Researchers propose ballistic capture as cheaper path to Mars

December 24, 2014 by Bob Yirka report
Structure of the ballistic capture transfers to Mars. Credit: arXiv:1410.8856 [astro-ph.EP]

(Phys.org)—Space scientists Francesco Topputo and Edward Belbruno are proposing in a paper they have written and uploaded to the preprint server arXiv, the idea of using ballistic capture as a means of getting to Mars, rather than the traditional Hohmann transfer approach. They suggest such an approach would be much cheaper and would allow for sidestepping the need for scheduling launch windows.

The traditional way to get to Mars is to calculate where the planet is going to be at a certain point in time and then launching a rocket to get there at the same time—this is known as the Hohmann transfer approach and it involves using retrorockets upon arrival to slow down as the rocket is sent as quickly as possible during its trip. Those retrorockets use up a lot of fuel which makes travel to the Red planet bulky and expensive. The Hohmann transfer approach also involves scheduling during optimal launch windows—when the Earth and Mars are closet together, which can also cause problems if there is a delay for any reason—having to wait for another can mean waiting up to two years. In their paper, Topputo and Belbruno suggest taking another approach altogether—instead of aiming for the planet directly, they suggest aiming for a spot ahead of the planet in its orbit around the sun and waiting for the planet to catch up—an approach known as ballistic capture.

Ballistic capture would eliminate the need for retrorockets, making a mission to Mars much cheaper—but it would also add months to the trip, which could be a problem for manned missions. For that reason, the researchers suggest it might best be used to send unmanned vehicles to the planet, some for observation and scientific purposes, others to send gear for use by humans once they arrive. Because such missions would not be time critical, they could be launched anytime, avoiding the necessity of launching during launch windows.

One drawback of the ballistic capture approach is that it does not lead to low orbit around the target planet—some sort of propulsion would still be needed to move into an orbit low enough for scientific study, or to get down to the surface itself. Such vehicles could carry some fuel for that purpose, the researchers suggest but it wouldn't take nearly as much as retrorockets used in the Hohmann transfer. The two are working with NASA contractor Boeing Corporation to further develop the idea to see if it might be feasible.

Explore further: Image: Kaleidoscopic view of Mars

More information: Earth—Mars Transfers with Ballistic Capture, arXiv:1410.8856 [astro-ph.EP] arxiv.org/abs/1410.8856

Abstract
We construct a new type of transfer from the Earth to Mars, which ends in ballistic capture. This results in a substantial savings in capture Δv from that of a classical Hohmann transfer under certain conditions. This is accomplished by first becoming captured at Mars, very distant from the planet, and then from there, following a ballistic capture transfer to a desired altitude within a ballistic capture set. This is achieved by manipulating the stable sets, or sets of initial conditions whose orbits satisfy a simple definition of stability. This transfer type may be of interest for Mars missions because of lower capture Δv, moderate flight time, and flexibility of launch period from the Earth.

via SciAm

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15 comments

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tadchem
4.3 / 5 (6) Dec 24, 2014
The catch is in the energy of the rocket. On Earth it has enough energy for an orbit matching the Earth's at 1.0000 AU (semimajor axis). To get to Mars it needs the energy for an orbit with 0.9833 to 1.0167 AU perihelion and 1.3814 to 1.660 AU aphelion. To land on Mars it needs to match it's orbital energy to that of Mars at 1.523679 AU (semimajor axis). Once it has matched orbits with mars it needs rockets only to compensate for the gravitation energy acquired during descent.
The minimum energy requirement is fixed by the orbital mechanics. The main difference is in how you aim it.
Torbjorn_Larsson_OM
5 / 5 (6) Dec 24, 2014
Or looked at from other perspectives:

- The Red Dragon approach is likely the cheapest way to land on Mars, and Mars is made for it due to its vast northern lowland. That approach can land any mass that is cylinder or capsule shaped from any interplanetary speed by using a Shuttle aerodynamic trajectory control. The propose to use the control surface (a side of the craft) to _dive_ as fast as possible to within hugging distance to the lowland surface. That places it at Apollo pressure regime braking, but uses Shuttle control algorithms to avoid the skips.

That means 2-3 minutes at 6 g until they drop out of the control regime at 2-4 Mach. Then they fire up the retrorockets to make a hover slam landing at about the same initial accelerations.

That means ballistic capture is fuel expensive in comparison.

