15 Days to Mars - Any Propulsion Method

tahanson43206 · Yesterday 21:02:10

In another topic in this category, PhotonBytes introduced a topic with the intriguing goal of showing that it might be possible to move a payload between Earth and Mars in 15 days, using chemical fuel. That proposition is certainly interesting and I am hoping that our members will study the idea to see if it is permitted by the Real Universe.

However, the basic idea, of a 15 day transit from Earth to Mars in 15 days would appear to be permitted in the Real Universe.

This topic is offered for NewMars members who would like to show us how it might be done.

The conditions to be met, for a demonstration of feasibility, are going to be reasonable.

We will start from LEO, and consider the flight a success when the vessel is safely in LMO.

To make the exercise realistic, I will specify that the payload to be delivered to LMO is 100 metric tons.

The mass of the vessel when it arrives at LMO is up to the contributor, but it needs to be reasonable/plausible.

The time frame for this flight is 15 days, from LEO to LMO.

Because Mars and Earth are varying distances apart, I'll provide a specific distance to be covered as 120,000,000 km.

Mars is 121,047,586 km away from Earth at 3:23:02 UTC on 2025/02/22. The two planets approached each other as close as they will get a week or two ago, in this cycle.

My guess is that there exists no technology able to perform this feat at present.

However, it should be possible for someone to work out the energies required, and to speculate on how a future technology might work.

It would be helpful if contributions were shown to adhere to the physics we can all agree upon.

This could be a very interesting topic for future readers, if our members have the time and energy to invest.

An optional detail that would be welcome is the G force to be experienced by the vessel during the flight.

(th)

tahanson43206 · Yesterday 21:07:03

This post is reserved for an index to posts that may be contributed by NewMars members over time.

It would help me greatly to update the index, if our contributors were to include a one line summary of the post. This is the first time I have asked for help with the index idea, but I am finding it difficult to keep up with our members as they add new content to the topics where index posts are present.

After you have submitted your post, please look it over and decide what it was about. You can edit that summary at the bottom of the post, and I will do my best to try to copy it to the index within a day.

Index:
Post #3: https://newmars.com/forums/viewtopic.ph … 22#p229922
GW Johnson - preliminary sketches and text for 15 day flight Earth-Mars

(th)

tahanson43206 · Yesterday 21:49:52

This post contains content delivered by email.

GW Johnson took an interest in the problem posed by PhotonBytes, and has agreed to participate in the new "Any Method" topic.

There are two images that go with the text below, which I will add as soon as possible (which might be Saturday)

Well, I simply used the data worksheet in the orbits+ course orbits spreadsheet to look up the average distances and speeds of Earth and Mars. To fly a short trip, the limit is straight radial. So I used a straight radial shot at constant speed, lasting 15 days per PhotonBytes, to find the necessary departure and arrival speeds.
To go straight radial, you have to kill Earth's orbital speed while you accelerate to your necessary radial speed. To arrive, you have to kill all that radial speed, but you must also acquire the orbital speed of Mars. The necessary vector speed changes are easy to figure, since these are right triangles. It's Pythagorean Theorem stuff.
Summing the departure and arrival, you are looking at something on the order of 133-134 km/s dV out of your vehicle, for the one-way trip. And that ignores going into orbit or landing. Those would be small additions. to the dV, in comparison. Further, these are impulsive velocity changes, requiring rather significant thrust/Earth-weight ratios out of your propulsion and vehicle designs. See the first png sketch "short trips to Mars.png".
<snip unrelated commentary>

Propulsion for Fast Trip
Image 1 goes here:
15 Day Flight Plan to Mars
Image 2 goes here;

I am hoping other NewMars members will feel empowered to participate. What I'm looking for are guesses about the technology that would make such a flight as this not only possible, but practical and economically justifiable. I expect that in 100 years, if the human race manages to survive that long, power in the required range will be available to the average person, just as a team of 100 to 400 horses is available to the average person in the United States right now.

As PhotonBytes has shown, it is possible to enlist the aid of computer aided software, but each participant is responsible for the accuracy of the results posted.

Update: The email snippet below is intended to help explain abbreviations used in the images above.

