New research seeks to optimize space travel efficiency

April 18, 2018, University of Illinois at Urbana-Champaign
Koki Ho, assistant professor of aerospace engineering at the University of Illinois. Credit: University of Illinois Department of Aeropspace Engineering

Sending a human into space and doing it efficiently presents a galaxy of challenges. Koki Ho, University of Illinois assistant professor in the Department of Aerospace Engineering, and his graduate students, Hao Chen and Bindu Jagannatha, explored ways to integrate the logistics of space travel by looking at a campaign of lunar missions, spacecraft design, and creating a framework to optimize fuel and other resources.

Ho said it's about finding a balance between time and the amount of —getting there fast requires more fuel. If time isn't an issue, slow but efficient low-thrust propulsion might be a better choice. Taking advantage of this classical tradeoff, Ho noted that there are opportunities to minimize the launch mass and cost when looking at the problems from a perspective—multiple launches/flights.

"Our goal is to make efficient," Ho said. "One way to do that is to consider campaign designs, that is, multiple missions together—not just launching everything from the ground for every like Apollo did. In a multi-mission campaign, previous missions are leveraged for subsequent missions. So if a previous mission deployed some infrastructure, such as a propellant depot, or if work had begun to mine oxygen from soil on the moon, those are used in the design of the next mission."

Ho used data from previously flown or planned missions to create simulated models of a combined campaign. The can be modified to include heavier or lighter spacecraft, a specified set of destinations, the precise number of humans on board, etc., to validate his predictions about the efficiency.

"There are issues with the sizing," Ho said. "In our previous studies, in order to make the problem efficiently solvable, we had to use a simplified model for the vehicle and infrastructure sizing. So creating the model was fast, but the validity of the model wasn't as good as we desired."

In one of the current studies, Ho and his colleagues addressed the fidelity issue in these previous simplified models by creating a new method to consider more realistic mission and vehicle design models while maintaining the mission planning computational load at a reasonable level.

"In this research we are designing the vehicles from scratch so that the vehicle design can become part of the campaign design," Ho said. "For example, if we know we want to send a human into space Mars by the 2030s, we can the vehicle and plan the multi-mission campaign to achieve the maximum efficiency and the minimum launch cost over the given time horizon."

Ho's research also incorporates the concept of propellant depots in space, like strategically located truck stops on a turnpike. He said it is an idea that has been tossed around for a while among scientists. "There are questions about how efficient the depots actually are," Ho said. "For example, if it takes the same or more amount of propellant just to deliver the depot then what's the point of sending it ahead?"

Ho's studies provide one solution to this question by leveraging a combination of high-thrust and low-thrust propulsion system.

"A preparatory mission might be conducted beforehand to deliver into orbit mini-space stations that store fuel, cargo, or other supplies," Ho said. "These craft can be pre-deployed so they are orbiting and available to a manned spacecraft that is deployed later. The cargo/fuel space craft can make use of low-thrust technologies because the time it takes to get to its destination isn't critical. Then for the manned spacecraft, we'd use high-thrust rockets because time is of the essence when putting humans in space. This also means that because the fuel is already at these stations, the actual manned ship doesn't have to carry as much fuel."

Explore further: Engineering team proposes storing extra rocket fuel in space for future missions

More information: Bindu B. Jagannatha et al, Optimization of In-Space Supply Chain Design Using High-Thrust and Low-Thrust Propulsion Technologies, Journal of Spacecraft and Rockets (2018). DOI: 10.2514/1.A34042

Hao Chen et al. Integrated Space Logistics Mission Planning and Spacecraft Design with Mixed-Integer Nonlinear Programming, Journal of Spacecraft and Rockets (2017). DOI: 10.2514/1.A33905

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granville583762
1.9 / 5 (9) Apr 18, 2018
And how are we going to do that, it takes a week to the moon and a year to mars, rockets are completely inadequate, which is why we are stuck on this planet. All were doing is finding ways to ensure we're efficiently stuck on this planet.
Da Schneib
4.7 / 5 (3) Apr 18, 2018
A crucial component is sensors to ensure that the expected supplies are present and viable, or are being stocked at the expected rate.

Robots, in other words-- noting the present articles on this subject on the site.

