This is by far the coolest thing I've read in a long time!!!

"Under DARPA's Demonstration Rocket for Agile Cislunar Operations (DRACO) program, the agencies plan on launching a spacecraft powered by a Nuclear Thermal Reactor (NTR) engine in Earth orbit by 2027."

The DRACO name alone is cool as shit..

One issue I have is how tf did Blue Origin get a contract... What have they proven to even get mentioned as a company worth contracting with?

They cracked the code. For Artemis they helped put together the "National Team" along with Lockheed Martin, Boeing, and many others. They figured out how to shmooze and lobby with the best of the best in the aerospace biz. Now they're a major sub-contractor for ULA and they've got their hooks into all the juicy government contracts.

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Tinfoil theory: Bezos reminded the decision makers that they have Alexa at their and their mistresses' homes.

I can't imagine being jeff and *not* doing that.

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Are these based on the kiwi engines that irradiated jackass flats ?

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Sort of? The article doesn't state whether it's going to be open cycle or closed cycle.

But I'm assuming it's going to be a closed cycle solid core nuclear thermal rocket so presumably, no irradiation plume in the exhaust.

For reaching alpha centauri in 15.000 years instead of 18.000?

By tinfoil hat you mean the most likely reason.

Considering their record is worse then India’s space program at this point.

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India’s space program is pretty amazing, comparing them to Blue Origin is an insult

I just punched the air and shouted 'YES!' loudly. Good news everybody.

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This is all I want out of life. Fuck this I'm going university.

NTRs are for getting stuff around the solar system more efficiently - though in many cases NEP would be better, I wish that was getting as much attention.

For interstellar travel though you want a fission fragment engine as a bare minimum, preferably fusion propulsion of some sort.

Lots of internet space bros claiming the benefit of higher Isp lost by increased mass due to reactor weight. Let’s finally build one and fly it to settle this once and for all. My two cents is that the anti-NTR space internet camp is also in the “Starship solves all problems” camp.

This is super exciting. We absolutely need nuclear propulsion if we are really gonna start colonizing the solar system, mining asteroids etc.

Starship (or at least that systems architecture) definitely solves more problems than NTRs.

NTRs are interesting, but I don't think they're as magical as many people claim. One of their biggest problems is that first generation NTRs have a super narrow niche of applicability. In the long run they might be more useful in more scenarios, but you have to get from here to there for that to happen.

From a perspective of humans in space getting somewhere fast solves many problems. Size does not solve all problems. Starship would be better utilized to build a fast human Mars transport vehicle in LEO than being used directly as the crew transport.

The primary advantage of early-generation NTRs is that they can operate with pure hydrogen, that's it. Doing that allows them to have an exhaust velocity of around 9 km/s. And because the rocket equation is exponential with respect to the ratio of delta-V and exhaust velocity NTRs start to look really good for single digit or low double digit delta-V. With a stage mass ratio of 5:1 you can achieve a delta-V of 14.5 km/s, which is a lot to work with. In contrast, with the same stage mass ratio you'd achieve maybe 40% of that delta-V with a LOX/methane stage.

However, things stop looking so rosy very rapidly. Because NTRs use a heavy reactor and rely on low-density hydrogen it is very challenging to achieve high stage mass ratios, which limits performance. Also, because liquid hydrogen is super cryogenic and has a high boil-off rate it is very challenging to build a high efficiency NTR which has significant longevity for deep space propulsion. Even if you can bring boiloff rates under control with thermal control systems and active cooling all of that stuff adds mass which again cuts into the stage mass ratio.

All of which conspires to make the most compelling use of a first generation NTR something like a trans-lunar (or interplanetary) kick stage for crewed missions. Which might be fine, but is still pretty limiting, and likely results in only a small number of NTRs ever being built.

Several different companies were awarded contracts. Not just Blue Origin. The DoD has handed out a few of these across different programs. DIU has a similar program as well.

Here's more companies that were awarded contracts

https://spacenews.com/diu-selects-nuclear-powered-spacecraft-designs-for-2027-demonstrations/

>Starship would be better utilized to build a fast human Mars transport vehicle in LEO than being used directly as the crew transport.

