Posted on 12/21/2020 9:34:04 PM PST by BenLurkin
The biggest challenge (or constraint) is the mass of the payload (spacecraft, people, fuel, supplies etc) needed to make the journey.
The payload mass is usually just a small percentage of the total mass of the launch vehicle.
For example, the Saturn V rocket that launched Apollo 11 to the Moon weighed 3,000 tons.
But it could launch only 140 tons (5% of its initial launch mass) to low Earth orbit, and 50 tons (less than 2% of its initial launch mass) to the Moon.
Mass constrains the size of a Mars spacecraft and what it can do in space. Every maneuver costs fuel to fire rocket motors, and this fuel must currently be carried into space on the spacecraft.
SpaceX's plan is for its crewed Starship vehicle to be refueled in space by a separately launched fuel tanker. That means much more fuel can be carried into orbit than could be carried on a single launch.
This saves a lot of fuel, but can result in missions that take years to reach their destinations. Clearly this is something humans would not want to do.
Both Earth and Mars have (almost) circular orbits and a maneuver known as the Hohmann transfer is the most fuel-efficient way to travel between two planets. Basically, without going into too much detail, this is where a spacecraft does a single burn into an elliptical transfer orbit from one planet to the other.
A Hohmann transfer between Earth and Mars takes around 259 days (between eight and nine months) and is only possible approximately every two years due to the different orbits around the Sun of Earth and Mars.
A spacecraft could reach Mars in a shorter time (SpaceX is claiming six months) but—you guessed it—it would cost more fuel to do it that way.
(Excerpt) Read more at phys.org ...
Ben, that was the core of Zubrin’s “Mars Direct” plan. NASA killed it because it could be done with existing technology, so no lucrative rakeoffs for private contractors and no revolving door for the corrupt administrators. Of course, whether it was worth doing is another matter.
I think the author may have pulled the 9 month figure from Wikipedia. The Perseverance rover trip is about 6.5 months. The Curiosity rover took a little over 8 months. The Insight lander took a bit over was 6.5 months or so. I am guessing the time travelled is dependent on nailing the launch window and the launch vehicle required to get there..
Like liberal democrats? I would be all for that. 😁🤪
Lionel Jeffries was a trip, wasn’t he?
This article is a joke. If we continue on the present path, we’ll be wearing rags and killing each other with sticks and rocks in a decade.
I’d just find a worm hole and get there in no time.
There are only two human habitable destinations in the Solar System - the Moon, and Mars.
Besides basic scientific research and space tourism, what else are we supposed to do there?
We need to invest in space robots.
Planet Earth will eventually progress to Star Wars level space travel.
But, not for thousands of years.
By definition, however, a Hohmann transfer is a minimum energy transfer. Any variation in timeframe, either longer or shorter, is no longer the minimum energy. But I have a history for nitpicking scientific inaccuracies. Especially in movies. You don’t want to hear them.
It will NEVER be possible to approach the speed of light. NEVER.
1. Send a rocket with robots and cameras. No need for oxygen, food, temperature control, gravity substitutes, and no time restriction.
2. Send the data and videos back to earth for anybody to watch and share.
[99% of the effort of a manned probe is involved in keeping the humans alive for the long trip, and all 99.9999999 % of humanity is going to see are videos anyway, so skip the humans, and send many more cheap and expendable robot probes.]
I only discovered that movie about five years ago and watch it every Christmas season.
That may be true.
On the other hand, it may not be necessary.
I mean, almost no one saw quantum physics or E=MC squared coming a hundred years ago.
I am thinking we will have a couple more big surprises to digest before the new millennium is over.
See 53.
I agree about robots, but not about Mars and the Moon being habitable.
If humans cannot walk around without being sealed within a self-contained environment in a pressurized space suit, breathing the local atmosphere, in a temperature range that won’t kill them, then the place by definition is not habitable.
To Manchester in a Ford Cortina.
Gene Hunt’s way.
I should have said survivable.
Every other place in the solar system...
No solid ground.
Too hot.
Too much radiation.
Not enough gravity.
Pluto might be survivable, but bring a winter coat.
I believe venus could be made habitable much easier than mars.
Rereading the article and a bit more reading on the subject, the author implies going to Mars in less than 9 months(Hohmann transfer)as some new concept. The Perseverance Rover spacecraft makes 5 trajectory-correction maneuvers along the way to arrive in ~6.5 months. The Mars transfer type depends upon what needs to be done when the spacecraft arrives at Mars.
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