[tbctd]
Torbjorn_Larsson_OM
5 / 5 (6) Dec 24, 2014
[ctd]

- The transfer orbit injection energy demands scales quadratically with orbit velocity (inverse transfer time). Let us say SpaceX can make hoisting fuel to low Earth orbit inexpensive, and that they would like to make their colonization project as cheap as possible. That means keeping the fleet size down, meaning fast transfer orbits, to minimize ticket prize as scaling fuel tanks and adding retrofit engines is little cost.

Nevertheless, they have preliminary chosen to stay around the Hohmann once-every-two-years transfer windows, likely because fuel cost scales so badly.

That means ballistic capture doesn't necessarily open up the Hohmann windows much.

On the other hand it is another tool, and hopefully it can be used elsewhere. It looks to me to be perfect for orbiters in the rest of the solar system. Especially if people want to use SLS to speed up science returns.
Modernmystic
5 / 5 (4) Dec 24, 2014
I KNOW I sound like a broken record, I do know it....BUT how about using a nuclear rocket? We've had the technology since the sixties...we've even done a lot of the testing for them.

Sure there are dangers, but there are ways to minimize them. I don't think we're going to be able avoid using them at some point if we're serious about colonizing the entire solar system.
indio007
5 / 5 (2) Dec 24, 2014
I KNOW I sound like a broken record, I do know it....BUT how about using a nuclear rocket? We've had the technology since the sixties...we've even done a lot of the testing for them.

Sure there are dangers, but there are ways to minimize them. I don't think we're going to be able avoid using them at some point if we're serious about colonizing the entire solar system.


I hear you. We need to stop kidding ourselves about current methods of space travel.
Current methods are a known dead end.

shavera
5 / 5 (4) Dec 24, 2014
Modernmystic, indio: Well then you'll be delighted to know that NASA is very very seriously considering Nuclear rockets. Really. There's a lot of internal discussion around that topic these days. Believe it or not, NASA engineers are on the internet too. We see and hear the arguments made for such technologies...
Modernmystic
5 / 5 (2) Dec 24, 2014
Modernmystic, indio: Well then you'll be delighted to know that NASA is very very seriously considering Nuclear rockets. Really. There's a lot of internal discussion around that topic these days. Believe it or not, NASA engineers are on the internet too. We see and hear the arguments made for such technologies...


YESSSSssssssss!!

*fist pump*
gulfcoastfella
5 / 5 (1) Dec 24, 2014
"...this is known as the Hohmann transfer approach and it involves using retrorockets upon arrival to slow down as the rocket is sent as quickly as possible during its trip."

I'm pretty sure that the Hohmann transfer orbit involves speeding up upon arrival, not slowing down. Also, the Hohmann transfer is not the path which leads to the craft arriving "as quickly as possible."
mjesfahani
1 / 5 (1) Dec 25, 2014
I only suggest wormhole which is like a tunnel.
freeiam
1 / 5 (2) Dec 25, 2014
Modernmystic, indio: Well then you'll be delighted to know that NASA is very very seriously considering Nuclear rockets. Really. There's a lot of internal discussion around that topic these days. Believe it or not, NASA engineers are on the internet too. We see and hear the arguments made for such technologies...


Nice but we no longer wait for NASA to 'lead' the way, it's now in the hands of more capable (and willing) men.
gkam
2 / 5 (4) Dec 25, 2014
Nuclear rockets? What could go wrong?

Name the first one the Chernobyl.
gculpex
not rated yet Dec 26, 2014
I guess we'll have to make a better way......

Space: 1999 is the story for me.
nevermark
3.7 / 5 (3) Dec 26, 2014
Nuclear rockets? What could go wrong?


gkam, your open question could have applied equally well to many initially dangerous technologies that became safe over time. Fortunately, progress on nuclear power safety, like everything else, continues to improve.
Agomemnon
5 / 5 (2) Dec 26, 2014
perfect for sending robots to mars
TheGhostofOtto1923
3.7 / 5 (3) Dec 26, 2014
I KNOW I sound like a broken record, I do know it....BUT how about using a nuclear rocket? We've had the technology since the sixties...we've even done a lot of the testing for them.

Sure there are dangers, but there are ways to minimize them. I don't think we're going to be able avoid using them at some point if we're serious about colonizing the entire solar system.
From a 2009 physorg article

"Perminov said the nuclear spaceship should be used for human flights to Mars and other planets. He said the project is challenging technologically, but could capitalize on the Soviet and Russian experience in the field.
Perminov said the preliminary design could be ready by 2012, and then it would take nine more years and cost 17 billion rubles (about $600 million, or euro400 million) to build the ship."
http://phys.org/n...450.html

-Did you look?

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