Hypography X Prize Entry

[CraigD]

Originally Posted by Turtle

The air-bag landing is a proven technology; shall we use it?

It’s important, I think, to distinguish between the airbag landing systems used in Luna 9 and Luna 13 (1966) and Mars Pathfinder (1997) and MER (2003, though same design as Pathfinder).

• The Luna probes used a single airbag “skin” that completely enclosed the roughly 80 kg lander capsule. After a roughly 45 sec braking rocket burn brought the vehicle to a near standstill close to the lunar surface, the capsule is ejected, the airbag inflated to roughly 1 ATM pressure, to hit the surface at about 15 m/s. From the photos, it appears the airbag is elastic, fitting snugly when deflated, with panels designed to rip out when the capsule extends the 3 petals of its spherical shell, which forces it upright and exposes its pop-up camera mirror and antennae.
• The Pathfinder lander is larger (264 kg), tetrahedronal, and had impact speed of about 11 m/s. It used 24 inelastic airbags, each with an internal cable connected to a motorized retraction mechanism (nasa.gov’s time-lapse quicktime movie). Partial failure of the retraction system of the MER resulted in a worrying moment when the Spirit rover had to be maneuvered to get around some unretracted airbag, and raised concerns that the lander’s solar cells might be forever partially blocked.

The engineering reasons for the use of airbags in the design of the Luna and Pathfinder/MER probes were also very different:

• On the Lunas, it was primarily because the vehicle guidance system – essentially a “get a fix, then fly blind on accelerometers and gyros” system – could be relied upon only to get within about 50 m of the lunar surface and a few m/s of stationary, requiring a passive system to “absorb the difference”.
• On Pathfinder and the MER, it was primarily because of uncertainty about surface wind conditions made it impractical to achieve a horizontal standstill, and to protect against dangerous ground debris – that is, the risk of getting blown against sharp rocks.

In both systems, separating the lander from the rockets used to brake it (fully in the case of Luna, only as a final landing maneuver for the parachute-equipped Mars probes) kept it clear of the rocket-containing portion of the vehicle’s crash site.

All in all, given how much better and cheaper self-contained radar units and computers are now than in the 1960s, when the Lunas were designed, and the 90s, when Pathfinder and the MER were, and given the wonderfully wind-free conditions on the moon, my instinct it to follow the KISS principle, and not have the additional cost, complexity, and potential for failure of an airbag landing system. Rather, I think it best to have the lander(s) automatically fly themselves to a soft landing using Apollo LEM-type RCS thrusters, about the simplest and most reliable kind of rocket motor possible.

[Jay-qu]

Originally Posted by CraigD

Rather, I think it best to have the lander(s) automatically fly themselves to a soft landing using Apollo LEM-type RCS thrusters, about the simplest and most reliable kind of rocket motor possible.

Would these motors be a little overkill? they had a much larger payload - would they be expensive? (I understand its hard to estimate expensiveness when there isnt much to compare to!)

[CraigD]

Originally Posted by Jay-qu

Would these motors [RCS thrusters] be a little overkill? they had a much larger payload - would they be expensive? (I understand its hard to estimate expensiveness when there isnt much to compare to!)

I was hinting at something closer the Reaction Control System thrusters on the LEM – the small nozzles seen in blocks pointing in 4 directions mounted on the side of the crew/ascent module –than the large motor on the underside the descent or ascent modules, although mechanically, these motors are all similar, differing primarily in size. The RCS thrusters (a LEM has 16 of them) can produce 441 N each, while its descent and ascent motors can produce 44400 and 15600 N, respectively.

“Hydrazine thrusters” (AKA hypergolic) of these kind are found in many sizes on nearly all spacecraft. Their main strength is simplicity – their only moving parts are the valves to control the flow of pressurized liquid fuel and oxidizer into the reaction chamber/nozzle assembly, where they react without the need for a spark, giving them instant on/off throttling, and making them very easy to control.

Engines like these are so mechanically simple, that this might be a situation where it’s more economical to build much of the motor from scratch than buy it COTS. I can’t find a price for one made by established manufacturer’s like Hughes and Rockwell, and fear this a case of “if you have to ask, you can’t afford it.”

