dragon conducting a propulsive landing on Mars, following its launch on a Falcon Heavy from SpaceX’s Pad 39A at the Kennedy Space Center (KSC).
Previously, Mr. Musk has claimed Dragon 2 has a “much greater reach”, thanks to the increased performance of the FH, with the rocket expected to conduct a debut launch this year.
“Dragon 2 is capable of transporting scientific payloads to anywhere in the solar system, with a liquid or solid surface, with or without an atmosphere. So Dragon is really a crew transport and science delivery platform,” Mr. Musk said, speaking after the Dragon 2 vehicle successfully conducted a Pad Abort test under the NASA Commercial Crew Program milestones.
“When boosted on a Falcon Heavy, Dragon can go pretty much anywhere, so we’re excited about exploring that possibility.”
Utilizing Falcon Heavy, Mr. Musk stated that Dragon will be capable of transporting two to four tons of payload to the surface of the Red Planet, with varying options for other destinations.
“With Dragon launched on a Falcon Heavy, it can go pretty much anywhere in the solar system, because that’s a heck of a big rocket,” he continued.
“Dragon, with the heat shield, parachutes and propulsive landing capability, is able to land on a planet that has higher entry heating, like Mars. It can also land on the Moon, or potentially conduct a Europa mission.”

All the pieces are there, the heat shield, the aerodynamics, the SuperDraco retrorockets, ect, but I still can't see the capsule as an effective payload delivery system. Either you have to get through the heat shield, which as far as I know is not designed to come off without expensive modifications to the base design, or your going to use up so much of the payload weight to get the payload out of the main hatch of the capsule, or your going to have to so butcher the entire capsule that your going to lose whatever economy of scale your where out to gain by using the capsule. It's like stuffing a turkey through the beak.

Maybe going down through the heat shield is simpler than I'm giving them credit for, and then it makes a lot of sense. I just haven't seen anything to indicate that is an option. If they are going to make the next launch window, they've got to haul.

If going through the shield is an option, how practical would it be to launch with an ascent stage missile in the trunk, and have it dock with the main hatch in transit, and then put samples into Mars orbit for pickup. Probably not this time around, but for future missions.

Last edited by Excelsior (2016-04-27 15:04:33)

RobertDyck · 2016-04-27 15:36:43

Ah, I posted the same article elsewhere. As I said, I wasn't sure where to post it. Ok, so here.

True, it's a spacecraft designed to carry crew. Putting instruments there is not the most efficient. But this means they have a contract to land Red Dragon on Mars! A capsule capable of carrying crew to Mars! All you need is life support for 6 months, and it could carry crew. In zero-G, and confined to a capsule the whole way. And no way to get off the planet. Mars One intends to deliver supplies and crew with Red Dragon. They were up-front that it would be a one-way mission. Mars One got over 100,000 volunteers, all of whom had to donate at least $100 each to get their name on the list. So they've made how much money so far? But demonstrating Red Dragon means SpaceX will have demonstrated technology to deliver crew. That's a major step.

SpaceNut · 2016-04-27 16:32:16

Yes you did and it had the images that say a thousand words....repost with images...

RobertDyck wrote:

I'm not sure where to put this, but it's so exciting I have to post it somewhere!
SpaceX plans to debut Red Dragon with 2018 Mars mission
SpaceX has entered into an agreement with NASA for a Dragon mission to Mars, set to take place as early as 2018. Known as “Red Dragon”, the variant of the Dragon 2 spacecraft will be launched by the Falcon Heavy rocket, ahead of a soft landing on the surface of Mars. The spacecraft is set to carry a suite of scientific instrumentation as part of the NASA agreement.
And SpaceX themselves posted two images to Facebook. Click image to see Facebook post. Their caption...
SpaceX is planning to send Dragons to Mars as early as 2018. Red Dragon missions will help inform the overall Mars architecture that will be unveiled later this year.
These missions will help demonstrate the technologies needed to land large payloads propulsively on Mars.

SpaceNut · 2016-04-27 16:36:19

I also notice that its a first launch of the triple first stage assembly of Falcon 9 heavy.....
This would also prove out the cruise stage and mar insertion ability for Space x as well.

A oneway topic of using the red dragon also crosses into the smallest manned capsule for mars as well of which we have both topics pretty well discussed....or maybe not...

SpaceNut · 2016-04-28 20:27:49

Bump here is the other Red Dragon topic....