I think Wp is Weight of Propellant true
I think Wpay is Weight of Payload true
Winert would be Weight of Inert mass true
Wign would be Weight at ignition true
Vex might be Vexhaust true (bear mind this is an effective velocity, not the expanded value)

The email below is to confirm that a flight to Mars in 15 days is already possible using known technology:

If we presume 2 gees is acceptable for a short interval, then that is 19.613 m/s2. To reach 69 km/s = 69,000 m/s, V= at soles as t = V/a, for t = 3518 sec = 0.977 hours. Spending an hour at modest elevated gee at each end of the journey would be quite acceptable. If your ship is big enough to carry the required number of devices, an old Project Orion pulse propulsion design could do this. Depending on the size, Isp for those was somewhere in the 5000 s to 20,000 s Isp range better the bigger the ship. It was hard to hold the pusher plate and shock absorbers-averaged gees to the 2 to 4 gee range, especially in smaller sizes. That design and performance estimate was based on 1955-level fission technology, as modified for the shaped charge effect instead of omni-directional blast (the key technology to make this propulsion efficient). It should be possible to decrease the size and mass of the charges for the same few-kiloton yield today.
It is probably not possible, even today, to get yields that low with thermonuclear fusion devices. But you could likely propel a type M metallic asteroid with much larger (100-ish kiloton) small fusion devices, which are even more efficient for the mass of the charges. Those M-type asteroids would be solid enough to push, but they are quite rare. Hollowing the thing out would be difficult, but worth it. Those things are thought to be solid lumps of iron-nickel alloy, not unlike what's in Earth's core.
I see a lot less than 100 years to get propulsion that highly capable, if we go the pulse propulsion route! It could be done in a decade or two! We already know it will work. The critical experiments had been done by 1959, including accidentally discovering the survivability of the pusher plate from the surface nuclear tests in Nevada at Frenchman's Flat.
The main issues relate not to radiation, but to EMP, something not anticipated in 1955, when they intended to surface-launch these things using fractional-kiloton devices down in the atmosphere (a technology not yet available in 1955). The intense reality of those EMP effects was not known until the 1962 "Starfish Prime" nuclear test of a few megatons about 200 miles straight above Johnston Island in the Pacific. It caused a partial crash of the electrical grid and phones in Hawaii some 900 miles away (the explosion was line-of-sight visible in the sky from there). You probably will never want to use one of those things as close to Earth as GEO. The intensity decay would be inverse square, as with any omnidirectional and incoherent light source.
GW

(th)

tahanson43206 · Today 08:38:24

As a follow up to Post #3...

The upcoming Google Meeting will likely include review of work by GW Johnson, exploring the interesting idea of PhotonBytes to consider a flight to Mars that would take 15 days. While the technology needed does not exist today, in 100 years it should be available.

At the time the Wright Brothers achieved human powered flight, the fastest travel opportunity on Earth was provided by the steam locomotive.

The Wright Brothers routinely used steam locomotive powered trains to travel between Ohio and North Carolina.

In 1903, per Google, the fastest train on Earth was a German Electric train that ran 130 mph (210 km/h).

In 2003, humans had traveled to the Moon and returned with a velocity of 39,897 km/h (Apollo 10 per Google).

Per calculator, the ratio between 39897 and 210 is 189.9857.

Rounding to 190, the corresponding ratio for velocity in 2103 would be: 7,580,430 km/h, or: 2105.675 km/s

The velocity estimated for the 15 day flight to Mars (as computed by GW Johnson) is 60 km/s.

It appears that if the trend is correct, humans will have the ability to travel at 60 km/s well before 2103.

(th)

tahanson43206 · Today 10:36:12

I asked ChatGPT4o to double check my calculations for a flight across the Solar system at 2000 km/s. It came up with a figure larger than my estimate, which is fine with me. I doubt anyone will be making that trip any time soon, but it does give a sense of the size of the Solar System.

Solar System Crossing Time Calculation
Given:
Diameter of the Solar System: 30 trillion km (30 × 10^12 km)
Speed: 2000 km/s
Step 1: Calculate Time in Seconds
Time (s) = Distance / Speed
= (30 × 10^12 km) / (2000 km/s)
= 1.5 × 10^10 seconds
Step 2: Convert Seconds to Years
Seconds per year ≈ 3.16 × 10^7 s/year
Time (years) = (1.5 × 10^10 s) / (3.16 × 10^7 s/year)
≈ 475 years
Conclusion:
At a speed of 2000 km/s, it would take roughly 475 years to cross the solar system. This result is very close to your original estimate of 452 years.

(th)

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15 Days to Mars - Any Propulsion Method

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Re: 15 Days to Mars - Any Propulsion Method

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Re: 15 Days to Mars - Any Propulsion Method

#4 Today 08:38:24

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