NASA’s Balance Mass Challenge | Hacker News Reader

NASA’s Balance Mass Challenge

innocentive.com

72 pointslochieferrier56 comments

>Balance mass should perform some type of scientific or technological function

So that's 661 lbs. I wonder how far we are from a solar powered 3D printer. Can we build a self-replicating robot of any kind that would work on Mars? What practical raw materials could a machine tap, if any? Imagine this platform being used to test off-planet manufacturing. Even on a small scale it would be pretty impressive.

Didn't the Mars society have a proposal for a low cost Mars mission with automated missions flown before-hand performing some kind of fuel extraction from Mars (hydrogen?) So that when humans landed, they'd tap these reservoirs of fuel instead of paying all this money to fly fuel with them. Even a small scale test of that would be a game-changer.

If that's too lofty, get 50 colleges to make mini robots/sensor/whatever with a 6lbs limit, kind of like we do with CubeSats today. That leaves NASA ~350lbs for a lander to safely drop these things. Having just one single winner seems a little short-sighted. I'd rather see lots of people given the chance to drop something on Mars than just one group.

The mass is in a number of non-connected pieces, and it gets ejected during EDL (entry, descent, and landing). Very unlikely that anything would survive once it hit the surface.

No you can't create self replicating anything in that space. The big issue is the chip fabrication.

You might be able to test making rocket fuel, but the practical point of that is probably not great (we already know it will work) as you couldn't store a useful amount, and at the moment there is nothing in the pipeline that would use it.

Also only 150kg is dumped during entry. The other 150kg have a much rougher task to survive descent. (As the doc says "material surviving atmospheric reentry would impact the Mars surface approximately 10 minutes after separation at nearly 9,000 mph (4,000 m/s)."

The 150kg that is dumped during the entry phase is still going to have a real rough time of it mind, but it is an easier task.

Small cube-style sensor dispersal would be unlikely to survive, could pose substantial risk of main craft damage, and would be unlikely to have enough radio power. Also these things have to be dense there is not a lot of volume to work with.

It is a challenge, because it is actually fairly challenging.

Even if its not fully self replicating being able to create the bulk of the structural mass and maybe even basic batteries would save a huge amount of fuel costs. Then you only need to bring control systems, motors, and radioisotope generators to mars rather then a bunch of multi ton robots.

Can't be done in that space or that mass. The hard part isn't the 3D printing (and that isn't easy, as anyone can tell you 3D printing in a controlled temperature environment with precision manufactured feed stock is still a bit touchy, using on site crafted feed in an environment that shifts 100 degrees Celsius day to night is going to be very challenging) it is the materials extraction and processing. You basically have to mine, refine, and mold Martian soil into whatever end product you have, and you have no fossil fuels to get things up to temp.

To do so at all would be a massive undertaking, to do so at any kind of scale in 300 kg (assuming that magically you ended up recalculating the trajectory or something to get all 300kg in one group on the surface) is, I'm pretty sure, beyond our technology at present.

> Payloads replacing Balance mass should perform some type of scientific or technological function adding to our knowledge base while closely matching the volume and weight characteristics of the original Balance mass.

Um, the one being replaced was solid tungsten, which is almost twice as dense as lead. How is anything going to come close to matching that?

> Because of the high density of tungsten, it is unlikely that payload concepts may be proposed that identically match the characteristics of the MSL BMDs. To maximize the potential for innovative concepts while still achieving the desired spacecraft EDL performance, NASA is requesting that proposed concepts target 90% of the original MSL BMD mass while matching the volumetric dimensions used for MSL.

Still, I agree with you. It's a very difficult target.

Where is that quote from?

It seems to me that the only way to hit the 90% target would be to include 270kg of dead-weight tungsten, and fit all the science into a 30kg budget.

Logging into innocentive lets you see more details about each challenge.

EDIT: To your second point: Even though it's 300 kg total, it looks like that's allocated to 2 75 kg objects and 6 25 kg objects. I would assume that means much less weight/space per unit to work with, given the dead weight to go along with it.

The relevant constraint isn't mass, but volume. Essentially you're limited you to a cube 12 cm on a side (plus 1 cm³ for every 19.25 g of payload mass).

What are you basing that claim on? The quotes elsewhere in this thread seem to contradict what you're saying.

My first thought for something actually doable would be a group of compressed gas cannisters with highly reflective balloons attached to them. Very simple mechanics, all you need is a strong valve on a timer, so it can be made to survive the impact with the ground.

Once they're inflated, they would rise to relatively high up, so they can be carried off by winds. Because of the high reflectivity, we would be able to track them from orbiting imaging satellites and probably even from earth, teaching us more about wind speeds and flows on Mars.

