Red Dragon Discussion Thread (1)

[simonbp]

It may or may not be true, but the only public reports are that it could land about a tonne of scientific instruments on the surface. That was apparently based on actual analysis at NASA Ames, which I'll trust more than internet armwaving.

Remember, this is a Falcon Heavy-launched Dragon, so it's not that ridiculous. For comparison, MSL has about 70 kg of instruments on a 775 kg rover. If you were to replace all of the mobility systems on MSL with instruments, you could probably double that to about 150 kg. Scaling based on Atlas 541 and Falcon Heavy performance (a factor of almost exactly 3.0) gives 450 kg. So, saying that Red Dragon can land 1000 kg of instruments on Mars is saying that it's about twice as efficient as MSL's Skycrane. That's a big claim, but not ridiculous. And, even if they could only do 500 kg, that would still be a big deal...

[go4mars]

I wish i could have been at the moment when someone was like, here is an idea, why don't we just drill through the hull. 

this thread has been here since last summer and I remember folks discussing how to get the drill out the hatch. I'm a little disappionted that none of us were able to think it up (unless I missed a post).

Here's one from a few months ago.  (Bold added)

A drill that only has to penetrate the dragons hull then 1 m of ice could be pretty simple and light. 

Idea:
Inside dragon ... a drill with a diamond coring-bit descends, cuts through the dragons hull, and 1 meter into the surface.  The core is retracted, and passes vertically up through a gauntlet of active and passive tests and imagers (with the more destructive tests near the top).  Then the data/results get transmitted back (via MRO?) before the dragon expires. 

[Kaputnik]

It may or may not be true, but the only public reports are that it could land about a tonne of scientific instruments on the surface. That was apparently based on actual analysis at NASA Ames, which I'll trust more than internet armwaving.

Remember, this is a Falcon Heavy-launched Dragon, so it's not that ridiculous. For comparison, MSL has about 70 kg of instruments on a 775 kg rover. If you were to replace all of the mobility systems on MSL with instruments, you could probably double that to about 150 kg. Scaling based on Atlas 541 and Falcon Heavy performance (a factor of almost exactly 3.0) gives 450 kg. So, saying that Red Dragon can land 1000 kg of instruments on Mars is saying that it's about twice as efficient as MSL's Skycrane. That's a big claim, but not ridiculous. And, even if they could only do 500 kg, that would still be a big deal...

Don't worry about the LV, it's all about the entry capsule. MSL is using a 4.6m heatshield; Dragon would be using a 3.66m one. The claim is that a mixture of extremely high lift generation during entry, plus high speed retropropulsion, will allow Dragon to reach the surface despite being hampered by a tiny cross-sectional area.

I do hope that it can be made to work as it would revolutionise Mars EDLS, however it relies on two untried methods working together, and I can't help but wonder if it were that easy to land a bigger payload this way, why haven't NASA utilised lifting entry to a greater degree in the past?

EDIT: should also add, we don't yet know the performance of the super-draco, but given that it is primarily designed for high thrust at low altitudes on Earth, I suspect that it's isp on Mars will be pretty poor. I don't see much room for nozzle extensions without them being burned off during entry. Couple that with major cosine losses and the retro-prop load starts to look very significant. The one tonne payload could easily disappear, IMHO.

[Dalhousie]

I didn't realize that Red Dragon was a serious proposal.  (Is it?)

Would this be a SpaceX-led mission?  Would would produce the said drills and other scientific equipment?

It is a serious concept which is advancing towards being a serious proposal.

The drills would be based on the Icebreaker, as discussed in the Planetary Society link, other science equipment and the people responsibility is detailed on the Karcz presentation, again linked to previously.

ARC, JSC and KSC are all involved, also the Spanish.

[Dalhousie]

Obsolete report, or Jim knows something.

That report is dated Oct. 31, 2011 so it's 5 months old.

Slightly more recent are the minutes of the presentation of the concept to the NAC science meeting by John Karcz and Larry Lemke.

http://science.nasa.gov/media/medialibrary/2012/01/23/NAC_Science_Meeting_ReportOctober_31-November_1_2011-finalTAGGED.pdf

It's on page 8

It seems to have gone down well.  There are a few additional details there as well on EDL.