A lot of missions are going to depend on robots that have gone before and prepared the ground.
Mark Thomas
3.2 / 5 (9) Apr 19, 2018
""There are questions about how efficient the depots actually are," Ho said. "For example, if it takes the same or more amount of propellant just to deliver the depot then what's the point of sending it ahead?"

The point is very simple. The faster we get our people to Mars, the less time they spend getting irradiated in interplanetary space and more time they have to get work done once they arrive.

The fastest way to Mars is to arrive with only a safety margin of fuel left and refuel in Martian orbit. That way we don't have to accelerate and decelerate all the fuel necessary for the return to Earth. We can either transport the fuel to Mars orbit in advance using solar-electric propulsion or possibly make it on Mars or its moons.

If we drive our interplanetary spacecraft fast enough, a single reusable interplanetary spacecraft could maintain a permanent human presence on Mars by dropping some people off and picking some people up every Martian opposition, i.e., ~26 months.
granville583762
2.3 / 5 (9) Apr 19, 2018
Were living in Cloud cuckoo land
unless we transport an armada of equipment to mars no one is going to stand the weekend out never mind mars radiation, 26 months for the resupply ship. Its not a carribean island, were living in Cloud cuckoo land
The fastest way to Mars is to arrive with only a safety margin of fuel left and refuel in Martian orbit. That way we don't have to accelerate and decelerate all the fuel necessary for the return to Earth. We can either transport the fuel to Mars orbit in advance using solar-electric propulsion or possibly make it on Mars or its moons.

If we drive our interplanetary spacecraft fast enough, a single reusable interplanetary spacecraft could maintain a permanent human presence on Mars by dropping some people off and picking some people up every Martian opposition, i.e., ~26 months.

Rockets are completly inadequate!
ShotmanMaslo
5 / 5 (3) Apr 19, 2018
It only takes 3-5 months to get to Mars, assuming refueling in Earth orbit. Not a short journey but certainly doable.
ShotmanMaslo
5 / 5 (3) Apr 19, 2018
unless we transport an armada of equipment to mars no one is going to stand the weekend out never mind mars radiation, 26 months for the resupply ship.


Radiation is an issue while in space, but once on Mars you can live underground. Several meters of soil is enough to bring the radiation down to Earth-like levels.

The fastest way to Mars is to arrive with only a safety margin of fuel left and refuel in Martian orbit.


Actually the fastest way may be to use aerobraking instead of stopping in Mars orbit.
rrwillsj
2.1 / 5 (9) Apr 19, 2018
Well finally! Somebody planning ahead and recognizing the importance of logistics.

Developing and Pre-Positioning an infrastructure using robots, drones and automated processing is the only sensible way to prepare for Human space travel.

Organization is necessary for any large-scale exploration of the Solar System.

However, I remain the village atheist about the probability of successful inter-planetary Human colonization.

For those of you who take offense at an honest evaluation of known and proven capabilities?

Realistically, your ambitions would only progress upon a strong foundation of robotic preparation.

Allowing you the time to crowdsource your funding. While you develop your Super-Duper Captain WhizBang Miracle Anti-Thermodynamical Space Drive.

For your marketing. I would generously offer calling your planned colony 'New Jamestown' or 'New Roanoke' or 'New Plymouth'?

Yes Siree! Homo Anthropophagus bravely marching to the stars!
Mark Thomas
2.6 / 5 (8) Apr 19, 2018
Actually the fastest way may be to use aerobraking instead of stopping in Mars orbit.


Of course you may be right, but I see no point in splitting hairs here, the important thing is to save months, not hours. Note that it may be possible to use aerobraking for both the interplanetary spacecraft and the Mars lander.

rrwillsj and granville, NASA and SpaceX both say we can reach Mars with chemical propulsion. Far be it from me to disagree. I would only argue that nuclear thermal propulsion of the type mostly developed by the U.S. and Soviet Union in the last century would be far more efficient. Mars is relatively close and no SDCWBMAT Space Drive is necessary to reach it. If you want to shave time off the trip to Mars you need more delta V, which means more chemical fuel (or propellant for an NTP). The media seems to have missed the fact that the successful Falcon Heavy launch this year means launching that fuel is now a fraction of the cost is was before SpaceX.
Mark Thomas
2.4 / 5 (7) Apr 19, 2018
However, I remain the village atheist about the probability of successful inter-planetary Human colonization.


