Quote from: MATTBLAK on 02/28/2017 10:30 pmI'd like to see how the Dragon 2 hatch could be adapted to work with a porch/ladder for EVA egress. And would it be a good idea to have the suits able to join with the hatch or hull as external 'suit locks' after the first EVA? I've become a bit of a fan of suit locks - keeps the dust out of the Lander interior, which was always strongly advocated by John Young and Gene Cernan in particular.I like these when multiple EVA's are planned or sustained surface ops. Might be different if you are looking at the requirements for a minimum basic lander...
I'd like to see how the Dragon 2 hatch could be adapted to work with a porch/ladder for EVA egress. And would it be a good idea to have the suits able to join with the hatch or hull as external 'suit locks' after the first EVA? I've become a bit of a fan of suit locks - keeps the dust out of the Lander interior, which was always strongly advocated by John Young and Gene Cernan in particular.
Quote from: Rocket Science on 02/28/2017 11:45 pmQuote from: MATTBLAK on 02/28/2017 10:30 pmI'd like to see how the Dragon 2 hatch could be adapted to work with a porch/ladder for EVA egress. And would it be a good idea to have the suits able to join with the hatch or hull as external 'suit locks' after the first EVA? I've become a bit of a fan of suit locks - keeps the dust out of the Lander interior, which was always strongly advocated by John Young and Gene Cernan in particular.I like these when multiple EVA's are planned or sustained surface ops. Might be different if you are looking at the requirements for a minimum basic lander...But if it's a reusable lander what's the effectual difference? Even if it is only 2 EVAs per mission if the Lander is used 10 times then that's 20 EVA's. Better to keep the interior clean for the next mission, plus negates the need to vent the cabin, which requires replenishment supplies.
Quote from: clongton on 03/01/2017 12:07 amQuote from: Rocket Science on 02/28/2017 11:45 pmQuote from: MATTBLAK on 02/28/2017 10:30 pmI'd like to see how the Dragon 2 hatch could be adapted to work with a porch/ladder for EVA egress. And would it be a good idea to have the suits able to join with the hatch or hull as external 'suit locks' after the first EVA? I've become a bit of a fan of suit locks - keeps the dust out of the Lander interior, which was always strongly advocated by John Young and Gene Cernan in particular.I like these when multiple EVA's are planned or sustained surface ops. Might be different if you are looking at the requirements for a minimum basic lander...But if it's a reusable lander what's the effectual difference? Even if it is only 2 EVAs per mission if the Lander is used 10 times then that's 20 EVA's. Better to keep the interior clean for the next mission, plus negates the need to vent the cabin, which requires replenishment supplies.Agreed for a reusable lander. I just didn't see the value of the additional complexity on a single use short stay along the lines of a Golden Spike proposal...
Quote from: Rocket Science on 03/01/2017 12:16 amQuote from: clongton on 03/01/2017 12:07 amQuote from: Rocket Science on 02/28/2017 11:45 pmQuote from: MATTBLAK on 02/28/2017 10:30 pmI'd like to see how the Dragon 2 hatch could be adapted to work with a porch/ladder for EVA egress. And would it be a good idea to have the suits able to join with the hatch or hull as external 'suit locks' after the first EVA? I've become a bit of a fan of suit locks - keeps the dust out of the Lander interior, which was always strongly advocated by John Young and Gene Cernan in particular.I like these when multiple EVA's are planned or sustained surface ops. Might be different if you are looking at the requirements for a minimum basic lander...But if it's a reusable lander what's the effectual difference? Even if it is only 2 EVAs per mission if the Lander is used 10 times then that's 20 EVA's. Better to keep the interior clean for the next mission, plus negates the need to vent the cabin, which requires replenishment supplies.Agreed for a reusable lander. I just didn't see the value of the additional complexity on a single use short stay along the lines of a Golden Spike proposal... Ghost said extra points for a reusable lander so why not go for that?
Quote from: MATTBLAK on 02/28/2017 10:30 pmI'd like to see how the Dragon 2 hatch could be adapted to work with a porch/ladder for EVA egress. And would it be a good idea to have the suits able to join with the hatch or hull as external 'suit locks' after the first EVA? I've become a bit of a fan of suit locks - keeps the dust out of the Lander interior, which was always strongly advocated by John Young and Gene Cernan in particular.Because you are flying under a fairing, these are quite possible (you'll at least need a minimal cover to reduce exposure in transit). Also, one of the troubles with Dragon as a lander is that the side hatch is insufficient in size for suited access. This would deal with that.
Are the Super Dracos on the Dragon pressure or pump fed?
