NASA tries a dropship

[Psychedelic Rhino]

i'm thinking that a modified hexacopter would be perfect for there.

We're talkin' some BIG blades. The 4 counter rotating thin blades from AMEE's exploratory flyer from the film Red Mars, would be grossly insufficient. As a matter of fact, I would also almost go as far and say a rotating blade craft could not fly on Mars, as I'm unaware of any rotating craft on earth that can achieve ~30,000 meter altitude, (the Earth atmosphere equivalent to the Mars atmosphere density) My only hesitation is a craft would get the benefit of being 62% lighter on Mars.

[Red Devil]

i knew it was thin, but not that thin. i wonder if a helium balloon would help.

[GSH]

Helium balloons would help mainly at relatively small velocities -- up to say 30km/h. When you're coming in at supersonic speeds, a balloon is only a little bit of a help. Parachutes and thrusters work far better when contributing lots of delta-v. The 'airbags' of the Spirit/Opportunity landings -- put the probe inside a big airbag, let that smack into the ground -- just doesn't scale enough to land something the size of a small car.

Eventually, I could see something using helium balloons/blades after landing. But not during the initial landing.

-- GSH

[Psychedelic Rhino]

I believe RD is referring to exploration and not orbital entry.

Helium would work, but it also would have to be extremely large. Before anyone says hydrogen, it would make no difference.

That leads to an interesting bit of trivia regarding helium and hydrogen. While helium is twice as heavy as Hydrogen, helium's lifting capability is around 98% that of hydrogen. What??!

It all has to do with relative density.

Here's an analogy to make it clear... A styrofoam float ring will keep virtually the same lead weight afloat in water as a child's thin plastic air filled float of the same volume. The styrofoam might weigh 5 times more. . .but the ratio of the two compared to water can be considered roughly the same.

[GSH]

Good history on past probes to Mars, including these:

Counting Curiosity, only 15 of the 41 missions that humans have sent to Mars have been successful.
[...]
Russia had not had a successful interplanetary mission in 25 years.

[Red Devil]

i wonder if they could use the leftover hydrazine fuel from the rocket thinger to make some hydrogen/lighter-than-'air' gas or use it to power something. shame it's going to waste now after having spent all that time, money, and energy t get it there.

[Psychedelic Rhino]

And still another would be electrolysis of the ice deposits since they have a fairly long term (subjectively infinite) radioisotope power system (MMRTG). During down time, or low demand events, convert discovered ice to O2 and H2. Dump the O2 and compress the H2 for future use.

The catch, as I said, would be the size of the balloon to raise even a modest lab, let's say a 2 earth kilo instrument cluster to transmit images, atmosphere and solar wind data back to curiosity or the orbiter. The balloon's initial inverted tear-shape would have to be in the neighborhood of 15 meters tall and 5 meters in diameter. Launching the balloon would be near impossible in all but dead calm. The balloon also would have to be an extra light and thin membrane. Remember, it's like launching a balloon on earth from a 95,000 foot high platform and expecting it go up in ever thinner atmosphere.

[Red Devil]

it doesn't have to go up, just neutralize some weight - then fire up the attached hexacopter!

[Zero Angel]

(removed dumb argument about there not being enough atmosphere on mars for it to work)

Thing is, how long would it take to generate enough solar energy to electolyze martian ice? Probably fricken ages.

[Red Devil]

i think he's talking about using the hydrogen for fuel.
instead of dumping the O2, save it for later.

[Zenophas]

I believe RD is referring to exploration and not orbital entry.

Helium would work, but it also would have to be extremely large. Before anyone says hydrogen, it would make no difference.

That leads to an interesting bit of trivia regarding helium and hydrogen. While helium is twice as heavy as Hydrogen, helium's lifting capability is around 98% that of hydrogen. What??!

It all has to do with relative density.

