Deep in the desert, army blasts way to a stronger, lighter bomb shelter

Deep in the desert, army blasts way to a stronger, lighter bomb shelter

Helped by hundreds of kilograms of explosives, the Home Front Command is testing new designs for the weakest part of civilian bunkers — the doors

Judah Ari Gross is The Times of Israel's military correspondent.

Can your shiny new bomb shelter survive a near-direct hit from a Scud missile?

Aside from waiting for war and rolling the dice, there’s really only one way to find out: Blow up a few hundred kilograms of explosives next to the shelter in the middle of the desert and see how it does.

That’s precisely what the Israel Defense Forces did on Wednesday, detonating a bit less than a ton of explosives next to concrete bunkers outfitted with three new designs for doors — meant to address one of the most vulnerable aspects of the protective rooms.

Over the past week, the army’s Homes Front Command has been conducting blast tests on new bomb shelter doors and designs for pipes and other underground infrastructure in the desolate Arava desert, on one of the firing ranges in the army’s Sayarim Base, which is mostly known for housing the Combat Intelligence training school.

The firing range is littered with bombed-out concrete structures and heaps upon heaps of rusting rebar, sheetrock and assorted building materials, the accumulated remains of years of blast tests.

The crater left by hundreds of kilograms of explosives going off to test the strength of new designs for bomb shelter in the army’s Sayarim Base in the Arava desert in southern Israel on December 27, 2017. (Judah Ari Gross/Times of Israel)

Wednesday’s explosion shook the entire area and left a four-foot crater, and yet two of the models performed admirably, showing nothing more than cosmetic damage, while the third decidedly failed, getting completely ripped off its frame and thrown into the bunker it was supposed to be protecting.

But that was expected. For the two working varieties — Dalit 1 and Dalit 3 — this was a final test, but for the more experimental Dalit 2, this was only the beginning, said Lt. Col. Avri Baranes, the head of engineering in the Home Front Command’s protection department.

Lt. Col. Avri Baranes, left, with two of his officers at the site of a blast test in the army’s Sayarim Base in the Arava desert in southern Israel on December 27, 2017. (Judah Ari Gross/Times of Israel)

Following the blast, representatives from the Home Front Command and the Standards Institute of Israel, a national company responsible for giving products a seal of approval, inspected the damage, measuring how much the doors buckled. While the final calculations still needed to be made, there were smiles all around. The doors looked great.

Israelis are required, under law, to build a protective room in their home or apartment, to defend against things like rocket attacks as well as earthquakes.

Currently, there are two main options for doors for the kinds of bomb shelters that people have in their homes: either the door can be of an exceedingly sturdy metal construction that weighs about 300 kilograms (660 pounds) or it can be of a somewhat lighter variety, but with a protective wall directly in front of it.

Neither of these options are particularly easy for contractors or for the homeowners who have to pay for it. In big cities especially, where apartments are smaller, having to either block off space for a thick wall in front of the bomb shelter or lug a massive metal door to a three-floor walk-up is not a fun choice to make.

The military has found that many Israelis are without effective bomb shelters. According to Home Front Command figures, some 27 percent of the country — or just over two million people — do not have “up to standard” protection against incoming rockets.

To address this issue, the Israel Defense Forces have been working to develop new options for people looking to either build new homes or refurbish existing ones, under a program known in Israel by the acronym Tama 38, which brings existing buildings up to code for earthquake preparedness.

‘Our gift to the country’

Once the Home Front Command completes testing for these new doors, the designs will move to the Standards Institute of Israel, where it will get final approval.

Once the Standards Institute gives the go-ahead, the plan is to disseminate the designs of the differnet Dalit varieties to any manufacturers that want them, free of charge.

“Our gift to the country,” said Baranes, a Technion-trained architect and civil engineer.

The Dalit 1 variety is a sliding door that tucks neatly into the wall, freeing valuable floor space for cramped apartments.

An employee of the Standards Institute of Israel inspects the damage of a blast test on a new kind of door for a bomb shelter on the army’s Sayarim Base in the Arava desert in southern Israel on December 27, 2017. (Judah Ari Gross/Times of Israel)

The Dalit 3 model is similar to the current models being sold, only it is less than half the weight, drawing its protective power from a superior geometric design rather than more material, Baranes said.

“At 140 kilograms (300 pounds), two workers can easily walk this up a flight of stairs,” he noted.

The result of a blast test on a new kind of door for a bomb shelter on the army’s Sayarim Base in the Arava desert in southern Israel on December 27, 2017. (Judah Ari Gross/Times of Israel)

The Dalit 2, on the other hand, is a completely different idea. It is not really meant to survive a blast, but rather to fail in a very specific way.

Much like how cars today are designed with so-called “crumple zones,” which collapse when they hit something, the Dalit 2 is also supposed to crumple when hit by a blast, absorbing the intense energy instead of letting it continue into the bomb shelter.

But that didn’t happen on Wednesday.

“Something was too hard and the whole thing failed,” Baranes said.

The designs for the Dalit 1 and 3, which took about two years to develop, will undergo a bit more polishing but are expected to reach manufacturers in about a year, he said.

For those wondering about the name, Dalit, it’s both the first name of a person who used to serve in the Home Front Command’s protection department — “It’s an homage to her,” Baranes said — and quite similar to the Hebrew word for door, delet.

“Plus it was easier to go with Dalit 1, 2, 3, etc. than to call them model updated, model improved, model upgraded,” the lieutenant colonel added.

Looking toward the next round of blast tests that are scheduled for May, the Home Front Command’s protection department will continue working on getting the Dalit 2 fully functional and is also focusing on another much maligned aspect of bomb shelter construction in apartment buildings.

The army currently dictates that the walls of multi-story bomb shelters need to extend deep into the ground. This is an onerous requirement, one that Baranes’s team is trying to scale back considerably, while still keeping the buildings secure.

The lieutenant colonel said that army is looking to review some of the instructions it gives to civilians for earthquakes and incoming attacks.

In such cases, Israeli citizens who don’t have access to a bomb shelter have been taught to run to either a stairwell or an interior room.

But in some cases, interior rooms can be more dangerous, depending on how the building was constructed.

For instance, the if the interior room is at the end of a hallway whose walls were made of solid concrete, the pressure from a blast can get compressed and multiplied, making the room at the end of it one of the last places you would want to be.

On the other hand, if that same hallway were made of concrete blocks, they would crumple and absorb the pressure and protect the interior room quite well.

“Those instructions were mostly based off common sense, not scientific study,” Baranes said.

read more: