New Red Dragon Mission?

louis · 2015-12-17 04:47:02

Are people aware of this Red Dragonn mission proposal (sounds at last like people at NASA are thinking outside the box):

"Nasa employees have revealed details of a 'budget' plan to send a SpaceX capsule to the red planet in 2020 to return samples to Earth.

The 'Red Dragon' project was developed by a team at Nasa looking at using SpaceX's spacecraft.

It would grab samples collected by the space agency's 2020 rover and return them to Earth.

The sample-return effort would keep costs and complexity down by using SpaceX's Falcon Heavy rocket and a modified version of the company's robotic Dragon cargo capsule.

The adapted Red Dragon would include a robotic arm, extra fuel tanks and a central tube that houses a Mars Ascent Vehicle (MAV) and an Earth Return Vehicle (ERV).

The Red Dragon team developed the concept independently, without any involvement or endorsement by SpaceX, but Elon Musk later backed the idea. "

I think this would be a great intro to a more concerted effort at a human mission.

http://www.dailymail.co.uk/sciencetech/ … lanet.html

SpaceNut · 2016-02-04 21:39:40

I am hoping that there will be more news soon as to the production model meant for manned flight....

GW Johnson · 2016-02-05 16:22:00

It's a little odd seeing claims that Red Dragon was a NASA idea and initiative. That's not right.

As best I can determine, this was a Spacex proposal for a Discovery class mission, that was never submitted, because NASA said it wouldn't work, and discouraged submittal. At least, that part of NASA to which such proposals would go.

Looking around the on-line document trail, I found a different group within NASA that looked at Red Dragon, and got enthusiastic, saying it would work. This group seems to have since won over most of the rest of NASA.

But, damn it, it was a Spacex idea, not a NASA idea. I get pissed off when those in positions of power appropriate other people's ideas and claim credit for them. Managers and government bureaucrats are the worst offenders.

I see no real substantive changes to the Red Dragon idea: Dragon v2 re-rigged to carry cargo and some other mods to land one-way on Mars with its Super Draco thrusters. The payload originally was 1 metric ton, over and above a fully-fueled but otherwise unloaded Dragon, which I think might be in the vicinity of 6 tons or so. This thing can ride Falcon-Heavy as a direct shot straight to Mars. It is based on a really shallow direct entry angle, or this sort of propulsive entry won't work, not with standard tankage for the Super Dracos.

I've seen some articles claiming up to 2 metric tons might be carried this way, but I tend to be conservative. I'm sticking with 1 ton until Spacex says otherwise.

GW

louis · 2016-02-05 17:32:26

GW Johnson wrote:

It's a little odd seeing claims that Red Dragon was a NASA idea and initiative. That's not right.
As best I can determine, this was a Spacex proposal for a Discovery class mission, that was never submitted, because NASA said it wouldn't work, and discouraged submittal. At least, that part of NASA to which such proposals would go.
Looking around the on-line document trail, I found a different group within NASA that looked at Red Dragon, and got enthusiastic, saying it would work. This group seems to have since won over most of the rest of NASA.
But, damn it, it was a Spacex idea, not a NASA idea. I get pissed off when those in positions of power appropriate other people's ideas and claim credit for them. Managers and government bureaucrats are the worst offenders.
I see no real substantive changes to the Red Dragon idea: Dragon v2 re-rigged to carry cargo and some other mods to land one-way on Mars with its Super Draco thrusters. The payload originally was 1 metric ton, over and above a fully-fueled but otherwise unloaded Dragon, which I think might be in the vicinity of 6 tons or so. This thing can ride Falcon-Heavy as a direct shot straight to Mars. It is based on a really shallow direct entry angle, or this sort of propulsive entry won't work, not with standard tankage for the Super Dracos.
I've seen some articles claiming up to 2 metric tons might be carried this way, but I tend to be conservative. I'm sticking with 1 ton until Spacex says otherwise.
GW

Is there any reason it couldn't be used as an equivalent of an Apollo lander then if you already had a functioning hab landed on the surface? 24 hour rest when you reach the surface. Then transfer to the hab.