SpaceNut · 2016-08-30 17:48:54

Sort of another topic that is using current technology to deliver a tonne to the surface to make use of.....

GW Johnson · 2016-08-30 18:22:11

Red Dragon is a mod to the crewed Dragon v2. They remove all the seats, instruments, and life support, and configure the interior more like the cargo unmanned Dragon v1. But it has the big Super Draco thrusters, and the landing legs, of Dragon v2.

It may not be the most "efficient" way to deliver cargo to the surface of Mars (or anywhere else), but it is one system with all its components and workings already proven. It's the same as using a pre-existing DC-3 to deliver 3 tons of cargo, even if you could design a more efficient airplane for that mission. Why bother, if you already have the DC-3? Good question!

The original Red Dragon stories I found mentioned 1 to at most 2 tons deliverable to the surface of Mars. More recent stuff talks 2-3-maybe 4 tons. We'll see soon enough, but I'd guess 2 to 3 tons is deliverable. Spacex is supposed to start shooting Red Dragons to Mars with Falcon-Heavies starting in 2018. That's coming up quite soon, actually.

On Mars, they do not use parachutes, the landing is retropropulsive, same as the design crewed landing on Earth. On the smaller bodies, you could carry more payload this way. On worlds like Titan with a significant atmosphere, you could carry even more, because you can use the chutes effectively. But chutes destroy landing precision. Precision is inherent with retropropulsion. It's a trade, depends upon what you intend to accomplish in detail.

This Red Dragon/Falcon-Heavy thing looks to me like a real future workhorse for unmanned probe shots, in the 2-5 ton delivered payload class. It should be able to go just about anywhere in the inner and middle solar system.

GW

Last edited by GW Johnson (2016-08-30 18:26:15)

SpaceNut · 2016-08-30 18:51:06

The only thing stopping anyone from going to mars it would seem is money and a scheduel for the deliveries to a selected site.

Looking at the single cargo drops one would need to cut into the delivered payload via monitoring electronics and power source so as to deliver timely reports of health of the payloads. One would not want to find out that once you get there that the oxygen drop or water were damaged and not available or the crew to use once there.

elderflower · 2016-08-31 11:15:43

If a thruster can be designed for the Dragon that uses propellants which can be manufactured on Mars, it could also serve as a hopper for exploration. Peroxide and methanol, or peroxide monopropellant may be the best choice as they don't require much in the way of refrigeration or heating on the Martian surface. Current NTO and MMH have similar storage properties, but are likely to need to be imported from Earth.

GW Johnson · 2016-08-31 14:50:54

Generally speaking, a new propellant combination means a new rocket chamber and feed equipment design. There are almost no exceptions, the only one I can think of being the old Army Redstone. It originally used LOX and ethanol, just like the old German V-2. They successfully switched to LOX and a hydrazine blend to get enough performance to launch Explorer 1 in 1958 and the Mercury capsules back in 1961. The blend was "hydyne": 75% UDMH and 25% diethylene triamine. It significantly outperformed LOX-ethanol, and was usable in the very same equipment.

There is another design issue that is quite critical for successful thrusters: spontaneous (hypergolic) ignition. Not having this has proven to be quite impractical in thrusters for decades now. You can only tolerate the delay and ramp-up of stimulated ignition in main engines of boosters. It's just not tolerable in attitude control and escape thrust options. Hydrazine blends and NTO are hypergolic. LOX-LCH4 is not.

RFNA and kerosene are hypergolic, and about the same Isp as hydrazine and NTO, but require different engine equipment, and present even more toxic handling hazards with the RFNA (red fuming nitric acid). Hydrazine presents about the same dangers as anhydrous ammonia.

There are monopropellant hydrazine thrusters that use catalytic decomposition flowing through a catalyst bed to achieve instant "ignition". Something similar happens with 90+% hydrogen peroxide. Neither has the performance of NTO-hydrazine, by far. Hydrogen peroxide above about 50% strength presents a long-term explosive decomposition hazard. But you have to distill it up above 90% to use it, whether alone as a monopropellant, or as an oxidizer for kerosene. It is hypergolic with kerosene, though.

Most of the rest require dedicated igniters and a slow, step-by-step ignition process.

Inconvenient little facts of life, but there you are. The truth will set you free, even if painful.

GW

Last edited by GW Johnson (2016-08-31 14:56:27)

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