guest blogger john hare
The Lunar Lander Challenge contest has really heated up in the last week. One discussion on arocket has been, “what is the next step?” Among the suggestions are flying both legs of the level two without refueling and an accurate landing contest without GPS. Since everybody already knows that I think pumps are a Real Good Idea for future development, I will throw one out there for getting landing accuracy in unknown terrain without GPS.
Modern electronics are tougher and smarter than ever before. A very small modern probe could hard land on the moon and still return data if properly designed. This wouldn’t have been possible in the 1960s. My thought is that a landing vehicle could carry a dozen or so hard landing probes with cameras linked back to the lander, and a transponder activated on impact. The probes are released a minute or so before landing when the lander is already braking.
The camera images while the probes are falling are relayed to the lander and then onto the operators on Earth. A suitable landing spot is selected from the images of multiple probes and sent to the lander. When the probes impact and the transponders activate, the onboard computer is getting it’s “land here” order based on vectors from surviving probes. If three or more survive, altitude and landing spot can be handled in a similar manner as the three awesome LLC teams that have already flown GPS guided vehicles to landing pads.
The probes will have to survive an impact of several hundred m/s which is a bit worse than the smart artillery shells under development. The landing spot decision will have to be made in about 10-15 seconds between receipt of imaging and the time the lander absolutely must have the information.
For an LLC3 competition, non GPS landers could be required to land on an unsurveyed pad out of their sight with a time delay on telemetry. Could be interesting.
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Rather than landing accuracy shouldn’t the reusable aspect be pushed instead. That appears to be what is lacking at the moment. I don’t know what is feasible, maybe 10 flights in 10 hours.
Do you have any idea how brutal on a team doing that many free-flights in a day is? Do you have any idea how logistically difficult it is to haul around enough propellant for that many flights? Having just been through the wringer myself, I’m not so sure you would be testing what you think you’d be testing.
A lunar base can have its own transmitters. A little rover can place these transmitters. The rover can be in the first lander. One of the other jobs of the little rover is to make regolith into the hard surface the rest of the lunar landers will use.
Lunar rovers can also use lunar GPS. Since there is no one to ask the way lunar GPS is probably more important than for landers.
Good points to put the lunar GPS transmitters are at the static Lagrange points L1, L2, L4 and L5. A second set of transmitters, permitting North/South location determination, can go into medium lunar polar orbit.
The lunar satellites can also act as radio relays, permitting over the horizon communication.
The problem is to get that kind of accuracy before you have a lunar base and GPS systems. While you are still trying to determine where or if to spend the money on infrastructure. The idea is to develop early methods of guaranteeing safe and accurate landing methods on Mars and Calisto and Mercury and………….
I have no experience of this (hence my statement of not knowing what is feasible :-). 10 flights in 10 hours is an arbitrary suggestion – I can understand that this would cause many challenges! Apologies if I have appeared clueless.
You are right in needing to know what wants to be tested, and then picking the right test.
What I really want to get is an understanding from people within the space launcher industry on which technical issues really are important and need to be addressed to achieve the goal of reducing orbital launch costs, why and would ‘X-prize’ type challenges be suitable for pushing any of these desired technological developments forward?
E.g. Some time in the future, and it may be many many decades, we will have single stage to orbit spaceplanes. In the interim period a two stage horizontal take-off and landing spaceplane is argued as technically feasible and seems to be a sound way to bridge the gap to re-usability, given the capital requirements are available.
But there are some technical issues that need to be addressed to bring about a re-usable two stage spaceplane, e.g. various rocket engine reliability and re-usability issues. Can or should these sort of issues be addressed with the aid of ‘X type’ prizes?
I’m not involved in rocketry, but as a space enthusiast I freely admit that I am impatient to see the step change in cost reduction that re-usable space launchers will bring.
As an LLC3 thread my question is probably misplaced for what you want to discuss here so feel free to ignore.
None of us here are high volume bloggers. You might have to wait a year or two for your question to be relevant if we went strictly by thread rules. I only tend to get bent out of shape when the comment is totally off base, as in GM’s “I thought of it first” or the “we need a scramjet rants during a rocket engine discussion.” This is Jons place, so I can’t speak for him, but I think he and Ken feel about the same way. I am the least professional of the three.
You are impatient?, I want in this so bad I can taste it, and I’m contributing nothing at the moment. Several years ago, I thought I was going to be able to get in the business to do something to move it forward and make money in the process. Not having the bucks means you can’t play Buck Rogers.
I’m going to somewhat take your side on the 10 flights thought, with the disclaimer that Jon is far more knowledgeable about all aspects of rocket operation than I am. If the 10 flights in 10 hours were the requirement, the teams would have to either design vehicles for easier servicing, hire a much larger staff, or work everybody to dangerous levels of exhaustion and beyond.
A winning team with your suggestion would probably be the one that built a vehicle that required a very minimum of turnaround labor and time. Gas, oil, and check the tires kind of turns. The other thing Jon brought up is propellant logistics. I believe commercial operations are going to have to reach the point that handling large quantities of propellant is just part of the business. Also propellant costs would start driving teams toward my hobby horse of pump fed engines for lower helium bills and higher Isp=less prop required.