Originally Posted by Jay-qu

I am toying with the idea of using current OTS jetpack technology for the lunar decent deceleration. The module for sale here carries payload 80kg for 9mins in Earth gravity, so I think that is more than adequate to be adapted for our needs - its nice and small for a start! can anyone see any shortcomings with using a system like this?

Got a link to the OTS product you’re referencing, Jay-qu? Hard to assess without the specifics, and they’re not so off-the-shelf that I’ve run into them browsing my local hardware store.

The basic shortcoming I can imagine for any “ready to fly out of the box” system is that its designed to fly in about 6 times the gravity of the moon, and in an atmosphere. Just increasing the vehicle’s mass to 6 times original might allow it to operate correctly, but that’s just a wild guess.

More serious, I think, is that a system designed for operation in a warm atmosphere might contain parts, such as ordinary plastic ones, that would become brittle to the point of failure in the shade in vacuum. If the product manual gives an operating temperature range of, say 0 to 70 C, I’d wager it won’t work on the moon, or even if left outdoors on a typical North American winter night.

[Jay-qu]

Originally Posted by CraigD

Got a link to the OTS product you’re referencing, Jay-qu? Hard to assess without the specifics, and they’re not so off-the-shelf that I’ve run into them browsing my local hardware store.

The basic shortcoming I can imagine for any “ready to fly out of the box” system is that its designed to fly in about 6 times the gravity of the moon, and in an atmosphere. Just increasing the vehicle’s mass to 6 times original might allow it to operate correctly, but that’s just a wild guess.

JET P.I. - Jetpack International - Home of the Go Fast JetPack

you make a good point - and this is one component that cant fail! I just thought perhaps a striped down/modded version of their engine might be applicable.

[Mercedes Benzene]

If we're going to go the rocket landing route, I would suggest a hydrazine-based propellent. I think NASA uses methylhydrazine for the space shuttles. I'm out of town right now, so I don't have time to do any research... but when I get back, I'll try to find the most appropriate fuel source.

Cheers!

[Turtle]

Originally Posted by CraigD

It’s important, I think, to distinguish between the airbag landing systems used in Luna 9 and Luna 13 (1966) and Mars Pathfinder (1997) and MER (2003, though same design as Pathfinder)...

All in all, given how much better and cheaper self-contained radar units and computers are now than in the 1960s, when the Lunas were designed, and the 90s, when Pathfinder and the MER were, and given the wonderfully wind-free conditions on the moon, my instinct it to follow the KISS principle, and not have the additional cost, complexity, and potential for failure of an airbag landing system. Rather, I think it best to have the lander(s) automatically fly themselves to a soft landing using Apollo LEM-type RCS thrusters, about the simplest and most reliable kind of rocket motor possible.

I'm all for KISS. In reading your wiki links on LUNA projects I see they used a hermetically sealed pressurized system similar to what I had mentioned; that's promising? I was thinking too about using a rotating mirror or prism for the camera as on the Luna projects, but then we may find the cameras are as much advanced as the radar etcetera you mention so there may be no advantage in the mirror/prism. Thoughts?



PS Had to look up "RCS", and still can't find what it's an acronym for, but found we can have engines custom made? >> resources

[TheBigDog]

OK team, here is the process I see...

Launch: Commercial, whatever gets us into LEO.

Transition: Rocket burn to reach escape velocity. Critical to aim at the moon when doing this, so guidance systems in conjunction with the main thrusters. Once we are on target for the moon the booster and thrusters detach and drift away.

Braking: I don't want to enter lunar orbit, it seems like an unnecessary step. I aim right for the equator of the moon. As we approach the moon we use an approach camera to view possible landing spots. We reach a target altitude and then thrust to slow the descent to a near stop at a predetermined altitude of 1 km (actual altitude to be determined).

Landing: A target descent speed is maintained by modulating the thrusters while we visually identify a landing field. We then target that spot and let the computer steer and land on the spot.

Base camp: Once we have touched down the lander transforms into the base station. It deploys its antennas, solar panels, checks its systems and establishes communications with the Earth.

Rover Deployment: There are multiple rovers I would like to have at least four. They are essentially durable, slow RC cars. They are equipped with cameras and loaded with batteries. The rovers are capable of making a 5K trip from the lander and back again with an elapsed time of about two hours (5 km/h). They are controlled via the lander on an 802.11Y network. The RC cars are capable of video streaming, which is then relayed to the earth by the lander. The rovers will fill the requirement of taking a self portrait and of discovering things on the moon. The rovers can recharge their batteries at the lander.

