Magnet Enhanced Aerocapture Would Enable 39 Day Mars Crewed Flights

Direct comparisons were made between aerocapture and competing orbit insertion techniques based on state-of-the-art and advanced chemical propulsion, solar electric propulsion, and aerobraking.

Aerocapture is enabling for three missions: delivery of spacecraft into elliptical orbits at Neptune and circular orbits at Jupiter or Saturn. Aerocapture significantly enhances five other missions by putting larger, and usually very much larger, spacecraft into the target orbit for approximately the same overall delivery cost as the best non-aerocapture alternative: delivery of spacecraft into Venus circular orbits (79% more mass), Venus elliptical orbits (43%), Mars circular orbits (15%), Titan circular orbits (280%), and Uranus elliptical orbits (218%).

Aeroassist orbit transfer at Earth showed that aerocapture technology offered a 32% cost per kg reduction compared to chemical propulsion.

A previous study showed that aerocapture at Neptune requires a lift-to-drag (L/D) ratio between 0.6 and 0.8 to fly a tight entry corridor to achieve orbit insertion. Since traditional 70-deg sphere-cone planetary entry vehicles can only achieve a maximum practical L/ D of ~0.25, a special Neptune orbiter concept was developed. A 2004 study showed that current thermal protection system (TPS) technologies, even when applied in large quantities over most of the entry vehicle, will not survive the heat pulse for Neptune entries. The latest advances in TPS will not survive either.

NASA has funded work to improve aerocapture that may address both the L/D and TPS issues for Neptune and other missions at these high entry velocities. Based on our past study on MHD aerospace applications, as well as on other early studies, our expectations are that a magnet placed near the nose of the vehicle will increase the bow shock stand-off distance, substantially decrease stagnation point heat flux, and considerably mitigate the TPS requirements for such missions. Likewise, our preliminary analysis shows that magnets placed on the side of the vehicle nose will produce side forces for increasing lift (and thus L/D).

This approach leverages our vast experience in entry systems, rocket and vehicle design, mission architectures, and mission analysis tools, specifically for Entry, Descent, and Landing (EDL) simulations to conduct trades that include vehicle design, atmospheric modeling, and interplanetary trajectories. Science instrument missions to the Ice and Gas Giants could fly larger payloads with faster trip times. Human-scale payload missions to Mars and Earth Return would benefit from this system approach and enable fast crew flights lasting only 39 days (instead of 3 months or more) to slow down upon arrival at Mars. Such fast transits would serve to mitigate crew radiation exposure.

Additional goals of the proposed Phase 1 activity are to illustrate large reductions in TPS mass for aerocapture trajectories involving high hypersonic velocities, to eliminate the need for a separate deployable decelerator, and to show opportunities for reusable TPS during aerocapture (including for reusable upper stages), thus avoiding system complexities and mass required for integrating a separate TPS. Furthermore, this approach could be validated through a series of ground and near-term Earth flight test opportunities.

50 thoughts on “Magnet Enhanced Aerocapture Would Enable 39 Day Mars Crewed Flights”

  1. Death is your co-pilot when you try to climb the highest peak. We are going to lose people going to Mars. My suggestion is that they pack suicide pills.

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  2. I don’t see how that’s a better analogy, when you’d actually die faster on the Moon than Mars. And Mars needs less infrastructure to sustain life.

    Both destinations have their merits and demerits.

    The Moon:
    Merits: Relatively close, in terms of both delta V and trip time. This permits substantial teleoperation, and reduced travel costs. For some purposes, vacuum is helpful.
    Demerits: Dry as dust and depleted in carbon, month long “day”, gravity almost certainly too low for long term health. Likely no hydrothermal ore deposits.

    Mars:
    Merits: Relatively plentiful water and carbon, day length nearly the same as Earth, gravity *maybe* high enough for health, and hydrothermal ore deposits.
    Demerits: Relatively far away in terms of delta V and trip time. Though atmosphere for aerobraking reduces the delta V disparity substantially.

    Note, for some purposes, (Political independence, utility as a species “lifeboat”, the Moon’s proximity is actually a demerit. And if Mars’ gravity isn’t high enough for long term health, building huge centrifuges on the Moon is easier due to the lack of atmosphere.

    But, really, which is better depends on what you want to do.

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  3. You need to at least have enough delta V for course corrections. The more of that you have, the less precision you need at launch.

    I tend to think that achieving enough precision, WITH course corrections along the way, is feasible.