SpaceNut · 2016-02-05 19:07:04

The Red Dragon was a sample return mission louis for the topic and less about its eventual useage in LEO as a taxi.
That said what are the numbers once you remove the seats, oxygen plus tanks, life support systems extra batteries for what would have been the crews. In fact there are other mass reductions that could be made in reducing the inside structural stuff that supports a crewed controlled vehicle reducing it to an atonomous robitically controlled system.

All these things once removed make it possible to do such a mission as it give margin for the alteration and for the return vehicle to launch from its internals.....

What thoughts do you all have to make the capsule a launch system once a sample is loaded into it as soon as its down on the surface as it will have a limit on available power. We could jetison the upper part of the capsule on the way down once the retro rockets take over for landing exposing the internals for a mars sample to be placed into the returning rocket once we can load it into it.

Do we add some sort of arm to get a sample with or hope that we land close to a robot previously sent to get a cache of samples for return?

SpaceNut · 2016-02-05 21:00:03

https://en.wikipedia.org/wiki/Dragon_V2

Dimensions
Height 8.1 meters (20 feet)
Diameter 3.7 meters (12.1 feet)
Sidewall angle 15 degrees
Volume 10 m3 (350 cu ft) pressurized
14 m3 (490 cu ft) unpressurized
Dry mass about 4,200 kg (9,300 lb)
Payload to ISS 3,310 kg (7,300 lb).

RED DRAGON-MSL HYBRID LANDING ARCHITECTURE FOR 2018

https://en.wikipedia.org/wiki/Red_Drago … cecraft%29

louis · 2016-02-06 09:03:13

SpaceNut, Not really sure why you are asking "What thoughts do you all have to make the capsule a launch system once a sample is loaded into it as soon as its down on the surface as it will have a limit on available power." My understanding of the proposal (I may be wrong) was that it aims to land a single integral Red Dragon which can then return to LMO...and I presume the main difference from the ISS-supplying Dragon is putting more fuel/propellant on board, in order that it can retro descend (I'm guessing it the mass would be too great for a parachute landing) and then ascend from the surface.

SpaceNut wrote:

The Red Dragon was a sample return mission louis for the topic and less about its eventual useage in LEO as a taxi.
That said what are the numbers once you remove the seats, oxygen plus tanks, life support systems extra batteries for what would have been the crews. In fact there are other mass reductions that could be made in reducing the inside structural stuff that supports a crewed controlled vehicle reducing it to an atonomous robitically controlled system.
All these things once removed make it possible to do such a mission as it give margin for the alteration and for the return vehicle to launch from its internals.....
What thoughts do you all have to make the capsule a launch system once a sample is loaded into it as soon as its down on the surface as it will have a limit on available power. We could jetison the upper part of the capsule on the way down once the retro rockets take over for landing exposing the internals for a mars sample to be placed into the returning rocket once we can load it into it.
Do we add some sort of arm to get a sample with or hope that we land close to a robot previously sent to get a cache of samples for return?

GW Johnson · 2016-02-06 10:26:22

The Red Dragon sample return mission did not return the capsule. Once on the surface, the Dragon stayed there.

The capsule had installed a small rocket ascent vehicle that carried a very tiny sample. That small rocket comes back to some high orbit about the earth, from which it is retrieved by another, unspecified, craft.

I personally have never seen any illustrations of how all this gear was to be installed. But some versions say there was a tiny rover. I suspect some sort of robot arm must be involved.

GW

kbd512 · 2016-02-06 10:30:49

How heavy a payload can Red Dragon land if JPL uses a supersonic parachute in conjunction with retro-propulsion? If it can land 2t of cargo, that's double what we were previously capable of, doesn't require complex sky cranes, and provides a healthy margin that permits us to land at higher elevations with lighter payloads.

