OTOH, I believe your 0.7 km/s from EML through TMI is low - you'll use about half that just leaving EML (the perigee lowering burn as you pass the Moon), so you can do an Oberth burn at earth. But the Oberth burn itself can be around 1 km/s (or some of the numbers appropriate for cargo mission do seem to be lower, as per your estimate).
You're easily amused.
It's a flat plateau after you reach C3=0? Um, no. Your Grand Canyon metaphor is way off base. Once you reach reach the edge of earth's Hill Sphere you still need another 3 km/s to raise your aphelion to 1.52 A.U.
Quote from: Impaler on 03/03/2015 09:51 pmYour correct that we can just depart from EML1 directly to Earth Escape without doing any swing buys of the moon or Earth. And the DeltaV is VIRTUALLY THE SAME. The Chemical high thrust system gets a LITTLE boost of something like 100 m/s from plunging deep into thouse gravity wells and burning with an Oberth effect. Wrong.Falling from a high apogee you'd be moving 10.8 km/s at perigee.At that speed, a .5 km/s burn will give you 3 km/s Vinfinity.
Your correct that we can just depart from EML1 directly to Earth Escape without doing any swing buys of the moon or Earth. And the DeltaV is VIRTUALLY THE SAME. The Chemical high thrust system gets a LITTLE boost of something like 100 m/s from plunging deep into thouse gravity wells and burning with an Oberth effect.
.4 km/s to drop from EML2 and a .5 km/s perigee burn for TMI. The delta V from EML2 to TMI is only .9 km/s. So the booster stage can be a lot smaller than the MTV. Accordingly I ditched your Hummer for the more appropriate Moped.After separation it will take the Moped another .9 km/s to get back to EML2 but this will take a lot less propellent since the Moped has much less dry mass. With an .18 km/s delta V budget and no need to endure an 8 km/s atmospheric re-entry, the Moped's reuse becomes a little more plausible.In the mean time the MTV is on its way to mars without the mass of the moped.If a one km/s acceleration takes 11 days, that LITTLE boost saves 33 days.
Very interesting progress update on ISDC 2015, presented by Dr. Franklin Chang DiazHighlights:1. Ions and electrons in the same plume, no neutralization needed2. Primarily using argon, 6N thrust level achieved (estimated isp 3000s)3. More than 10000 firings of VX-2004. 70% efficiency with argon and ISP of 5000s. 5. With krypton, they could reach 75% efficiency. 6. CDR milestone beginning 2016.7. ISS flight milestone beginning of 2018.8. ISS reboost currently requires 7t of fuel and 210 million USD per year9. Smaller 80kW unit would require 1/10 of this cost10. various application specific animations shown
I was just now going to post the link to that video. Comparing VX-200 to other electric propulsions for example hall effect thruster, VASIMR is looking good. I read that NASA is going to use hall effect thrusters for the ARM mission. VASIMR will be also a good choice to use.
Quote from: Raj2014 on 05/28/2015 12:51 pmI was just now going to post the link to that video. Comparing VX-200 to other electric propulsions for example hall effect thruster, VASIMR is looking good. I read that NASA is going to use hall effect thrusters for the ARM mission. VASIMR will be also a good choice to use.VASIMR is still TRL6, and it will not be TRL9 until 2018, so that is a probable reason why it is not considered. Besides, Hall thrusters have much more actual flight heritage. But the main reason is that for ARM you don't really need variable ISP so much.In my opinion, 70% efficiency is the real breakthrough, because it simplifies cooling requirements. I would expect that most of the losses are dissipated as heat inside the engine which has to be removed somehow. As far as I know, VASIMR has the highest thrust among electric propulsion devices produced so far.
Quote from: MP99 on 12/13/2014 07:02 pmOTOH, I believe your 0.7 km/s from EML through TMI is low - you'll use about half that just leaving EML (the perigee lowering burn as you pass the Moon), so you can do an Oberth burn at earth. But the Oberth burn itself can be around 1 km/s (or some of the numbers appropriate for cargo mission do seem to be lower, as per your estimate)..15 km/s suffices to drop from EML2 to a 111 km altitude perilune. At perilune it's traveling near lunar escape and so enjoys an Oberth benefit. A .18 km/s perilune burn will drop the ship to a deep perigee.At perigee the ship is traveling 10.8 km/s. Hyperbolic velocity for Trans Mars Insertion is 11.3 km/s. So a .5 km/s perigee burn sends the ship on its way to Mars..15 + .18 + .5 = .83. From EML2 to TMI is about .8 km/s.