    The payoff of a rotovator at Mars’ end of things is much higher than at Earth’s end, because it spares you fuel you needed to bring to Mars. And because a rotovator is easier to pull off when you’ve already got a handy anchor.

    I don’t see much two way traffic for a long while. Isn’t Musk planning on using Starships near the end of their operational lives for the colonization trips?

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  4. The physics are super appealing. If you have two way traffic the rotorvator substitutes one largish mass (say at least 20 times the payloads) launched once, for effectively unlimited amounts of fuel use over the years.

    The devil is (as always with that sneaky bastard) hiding in the details. Just how easy is it to catch and release multiple parcels flying back and forth at kilometres per second? And release them with enough precision to hit a target zone at literally interplanetary distances?

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  5. No, I’m saying that nobody in their right mind would want to live anywhere but on Earth, and that bragging rights to say you’ve been to the Moon will be way expensive. The Moon does have one compelling attraction – you can look at the beautiful Earth from it. Mars has no drawcards at all. If you don’t like your government, change it – running away 100 million miles loses you every other thing humanity’s ever had. You’d have the freedom to freeze, to starve, and to get irradiated. The freedom to never feel the sun on your face, swim in the ocean, or watch a cloud.

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  6. So your saying that you want to keep Mars the place only rich people go and make sure all the peasants stay home so you can keep a eye on them so they know their place.

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  7. Yes they used that BUT the speeds coming into Mars from a high speed couple months journey to a 4 day journey around the moon are a different thing. Also a lot easier to hit the mark that way.

    Also heat shielding is insanely heavy

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  8. Apollo return capsules were using aerocapture – they hit the atmosphere and slowed down until they could use parachutes to slow further. So aerocapture is nothing new. To do something similar for Mars, you don’t need magnets – all you need is a shallower descent trajectory, but not so shallow that you skip off the top of the atmosphere.

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  9. The MHD approach for controlling a plasma flow around an aero shell allows for drag reduction and increased maneuvering capability. The ‘Rods of God’ could in theory be delivered by a sub-orbital trajectory launch and preserve their kinetic energy through control of a plasma shell formed around the device, as did the Soviet AJAX space plane prototype.

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  10. In the case of Mars, you’ve got those moons, not much more than captured asteroids, to anchor the rotovator to. That solves most of the momentum balancing problem, it would take a LOT of one-way traffic to shift their orbits enough to matter.

    Granted, there’s the issue of how to mount it without torquing the moon, but I’d say you could put two rotovators at opposite poles, and just load balance between them.

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  11. True, true, true.  There is a bit of a magic-wand feel to rotovators, though at this point. Its not like we have one … here, today, or on the books, for 2 decades away. Zubrinesque, still.

    Talk about built-in-bias! Until about a year ago, I had always salted away ‘rotovators’ to devices that’d spin in orbit around significant gravity wells (AKA planets and their moons); they’d snatch craft wishing a ride down, and decelerate them, or … vice-versa. Unusual but fairly widely discussed SciFi fodder. 

    I hadn’t considered that they might well be the answer to nearly-lossless interplanetary high-speed transport. I’m disappointed with myself, actually.

    Marvelous idea! Answers SO MANY THINGS that otherwise are ‘dirty’ chemical or ion reaction-mass thruster situations. Tell you what though… they’re not also without a set of wicked problems.  

    Every-action-garners-an-equal-and-opposite-reaction is one of Physics most demanding goddesses. Doesn’t matter how big the rotovator, capture (or release) one spacecraft, and the ‘vator’ goes the other way. IF trying to CATCH incoming whizzers, this could be some no-small-problem.  Its one thing to ‘miss by a few meters’. Another a few thousand or million kilometers.

    I guess the incoming would keep a bit of reaction mass aboard, to significantly last-minute-adjust flight plan.  

    Easy enough.  
    No pure solutions.
    Oh well.

    ⋅-=≡ GoatGuy ✓ ≡=-⋅

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  12. a) The risk to the heart is not well studied due to the limited sample size. Besides, those Apollo Astronauts all lived very long lives or are (still) doing just fine. Only two died in their sixties (not counting the ones who died during tests). You can check here: https://en.wikipedia.org/wiki/List_of_Apollo_astronauts

    b) Shielding against the majority of the spectrum of radiation incurred during solar storms is available in the form of water shelter. Apollo had no shielding, even ISS level shielding would have greatly reduced their exposure.

    c) only the neutral heavy nuclei are a problem, thin shielding and even small electric fields can take care of the rest.