[Jim]

It is a serious concept which is advancing towards being a serious proposal.

Karcz" believes" it is viable.  Typical PI spin in trying to sell his proposal.  The concept requires two unproven vehicles FH and propulsive landing Dragon.

 FH won't  be on contract for at least 5 years.
The KSC that matters is not working this either.

[go4mars]

The concept requires two unproven vehicles FH and propulsive landing Dragon.

FH won't  be on contract for at least 5 years.

This is looking at 2018 or so IIRC.  So launch in ~6 years.  Does the 1 year between when FH is on contract and the launch date provide enough time for this to possibly happen?  Or would the launch date need to be later? 

As to propulsive landing dragon, I don't understand why being unproven would be a show-stopper (would it?)  It isn't like MSL EDL is more proven (as far as I am aware).   

[Jim]

As to propulsive landing dragon, I don't understand why being unproven would be a show-stopper (would it?)  It isn't like MSL EDL is more proven (as far as I am aware).   

yes it is. 

[Jim]

This is looking at 2018 or so IIRC.  So launch in ~6 years.  Does the 1 year between when FH is on contract and the launch date provide enough time for this to

3 years between

[starsilk]

EDIT: should also add, we don't yet know the performance of the super-draco, but given that it is primarily designed for high thrust at low altitudes on Earth, I suspect that it's isp on Mars will be pretty poor. I don't see much room for nozzle extensions without them being burned off during entry. Couple that with major cosine losses and the retro-prop load starts to look very significant. The one tonne payload could easily disappear, IMHO.

could you make nozzle extensions burning off 'work for you' - ie altitude compensation? build in some weak points (or actively drop off) the nozzle extensions once you encounter enough atmosphere.

[Robotbeat]

EDIT: should also add, we don't yet know the performance of the super-draco, but given that it is primarily designed for high thrust at low altitudes on Earth, I suspect that it's isp on Mars will be pretty poor. I don't see much room for nozzle extensions without them being burned off during entry. Couple that with major cosine losses and the retro-prop load starts to look very significant. The one tonne payload could easily disappear, IMHO.

could you make nozzle extensions burning off 'work for you' - ie altitude compensation? build in some weak points (or actively drop off) the nozzle extensions once you encounter enough atmosphere.

Not enough atmosphere on Mars to make that worth it.

[Robotbeat]

Everyone keep in mind that the 1-ton payload is probably to low-altitude sites. Landing at low altitudes (2 or 3 miles below Mars "sea level") is considerably easier than landing on the Martian highlands.

[baldusi]

Everyone keep in mind that the 1-ton payload is probably to low-altitude sites. Landing at low altitudes (2 or 3 miles below Mars "sea level") is considerably easier than landing on the Martian highlands.

I would love to see someone land on top of Mount Olympus. That would be a feat.

[Comga]

Everyone keep in mind that the 1-ton payload is probably to low-altitude sites. Landing at low altitudes (2 or 3 miles below Mars "sea level") is considerably easier than landing on the Martian highlands.

Is that necessarily true for propulsive EDL?

That seems to contradict statements about the value and capabilities of braking without parachutes.

Note that the March 5 Aviation Week (Page 38) has an illustration of a "Low-Density Supersonic Decelerator" as a possible EDL tech demo.  This would be an inflatable structure to reduce the terminal velocity of a Mars probe that would still descend under a parachute.  It would probably have to stack on top of a Skycrane, making for a pair of systems with limited potential for growing landed mass. They would be limited to low altitude sites as you say. 

The idea of propulsive EDL is a way to get around this limit.

[Robotbeat]

Everyone keep in mind that the 1-ton payload is probably to low-altitude sites. Landing at low altitudes (2 or 3 miles below Mars "sea level") is considerably easier than landing on the Martian highlands.

Is that necessarily true for propulsive EDL?

That seems to contradict statements about the value and capabilities of braking without parachutes.

