I'd argue that this is what Orion should be replaced with. Since it is more expensive and less likely to get us to Mars than the ARM.
The ARM spacecraft would actually be a very useful thing for getting your proposed deep space hab to Mars. A Falcon Heavy with an ARM-derived tug is capable of delivering more payload to Mars than any version of the SLS could with a chemical transfer stage. In fact, drawing that comparison further, the ARM spacecraft is cheaper than just the exploration upper stage of the SLS.
Focus - we're talking asteroids not SLS or Orion, and you've already admitted we're using both which makes arguing over them moot.
Focus - we're talking asteroids not SLS or Orion, and you've already admitted we're using both which makes arguing over them moot.
SLS/Orion needs ARM for missions, but the ARM does not need SLS/Orion. A Falcon Heavy launched Dragon could perform the manned randezvous just as well.
The ARM is a very worthwhile mission to do regardless of whether your budget is constrained by SLS/Orion, because it creates a new asteroid mining industry and matures SEP technology, all at a much lower price than any other mission. It just happens that with SLS/Orion, it is the only mission that fits the Nasa budget. But that is the fault of government pork programs, not of the ARM which is the highest ROI mission that Nasa is currently planning.
The ARM is a very worthwhile mission to do regardless of whether your budget is constrained by SLS/Orion, because it creates a new asteroid mining industry and matures SEP technology, all at a much lower price than any other mission. It just happens that with SLS/Orion, it is the only mission that fits the Nasa budget. But that is the fault of government pork programs, not of the ARM which is the highest ROI mission that Nasa is currently planning.
ARM would be considered another piece of pork, as the ISS and even Cassini were in years past.
Since you are speaking of SEP, bear in mind it is slow. For trajectories to the Moon, Mars, and NEAs traditional chemical is more practical. I would say use SEP for trajectory corrections, but for the big maneuvers like orbital insertion something with stronger, immediate thrust is called upon. SEP is efficient but it has limits, even if you scale up the engines we're dealing with thrust literally on the scale of a cough. The tradeoff is time, and if you try to tell Congress or a corporation even the small rock you're hauling will need 15 years to swing around Earth...don't expect smiles.
The ARM is a very worthwhile mission to do regardless of whether your budget is constrained by SLS/Orion, because it creates a new asteroid mining industry and matures SEP technology, all at a much lower price than any other mission. It just happens that with SLS/Orion, it is the only mission that fits the Nasa budget. But that is the fault of government pork programs, not of the ARM which is the highest ROI mission that Nasa is currently planning.
ARM would be considered another piece of pork, as the ISS and even Cassini were in years past.
Since you are speaking of SEP, bear in mind it is slow. For trajectories to the Moon, Mars, and NEAs traditional chemical is more practical. I would say use SEP for trajectory corrections, but for the big maneuvers like orbital insertion something with stronger, immediate thrust is called upon. SEP is efficient but it has limits, even if you scale up the engines we're dealing with thrust literally on the scale of a cough. The tradeoff is time, and if you try to tell Congress or a corporation even the small rock you're hauling will need 15 years to swing around Earth...don't expect smiles.
High power SEP is certainly not as slow as you describe. Mega-ROSA solar arrays are already pushing past 200 W/kg. At ~2000s isp, the burn times for Mars with these panels can easily be reduced to timescales on the order of weeks. The trajectories end up being very much like Hohmann trajectories with the biggest chunk of the trajectory being spent coasting. The exception is if you have a variable specific impulse system, in which case the delta-t optimum with finite fuel is shifted towards longer burns at higher Isp after an initial kick.
There are no signs of improvements in solar panel performance stopping soon either. Tethers unlimited has recieved funding for developing >1 kW/kg arrays, which are made possible by in-orbit construction using their trusselator. There is lots of room for performance to grow when you don't have to optimize for the launch environment.
Eventually, SEP is by far the best option for Mars colonization. Chemical is limited by transfer windows outside of which it can't reach Mars at all, while higher-isp SEP allows you to go to Mars and back within a reasonable timeframe regardless of whether or not you launch within a narrow window. This means you are not limited to spikes of activity once per synodic period where you have to launch everything in a short timeframe, and can distribute launches throughout most of the Earth-Mars synodic period. This makes a huge difference in logistics.
{snip}
NEAs were floated because they're a step beyond the 'already-done' Moon and closer than Mars. Dragging the asteroid to the Moon sounds like a step backwards. It already IS an Apollo 8 redux with a piece of charcoal thrown in.
Focus - we're talking asteroids not SLS or Orion, and you've already admitted we're using both which makes arguing over them moot.