Perhaps we could land two smaller rovers at a time. The rovers could be equipped with manipulators to roll out a rollup solar panel connected to a battery charging station. The rovers could swap their own battery backs to permit faster travel around the landing site, facilitating more samples collection. Maybe we could also send our first aerial drones. The rovers would retrieve them after they land, swap their battery packs, and download imagery. The collected imagery would be useful for targeted exploration. If the aerial drones spot something that looks interesting, the imagery collected would be used to plot either a minimal power usage or maximum speed course for a sample retrieval.

GW Johnson · 2016-02-06 15:59:09

I have not run any direct entry scenarios. I have run entries from the far less challenging low Mars orbit as a function of ballistic coefficient (essentially, mass at entry), using an over-simplified 2-D model for warheads from 1956.

That model shows lower altitudes coming out of hypersonics with higher ballistic coefficients, steeper entry angles, and higher entry speeds. Steeper angles and higher speeds at entry also correlate with higher peak gees, and with higher heating rates. All of this is as expected. This quite literally is how we learned to have warheads off ICBM's survive to target.

That model indicates quite clearly a severely-lowered altitude at high ballistic coefficient (over about 1 ton) for exit-from-hypersonics at local Mach 3. At 10 tons +, there is quite literally not enough time left to impact to even deploy a chute, much less time for a chute to decelerate anything significantly. There are only a single handful of seconds left to impact. This is inherent, with an atmosphere as thin as what Mars has. We do not see exaggerated effects like this at Earth.

Add to that the fact that there is no such thing as a ringsail chute that will open at speeds over local Mach 2.5, and things are "iffy" even for that. You'd best be under Mach 2 before opening a ringsail (or a ribbon) chute. These kinds of supersonic chutes simply do not have equivalent drag to a subsonic cargo chute, they are less draggy, because they are more leaky. In other words, they decelerate less for the same diameter.

I'm sorry, physics says that chutes are of no value over about 1 to 3 tons on Mars, even from LMO. My ancient model might be too crude to be accurate, but it is quite illustrative. You can forget using chutes with any version of Dragon on Mars, even from "only" LMO. It's far worse from direct entry.

My crude calculations say that even a subsonic cargo chute fails to provide enough drag to get you under half a Mach number terminal velocity, at any "reasonable" canopy loading (mass per blockage area). And if that canopy loading is too low, the chute WILL NOT spontaneously open at all.

There might be room to examine some sort of positively-forced opening by something inflatable here, but you cannot do bluff non-leaky shapes like that at supersonic speeds with real-world materials. The opening shock is just too bloody damned high.

GW

Terraformer · 2016-02-06 17:02:45

GW, how would a Mars glider handle atmospheric entry? I'm thinking something inflatable, along the lines of FIRST. That should allow you to stretch out entry time significantly, as well as possibly offering better targeting of locations.

GW Johnson · 2016-02-06 17:32:25

"GW, how would a Mars glider handle atmospheric entry?"

I honestly don't know. I would presume like a lifting capsule, but with an L/D approaching closer to 1 than 0.1.

I don't have any sort of analysis I can run on such a thing.

GW

SpaceNut · 2016-02-06 20:37:44

My understanding is that if we can shed mass on the way down we will make terminal velocity lower such as when we use a backshell for the other mars lander where we eject it to allow for parachutes we can do the same for the top of the capsule. Then much like when we want the engines to fire we could drop the heatshield which would leave us in the basic skycrane mode for retro rocket firing.....

louis · 2016-02-06 21:24:54

OK - my apologies to Spacenut and thanks for putting me right on that!

GW Johnson wrote:

The Red Dragon sample return mission did not return the capsule. Once on the surface, the Dragon stayed there.
The capsule had installed a small rocket ascent vehicle that carried a very tiny sample. That small rocket comes back to some high orbit about the earth, from which it is retrieved by another, unspecified, craft.
I personally have never seen any illustrations of how all this gear was to be installed. But some versions say there was a tiny rover. I suspect some sort of robot arm must be involved.
GW

SpaceNut · 2016-02-07 20:47:33

The thrusters will need to fire for quite a bit of time to slow the capsule before making contact with mars for the sample return.

https://en.wikipedia.org/wiki/Draco_(ro … ne_family)

Engines: eight side-mounted SuperDraco engines, clustered in redundant pairs in four engine pods, with each engine able to produce 71 kilonewtons (16,000 lbf) of thrust Each pod—called a "quad" by SpaceX—contains two SuperDraco engines plus four Draco thrusters. "Nominally, only two quads are used for on-orbit propellant with the Dracos and two quads are reserved for propulsive landing using the SuperDracos."