    D) The risk of incurring cancer is only 3% higher when going on a 500 day roundtrip of which 300 days in space (this risk was measured using instruments that had no shielding. Add shielding and it would already be lower). So, when travelling only 35 days in space the risk has to be much lower (also less chance of accidently stumbling into a surprise solar storm).

    e) Solar storms follow a predictible cycle which has been studied. Nasa has a list of years when risk and intensity of storms is lowest (i.e. 2032-2033)

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  13. If you can use aerocapture, you can burn all your propellant blasting along like a maniac and achieve ludicrous speeds. If you need to save some fuel to slow down you can only achieve underwhelming speeds.

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  14. Pretty sure you need Rad shielding even in Mars orbit. IIRC Mars has little to no Magnetoshpere. That’s why there’s very little atmosphere.

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  15. Jennifer’s solution is totally compatible with the high Δv . Indeed it helps with the high Δv for the return journey.

    It does however assume that you are dealing with a target that has a large volume of interplanetary traffic (where large means enough to justify putting in a tether).

    As to how you send the tether to low Mars orbit? Well you can use aerobraking…

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  16. Oz is going fairly well ATM.

    Pleasant autumn weather, plague is [s]dying down[/s] errr… going away, and I’m averaging about 180 km a week on the bike(s).

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  17. A better analogy would be, the Moon is Antarctica, and Mars is the bottom of the ocean. A few researchers live on the one, and the other is reserved for a very few rich adventurers, and robots. In the movie, ‘ The Martian ‘, the Americans go to inordinate trouble, and the Chinese throw away a scientific mission, just to save one man. Think how much more science they’d get done without having to haul these fragile, demanding bodies around ? Keep them safe in Mission Control, where they can play with their kids after the shift, and let robots, specifically optimised for the task, perform it. Without the need for radiation shielding, or stopping the crew getting bored after a few months on freeze dried food, you could send far more payload. If it burnt up trying to aerobrake, well, it’s all useful experience.

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  18. I fully agree with your ‘back-of-the-mind’ concern, Jennifer. Yet, as i understand how The Physics works, if you are going to get there quickly, then that — without exception — means your Δv needs to be fairly high in order to traverse “the gap” in minimal time.  

    Remembering Tsiolkovsky’s Rocket Equation:

    Δv ≈ G₀ ISP ln( M / m );  where
    G₀ → 9.81 N/kg … Earth gravity
    ISP → ‘seconds’ in rocket science units

    Mnemonically, it is also (Δv = exhaust-velocity × ln( start mass / end mass );)  

    IF one considers ‘doing the trip fast’, then not only does ISP (or exhaust velocity) need to be as high as reasonable, but the ‘start mass’ and ‘end mass’ must be quite a large proportion different.  

    For instance, with ‘nice’ xenon ion exhaust delivering ISPs around 2,500 or so, and figuring that maybe 70% of the spacecraft mass is Xenon:

    Δv = 9.81 × 2,500 × ln( 1 / (1 – 0.7));
    Δv ≈ 30,000 m/s

    Just about right for our intrepid 39 day to Mars pod!  Yet, if that pod is actually substantial in mass, then it carries

    E = ½mv²
    E = ½ (1 kg) 30,000²
    E = 450,000,000 J per kg

    of kinetic energy that needs to ‘burn off’ one way or the other. Moreover, if the total energy is 2.7x to 3.2x greater than that, 1.2 GJ/kg to 1.5 GJ/kg needs to be supplied from some really energetic source, while accelerating away.  

    Earth based orbital Lasers?  
    Makes the most sense. 

    ⋅-=≡ GoatGuy ✓ ≡=-⋅

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  19. The NASA research unit near Cleveland, Ohio examined magnetic manipulation of the atmospheric plasma surrounding a vehicle at reentry velocities for various purposes. Look for Dr. Isaiah Blankson’s work back a bit more than two decades ago.

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  20. A 39 day journey to Mars would still require a substantial amount of radiation shielding since you have to protect the brains and the hearts of astronauts from the– heavy nuclei– component of cosmic rays. Plus you have to protect them from potential solar storms during the journey.

    Even the Apollo astronauts appear to have incurred more heart damage traveling just a few days beyond the Earth’s magnetosphere than astronauts on multi-month missions under the protection of the Earth’s magnetosphere in Low Earth Orbit.

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  21. Maybe it something wrong with me but I feel it’s a waste of energy dumping all that expensive kinetic energy into heat. A momentum exchanging rotovator that slows down incoming stuff and reuses the energy for outgoing stuff at nearly full efficiency is kind of attractive. Not much sci-fi high-tech either. Just a resilient tether and high precision navigation and timing. Wouldn’t that be nice for earth/mars or earth/moon infrastructure where there is significant two-way traffic?