Here's an analogy to make it clear... A styrofoam float ring will keep virtually the same lead weight afloat in water as a child's thin plastic air filled float of the same volume. The styrofoam might weigh 5 times more. . .but the ratio of the two compared to water can be considered roughly the same.

I can't remember if NASA uses nuclear propulsion engines or whatever they're called.

[Psychedelic Rhino]

I can't remember if NASA uses nuclear propulsion engines or whatever they're called.

Curiosity uses "nuclear power" with a radioisotope thermoelectric generator. Interestingly, Arthur C. Clarke was one of the first, if not the first, to suggest a radioisotope thermocouple as a space-based power source. Basically just a hunk of radioactive material that gets hot to generate electricity.
NASA learned a hard lesson using solar arrays with Spirit and Opportunity when the rovers periodically lost a large percentage of power from dust covering the panels till clean air blew them clean. Also Curiosity will not be plagued with having to search out a location and park inclined with the panels facing the sun for the winter months.

i think he's talking about using the hydrogen for fuel, instead of dumping the O2, save it for later.

I'm not sure what an oxidizer could be used for, but yes, maybe the oxygen could be useful in some way. But I was saying to electrolyze the ice and collect the hydrogen to fill a balloon for aerial reconnaissance or research. I'm assuming the team didn't see the need for doing that since they have a pretty advanced orbiter doing much the same, AND, has a predictable flight path.

But to tie both of the above together, electrolysis was used on Mars in 1965 for exactly that. . . propulsion when the Mark II Badger was introduced.

[Nielk1]

I thought putting any nuclear material into space aside from very small lab samples was illegal.

[Zenophas]

I can't remember if NASA uses nuclear propulsion engines or whatever they're called.

Curiosity uses "nuclear power" with a radioisotope thermoelectric generator. Interestingly, Arthur C. Clarke was one of the first, if not the first, to suggest a radioisotope thermocouple as a space-based power source. Basically just a hunk of radioactive material that gets hot to generate electricity.
NASA learned a hard lesson using solar arrays with Spirit and Opportunity when the rovers periodically lost a large percentage of power from dust covering the panels till clean air blew them clean. Also Curiosity will not be plagued with having to search out a location and park inclined with the panels facing the sun for the winter months.

Ooo, that's pretty cool.

[GSH]

All of the US probes sent to Jupiter or further have had to use a small radioactive power source. Voyager 1/2 are the spacecraft sent furthest away from earth. The sun is really small from their perspective:

The sun is not large as seen from Voyager, only about one-fortieth of the diameter as seen from Earth, but is still almost 8 million times brighter than the brightest star in Earth's sky, Sirius.

See also this.

Solar energy falls off proportional to 1/r^3, or one divided by the radius cubed. Voyager 1/2 would probably need at least a football field's total area of solar panels to generate the same power as their radioactive sources, and that solar panel would have to get bigger by the day. Even on Mars, the falloff in solar power (i.e. photons) available per square meter is quite noticeable.

NASA has exemptions for launching small radioactive power sources. The usual nitwits have protested such launches. Nukes meant to go *boom* are far different from radioisotope thermocouples. There'd be more danger from debris falling on your head from a failed launch than from the power generators.

There's also Ion Thrusters which don't involve radioactive substances. Ion thrusters have very low thrust per second (i.e. don't use them for braking in-atmosphere), but they're really efficient in generating thrust-per-pound of fuel.

Only the Project Orion nuclear pulse propulson would use actual *boom* nuclear power to move anything. Basically, make a ginormous steel plate. As in dozens of meters thick. Put your crew/capsule on top. Put a nuke (yes, bomb) underneath.

Release the canned sunshine.

You'll lose a small percentage of your steel plate, and your whole stack of capsule and plate will move upwards. Now the trick is, before gravity starts pulling you back down, send another nuke out the bottom, and fire it off, too. Repeat, until velocity is achieved.

The Project Orion drive has never been tried in action. Really illegal under current international law. Do not try this at home, kids.

-- GSH