SuperDracos utilize a storable propellant mixture of monomethyl hydrazine (MMH) fuel and nitrogen tetroxide oxidizer (NTO), the same propellants used in the much smaller Draco thrusters used for attitude control and maneuvering on the first-generation Dragon spacecraft. Burn time 25 seconds for Propellant capacity 1,388 kg (3,060 lbs).

http://www.grc.nasa.gov/WWW/K-12/airplane/rockth.html

http://www.thrustcurve.org/motorstats.shtml

GW Johnson · 2016-02-08 11:20:45

25 sec burn to slow for a landing and just barely have enough propellant is right in line with my crude entry calculations for a high ballistic coefficient coming in very shallow: a double-handful of seconds to impact from end of hypersonics at local Mach 3. That's way too short a timeline to do anything at all with a chute of almost any design. That's why I have been an advocate of propulsive landings on Mars for quite a while now. Having an extendible or inflatable heat shield will buy you the equivalent of a somewhat lower ballistic coefficient, which might (or might not) be enough to replace some of the retropropulsion with chute drag. You'll need 3-5 minutes minimum worth of timeline to deploy and get any benefit out of a chute.

GW

kbd512 · 2016-02-08 12:55:19

Thanks, GW. That's a fairly instructive explanation as to why parachutes have issues with the atmosphere on Mars. Still, there has to be some passive way to but the brakes on higher in the atmosphere.

SpaceNut · 2016-02-08 20:57:48

From Mars curiosity:
Curiosity will slam into the discernible atmosphere of Mars at an altitude of about 81 miles and a velocity of 13,200 mph. At that point, it will be about 390 miles -- seven minutes -- from touchdown in Gale Crater.

One minute and 15 seconds after entry, the spacecraft's heat shield will experience peak temperatures of up to 3,800 degrees Fahrenheit as atmospheric friction converts velocity into heat, accounting for 90 percent of the spacecraft's deceleration.

Ten seconds after peak heating, that deceleration will max out at 15 times the force of Earth's gravity at sea level.

Normally: The parachute, which is 51 feet (nearly 16 meters) in diameter, deploys about 254 seconds after entry, at an altitude of about 7 miles (11 kilometers) and a velocity of about 900 mph (about 405 meters per second).

Then the skycrane:
entry-descent-landing (EDL) system (2,401 kg (5,293 lb) including 390 kg (860 lb) of landing propellant). The descent stage is a platform above the rover with eight variable thrust monopropellant hydrazine rocket thrusters on arms extending around this platform to slow the descent. Each rocket thruster, called a Mars Lander Engine (MLE), produces 400 to 3,100 N (90 to 697 lbf) of thrust and were derived from those used on the Viking landers.

There are eight Aerojet MR111C 1.0lbf thrusters that will be used for trajectory correction maneuvers during the transit to Mars and eight Aerojet MR-107U 68 lbf thrusters that will stabilize the spacecraft during its entry. Additionally, the MSL Sky Crane that will do the final lowering of the payload to the Martian surface includes eight Aerojet MR-80B 700-lbf thrusters with a throttleable thrust range of >100:1.

pg 10 http://solarsystem.nasa.gov/docs/pr478.pdf gives the timing and firing of the thrusters....

Some real numbers to work out the scaling for what we would want to land on mars for tonnage....

kbd512 · 2016-02-09 02:07:36

Obviously this must be tested, but we need to figure out how to kill reentry velocity by skipping off the upper atmosphere, employing a modified ADEPT geometry to decrease ballistic coefficient for cargo, and/or using airfoils to decelerate the reentry vehicle at sufficient altitude above the surface for parachutes to be effective.