I agree, but the way to do that is with NEP, not NTP. Or at least not of the solid core variety anyway; gas core NTRs might do the job, but it doesn't seem likely they'll be a thing anytime soon.

Solid core NTRs don't really get you to Mars any quicker than Starship. With an Isp of 900s and a mass ratio of 5 you're looking at 14.2km/s. Starship with it's 380s Isp and ~12 mass ratio only gets 9.2km/s - 5km/s less.

On the face of it, that seems like a 50% speed increase, which is nothing to scoff at. The problem lies in slowing down at Mars. Starship is able to aerobrake, saving it ~4km/s of delta-v as compared to propulsively braking into orbit.

So there goes most of that 5km/s lead for the NTR stage, and the remaining 1km/s has to be split in two - a 500m/s higher cruise speed also incurs 500m/s more braking requirement - a much more modest 6% speed increase.

You could fit the NTR stage to aerobrake as well, but given the massive size of the tanks and the high dry mass of the NTR, it's likely to suffer a proportionally larger performance hit than Starship paid for the same capability.

 

Now, to an airless body such as Ceres or the Jovian moons it's obviously a different story and the NTR takes a considerable lead over Starship. However, NEP's advantages over NTP grow even more pronounced over larger distances, bringing me back to my original point.

The only real exception is of course Luna, where you can't aerobrake, and it's very close proximity puts NEP at a huge disadvantage.

NTRs perform a bit better if you focus on payload capacity instead of speed, but only in terms of mass fraction. In terms of cost the pure hydrogen and enriched uranium might well cancel out any mass savings if you've got cheap LEO lift. And in terms of ISRU, pure hydrogen is an order of magnitude more energy intensive to produce than hydrolox or methalox.

I'm definitely a Starship enthusiast, but I don't think Starship 'solves all problems'. It solves many problems, and NEP solves most of the other ones, while NTP only solves a few niche ones in between, so I have to wonder if it's really worth the trouble.

Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:

|Fewer Letters|More Letters| |-------|---------|---| |DARPA|(Defense) Advanced Research Projects Agency, DoD| |DoD|US Department of Defense| |ISRU|In-Situ Resource Utilization| |Isp|Specific impulse (as explained by Scott Manley on YouTube)| | |Internet Service Provider| |LEO|Low Earth Orbit (180-2000km)| | |Law Enforcement Officer (most often mentioned during transport operations)| |LOX|Liquid Oxygen| |NEV|Nuclear Electric Vehicle propulsion| |NTP|Nuclear Thermal Propulsion| | |Network Time Protocol| |NTR|Nuclear Thermal Rocket| |ULA|United Launch Alliance (Lockheed/Boeing joint venture)|

|Jargon|Definition| |-------|---------|---| |cryogenic|Very low temperature fluid; materials that would be gaseous at room temperature/pressure| | |(In re: rocket fuel) Often synonymous with hydrolox| |hydrolox|Portmanteau: liquid hydrogen fuel, liquid oxygen oxidizer| |methalox|Portmanteau: methane fuel, liquid oxygen oxidizer|

^(13 acronyms in this thread; )^(the most compressed thread commented on today)^( has 32 acronyms.)
^([Thread #8600 for this sub, first seen 23rd Feb 2023, 08:44]) ^[FAQ] ^([Full list]) ^[Contact] ^([Source code])

Starship and NTR are different use cases.

You don't launch them from earth, you'd use them in space.

They’re both being proposed for transporting people from Earth to Mars. Same use case.

NEP need to get rid of lots of waste heat. The designs I've seen either used massive radiators or liquid metal and high temperatures. Neither is particularly exciting.

I support the ntr program because I also want to see somebody try to do one for real.

That doesn't mean I think they will be practical. The NASA reactor program is very conservative in their mass goals, and I can't find any details on what this project is actually trying to build.

There's no shielding behind the reactor so there's a ton of radiation coming out. The hydrogen won't be radioactive.

For solid core NTRs, the exhaust hydrogen being irradiated isnt the worry, it's that the pieces of the core may be eroded and present in the exhaust.

Also no shadow shields for crew?

Starship would still land on Mars, but whether it's refueled X times or docked with NTR from another trip seems interchangeable to me