Instead of generic ion engines, how about multiple instances of the SEP tug? I have seen images implying it would stack nicely and even is designed to do so. I think this is more in line with the OP's goal of working with what we have (though I admit the term 'have' is a bit flexible here )We could have the DSH being tested out for a few years in high lunar orbit. We could have several SEP tugs visiting asteroids or whatever, and perhaps time the mars orbit mission for the point at which we have most trust in the hardware: not too new, not to old.My layman's feeling is that a single orion would be best, just for the initial push with whatever propellant it can reasonably have on arrival at the DSH, then keep the command module and perhaps immediately dump the service module. Use electric thrust for the rest and aim for Deimos due to it being easier in terms of delta-v.Perhaps the DSH orbit could be nudged into a near earth approach before the mission begins to exploit Oberth effect for this one small burn.About this Orion one year and speed of earth reentry issue, how big a job is that to fix? Seems to me that if we are going to build that Orion thing we should at least have an upgrade path planned. It doesn't need to be the first Orion that flies, but this would have to be a few years later (after the DSH and SEP tug shakedown mentioned)
The problem with that is the Orion Service Module supplies the crew with oxygen and water. The Command Module can only support life for a few hours.https://en.wikipedia.org/wiki/Orion_Service_Module
I ranted about something along these lines at my own blog a couple of months ago (https://chilesfiles.wordpress.com/2016/04/22/halfway-to-nowhere/#more-2489). I'd dearly love to see NASA take advantage of the 2021 free-return window as outlined by the Inspiration Mars crowd. If we can't afford to launch SLS much more than once a year, then let's make it count for something before the whole thing is steamrolled into obsolescence by the private sector.A manned flyby of Venus and Mars would be an audacious and extremely valuable proof-of-concept mission. There's a golden opportunity here for a one-off, Apollo 8-style home run if we only had the stones to pursue it. But that would require focused leadership and political will to see it through over a couple of election cycles. Therefore, it won't happen. But damn if it wouldn't be glorious.
If SpaceX is successful, then NASA can ... either cancel Orion/SLS or use it for lunar or asteroid missions.
Quote from: RonM on 07/17/2016 03:30 pmIf SpaceX is successful, then NASA can ... either cancel Orion/SLS or use it for lunar or asteroid missions.A nit but an important one. NASA cannot cancel SLS; only Congress can do that.
Quote from: Arb on 07/17/2016 10:46 pmQuote from: RonM on 07/17/2016 03:30 pmIf SpaceX is successful, then NASA can ... either cancel Orion/SLS or use it for lunar or asteroid missions.A nit but an important one. NASA cannot cancel SLS; only Congress can do that.Yes, thanks for pointing that out.
How are we going to have even one human qualified Orion, a few SLS launches, or an SEP tug by 2021?
The back end of the Asteroid Redirect Robotic Mission (ARRM) spacecraft is a Solar Electric Propulsion (SEP) tug. This is due to be launched in December 2021. So by about 2021 NASA will be able to buy SEP tugs.The tug design may need upgrading to reach human rating standards.
Quote from: A_M_Swallow on 07/18/2016 05:11 pmThe back end of the Asteroid Redirect Robotic Mission (ARRM) spacecraft is a Solar Electric Propulsion (SEP) tug. This is due to be launched in December 2021. So by about 2021 NASA will be able to buy SEP tugs.The tug design may need upgrading to reach human rating standards.NASA can buy SEP tugs now if it wants to. See Dawn.
There is no need to bring any Orions along for the ride. A simple mission like this could be staged out of L1, L2, or DRO. Have the crew launch on Orion out there to meet the Mars bound spacecraft. The return the crew to one of these places to meet up with a waiting return craft.
Hey, engineers of the past would've KILLED for a simulator like Kerbal.
Quote from: Jim on 07/18/2016 05:26 pmQuote from: A_M_Swallow on 07/18/2016 05:11 pmThe back end of the Asteroid Redirect Robotic Mission (ARRM) spacecraft is a Solar Electric Propulsion (SEP) tug. This is due to be launched in December 2021. So by about 2021 NASA will be able to buy SEP tugs.The tug design may need upgrading to reach human rating standards.NASA can buy SEP tugs now if it wants to. See Dawn.Is a 0.09Newton (0.02lbf) 'SEP tug' for a 212 tonne (466,400lb) mission a bit undersized for a manned mission in deep space rad environment?
Quote from: AncientU on 07/20/2016 09:41 pmQuote from: Jim on 07/18/2016 05:26 pmQuote from: A_M_Swallow on 07/18/2016 05:11 pmThe back end of the Asteroid Redirect Robotic Mission (ARRM) spacecraft is a Solar Electric Propulsion (SEP) tug. This is due to be launched in December 2021. So by about 2021 NASA will be able to buy SEP tugs.The tug design may need upgrading to reach human rating standards.NASA can buy SEP tugs now if it wants to. See Dawn.Is a 0.09Newton (0.02lbf) 'SEP tug' for a 212 tonne (466,400lb) mission a bit undersized for a manned mission in deep space rad environment?The NSTAR thruster is fairly low-power at 2.3kW. But commercial units are at least 4.5kW and can be ganged together. And the NEXT thruster is 7kW. Gang 15 together, and you have >100kW, which is good enough for a basic tug.
Power and thrust are proportional to each other, and the proportionality constant is exhaust velocity. THAT'S why I said power.Power = thrust*exhaustvelocity
Quote from: Robotbeat on 07/21/2016 05:30 pmPower and thrust are proportional to each other, and the proportionality constant is exhaust velocity. THAT'S why I said power.Power = thrust*exhaustvelocityThanks, that (proportionality) is pretty much what I figured, as you can see from my post. However, now I'm curious as to the power ratings of the thrusters that you mentioned. Is that the power output of the thruster, using the equation you gave? Or is it the electrical power input required to operate the thruster at the given thrust level? When you stated the thrusters' power levels in watts, I thought it was the latter. Given the context of your reply, it would seem to be the former.Anyway, the bottom line seems to be that you need ~1 MW of power for every 10 lbf of thrust. Please correct me if my math is wrong, or if I have a bad understanding of the underlying principles.Thanks again.
What most people fell to appreciate is that the Falcon 9 Heavy, with its kerolox upper stage, has low performance beyond LEO. nothing beats LH2 there.
So what? Stage in LEO. We have lots more experience there anyway.
Quote from: Archibald on 04/15/2017 08:15 pmWhat most people fell to appreciate is that the Falcon 9 Heavy, with its kerolox upper stage, has low performance beyond LEO. nothing beats LH2 there. True.OT but I'm surprised Spacex never designed a third stage for the Falcon vehicles as even something like a Star derivative would help enormously on high energy orbits.
Falcon Heavy can put 64 tonnes in LEO. For 100 mill.
Instead of 3 Orions, why not have another ICPS for boost operations?
Falcon Heavy can put 64 tonnes in LEO. For 100 mill. Surely NASA should drop the SLS and just work out a way to send the DSH , Orion etc up on top the falcon heavy, just think of the extra exploration missions they could run with the money they saved. SLS is dead in the water, 40 year old technology with a huge price tag.Many of the NASA exploration parts could be put into space with falcon heavy recovery of the first stages. That should make it cheaper again.
The 100 million price is not for the full performance of the Falcon Heavy. Last time I checked, $90 million is for up to 8 mT(could be dated) to GTO while the full performance was ~3x that. Common misconception on the internet.
NASA tends to pay a lot more than the published prices regardless.