SLS/Orion needs ARM for missions, but the ARM does not need SLS/Orion. A Falcon Heavy launched Dragon could perform the manned randezvous just as well.
Since you are speaking of SEP, bear in mind it is slow. For trajectories to the Moon, Mars, and NEAs traditional chemical is more practical.
and if you try to tell Congress or a corporation even the small rock you're hauling will need 15 years to swing around Earth...don't expect smiles.
Since you are speaking of SEP, bear in mind it is slow. For trajectories to the Moon, Mars, and NEAs traditional chemical is more practical.For nudging heliocentric asteroid orbits, ion is much better than chemical.and if you try to tell Congress or a corporation even the small rock you're hauling will need 15 years to swing around Earth...don't expect smiles.
15 years? The Keck proposal suggested 6 years. Two of those years spiraling out of earth's gravity well. EDS[/url] might eliminate that two years.
Since you are speaking of SEP, bear in mind it is slow. For trajectories to the Moon, Mars, and NEAs traditional chemical is more practical.For nudging heliocentric asteroid orbits, ion is much better than chemical.and if you try to tell Congress or a corporation even the small rock you're hauling will need 15 years to swing around Earth...don't expect smiles.
15 years? The Keck proposal suggested 6 years. Two of those years spiraling out of earth's gravity well. EDS[/url] might eliminate that two years.
TWO YEARS....JUST TO LEAVE EARTH ORBIT?! That's beyond crazy talk! If we wish to apply SEP practically to even the unmanned portion of human space flight the escape from Earth shouldn't need more than 6 months! Humans and Van Allen belts anyone? Wasting time is just as bad as wasting money!
TWO YEARS....JUST TO LEAVE EARTH ORBIT?! That's beyond crazy talk! If we wish to apply SEP practically to even the unmanned portion of human space flight the escape from Earth shouldn't need more than 6 months! Humans and Van Allen belts anyone? Wasting time is just as bad as wasting money!
TWO YEARS....JUST TO LEAVE EARTH ORBIT?! That's beyond crazy talk! If we wish to apply SEP practically to even the unmanned portion of human space flight the escape from Earth shouldn't need more than 6 months! Humans and Van Allen belts anyone? Wasting time is just as bad as wasting money!All-caps aren't necessary. It's a fairly straightforward trade-off between mass and time. You pick which is most important, then adjust your Isp accordingly.
The amount of time SEP needs varies according to the mission and it can be used above the Van Allen belts. Because SEP can apply trust all the way to the destination it can arrive faster than chemical(if the destination is far away like Mars) or arrive slower(yet mass much less). It's efficiency means that an SEP powered spacecraft could make an round trip between the moon or mars where as chemical can't without refueling. It just bites if you need to get into or out of orbit in terms of time.(i.e. Chemical to an high Earth orbit or to eascape followed by SEP, then aerobraking or landing at Mars and you could arrive very fast).
It depends on what that unmanned cargo or spacecraft needs to do. Some cargo like an habitat just needs to be in place on mars or the moon before the crew arrives in which case an slow trip is not an problem. For this mission chemical propulsion probably can not move the rock or can not do it efficiently enough.
TWO YEARS....JUST TO LEAVE EARTH ORBIT?! That's beyond crazy talk! If we wish to apply SEP practically to even the unmanned portion of human space flight the escape from Earth shouldn't need more than 6 months! Humans and Van Allen belts anyone? Wasting time is just as bad as wasting money!All-caps aren't necessary. It's a fairly straightforward trade-off between mass and time. You pick which is most important, then adjust your Isp accordingly.
For a departure flight that needlessly long, a caps-worthy scream felt just. Weeks and months are a negotiable timescale, but years is too much just to leave Earth alone. Surely, either SEP, chemical, or hybrid, there's better.The amount of time SEP needs varies according to the mission and it can be used above the Van Allen belts. Because SEP can apply trust all the way to the destination it can arrive faster than chemical(if the destination is far away like Mars) or arrive slower(yet mass much less). It's efficiency means that an SEP powered spacecraft could make an round trip between the moon or mars where as chemical can't without refueling. It just bites if you need to get into or out of orbit in terms of time.(i.e. Chemical to an high Earth orbit or to eascape followed by SEP, then aerobraking or landing at Mars and you could arrive very fast).
It depends on what that unmanned cargo or spacecraft needs to do. Some cargo like an habitat just needs to be in place on mars or the moon before the crew arrives in which case an slow trip is not an problem. For this mission chemical propulsion probably can not move the rock or can not do it efficiently enough.
