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The escape velocity for Mars is about 5.02 km/s and that is a decent first approximation for the arrival speed in #1. Unfortunately, it is a little low.
1. The sphere is not descending from infinity in the Martian gravity well. It is descending from the edge of the Martian sphere of influence (SOI) with respect to the sun. I put that distance around 38 Martian radii since that is where the gravity force vectors for Mars and the Sun have about the same magnitude. If you fall from there you develop a speed of 4.96 km/s.
I'm not nit-picking here even though this speed is essentially the same as the first approximation. I mention this so I can point out the SOI because...
2. The sphere arrives at the SOI with a non-zero residual velocity. If you just use averages, Mars is moving at about 24.13 km/s around the Sun. The sphere is sent on a Hohman transfer orbit from Earth and arrives at the Martian orbit doing about 21.48 km/s around the Sun. If it arrives in front of Mars, a Martian observer would think the sphere was falling at them with a speed of about 2.65 km/s while the sphere was still at the SOI. Once you add on the descent velocity gained by falling through the Martian gravity well, the speed could be in the neighborhood of 7.61 km/s.
Dealing with these numbers properly involves a little celestial mechanics. A physics student should be able ot do it, though someone with more practice could do a better job with patch-work oribit fits.
By the way, that 2.65 km/s residual velocity shows you why you need retro-thrusters on current spacecraft that intend to stick around instead of doing a fly-by. No matter which way you cut it, that residual velocity gives you a net positive orbital energy with respect to Mars which determines that you will fly by on a shallow hyperbolic path. The arriving spacecraft has to shed a little over 90% of its kinetic energy to enter a closed orbit.
You don't need to deal with shocks until you get to #5. Up to that you stick with the assumption that the sphere absorbs all the energy upon entering the atmosphere. We calculate that to get an upper bound for the heat load.
If you can answer #1 the second follows along pretty quick. It's all freshman physics.
The next two involve some experience with thermodynamics. If you can get through #4 you will see the bulk of the argument in favor of ATO for the descent phase of a flight.
#5 helps to make the bounds from #4 more realistic.
#6 helps point out the connection to the ascent phase of a flight. In your mind, you run the problem in reverse. 8)
8)
I'm sure the group supporting the interests of the Vets will make the City's case long and hard to finish. You have to have money to fight those kinds of fights and we aren't in that league yet.
Besides, we probably don't have to fight. There are large unpopulated areas in this country to this day. Some of them have local government that might fight FOR us is we can bring in a few jobs. That's the American Way just as much as those sports domes and arenas are.
Let's treat it as an opportunity then. 8)
If this works out, there will be a number of new pages and research quality material in them too.
As for what can be done I think it might be wise to start with a training-wheels exercise to see if others have the same idea and if there is real interest in this.
Consider the following problem to see if there is a solution and what the constraints upon it would be. I'll call it GO challenge #1.
A fabric (rip-stop nylon like ski jackets) sphere pressurized with N2 moves outbound along a minimal energy transfer orbit between Earth and Mars. It will intersect Mars in a manner that produces the smallest arrival speed. We want to know the following.
1. What is the arrival speed at Mars assuming the sphere just grazes the Martian surface under the assumption of no Martian atmosphere?
2. How much kinetic energy/kilogram must be dissipated by atmospheric drag for the sphere to land upon the surface at a zero speed?
3. How much energy/kilogram can the sphere hold without any part of it rising above a temperature of 400K? What percentage of that energy is in the N2 compared to the fabric?
4. How large would the sphere have to be to absorb the kinetic energy in such a manner as to never have its surface temperature rise above 400K? What is the resulting average density?
5. What percentage of the kinetic energy would the sphere actually absorb upon arrival compared to the energy absorbed by the atmosphere while creating the sonic shock? From this, how would you change your answer to 4 to account only for the absorbed energy?
6. At what pressure must the N2 be maintained to ensure the sphere retains its shape during the entire entry into the Martian atmosphere? Is the pressure physically sensible for the fabric described?
These questions get progressively harder as you work through them, so don't jump ahead unless you are ready to ride without training wheels. Also realize that there might not be unique answers to them. The best answers might be functions describing allowed ranges and the constraints that make them sensible.
I haven't run these numbers for Mars, so I don't know what the results would be. I do know that dust particles striking the Martian atmosphere can slow to a 'stop' before hitting the ground, so the concept of a soft landing isn't too far fetched. Dust has a low density, so I expect the density for the sphere would have to be very low too. You need to know something about the structure of the Martian atmosphere to get very far, though, and I haven't bothered to look up what we know.
What I have done is run calculations like these for more interesting shapes involving Earth's atmosphere. We have a lot more air, so it's less surprising that you can slow to a stop before hitting the ground. What wasn't so obvious, though, is that you could do it without burning up. Look up at the sky at night and watch all those zips and flashes and you'll see what I mean. Of course, they aren't arriving on minimal energy transfer orbits. 8)
If there are good answers to these questions, it begins to make sense to consider other shapes that might be more flyable after arriving. If so, I would conder the numbers and see if our Earth vehicle designs can't accomodate Martian interests.
pft!
Open arrangements are enforced through licenses of copyrights. A new set of investors might choose not to participate anymore by withholding their newest material, but a good license defends participants access to older material.
We were considered unresponsive.
Tustin really wanted to tear the places down and produce something to add to their tax base. Cities have to think about budgets like that, so it is understandable.
I can't speak for anyone else, but I can put my General Orbital hat on and say that we would benefit to some degree from an open project. I've done open source software in the past (GPL'd to boot) so I understand the arguments for and against. While I'm not sure a complete document of the past art is necessary, I would be willing to go as far as my partners are willing to tolerate and maybe a little beyond.