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  22. You could also use this tech to take 6 to 9 months to get to Mars & send a more massive spacecraft for the size of the rocket used to launch it.
    Of course testing the technology should be done with Earth’s atmosphere. It would be really useful for returning from the moon.

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  23. Your backup plan is to die. You know, just like it is if your main engine doesn’t work for the insertion burn at the other end of the trip?

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  24. You know its not the purpose of the article, but it inspired me to have the idea that you could use a conductive web to slow down on planets with a magnetic field. Like the electromagnetic tether deployed from the space shuttle but made into some kind of inflatable web and controls for stabilization.

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  25. We went to the moon; never went back. Why, other than pure science, is there such a dream to get to Mars? Don’t say Tang 2.0.

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  26. This also assumes that you use your reaction mass in the transit vehicle. In the potential timeframe when this is relevant you may have a mass driver on Luna, an orbital slingshot, or possibly the USS Gerald Ford’s electric catapults might work.
    The magnetic shielding of the vehicle’s occupants might be an issue.

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  27. Yes, it’s very important that your warhead has decelerated to non-damaging velocities before it vapourises its target.

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  28. Mmmm… 
    Mmmmmmm….
    M…..

    OK, that’s a really good suggestion. 
    As always, hoping things are going Well in Auz, mate.

    ⋅-=≡ GoatGuy ✓ ≡=-⋅

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  29. A stylistic note: Maybe avoid using N as a variable when describing equations about force and acceleration. (also avoid v, a, T, t, m, g and probably c)

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  30. Is this any different from any other form of velocity change? Are any proposed space missions equipped with backup drives? Spare solar sails? Extra ion drives?

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  31. Well, tho’ the whole article is a bit far-fetched, that IS the idea here. 

    You expend a lot of fuel and/or reaction mass to speeding toward the destination. Then there, your spacecraft emits a magnetically bound plasma that interacts with the atmospheric plasma generated by its hypersonic passage. Done in the way the researchers envision, the magnetic field blooms out the plasma into a substantial slowing-force.  

    Maybe it isn’t quite a ‘one pass = injection’.  
    Maybe it takes a few passes. 
    But even so, it perhaps is the least-time-to-transit solution.  

    There remains the problem of tightening up the “expend fuel at such a rate that it only takes 39 days to traverse 80 million kilometers”. That’s 2 million a day, or 85,000 km/hr, or nearly 24 km/sec. In terms of ‘invested energy dynamics’, at its most efficient, rocketry cannot deliver ‘N’ joules of spaceship speed without expending about 2.7⋅N joules of reaction-mass thrust energy.  

    Each kilogram of not-yet-space-junk heading toward Mars at 24 km/s … 

    E = 2.7( ½ mv² )
    E = 1.35 × 1 kg • (24,000 m/s)²
    E ≈ 750,000,000 J/kg.

    That turns out to be a lot of energy. A ton of TNT holds 4.186×10⁹ J, so 0.75×10⁹ (above) is what, about ⅕ a ton of reaction-mass-and-its-energy per kg of heading-toward-Mars spacecraft?

    Or, upside down, ⅕( 1000 kg ÷ 1 kg) = 200× the drifting-toward-Mars mass in fuel-and-expelled-other-airframe mass.  

    Wow.
    Just Wow.

    ⋅-=≡ GoatGuy ✓ ≡=-⋅

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  32. Not exactly true. Your speed on arrival is usually less than your speed when you left. The Earth’s gravity well is deeper than the Moon’s or Mar’s.

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  33. I have always thought areobraking was the way to go. Especially for a manned mission with a return to earth. Areobraking on the trip out and on the trip back would reduce the delta V needed and the expense.

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  34. I’m assuming the idea is aero braking vs burning propellant to slow down on arrival. If you’re going to the moon or an airless planet you have to expend about as much propellant to slow down as to speed up. You have to speed up all that extra (Braking) propellant too. If you can count on aerobraking you can put your whole budget into speeding up and get there faster. If you get the calculation a little bit wrong though you miss and keep going or burn up or slam into the destination.

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  35. I have seen a lot of strange articles here but this takes the cake. What does aerocapture – orbital braking insertion technology/procedures have to do with getting to mars in 39 days?

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  36. It’s easy to get to mars in 39 days if you don’t mind making a giant crater on mars by skipping the step of slowing down the spacecraft before landing,,, think of all the fuel And time you can save by not slowing down before landing,,,

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