That is correct, but what concerns me regarding the low-thrust of ion propulsion is, even for asteroids, there will always be orbital insertion at the target. Given that ARM's justification is Mars, and Mars involves a 3-year mission, we should likewise presume 2 or 3 years for an asteroid expedition's length, at least out beyond cis-Lunar space (and discounting the flight to the captured asteroid, since from the crews' POV it is only an Apollo 8 repeat). You'll need engines capable of doing large changes within spans of months if not better.
TWO YEARS....JUST TO LEAVE EARTH ORBIT?!
That's beyond crazy talk! If we wish to apply SEP practically to even the unmanned portion of human space flight the escape from Earth shouldn't need more than 6 months!
Humans and Van Allen belts anyone?
Dragging the asteroid is a practice for planetary defence. We are learning by capturing the drunk dwarf before going on to Goliath.
You state the same Option B hardware could be used to return samples from Phobos and Deimos. These are much larger than the 100m to 500m asteroids that seem to be the target of Option B.
1. I was curious as to how much of gravity well option B hardware can handle?
It depends on the specific design. You'll definitely be stuck grabbing a smaller boulder. And there's no way you'll be able to leap off the asteroid into escape like you can from something more Itokawa sized. But the same hardware could at least grab something on the order of ~2m diameter (instead of 4m), and jump up high enough for some other form of thruster to take you the rest of the way home. That would only be like 10-15mT for a rocky boulder, but still enough to do some decent ISRU work with (and a lot bigger than you'd get back via any other realistic near-term method).
A group at Langley will be presenting a paper on the concept in about a week. Once they've presented it, I'll see if I can post a link or copy here.QuoteYou state a 3.75 m ~90mT design target.
(edit: for potential subsequent missions:)
2. By what factor do you feel this could be somewhat easily scaled up?
3. What are the main hurdles to get to say 500mT or 1k mT?
We'd have to put more structural design work into it to handle a 1000mT boulder, but there's no fundamental reason we couldn't. The surface weight of a 90mT boulder on an Itokawa type asteroid is ~2lb. So for a 1000mT boulder, you'd be talking about 25lb or so, with a diameter around 8.33m (assuming a spherical boulder of 3300kg/m^3 density). The arms would need to be about twice as long.
If I were trying to do something that big, I'd try to do a hybrid of the concept we're doing, and the TALISMAN concept from NASA LaRC. I'm pretty sure we could make a design that size close that could realistically be launched on say a Delta-IVH or maybe FH.
We were just given a much more modest design point to shoot for.
~Jon
You state the same Option B hardware could be used to return samples from Phobos and Deimos. These are much larger than the 100m to 500m asteroids that seem to be the target of Option B.
1. I was curious as to how much of gravity well option B hardware can handle?
It depends on the specific design. You'll definitely be stuck grabbing a smaller boulder. And there's no way you'll be able to leap off the asteroid into escape like you can from something more Itokawa sized. But the same hardware could at least grab something on the order of ~2m diameter (instead of 4m), and jump up high enough for some other form of thruster to take you the rest of the way home. That would only be like 10-15mT for a rocky boulder, but still enough to do some decent ISRU work with (and a lot bigger than you'd get back via any other realistic near-term method).
A group at Langley will be presenting a paper on the concept in about a week. Once they've presented it, I'll see if I can post a link or copy here.QuoteYou state a 3.75 m ~90mT design target.
(edit: for potential subsequent missions:)
2. By what factor do you feel this could be somewhat easily scaled up?
3. What are the main hurdles to get to say 500mT or 1k mT?
We'd have to put more structural design work into it to handle a 1000mT boulder, but there's no fundamental reason we couldn't. The surface weight of a 90mT boulder on an Itokawa type asteroid is ~2lb. So for a 1000mT boulder, you'd be talking about 25lb or so, with a diameter around 8.33m (assuming a spherical boulder of 3300kg/m^3 density). The arms would need to be about twice as long.
If I were trying to do something that big, I'd try to do a hybrid of the concept we're doing, and the TALISMAN concept from NASA LaRC. I'm pretty sure we could make a design that size close that could realistically be launched on say a Delta-IVH or maybe FH.
We were just given a much more modest design point to shoot for.
~Jon
The thing that I do not like about "pluck' a little boulder off the rock - how do you know that the little boulder is not part of the rock? To me --this looks like walking up to tree and thinking that you can pluck the tree from the ground but you cannot see that there are roots attaching the tree the ground. Now how do break the tree from the ground?