Note that the March 5 Aviation Week (Page 38) has an illustration of a "Low-Density Supersonic Decelerator" as a possible EDL tech demo.  This would be an inflatable structure to reduce the terminal velocity of a Mars probe that would still descend under a parachute.  It would probably have to stack on top of a Skycrane, making for a pair of systems with limited potential for growing landed mass. They would be limited to low altitude sites as you say. 

The idea of propulsive EDL is a way to get around this limit.

Yes, it is a way to get around that limit, but it takes a lot of mass. On the extreme end, you could do it all propulsively and have no heatshield, but that's not what Red Dragon is.

It still helps a lot to have a low altitude landing site. Seriously, the difference in payload can be double or triple.

[ugordan]

Everyone keep in mind that the 1-ton payload is probably to low-altitude sites. Landing at low altitudes (2 or 3 miles below Mars "sea level") is considerably easier than landing on the Martian highlands.

Is that necessarily true for propulsive EDL?

For the "classic" propulsive EDL method where it kicks in subsonically after a parachute phase, probably. I don't see why it would make much of a difference if you went with what they're proposing - starting the burn while still supersonic.

[go4mars]

Some noteworthy quotes from that proceedings summary:

http://science.nasa.gov/media/medialibrary/2012/01/23/NAC_Science_Meeting_ReportOctober_31-November_1_2011-finalTAGGED.pdf

It's on page 8

If quoting from the NASA website is a faux pas here, please swiftly delete this and let me know what the guidelines are.  Thanks!

"Regarding costs, Dr. Karcz said that SpaceX estimates a cost of $150 million to $190 million for a launch vehicle and lander. The Dragon already has most of the necessary capabilities: sufficient lifetime and resources for a Mars transfer trajectory; atmospheric entry systems capable of guided lifting and highly capable retro-propulsion thruster. Falcon Heavy, he noted, could throw Dragon to Mars. He also noted that Dragon offers a large interior volume. He believed the EDL technology was scalable to large cargo and human landers. Assuming launch by Falcon Heavy, he said, the trunk would separate nears Mars; the capsule would decelerate through retro-propulsive action. The version under discussion would land on its legs."

"Lemke said that retro-propulsion would start at supersonic speeds. This approach, he stated, should make it possible to land the capsule at much higher Martian elevations than could be done if a parachute was used...He noted that retro-propulsion had been studied by NASA for human landings."

"the group was very comfortable that it could put down more than a ton of payload on the selected landing site."

"Karcz said the angle of attack in landing would not be controllable; however, the length of the flight path could be altered by rolling and banking. Extending the ‘flight path’ of descent would in effect, compensate for adjustments in speed."

[Robotbeat]

Everyone keep in mind that the 1-ton payload is probably to low-altitude sites. Landing at low altitudes (2 or 3 miles below Mars "sea level") is considerably easier than landing on the Martian highlands.

Is that necessarily true for propulsive EDL?

For the "classic" propulsive EDL method where it kicks in subsonically after a parachute phase, probably. I don't see why it would make much of a difference if you went with what they're proposing - starting the burn while still supersonic.

It definitely still makes a big difference in how big of a payload you can get to the surface for a certain TMI mass. Just because supersonic retropropulsion makes landing at high altitudes possible doesn't mean it isn't helped tremendously by the increased density and length of descent of landing at lower altitudes!

[Jim]

The Dragon already has most of the necessary capabilities: sufficient lifetime and resources for a Mars transfer trajectory; atmospheric entry systems capable of guided lifting and highly capable retro-propulsion thruster.

It has not demonstrated any of that.

[Dalhousie]

It is a serious concept which is advancing towards being a serious proposal.

Karcz" believes" it is viable.  Typical PI spin in trying to sell his proposal.  The concept requires two unproven vehicles FH and propulsive landing Dragon.

 FH won't  be on contract for at least 5 years.
The KSC that matters is not working this either.

Larry Lemke's professional opinion is that it is viable.  And that of the other engineers involved.

Still no evidence that it is unworkable?