Red Dragon Discussion Thread (1)

[Robotbeat]

They're not cleared for over 10,000 feet at this time. Doesn't mean it isn't technically capable of that altitude. We're talking about a quite high performance engine (compared to the other VTVLs of late, not counting DC-X).

And it probably won't be.  The test area is small.  It isn't the southwest where Viking chutes were tested or like Blue Origin's test area.

So doing testing at 100K not going to happen in Waco.

Yes, I believe you're right. I think that may be why SpaceX was looking around to other launch sites in Texas (not because they're looking for a new place to base orbital operations from).

[Zed_Noir]

Slightly off topic, but this thread seems to be place to ask the following query.

Can the X-37B or something similar survive atmospheric entry on Mars from either Martian orbit or direct descent?

Was thinking of a Falcon Heavy or similar LV lifting a spaceplane of some sort mated to a hypergolic propellants module inside a payload fairing. The prop module would be on the bottom with the spaceplane mounted upside down on top.

[Jorge]

Slightly off topic, but this thread seems to be place to ask the following query.

Can the X-37B or something similar survive atmospheric entry on Mars from either Martian orbit or direct descent?

Could possibly survive entry, but terminal velocity would be far too high to survive descent and landing. That is the trick with Mars. Entry/Descent/Landing (EDL) must be considered as an integrated problem.

[Zed_Noir]

Slightly off topic, but this thread seems to be place to ask the following query.

Can the X-37B or something similar survive atmospheric entry on Mars from either Martian orbit or direct descent?

Could possibly survive entry, but terminal velocity would be far too high to survive descent and landing. That is the trick with Mars. Entry/Descent/Landing (EDL) must be considered as an integrated problem.

Even from a craft orbiting around Mars in a low orbit?

[Kaputnik]

Slightly off topic, but this thread seems to be place to ask the following query.

Can the X-37B or something similar survive atmospheric entry on Mars from either Martian orbit or direct descent?

Could possibly survive entry, but terminal velocity would be far too high to survive descent and landing. That is the trick with Mars. Entry/Descent/Landing (EDL) must be considered as an integrated problem.

Even from a craft orbiting around Mars in a low orbit?

The clue is in the word 'terminal'. The terminal velocity is the same regardless of the initial velocity.

[ugordan]

The terminal velocity is the same regardless of the initial velocity.

For relatively small objects, that is.

[Robotbeat]

The terminal velocity is the same regardless of the initial velocity.

For relatively small objects, that is.

Again, we're talking about semantics here, but "terminal velocity" doesn't, by definition, depend on initial velocity. That was Kaputnik's point. Of course, we know that if you don't have enough time to reach terminal velocity, then your "final" (i.e. moment before impact) velocity does indeed depend on initial velocity. That's not strictly terminal velocity (which is what Kaputnik was talking about).

[ugordan]

True that.

[oiorionsbelt]

Slightly off topic, but this thread seems to be place to ask the following query.

Can the X-37B or something similar survive atmospheric entry on Mars from either Martian orbit or direct descent?

If it did survive entry, which runway would it use?

[Robotbeat]

If X-37B did survive reentry, it would soon be saying Happy Birthday to the ground.

The air is ridiculously thin on Mars. No way it'd survive landing.

[kevin-rf]

it did survive entry, which runway would it use?

Hoagland has that list

In all seriousness, any indication on a reentry date yet?

[Ben the Space Brit]

Whilst Red Dragon is presumably a ballistic capsuile, it could have a parafoil in place of its standard parachutes.  This would allow a degree of guidence during most of the descent phase.  Any idea of how big a foil a fully loaded Dragon RV would need for Mars's atmosphere?

[Jim]

Whilst Red Dragon is presumably a ballistic capsuile, it could have a parafoil in place of its standard parachutes.  This would allow a degree of guidence during most of the descent phase.  Any idea of how big a foil a fully loaded Dragon RV would need for Mars's atmosphere?

Still can't land with it.

[ChefPat]

[Kaputnik]

Whilst Red Dragon is presumably a ballistic capsuile, it could have a parafoil in place of its standard parachutes.  This would allow a degree of guidence during most of the descent phase.  Any idea of how big a foil a fully loaded Dragon RV would need for Mars's atmosphere?