One thing I'm not sure about is if this could meet the weight/space requirements.

ExoLance project is supposed to use that dead mass to shoot darts under the Mars surface to look for signs of life:

https://www.indiegogo.com/projects/exolance

Is that actually their plan? I haven't found anything about balancing mass on their site.

300kgs of gold. To encourage someone to come looking for it.

The most expensive element you can currently send to Mars is platinum [1], which would equate to a value of roughly €10 million. All other things you could send either decay quickly (plutonium) or otherwise devalue over time (micro sd cards) or fluctuate too heavily to depend upon (microSD cards filled with Bitcoin private keys, LSD).

I wonder what would happen if a space agency went to Mars and dropped a minted coin valued €50 billion (or something) by the US Treasury/European Central Bank/National Bank of China and see who could retrieve it the quickest. That should be an interesting competition.

[1]: http://what-if.xkcd.com/108/

(Edited because for wrong terminology)

So out of curiosity:

Wolfram has the weight of a MicroSD card at half a gram.

So 300kg of those cards would work out to about 600,000 of them.

Let's say they're 8 gig cards. The largest BTC private key size is 512 bytes, so you could fit about 15.62 million of those large keys on a single card, or 9.36 trillion individual keys in the entire lot.

Now for sake of sheer bloody-mindedness, let's assume each of those wallets have 1BTC to their name. (Nevermind this is impossible since there will never be that many bitcoins)

3 quadrillion 718 trillion 728 billion dollars.

That's the entire GDP of the world, about 44 times over.

Damn.

You could fit every bitcoin currently minted on one single card, and have a card worth about 5.5 billion USD.

(5.5bn in .5g. That's a pretty crazy value to weight ratio)

The maximum amount of BTC that can be created is only around 21 million.

Cryptocurrency stuff might be needlessly complex for a reward mechanism.

Just put a secret on the weight (stamp it on the tungsten or something) and promise the one who reads it some sum that was deposited on a bank account before launch.

It should survive entry and impact.

This should be really interesting to do with public key cryptography.

Generate an RSA private key and corresponding 32+ kbit RSA public key. Send off the private key to Mars, and afterwards publish the public key. Award €50 billion to the party which can prove possession of the private key and give a demonstration of how it was obtained.

Anyone claiming the price has either:

- Gone to Mars and returned with the private key

- Broken the prime factorization problem from a theoretical perspective

- Built a practical quantum computer and thereby broken the prime factorization problem practically

Admittedly, the first and last would be big advancements for humandkind, but the second one would probably mostly give some really nasty problems.

That sounds excellent, though 50 billion is a bit too much. Say 10 billion?

You could send stuff to Jupiter's moons, to asteroids or to Mercury as well.

It would need to have some kind of a passive beacon to aid retrieval and prove that it is there. On Mars dust is a problem so a retroreflector might not hold up for long.

Ah, I falsely remembered hearing quotes on a sample return mission to be $20 billion, and was factoring in estimation errors and profit incentives.

Mars should be the first goal, I think. IANAP, but I think Jupiter's moons and Mercury are very substantially harder to collect samples from when compared to Mars. For Mercury it would be very difficult to escape the Sun's gravity well and get enough momentum to return to Earth orbit. Jupiter is also much further away than Mars and has a huge gravity well to escape from too. I'd wager that sample return missions are possible to them practically even given unlimited budget.

You'd likely read the data in situ and just beam the info back. That's orders of magnitude easier than sending anything back here.

As a note, there is only 13.3 Million BTC in existence, which comes to ~$5 Billion USD market cap.

> The most expensive rare earth element you can currently send to Mars is platinum (...)

> All other things you could send either decay quickly (platinum) (...)

I don't understand. Did you mean platinum in both places? In that case, I got confused by the "other". Or did you mean something other than platinum in one of the cases? Or am I just failing to comprehend? :)

Based on the xkcd link I'm sure he meant plutonium decays quickly.

Gold and platinum are each a smidgen more dense than tungsten, so if you're willing to splash out for one of those metals you'd even have a bit of volume left over for a really tiny science experiment.

> The most expensive rare earth element you can currently send to Mars is platinum

Platinum is not a rare earth element. REE is a specific term which describes the lanthanides, scandium and yttrium. Platinum instead belongs to the imaginatively named platinum group.

Shape it into a kinetic projectile. With the orbital velocity it should make a crater exposing underground materials.

A solid lump of duct tape. Guaranteed to be useful in future.