(My weak java code for high altitude balloon flights I developed while at JPA is available under the High Flyer project at SourceForge.net.)
I'm not trying to rope anyone in here. If there is interest in making a design Mars-capable then it might be worth putting stuff up on the wiki. I say all this on the off chance a group would form with a bit of support from a motivated user of the designs. Our company can't be the center of the team because our corporate interests would dictate team actions. Down that path lies trouble. What we can do is sit at the table and see if a team forms up. I'm willing to share some of what I know if I see value returned for it.
I'll make you all a deal then.
If you want one of these space-capable airships to be useful on Mars help put some work into the engineering effort. If you do and the design is good I'll fold it in to the plans and give credit where it is due. If the design is exceptionally good, we'll talk business.
There are a few constraints to consider though.
1. Assume from the start the use of chemical propulsion for ascent and very little fuel being available for descent. I'm not inclined to wait around for exotic engines. Just because someone has proved them in the lab doesn't make them ready for industrial use.
2. Assume from the start that you can't use exotic materials for the load envelope. That means you need to descend from orbital altitudes and speeds without burning up your typically available fabric used for the outer envelope. That means you have to keep the decelleration g-loads small and the change of velocity spread out over as much time as is reasonable.
3. Consider the usefulness of your design for other bodies with atmospheres. If your idea can operate at the top of Venus' and Earth's atmosphere and all through Mars' atmosphere, you have a potential winner.
4. Assume from the start that we will never raise government money either from projects or contracts. You are welcome to go that way if you like, but I have a moral problem with that path. I'm also getting too old to wait any longer.
I appreciate an attractive dream of the future, but I have far more respect when it is turned into a plan that can be made real through fundable actions of the faithful.
I'm familiar with it. 8)
I was with JPA LLC during the NSMV contract. If you look at any of the pictures and see the keel trusses underneath, they are the labor of my sweat. 35 lbs/100 feet on the keels and we could have done better by 25% I think. We spent many late nights in that cold hangar finishing the vehicle we intended to fly. I still dislike pigeons to this day for crapping on my stuff all the time.
What isn't visible in the pictures, though, is the analysis we did. I was the team physicist responsible for making sure we didn't do things like violate the conservation of energy law and for not being scared off by any math. I wrote up software and ran some of the simulations, so I have a pretty good idea of what to expect up there.
I also ran mission control for a short while and had to know the big picture for what was flying on a particular test flight. I got to know the equipment involved in ground support and what we typically flew back then. They have changed a few things to newer, spiffier stuff since I left (from what I've heard) so what I'm saying is that I got to do some of the hands on and a lot of the pure thinking stuff.
Nowadays I'm with a new team at General Orbital that brings a different set of experiences to the effort. I have some new friends with backgrounds covering investor funded start-up companies, communications and networking, and some excellent talent in the embedded software arena. We intend to raise money and hire the engineering talent we need to flesh out the team.
Am I a mad scientist? Maybe. That's all right though. The only folks I need to convince I am sane right now are my new partners and our potential investors. After that I focus on the engineers who work for the regulators. After that I might get around to everyone else.
Where we fly blue is below while above is black.
We set course for the other side of the sky.
Regarding the USPTO and other nation's equivalent agencies, we will find out. Our paperwork is filed, so I can use the patent pending term where I need it. Some ideas are old and some are new, so it will be interesting to see.
Regarding a Mars flight I would say I suppose so. Big airships give you options for Mars landings you might not have otherwise. They also give you a lot more volume during the transit flight so your people don't go batty locked in a tin can. I don't know that the advantages warrant their development, though, if you only focus on Mars. These big airships are meant to provide us with a way to work with the thick atmosphere of Earth instead of fighting with it.
I will admit that I'm a little more focused on getting to LEO than I am getting to Mars. You all are welcome to look that far ahead, but I'm going to have to satisfy an investor or three along the way. I haven't found anyone who is willing to let me play with their millions of $'s, so I'm keeping a short focus for deliverables and a wide focus for designs.
If you did find a substance that worked to float one sphere up, grouping them together inside one load envelope probably wouldn't work better. Once you group them near each other they would be subjected to other compressive forces besides atmopsheric pressure.
Think about the environments for the sphere at the top of the pack and the one at the bottom and you'll see that they are different.
no thanks
Yes. I have not given up on the approach and have a new team that likes it. I think my designs have diverged over time, so I don't know that I would call them competing. We will all be out there slugging away at the real, shared goal to put people in space.
Everything you fly impacts your payload mass. You just have to plan for it and scale the systems appropriately. If you have the ability to replace lift cells or patch them you have one way to do it.
They are meant to be re-used a lot.
It wouldn't make any sense to build these things for only one use.
How fast does a bathtub empty if you punch a small hole in it?
How about a pool sized tub?
First of all, these things don't go POP like a latex balloon. They aren't all that elastic.
Second, the gas volume is pretty large AND segmented. It would take a while to notice the pressurization change.
Third, the vehicle design has to have a way to cope with small leaks anyway like with do with ocean going ships. Assume leaks from the start and plan for them.
Lastly, not all the orbiting vehicle designs are that large. The design I'm playing with right now is about 600 meters long with lox/kerosene rockets on it.
I don't need that kind of help. Heaven forbid.
Keep your ideas away from my potential financiers, please.
We are doing fine, thank you.
That's about what I thought they would say. They got a nice opportunity to look at a competing vehicle and declare it unworthy. It would have flown, though. There is nothing surprising in that old news.
I am now the CTO at General Orbital. I've carried my interests in inflatables over to our new company where we are putting our own stamp on things. We are a little busy trying to raise cash right now, so I haven't kept up with what people are saying. I'll try to check in occasionally, though.
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