There has to be a workable method for killing velocity that does not involve transporting significant quantities of hypergolic or cryogenic propellants millions of miles for a few minutes worth of use.

I'm not against propulsive landings if that is truly required, but I don't think we've exhausted all other reasonable approaches yet.

Terraformer · 2016-02-09 09:43:31

I think one of the big problems you'll have with that is that it will make targeting much more difficult. Unless you have significant cross-range gliding capability. Hypersonic circles?

GW Johnson · 2016-02-09 10:02:48

The pressures and densities of the Martian surface look about like those we see at or above 110,000 feet altitude here. And things get thinner higher up. Aerodecelerator schemes for Mars can be tested way up high here, and with fair fidelity. That was done for the original Viking landers; I remember.

What you do to test is this: send your scheme up on a rocket or balloon, then use a rocket to accelerate it to your test speed, and try it out. It ain't cheap, but it ain't all that expensive, either.

My engineering intuition tells me that aerodecelerators will destroy any capability for pinpoint landing accuracy, because of inherent variability and drift. It takes retropropulsion over most of the final descent to give you pinpoint accuracy. Both Spacex and Blue Origin are beginning to prove that point.

GW

RobertDyck · 2016-02-09 10:42:31

GW Johnson wrote:

My engineering intuition tells me that aerodecelerators will destroy any capability for pinpoint landing accuracy, because of inherent variability and drift. It takes retropropulsion over most of the final descent to give you pinpoint accuracy. Both Spacex and Blue Origin are beginning to prove that point.

I've posted this before. It shows mass to Mars surface using different systems. To land 40 metric tonnes of payload, the first 3 use an aeroshell and retropropulsion, with various size ADEPT heat shields and propulsion starting at various altitudes. The first requires 90 tonne total mass, the second 87 tonne, the third 81 tonne. The last uses ADEPT for atmospheric entry, then parachute, then retropropulsion for landing. The last has entry mass of 78 tonnes, so the lowest launch mass. That's why NASA uses this system.

Curiosity also used aeroshell, parachute, and retropropulsion. Instead of landing legs with shock absorbers, it landed on its wheels. That eliminated the need for a separate lander, but instead of retropropulsion built into the lander, it was a sky crane. Curiosity rover mass was 900kg (2000 pounds), so that was one ton. Not quite a metric tonne, but a US short ton. The aeroshell did not have a deployable heat shield, the heat shield was the lower half of the clam shell. A larger (40 tonne) payload would require ADEPT. Curiosity aeroshell used weights. It was balanced during initial atmospheric entry, then jettisoned weights to shift the centre of gravity off-centre. It used that to "steer" during high speed atmospheric flight. You could do that with a motor that moves the heat shield a bit so centre of the heat shield is no longer aligned with centre of gravity. I suspect for a large payload the arms and motors would be lower mass than weights. Either way that allows the aeroshell to steer the same as Curiosity. You could easily land with the same precision.

kbd512 · 2016-02-09 14:05:33

GW Johnson wrote:

The pressures and densities of the Martian surface look about like those we see at or above 110,000 feet altitude here. And things get thinner higher up. Aerodecelerator schemes for Mars can be tested way up high here, and with fair fidelity. That was done for the original Viking landers; I remember.

Ok.

GW Johnson wrote:

What you do to test is this: send your scheme up on a rocket or balloon, then use a rocket to accelerate it to your test speed, and try it out. It ain't cheap, but it ain't all that expensive, either.

Is it possible to do any testing in a wind tunnel?

GW Johnson wrote:

My engineering intuition tells me that aerodecelerators will destroy any capability for pinpoint landing accuracy, because of inherent variability and drift. It takes retropropulsion over most of the final descent to give you pinpoint accuracy. Both Spacex and Blue Origin are beginning to prove that point.
GW

Here's what I want to try:

* X foil attached to struts connected to the top of the habitat module and ADEPT attached to bottom of habitat module with interface ring

* each petal is folded down over the habitat module during reentry

* each petal is independently manipulated to alter AoA to permit vehicle maneuvering and deceleration

* ADEPT fabric panels folded over the X foil petals before deployment for reentry

* Following initial stage of reentry where maximum aerodynamic heating occurs, X foil is deployed and ADEPT jettisoned

* Intended primarily to provide lift, maneuvering capability, and to reduce the landed payload mass by jettisoning ADEPT because it's a poor wing

How large would the petals have to be when combined with the fixed center wing section to provide enough lift to sufficiently control rate-of-descent for a 20t payload and maneuver it to the landing area? Would the petals be small enough to fold down over the habitat? In short, how big a wing are we talking about?