I am a horizontal take off and landing fan, but I think the golden trio of the LLC has put serious doubts as to that being a requirement. No matter how it takes off, flight rate is the key, which is part of what you addressed in the first comment.
I would really hate to see a level 3, seems like a waste of money. Armadillo, Masten, and Unreasonable already have the equipment to build vehicles that can reach 100km. Why continue funding THIS approach, 3 is the perfect number for competition. There are hundreds of Xprizes out there for NASA to follow this model with, go fund those.
If you wanted something that these teams could sink their teeth into, but could also draw in other competitors, and create something new:
Fast Ansauri X prize:
-Level 1 vehicle must go twice to 50km in 24 hour period. Only fuel may be added, no modification of vehicle besides refueling.
-Level 2 vehicle must go twice to 100km in 24 hour period. Only fuel may be added, no modification of vehicle besides refueling.
**Tie break by maximum altitude reached
-Level 1 No limit to stages or equipment. All components must be able to be returned to launch facility and reused within 1 month without more than 50% of their value replaced (minus fuel). Some portion of the vehicle must make 1 full orbit and return to within 50 miles of the launch pad.
-Level 2 No limit to stages or equipment. All components must be able to be returned to launch facility and reused within 2 weeks without more than 25% of their value replaced (minus fuel). Some portion of the vehicle must make 1 full orbit and return to within 50 miles of the launch pad.
**Tie breaker by speed of turn around
All 3 of these teams have compenents that COULD be used in these two contests, but their hardware would not be the only possible approach to the problems. All the NGLLC contests I have seen advocated to date would basicly be a hand out to the 3 current teams, and maybe Nova.
@ John Hare
“The problem is to get that kind of accuracy before you have a lunar base and GPS systems. While you are still trying to determine where or if to spend the money on infrastructure. The idea is to develop early methods of guaranteeing safe and accurate landing methods on Mars and Calisto and Mercury andâ€¦â€¦â€¦â€¦.”
Or you do it the other way, install the GPS satellites before the first landing. We are basically modifying Earth GPS for the Moon and Mars. You do need lots of satellites.
Calistro, asteroids and other near Earth objects will need a different technique. Low gravity may mean the landing is happening on a rough object at about 25 mph. Something based on an infra-red spacecraft docking system or even a radar controlled car parking system may be more appropriate. If several landers need to be close together home in on the first lander’s transmitter.
â€œwhat is the next step?â€
A couple of suggestions:
1) Add a substantial useful payload requirement, say 1000 kg.
2) Up the hover time requirement to approximate the delta V for lunar orbit injection and decent to the surface. Lunar orbit injection is around 1100 m/s and the Apollo LEM descent stage had a delta V of around 2500 m/s for a total of 3600 m/s. That would imply a hover time of around 360 seconds.
3) Make entrants vibe and thermal vacuum test before flying based on the payload environment for a typical launch vehicle an a trans-lunar mission profile.
Incidentally, if you can achieve 1) and 2) then you are pretty close to the requirements for the first stage of a small TSTO system.
I like RedMars’ idea. I don’t think LLC was ever testing what they thought it was testing – a major advantage of prizes, where we can get a statistical sampling of what’s really hard about it. And what’s really hard about it is repeatability and operations. Four teams entered, each with some success in tethered and free-flight tests. Two managed to finish successfully, after something like 12 tries between them over 3 years.
Now, since it is a NASA competition, and it’s called the Lunar Lander Challenge, one could argue that non-GPS landing accuracy is more important than fast cycling. But whether you’re carrying a suborbital experiment or a lunar science package, reliability is going to be a far more important part of the equation than accuracy. If your gremlins prevent you from doing 10 consecutive hops, you’re not of much use on the moon.
Companies like Masten and Armadillo presumably have two business cases they can pursue from the capabilities and credibility the LLC has given them. The first is being contracted to build the chassis for NASA planetary probes. The second is flying high-altitude science packages and, eventually, people. Operational repeatability is a huge component of both of those – the first because you need a very high demonstrated reliability if you want NASA to spend millions to launch you toward a planetary body, and the second because the faster and more predictably you can turn experiments and people around, the more money you’ll make (not to mention what happens if you actually crash the thing).
I would personally like to see something that would be useful for atmospheric science, which looks like the best immediate option for making money off these things. I think a good prize would go to the highest 30-second dwell. In this case, the vehicle would have to reach an altitude, and dwell at that altitude within a prescribed margin (say, +- 100′) for 30 seconds, then return safely to base. This would presumably be enough time for hypothetical experimenters to take several air samples, recon photos, or cosmic observations. An extra purse should be available for any teams who are able to dwell at altitudes higher than high-altitude balloons can go.
A simulated reusable cargo Moon mission could be:
a. Fly between two points carrying a significant payload.
Hover to simulate a delta-V of 1.87 km/s = low lunar orbit to surface
Or hover to simulate a delta-v of 2.52 km/s = L1/L2 to surface
Automatically unload payload
Fly back to start point with same delay and no refuelling.
b. Refuel, repair and repeat with (new) payload. Penalty for every kg that needs replacing.
Automated refuelling and loading of cargo can come later.