How does that work in zero-g? What keeps the liquid between the orifice and the pressure boundary?Is the propellant in a bladder?
Dragon V2 has a NASA Docking System port on its roof. This allows the transferase of power and air. Can the water, fuel and LOX tanks be connected to the port? This would allow either refueling or the attachment of drop tanks.
I may have come up with a solution using the Dragon V2 as a lunar lander. Which avoids new technology developments, refuelling, drop tanks and other low TRL items.Launch dragon (wet 7400kg) on FH with a trunk pallet consisting of 19,600 kg of hypergolic fuel, a properly expanded engine, tank, trunk mounting and stubby legs - I estimated 1000kg for hardware.The dragon would get to LEO + 1670 m/s, now that abort capability is no longer needed - separate from the second stage then burn the superdraco's to bring the dragon mass down to 5000kg and add a small amount more of delta V.Launch a second FH with a payload of just an IDA (500kg) - no fairing or minimal nosecone. Rendezvous with the dragon and dock. At this point dragon is facing the second stage (rather than being mounted in the way it launched).If docking fails then dragon can drop the trunk pallet and return home.If docking succeeds then at this point the new second stage should still have 20,350kg of fuel, sufficient to push the lightened dragon (with its trunk fuel and engine) into TLI (3150 m/s above LEO).Separate from the second second stage once translunar and the dragon has enough fuel for LOI, to meet the Orion etc then to land on the lunar surface. Later it can launch back to LLO then the dragon can TEI for a parachute landing (total 4560 m/s).It appears to meet the requirements of the OP at the cost of two FH launches and requires no new technology. The dragon is returned to earth each mission, so learning and development can take placeIve based all this on the figures I've been able to find for delta V budgets, weights and capacities etc - I'm happy to share the numbers.
I think to fully close the mass budgets here you need a 3rd FH launch, which launches a crew Dragon with a similar trunk pallet (with less fuel) and vac engine directly to TLI. The crew rides the crew Dragon to LLO, then transfers to the lander Dragon for the the ride to the surface and back to LLO. This eliminates the need for the lander Dragon to have SuperDracos or parachutes or a heatshield, saving ~1000 kg, and it can be discarded on return to LLO.
Which engine are you proposing? SuperDraco fully expanded would get 340 - 345 sec I_sp at 90 kN, but will not hit your mass budget since it needs heavy tanks that can be pressurized to 1000 psi. You probably need a pump-fed engine like Aestus 2/RS-72, which gets 340 sec I_sp at 60 kN.
Quote from: CJ on 02/28/2017 06:30 amI may be pushing the boundaries of Dragon or Starliner-derived lander here - so, SpaceGhost, if you feel I have, let me know and I'll delete my post. It's a fine post. On topic and relevant. I'll attempt to give you feedback.
I may be pushing the boundaries of Dragon or Starliner-derived lander here - so, SpaceGhost, if you feel I have, let me know and I'll delete my post.
QuoteOperating premise; keep costs down, including R&D. Use existing tech (Dragon2, in this case) as much as possible. That means, in part, keep it as simple as possible. It also means avoiding unneeded mass. It would require lunar orbit rendezvous like Apollo. Correct. And the existing tech also includes associated mission systems. Since docking is standardized, other vehicles that may be used like Orion have systems as well, but outside of such standardized interfaces, you don't "mix and match". You do LOR because of the limitations of the combined systems. Each has a means to arrive on LLO. Adding complexity to share the ride slows things down. And you can use the excess performance margin for extended capabilities later. But it introduces risk, contingencies, and variables. Likely you want the CC derived lander on LLO ahead of crew launch, and thus it must last significantly longer.
Operating premise; keep costs down, including R&D. Use existing tech (Dragon2, in this case) as much as possible. That means, in part, keep it as simple as possible. It also means avoiding unneeded mass. It would require lunar orbit rendezvous like Apollo.
Wouldn't call it a SM. Dragon has an integral SM.Would call it a jettison-able propulsion assist pallet (JPAP). Use the Dragon's trunk/radiator/other systems to keep PMF low, might construct CF tanks with integral thrust structure and membranes to get below F9US PMF.
QuoteEssentially, a cylinder, slightly smaller in diameter than the F9 (to fit within the Dragon trunk), containing Superdracos (2, for redundancy) and fuel. Theoretically, you should be able to make this with about the same mass ratio as the upper stage. It'll be a short cylinder, mounted behind the trunk, size dictated by needed delta/v and thus tankage capacity.Not how you do it.You calculate your mission's needs, including contingencies venting etc, the length of engines/nozzles/gimbal freedom/recontact margin/jettison compliance/other. From these you get the overall tanks/pallet dimensions, size the trunk from that. Not the other way round. Oh, and I forgot, you need to add mission growth margin.Then you can call it short, medium or long.