If you are the atheist, I suppose that makes me the true believer. However, I respect healthy skepticism because that is fundamental for science, and it keeps us on our toes.

My journey began with a hard look at the technological and biological issues that confront us in getting to Mars. After decades of considering and reconsidering this question, I KNOW we can reach Mars from my brain to my bones. For me, this is no longer a 99% certainty thing. I am 100% certain we can reach Mars if we put our collective minds to it. Once we reach Mars, it is not much of a stretch to conclude that some level of colonization is possible. We have already debated about how far that is likely to go. I see Mars being terraformed, perhaps all the way to breathable atmosphere, but at least to the point where pressure suits are no longer required.
Da Schneib
5 / 5 (4) Apr 19, 2018
No matter what the mission profile is, it's unquestionable that sending supplies ahead by a lower energy orbit saves money and fuel over the whole mission, and mission time for the human-occupied mission. Any ability to generate resources from locally available materials is bonus.

Sounds like better efficiency to me. And that's the point of this article, I think.
granville583762
3 / 5 (8) Apr 19, 2018
It takes rocket propelent to lift the nuclear powered propulsion engine

Can a nuclear powered rocket take of from planet earth and land on mars or does it take a rocket spewing rocket propellant to lift the nuclear powered propulsion enigine
Mark Thomas > I would only argue that nuclear thermal propulsion of the type mostly developed by the U.S.

Why pussy foot round the problem, use Newtons laws of acceleration , momentum and inertia - no need to worry over radiation or constantly replacing ejected rocket propellant.
Whydening Gyre
5 / 5 (3) Apr 19, 2018
No matter what the mission profile is, it's unquestionable that sending supplies ahead by a lower energy orbit saves money and fuel over the whole mission, and mission time for the human-occupied mission. Any ability to generate resources from locally available materials is bonus.

Sounds like better efficiency to me. And that's the point of this article, I think.

Just do what the airlines do...
rrwillsj
1 / 5 (5) Apr 19, 2018
What means is eventually chosen it will be the robot-built infrastructure that will make your success. And it is Human nature that will be the ruin of your expedition.

Mark in general I agree with your projection for inter-planetary transport. Except for your opinion that the issues for biological survival is space have been resolved.

No, no, and yes, NO!

There is absolutely no evidence for long-term biological survival beyond the Earth's Mesosphere. Baby-steps here. Cause real babies lives will be at stake!

Please, you scientific boffins correct me if I am wrong.

The faster you travel in Space? The harder the debris and radiation will strike your vehicle? The greater the cascade of secondary-radiation within your hull?

So to have enough mass to sufficiently shield the craft interior will require magnitude more accelerant?

And cheaper? Now we're approaching fantasy-land. Bite the bullet and admit the fortunes needed to accomplish your stated goals.

Whydening Gyre
5 / 5 (3) Apr 19, 2018
What means is eventually chosen it will be the robot-built infrastructure that will make your success. And it is Human nature that will be the ruin of your expedition.

And we've done a pretty good job of it so far. On this expedition, anyway...
granville583762
2.7 / 5 (7) Apr 20, 2018
Every one is missing the the vital point, rockets whether there spewing rocket propellant or nuclear propellants are totaly inadequate because a point is reached when the ballon is finaly deflated, travelling to space is not like some rocket propellant community, whats stopping everyone from applying Newtons laws of acceleration , momentum and inertia now we have got over our little angst that Newton is for little children.
Mark Thomas
3.4 / 5 (10) Apr 20, 2018
Except for your opinion that the issues for biological survival is space have been resolved.


I have read that the radiation issues are manageable for a trip to Mars This is the conclusion of experts, but spending less time in interplanetary space and more time in a protective structure on Mars would help. Can you support your opinion it is not survivable?

granville, you are not making any sense at all. Newton's Second Law gives us f = ma. Rockets are required to provide f. Would people expend so much time and effort to build rockets if we had much easier ways to get to space? Of course not.
rrwillsj
2.1 / 5 (7) Apr 20, 2018
Granville, congratulations on your inventive spirit.

How soon will you have a working prototype of your launch system/space drive available for analysis?
rrwillsj
1.7 / 5 (6) Apr 20, 2018
Mark, I'll bet we are reading the same material and drawing diametrically opposite conclusions.

Of course that does not make your opinion wrong. Neither does it mean that my opinion is correct.