If the center section is roughly 64M^2 and each petal is roughly 12.5M^2, so do we have enough wing area to provide sufficient lift to eventually pop a parachute and soft land a 20t payload?

To recap:

I want to mount a 9M diameter X foil wing with deployable wings/petals to the top of a 8.4M diameter tuna can habitat using four struts to connect the wing to the tuna can. Each wing/petal can independently alter AoA for maneuvering and to enhance lift. Each wing/petal would look similar to the Space Shuttle's body flap and probably be made of RCC to withstand reentry heating.

ADEPT is pyrotechnically separated after peak heating. Initially, the wings would rotate the payload so the entire wing faces the oncoming airflow. Lower in the atmosphere, the wings rotate the habitat back to that landing configuration such that the wings and habitat are both facing the oncoming airflow, in much the same way that a helicopter carrying a slug payload would look.

Nearer to the surface, a forced inflation parachute would deploy using CO2 cartridges and the payload would soft land. Alternatively, if enough lift is provided by the X foil, maybe the parachute isn't necessary and the payload can be skid landed. Could we do away with ADEPT entirely and gift wrap the payload with the same material ADEPT uses and simply point the RCC X foil into the oncoming airflow during reentry?

The basic idea is a 114M^2 X foil intended to be a real wing versus a cone lifting body, and possibly a reentry protection device when the payload is wrapped in the fabric used in ADEPT or sprayed with aerogel- assuming RCC could survive the reentry heating, that should produce more lift than a cone like ADEPT because each wing/petal can independently alter its AoA and the 9M center section is connected by struts to the payload so the entire 114M^2 surface is a wing.

Dr. Zubrin though the EDL hardware would weigh 5t or something like that. I think that's wildly optimistic. Can anyone provide mass numbers for what a 314M^2 (20M diameter ADEPT reentry shield) capable of landing a 20t payload would weigh?

Practical? I have no idea. Complicated enough? Mars EDL is extremely complicated. I'll leave it at that.

Maybe someone smarter than I am like GW or someone from JPL can tell me how stupid I am for thinking that might work.

Edit: This idea was derived from NASA's Sikorsky S-72 X wing rotor and the Boeing Dragonfly. It's not my idea.

Edit 2: I corrected the X foil surface area numbers.

Notes:

Attachment:

If the X foil was directly connected to the top of the tuna can habitat, the center section wouldn't provide much lift. However, if the payload is slung beneath the X foil by attaching it to the payload with struts, then the center section should be able to provide some measure of lift. I think the petals will likely have to be longer than 5M, but how much longer is the question.

Mass:

I estimate that the RCC material for this wing body to weigh about 3t, assuming the material is about 7MM thick and has a density of 1.8g/cm^3. I have no idea what the actuators would weigh, but I'm guessing that the complete solution, to include landing gear/skids, to weigh about 5t. Even if the total mass of the solution is nearer to 10t, it's still a fraction of the mass of propellants required for retropropulsion.

Mechanics:

Each wing/petal would be mounted to the center wing/body with a ball joint. The ball joint would fold the petals over the tuna can for launch aboard SLS or Falcon Heavy in the case of a system designed to EDL a Dragon capsule. The surfaces of the panels could be covered with thin film solar cells to provide power during the transit to Mars and then vaporized during reentry.