Essentially, a cylinder, slightly smaller in diameter than the F9 (to fit within the Dragon trunk), containing Superdracos (2, for redundancy) and fuel. Theoretically, you should be able to make this with about the same mass ratio as the upper stage. It'll be a short cylinder, mounted behind the trunk, size dictated by needed delta/v and thus tankage capacity.
QuoteThe math. It takes about 680 m/s to enter low lunar orbit. About the same for the TEI burn. So, 1360MS.Why leave LLO? That's the crew mission segment, an entirely different vehicle.You only need to enter LLO. And, if Dragon was just used as a cargo vehicle to surface, it doesn't even need that, could do a direct landing. If the point was instrument/cargo on the Moon's surface at lowest delta v, one can use the mascons and the cancellation of angular momentum to land at even less delta v budget (very limited number of locations for this).Now, for a mission planning POV, lets assume we choose an optimum LLO polar access orbit (10km periapsis, 200km apoapsis, longitude 32 degrees) - this is about as low as you'll go, and it will require deft care with small thrusters to maintain such for a month. You could eventually work up to a number of repeat sorties from a single Orion mission, perhaps as many as ten (this would be a logistical challenge requiring multiple "lunar CRS" vehicles/resupply, likely all of them, thus a mission worth doing not EM 1/2). It will cost more to enter this orbit then you've budgeted above - close to 800 m/s given optimal timing. Also, altitude will greatly vary, dropping to 8km and exceeding 200 km as the mascons retard/accelerate the combined SC, not to mention the dispersions either.Each descent, hover, landing, ascent will require 5 km/sec delta v budget because the sites visited won't be as "easy" as the Apollo ones. So on orbit props will need to support 50 km/sec of props eventually for such a mission.For comparison - LM two stage system delta-v: DPS 2.5 km/sec, APS 2.2 km/sec
The math. It takes about 680 m/s to enter low lunar orbit. About the same for the TEI burn. So, 1360MS.
QuoteRound up for margins, 1500 m/s. ISP of a SuperDraco is about 240 at sea level. But, the fuel is MMH/NTO, which has a theoretical max of 336, so a superdraco with a vacuum expander bell (with electric actuators for steering) should do a lot better than 240. I'll ballpark it at 275, which I think is conservative.No I wouldn't - its not so easy to get, and not enough.By my measure you'll need to exceed 300 sec-1 (APS/DPS 311). Delta II's AJ10-118K is 319 for reference. No slouches here.What I would do is work backwards from the mass flow needed to get the thrust/iSP for the pumps/nozzle, and then you'd deal with the engine/tankage weight as part of the total vehicle's PMF.
Round up for margins, 1500 m/s. ISP of a SuperDraco is about 240 at sea level. But, the fuel is MMH/NTO, which has a theoretical max of 336, so a superdraco with a vacuum expander bell (with electric actuators for steering) should do a lot better than 240. I'll ballpark it at 275, which I think is conservative.
QuoteDragon2 plus internal SD fuel, etc, has reported mass of 7385kg. I'll add 1000kg for crew plus non-life-support consumables, putting it as 8385kg. That, plus dry service module (I've rounded that up to 1000kg - a very poor mass ratio compared to either F9 stages), 9385kg. So, per the rocket equation, we have a fuel mass for the service module (to get 1500 m/s delta/v) of 7000kg. That's about 1555 gallons. Even assuming the same density as water, it should therefor fit in a cylindrical unit within the trunk. See above. You don't have delta-v budget to surface and back.
Dragon2 plus internal SD fuel, etc, has reported mass of 7385kg. I'll add 1000kg for crew plus non-life-support consumables, putting it as 8385kg. That, plus dry service module (I've rounded that up to 1000kg - a very poor mass ratio compared to either F9 stages), 9385kg. So, per the rocket equation, we have a fuel mass for the service module (to get 1500 m/s delta/v) of 7000kg. That's about 1555 gallons. Even assuming the same density as water, it should therefor fit in a cylindrical unit within the trunk.
QuoteIt'll need a few mods; add legs plus draco thrusters and Dragon avionics.Unneeded. Use existing Dragons.
It'll need a few mods; add legs plus draco thrusters and Dragon avionics.