One important point. space travel faces a number of dangers. And they are cumulative in scope.

Recent publications of micro-to-zero gravity health risks.
https://medicalxp...ars.html

for the helth issues from known radiation sources https://en.wikipe...mic_rays

I posted that wikiarticle because it includes a number of sources from NASA and other relevant research programs. So I needn't repeat those source material.

One issue not really covered by this wikiarticle is secondary radiation cascading throughout the hull and interior.

Such secondary material should be available from the SEC and research into nuclear reactors and weaponry production programs.

- cont'd -
rrwillsj
2 / 5 (8) Apr 20, 2018
- cont'd -
The wiki article mentioned the concern about cataracts afflicting space travelers.

SAC aircrews would wear a lead eyepatch. If blinded by a nuclear blast, they could just move the patch over and continue their mission.

Today, it would be a sensible precaution that deep space voyages are equipped with devices including auditory and tensile feedback. Just in case the crew was blinded by radiation or hypoxia. Ain't no tow service available that far off the main highway!

I think physical shielding is not a viable means of protecting biological functions. Maybe a double hull? Dump the contaminated outer hull for the return voyage?

I think though that some sort of EM field that can shunt aside incoming radiation (& maybe small debris?) away from the craft. Will be needed.

Being able to re-direct the impact might even contribute a modest boost to the vessel's delta/V?

Of course they'd have to be pretty damn careful where they aimed the plume.

Mark Thomas
2 / 5 (6) Apr 20, 2018
I think though that some sort of EM field that can shunt aside incoming radiation . . .


Agreed, and a good place to find the electrical energy needed to generate a strong EM field to deflect most of charged particle radiation is a nuclear reactor. A nuclear thermal propulsion rocket can double as an electric generator, i.e., bimodal. That way there is plenty of electrical power for sustained EM shielding. Electricity can be generated with Stirling engine.

I don't have time to go through everything else at the moment, but suffice it to say I agree radiation may be the most important consideration, but not the only one. I believe you would agree the faster we get our astronauts through interplanetary space, the better. I would like to see the journey cut down to 1.5 to 3 months each way max, depending on the particular Mars opposition the mission is being launched on. The distances vary a lot.
Mark Thomas
2 / 5 (6) Apr 20, 2018
The number of variables for designing a Mars mission, including unknowns, is daunting, to say the least. One place to start is with the minimum number of interplanetary spacecraft necessary to sustain a permanent crewed Mars base. Mathematically, the minimum number is one. Now design a Mars program around that and compare against all other Design Reference Missions, etc. When you start to compare with other possibilities, you may conclude this is highly effective approach that maximizes the time on Mars while minimizing the risks associated with travel through interplanetary space.

In short, we need a reusable, nuclear-powered, interplanetary spacecraft capable of reaching Mars in no more than ~3 months. This spacecraft should be designed to go from Earth orbit to Mars orbit and back (no landings) every Mars opposition. We can probably begin a Mars program without this, but before long the advantages to this approach will become apparent.
rrwillsj
1 / 5 (5) Apr 22, 2018
This just in: https://phys.org/...ipe.html

In the comments I opinionated why I think this article is important for planning manned space missions. And facing the multitude of risk-factors establishing bases inside asteroids or utilizing caves on Luna or Mars.
granville583762
3 / 5 (6) Apr 25, 2018
rrwillsj> Granville, congratulations on your inventive spirit.

How soon will you have a working prototype of your launch system/space drive available for analysis?

rrwillsj:- it seems congratulations returned as your the first to recognise what is written in Newton's laws It's that time in propulsion to step up a gear because we're looking hungrily at the planets with no way at the moment of reaching them!
flueninsky
2.5 / 5 (8) May 20, 2018
Mark Thomas> rrwillsj and granville, NASA and SpaceX both say we can reach Mars with chemical propulsion. Far be it from me to disagree. I would only argue that nuclear thermal propulsion of the type mostly developed by the U.S. and Soviet Union in the last century would be far more efficient. Mars is relatively close and no SDCWBMAT Space Drive is necessary to reach it. If you want to shave time off the trip to Mars you need more delta V, which means more chemical fuel (or propellant for an NTP). The media seems to have missed the fact that the successful Falcon Heavy launch this year means launching that fuel is now a fraction of the cost is was before SpaceX.

It is possisble to reach Mars, but given time so can a snail.

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