Here is an update on VASIMR. You will need to translate it if you can not read Spanish.
Quote from: Raj2014 on 07/18/2015 10:35 pmHere is an update on VASIMR. You will need to translate it if you can not read Spanish.In March they got $10 mill from NASA. They plan to test the engine for a continuous 100 hours. May be ready to fly in late 2017. The International Space Station is mentioned by I'm unsure if VASIMR is still planned to be tested there.
Ad Astra Rocket Company and NASA move to execution phase of NextSTEP VASIMR partnershipPress Release From: Ad Astra Rocket Company Posted: Monday, August 10, 2015Ad Astra Rocket Company and NASA have successfully completed contract negotiations on the company's Next Space Technology Exploration Partnerships (NextSTEP) award, announced on March 31, 2015, and now enter the execution phase of the project.The parties executed the contract, a three-year, fixed price agreement, on August 7, 2015 for a total value of just over $9 million. The agreement is structured as a one-year contract with two additional one-year extensions based on the accomplishment of mutually agreed upon progress milestones.NASA's Advanced Exploration Systems Program sponsors NextSTEP awards in a 50/50 cost partnership with industry. Under this award, Ad Astra will conduct a long duration, high power test of an upgraded version of the VX-200TM VASIMR prototype, the VX-200SSTM (for steady state), for a minimum of 100 hours continuously at a power level of 100 kW. These experiments aim to demonstrate the engine's new proprietary core design and thermal control subsystem and to better estimate component lifetime. The tests will be conducted in Ad Astra's large, state-of-the-art vacuum chamber in the company's Texas facility.Since its inception in 2005, Ad Astra has continued to advance the technology readiness level (TRL) of the VASIMR engine almost exclusively with private funding. This funding enabled the company to complete more than 10,000 successful high power firings, demonstrating the engine's excellent reliability and performance (6 N thrust, 5000 sec Isp at greater than 70% efficiency) with no measurable signs of engine wear.To optimize company resources, these tests were of short duration (less than 1 minute), but sufficiently long to reliably establish the rocket's performance and measure thermal loads. Now, a longer duration test is needed to validate the new rocket core design for extended operation in space. Going forward in partnership with NASA under the NextSTEP award, Ad Astra continues the technology maturation of the VASIMR to a TRL level greater than 5, a step closer to flight."We are proud of our accomplishments and thrilled by this announcement, which gives us a big boost toward space," said Dr. Mark D. Carter, Ad Astra's Sr. VP, Technology Development. "I am proud to be a be part of this project, an example of a progressive commercial-NASA partnership, seeking to advance the United States' electric propulsion capability for the future of spaceflight," said Dr. Jared P. Squire, Ad Astra's Sr. VP, Research. Drs. Carter and Squire are leading the project at Ad Astra as Principal and Co-Principal Investigators respectively.ABOUT THE TECHNOLOGYShort for Variable Specific Impulse Magnetoplasma Rocket, VASIMR works with plasma, an electrically charged gas that can be heated to extreme temperatures by radio waves and controlled and guided by strong magnetic fields. The magnetic field also insulates nearby structures so exhaust temperatures well beyond the melting point of materials can be achieved. In rocket propulsion, the higher the temperature of the exhaust gases, the higher their velocity and the higher the fuel efficiency. Plasma rockets feature exhaust velocities far above those achievable by their chemical cousins, so their fuel consumption is extremely low.
Does NASA have a use for the VASIMR in mind?Or is this a general research project?
This is a very controversial proposition and we're going to debate it. And, I must say, that both sides here are to be congratulated for having the integrity and courage to come out and defend their point of view in clear and open debate face to face. [Applause] Because we've had too much in the space business of people going around saying stuff behind other people's back and not coming out in the open to say it openly and confront it. Or other people saying things openly to the press but not being willing to come and defend their point of view. We of course had the incident of Franklin Chang Díaz saying very detrimental things, that radiation is a show stopper on the way to Mars so we must go to Mars much quicker than is currently possible and only the VASIMR drive can enable this and thus you can't go to Mars until the Warp VASIMR is developed and you can't do your program until we do his program. And he's been challenged to come and defend these statements repeatedly and not done it, which should tell you something that not only are his statements not defensible, but he doesn't consider them defensible.In this case one of these two parties are wrong. [Laughter] But they're honest and they're willing to come out and say it.