300kg of fireworks would make one heck of a display

Need atmosphere to combust though

No, most fireworks carry their own oxidizer. Otherwise even in Earth's atmosphere their power would be quite limited by airflow.

is there any logic to bringing some fissile material to mars for use as a future fuel source? My gut instinct says no, but its among the only things I can think of that would be heavy enough. Uranium and Plutonium are pretty heavy.

The only other things I could think of would be common catalyst materials like platinum. Something that could be collected and used later by some future mission. Lead might be useful, as a battery component, but forming it would be problematic.

If it remains tungsten, and the impact is going to be at very very high speeds, do any of the other mars rovers have instruments capable of detecting the seismic waves produced? Could that provide us any details of the makeup of the crust? A 150kg tungsten mass would likely make quite a crater traveling at 9000MPH.

Better still: figure out a way to land without needing 300kg of dead weight.

Bottle-sized greenhouses.

Weight, though...

They would still have to live through the 6+ months of hard space before making it to Mars. So you'd also have to include a heater and a window, at a minimum. Also, it would need to be a biosphere, to generate carbon dioxide until it reached Mars.

A lot of care is put into making sure we don't track Earth microbes to Mars in the first place to make sure if we do find life we'll be pretty sure it's not just a hitchhiker flown in from Earth in the last 40 years of space exploration.

That's historically been true, but won't always be the case. NASA has talked about putting humans on Mars within a couple of decades. It may be sensible to try putting other living things on Mars in advance of humanity...

This! Having supplies/environment primed and ready when humans arrive could make the difference between a thriving colony and a miserable death.

The first colonies won't get any help from microbes on the surface of Mars, it's too cold and dry for much of anything useful from Earth to survive much less thrive. And the timescales for anything that could a) thrive and b) have a measurable impact on the lives of colonist are way longer than (I hope) any mission will land since it'd take decades/centuries for there to be a useful impact. Eventually yeah introducing life to Mars will be a useful prospect but we're talking about kickstarting a whole planet's ecosystem not something to do haphazardly or that will show large impacts in a single lifetime.

All we'd need is a bubble-greenhouse to be growing some wheat or something - don't have to terraform the entire place.

For a long time this will still be the case. Until we're going to be putting humans on Mars (at which point there are very limited options for continuing the sterility, because we're lousy with them) avoiding contamination will be a pretty high goal for missions.

Why isn't this just given to amsat.org for a nice RF transponder? Could be the location is non-optimal for solar / antennas, but ...

My guess is that they're having a hard time coming up with something that has a similar density. Most ideas just aren't heavy enough in that volume to act as counterweights...

These aren't going into orbit, these will be ejected during entry and landing. They will end up on the surface of Mars and they won't have the benefit of parachutes or rockets (unless you bring your own) slowing them down before they hit the ground. That's a very demanding proposition to expect any sort of system to survive, which is why it hasn't been done before and why this is being set up as an open challenge now. Maybe someone will come up with an intriguing possibility here that nobody else thought of, rest assured there are no widely obvious, easy answers to the problem as yet.

google for the amsat suitsat program, its remarkably similar other than re-entering earth instead of mars and being obsolete space suits rather than counterweights.

I'm well aware there are subtle technical differences but the mission profile isn't all that different. It would be an interesting place to start.

Railgun.

Use the momentum just before it goes into orbit to blast it into deep space with a message.

It could outpace Voyager easily.

Wouldn't the subsequent recoil push the MSL wayyyy off course?

OK, two railguns pointed in opposite directions :)

Mars missions have to do a lengthy burn to drop into orbit. Point it the right way and you're even using less fuel.

Well, they /could/ factor the recoil into their insertion burn calculations. That's just a matter of the repeatability of the railgun's acceleration.

Of course the better way to outpace Voyager at this point is probably an ion engine, Voyager is sailing along at 17 km/s and the highest number I could find for a current railgun is 2.4-3 km/s (and these way waaay more than 300kg), that leaves the orbiter with >14km/s of the velocity required to beat Voyager. Each mission will come in at different orbital velocities but I found that Odyssey had a velocity of "5.907 kilometers per second" [1] before it's orbital insertion burn. Missions are more inclined to come in at or around their final orbital velocity (getting there faster requires more fuel for braking into orbit and more weight dedicated to that fuel requiring more fuel [repeat until your entire launch weight is fuel with a postage stamp as your probe]).

[1] http://mars.jpl.nasa.gov/odyssey/mission/timeline/mtmoi/moid...

That would work for the pre-entry mass ejection, but that's only half the challenge. Half the balance mass is ejected after entry begins.

Step 1: Fire railgun.

Step 2: Eject railgun.

Please show your math work here.

(P.S. No, no it could not outpace Voyager (1 or 2) "easily", it could not outpace either Voyager even if the entire mission mass was dedicated to a railgun for that purpose.)

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