Parafoils aren't all they're cracked up to be. Because they have two skins plus internal structure, many more support lines, etc, they are far bulkier and heavier than a similarly sized conventional chute. They can also be harder to deploy and inflate properly, with the higher performance types (i.e. greatest cross-range potential) not being designed for high-speed deployment at all. I am sure it would an absolute nightmare to get one to inflate at anything other than low subsonic speeds, without risking cell blowout or a tangle or some sort. And by the time you reach low subsonic speeds on Mars, you are switching back to propulsive mode anyway.

Slightly more practical would be a steerable conventional chute, with openings in the canopy which can be controlled to effect crude steering. But these are really for last-second hazard avoidance rather than cross-range, and would significantly add to the complexity of the chute. And, again, the propulsive final landing approach is much better suited to effecting some guidance.

[Zed_Noir]

Slightly off topic, but this thread seems to be place to ask the following query.

Can the X-37B or something similar survive atmospheric entry on Mars from either Martian orbit or direct descent?

If it did survive entry, which runway would it use?

If X-37B did survive reentry, it would soon be saying Happy Birthday to the ground.

The air is ridiculously thin on Mars. No way it'd survive landing.

Was only asking about if a spaceplane can make reentry on Mars.

But why would you need a runway? Think it can do a powered  landing vertically like a Harrier jump jet. Or taking us way back to the Thunderbird 1 of the British mid-60s TV series. Vertical thrusters on the bottom of the spaceplane along with RCS to provide attitude control. The spaceplane would have a full propellant load after the Martian re-entry burn. I include a hypergolic propellant module (big drop tank) to the interplanetary transit stack to get it pass the Mars deorbiting stage of a mission in my initial thread post (#261). It's not that dissimilar to the DTAL moon lander concept.

[kevin-rf]

But why would you need a runway? Think it can do a powered  landing vertically like a Harrier jump jet. Or taking us way back to the Thunderbird 1 of the British mid-60s TV series. Vertical thrusters on the bottom of the spaceplane along with RCS to provide attitude control. The spaceplane would have a full propellant load after the Martian re-entry burn. I include a hypergolic propellant module (big drop tank) to the interplanetary transit stack to get it pass the Mars deorbiting stage of a mission in my initial thread post (#261). It's not that dissimilar to the DTAL moon lander concept.

Since at 0.087 psi the mars atmosphere (vs. earth's 14.7psi) is to thin to use anything but rockets for a vertical landing, why you use wings again? It buys you what, besides forward momentum that you now have to kill? A capsule will do just fine and has less failure modes.

[butters]

How much dV have previous Mars EDL vehicles been able to achieve on supersonic parachutes? In other words, how bad is the propellant mass ratio penalty for eliminating the supersonic parachute phase and going straight from aeroshell to rockets?

[jwade]

How much dV have previous Mars EDL vehicles been able to achieve on supersonic parachutes? In other words, how bad is the propellant mass ratio penalty for eliminating the supersonic parachute phase and going straight from aeroshell to rockets?

This was answered previously in the thread,  the paper simonbp references is a good read on the challenges of Mars EDL and is very informative.

On the general point, here's a paper on the issues: http://smartech.gatech.edu/jspui/bitstream/1853/8390/1/IEEEPaper06ID0076FINAL.pdf

An additional supersonic decelerator possibility is simply to use propulsion. While this appears straightforward, there is little experience firing larger thrusters directly into a high dynamic pressure supersonic flow. Flow stability, flow-control interaction and thermal protection are some of the design issues that surround use of this technology.

And I recall being told point-blank by the coauthor (Rob Manning, designer of the Pathfinder/MER EDL system) that he has no idea how you would do a supersonic retrorocket. Apparently, SpaceX thinks they know.

There is also another thread on the forum on Mars EDL technologies http://forum.nasaspaceflight.com/index.php?topic=18387.0 that would help inform the discussion here.

[RocketJack]

Whilst Red Dragon is presumably a ballistic capsuile, it could have a parafoil in place of its standard parachutes.  This would allow a degree of guidence during most of the descent phase.  Any idea of how big a foil a fully loaded Dragon RV would need for Mars's atmosphere?

All I have seen on Red Dragon is a "no parachute" EDL. Current chutes on Dragon would be ineffective in Mars atmosphere and no redesign is planned for different chutes (wouldn't fit anyway). The concept is a large skip maneuver to bleed off most energy, then a terminal descent and firing of abort thrusters in final phase. Sporty, but could be cheap science mission...