Survival: The lander will have an insulated compartment on its belly. It will have a reservoir of oil that will heat in the sunlight during the lunar day. As night approaches the superheated oil will be pumped into the insulated compartment where it will be used over the lunar night to keep critical parts warmed. The lander and rovers will be built to function in the heat of the lunar day. I am not positive if this heat exchanger will be needed, but I have it as a way of helping to insure a near indefinite life for the lander and rovers (until they wear out and break).

I want to be capable of a grand slam. I think that the rovers don't need to be more than a couple of kilos each. But for the sake of round numbers lets work with 5 kilos for each of the four rovers. Each is equipped for doing detailed photography in panoramic, video, still, telephoto, and microscopic modes. Telemetry from the rovers is streamed to the lander where it is sent back to the earth.

The rovers are actually controlled from the command center on earth. The lander can be given instructions to send a rover from point a to point b. It can use a virtual map of the area to navigate them. One of the first things that we do when we land is begin making a virtual map of the surrounding area so the lander can make the rovers navigate in an autonomous mode saving the need for real time steering from the earth. The ultimate would be to have a detailed map of the 5K radius around the lander so it could send the landers anywhere in that circle doing its own routing of the rovers. That would allow them to maximize their time at a location to take pictures of details for science.

That is my suggestion for the general mission profile.

Obviously there is much to be discussed. Taking a picture of the landing area from the preset altitude is part of the surface mapping process. The lander and rovers will send further digital data that will be manipulated on earth into a virtual moon for the ongoing mission and for distribution to the public.

From a technical perspective we will need to divide and conquer. I would like to mock up as much as possible on earth to demonstrate the feasibility of the ideas. I would also like to have a team dedicated to building a mission simulator that we can use for running scenarios and eventually for programming the automated features of the mission.

I think I am most interested in the lander/rover portion of the mission. I will be focusing on that. My first step is making a prototype rover, then we mock up a lander. The design of the rover will determine critical details of the lander. Once we have the essential parts mocked up we tweak the engineering as needed to allow for the rocketry. Then we calculate the engineering requirements for a final assembly lander and rovers. By that time we should be able to leverage our prototyping into the revenue we need for assembling a moon worthy machine.

As Craig said, KISS.

I would like to have conversations about each phase of the mission profile, and come to a concensus about our final approach for each portion. Then we divide into teams and do the detailed work. But first we need to have a shared vision of exactly what we are accomplishing.

Now, give me some feedback!

Bill

[Jay-qu]

First feedback - do you think that multiple rovers fits under the KISS banner? I dont think so - it doesnt mean it shouldnt be done, but its definitely more complex than a single rover.

[TheBigDog]

Originally Posted by Jay-qu

First feedback - do you think that multiple rovers fits under the KISS banner? I dont think so - it doesnt mean it shouldnt be done, but its definitely more complex than a single rover.

Excellent question. The way the rovers are controlled I think it adds minimal complexity to the mission. It also adds redundancy to increase our odds of success when we reach the moon. Up until that point everything we do represents a single point of failure that can scrub the whole mission. Once we actually land on the moon I want as much opportunity to do things as we can enable. One rover is the simplest, but it if fails you are done. More rovers means more opportunity for success, until they become more than you can manage, or they make the other parts of the mission too complex.

The rovers could actually be run by separate teams, with the lander as nothing more than infrastructure for the rover missions.

Bill

[freeztar]

I love this concept and would like to help in any way possible.

Originally Posted by TheBigDog

I would like to have conversations about each phase of the mission profile, and come to a concensus about our final approach for each portion. Then we divide into teams and do the detailed work. But first we need to have a shared vision of exactly what we are accomplishing.

I agree. We need a rough outline to start and then fill in the outline as more details are agreed upon.

Here's a start:
I. Mission objective
II. Design
III. Cost Analysis
IV. Mission
A. Launch
B. Transition
C. Landing
V. Summary

Obviously this was thrown together quickly, but it is a reliable method of planning imho. This can be in tandem with Pyro's breakdown of "the whole shebang". I suggest that we create a circulating outline and WBS in a portable format, convenient to everyone, that we can individually amend and submit for peer review.