Quote Without cargo, by itself, it has a delta/v of 5.5 kps, more than enough to land on the moon and take off again (you need 4.4 kps for that.)How do you get these numbers?One usually works from the mission architecture/profile and the desired orbit as a basis.Then you need to determine LLO entry weight, descent weight at PDI, ascent weight at launch to LLO.
Without cargo, by itself, it has a delta/v of 5.5 kps, more than enough to land on the moon and take off again (you need 4.4 kps for that.)
QuoteThat same lander type, in one-way cargo mode, could land 2500 kg of cargo on the moon - for example a BEAM type module (With a dragon-based life support) for a short term hab, and other supplies. If added capacity is needed on the crew and cargo versions, it could be attained by stretching the tanks;Nope.BEAM is an experiment used to increase the TRL of an inflatable module. There is no "off the shelf" surface or orbital hab. Development of such is outside the scope of this thread.
That same lander type, in one-way cargo mode, could land 2500 kg of cargo on the moon - for example a BEAM type module (With a dragon-based life support) for a short term hab, and other supplies. If added capacity is needed on the crew and cargo versions, it could be attained by stretching the tanks;
Quote it could land and take off with one superdraco even with an additional couple of tons of fuel, due to the low lunar G. (The stretched version could thus include a stowed expandable hab on the crew lander). Prove this assumption.
it could land and take off with one superdraco even with an additional couple of tons of fuel, due to the low lunar G. (The stretched version could thus include a stowed expandable hab on the crew lander).
QuoteThese go to low lunar orbit.You need an LOI burn.
These go to low lunar orbit.
QuoteA third launch is a fuel depot - not technically hard, as the fuel is storeable hypergolic.Another vehicle to be developed. How does the fuel get to the vehicle. Where is the crew when the vehicle is fueled?
A third launch is a fuel depot - not technically hard, as the fuel is storeable hypergolic.
Quote4th launch, crew Dragon plus service module.So no Orion as this thread is written? Does your crew Dragon have all of Orion's capabilities? Can it handle contingencies needed? What if the lander has a shortfall in performance and cannot reach crew vehicle?
4th launch, crew Dragon plus service module.
Quote Rendezvous in lunar orbit. Crew handles docking plus topping up the two stages.What if crew can't transit vehicles? What happens if theres a fueling mishap?
Rendezvous in lunar orbit. Crew handles docking plus topping up the two stages.
QuoteCargo lander lands the cargo - if successful, a crew descends on the crew lander, stays a few days, then ascends to rejoin Dragon for a return to Earth.Is this the fuel vehicle or another?
Cargo lander lands the cargo - if successful, a crew descends on the crew lander, stays a few days, then ascends to rejoin Dragon for a return to Earth.
QuoteCrew lander remains in low lunar orbit, to be refueled from the depot for the next mission. This architecture is flexible; could be used to set up a base, or have a standby emergency ascent vehicle. Autonomous fueling? Autonomous landing? Lifetime? Other consumables replenishment? Means?
Crew lander remains in low lunar orbit, to be refueled from the depot for the next mission. This architecture is flexible; could be used to set up a base, or have a standby emergency ascent vehicle.
QuoteI tried to be conservative, but I'm sure I missed some big things. I tried to keep it as cheap as possible, to make it viable for tourism. As part of this, I tried to keep it efficient (such as just couches on the lander, no structure or shell, and no staging, plus possibly reusable.)To be fair you handwaived.Sure - try taking the feedback and do some more homework.
I tried to be conservative, but I'm sure I missed some big things. I tried to keep it as cheap as possible, to make it viable for tourism. As part of this, I tried to keep it efficient (such as just couches on the lander, no structure or shell, and no staging, plus possibly reusable.)
QuoteA few huge technical challenges/issues; Can a FH push 16385kg (Dragon plus service module) through TLI? If they can, as claimed, throw 10 tons at mars, maybe, but my guess is probably not. If they do stretch the second stage, then I'd feel better about it being plausible.A larger F9US would decrease landed mass. They've sized F9US appropriately. Raptor US, if built, would increase landed mass.
A few huge technical challenges/issues; Can a FH push 16385kg (Dragon plus service module) through TLI? If they can, as claimed, throw 10 tons at mars, maybe, but my guess is probably not. If they do stretch the second stage, then I'd feel better about it being plausible.
QuoteI'm sure there are major flaws I didn't see - and I'd appreciate criticism and correction. Hope you make careful use of it.Many times one gives little here, because no one makes good use of the feedback.You want more critical feedback, you do the "homework", show your work, and you'll get more involvement.
I'm sure there are major flaws I didn't see - and I'd appreciate criticism and correction.