For reentry at Mars, the wings would be locked into a swept back position to give the device a rough sphere/cone geometry. The payload would be wrapped in a carbon fabric similar to the fabric ADEPT uses to withstand reentry heating. After peak heating occurs, the wings/petals would then be locked into position for maneuvering and would pivot about the axis of the wing to change AoA and provide deceleration or braking in the upper atmosphere. The entire wing would initially face the oncoming flow to decelerate the payload and then change configuration between 20km and 10km in altitude for final approach and landing. Slats and flaps could be added to further increase lift.

Obviously a relatively smooth surface is required for landing, but here on Earth there are plenty of 25t+ aircraft that have very good rough field performance.

Mutli-Purpose Uses:

The device would also contain the RCS to de-orbit the payload.

After landing, a fabric cover similar to a bed sheet would be wrapped over the tips of the wings/petals using a small robot or manipulator arm attached to the device. The robot would then attach roll up solar arrays wrapped around the sample return capsule or habitat to the sheet to provide a trackable solar array atop the habitat or sample return capsule.

Final Thoughts:

It may seem crazy, but using a lifting body to land payloads on Mars (sample return rover and rocket or habitat module) is no crazier than sky cranes or super sonic retro-propulsion and should dramatically increase landed payload mass through the attendant reduction in propulsion systems mass.

The solution may end up weighing more than estimated because the wings may need to be bigger, but it'd have to be quite a bit larger to approach the weight of retro-propulsion solutions and even though the Martian atmosphere is pretty thin, it's not so thin that lifting bodies are impractical.

The demonstrator would use Red Dragon to provide RCS, power, avionics, etc. The device would attach to Red Dragon's docking ring and the capsule would not have have any hardware fitted for retropropulsion or a heat shield, so it should be much lighter. In other words, empty aluminum capsule with RCS wrapped in a thermal protection blanket for reentry. The setup should be light enough to land a substantial rocket, related launch hardware, and a rover.

Last edited by kbd512 (2016-02-10 11:47:02)

SpaceNut · 2016-02-09 18:31:45

The red dragon mission as culture has been calling it is an unmanned robotic mission to get samples from mars back home...

GW Johnson · 2016-02-10 10:25:52

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.

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.

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.

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.

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.

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

Last edited by GW Johnson (2016-02-10 10:30:19)

New Mars Forums

Announcement

#1 2015-12-17 04:47:02

New Red Dragon Mission?

#2 2016-02-04 21:39:40

Re: New Red Dragon Mission?

#3 2016-02-05 16:22:00

Re: New Red Dragon Mission?

#4 2016-02-05 17:32:26

Re: New Red Dragon Mission?

#5 2016-02-05 19:07:04

Re: New Red Dragon Mission?

#6 2016-02-05 21:00:03

Re: New Red Dragon Mission?

#7 2016-02-06 09:03:13

Re: New Red Dragon Mission?

#8 2016-02-06 10:26:22

Re: New Red Dragon Mission?

#9 2016-02-06 10:30:49

Re: New Red Dragon Mission?

#10 2016-02-06 15:59:09

Re: New Red Dragon Mission?

#11 2016-02-06 17:02:45

Re: New Red Dragon Mission?

#12 2016-02-06 17:32:25

Re: New Red Dragon Mission?

#13 2016-02-06 20:37:44

Re: New Red Dragon Mission?

#14 2016-02-06 21:24:54

Re: New Red Dragon Mission?

#15 2016-02-07 20:47:33

Re: New Red Dragon Mission?

#16 2016-02-08 11:20:45

Re: New Red Dragon Mission?

#17 2016-02-08 12:55:19

Re: New Red Dragon Mission?

#18 2016-02-08 20:57:48

Re: New Red Dragon Mission?

#19 2016-02-09 02:07:36

Re: New Red Dragon Mission?

#20 2016-02-09 09:43:31

Re: New Red Dragon Mission?

#21 2016-02-09 10:02:48

Re: New Red Dragon Mission?

#22 2016-02-09 10:42:31

Re: New Red Dragon Mission?

#23 2016-02-09 14:05:33

Re: New Red Dragon Mission?

#24 2016-02-09 18:31:45

Re: New Red Dragon Mission?

#25 2016-02-10 10:25:52

Re: New Red Dragon Mission?

Board footer